Blog Feed: Science Natural Phenomena and Medicine

Origin of the Mississippi River

Published on 2013-04-12 12:10:00

The source or origin of the Mississippi River is Lake Itasca, a 1.8-square-mile glacial lake in Clear Water county, central Minesota. This lake, in turn, is fed by Nicollet creek, Elk Lake outlet stream, and winter snowfall. Receiving high volume of

Convection

Published on 2013-04-01 21:11:00

Convection is the transfer of heat within fluids through the flow of molecules in a circulatory pattern. It is due to the variation of density and the action of gravity.

Origin of the Nile River

Published on 2013-03-28 10:48:00

The origin of the Nile River is Lake Victoria, situated on the Uganda-Tanzania-Kenya border, in east central Africa. The headstream, or main river, that feeds this lake is Kagera River. As it flows northward, the Nile River receives three times its v

Andean Volcanic Belt

Published on 2013-03-23 21:16:00

The Andean Volcanic Belt is a chain of active volcanos that stretches along the Andes Mountain Range, from Colombia to Chile. It is composed of four volcanic zones; the first one begins with Nevado del Ruiz volcano in Colombia and ends in Ecuador; th

How did the Andes Mountain Range Originate?

Published on 2013-03-20 23:20:00

The Andes mountain range originated by the collision of the Nazca tectonic plate against the South American plate 45 million years ago, during the Tertiary. It was the result of a collision of plates, with the Nazca plate sliding underneath the South

Marañón River

Published on 2013-03-15 20:10:00

The Marañón River originates at the confluence of Nupe and Lauricocha Rivers, near the town of Rondos, at 5,800 m of altitude in the Andes Range, Peru. With a course of 1,100 miles, it ends at a point where it flows into the Ucayali River, to becom

Orinoco River

Published on 2013-03-12 21:39:00

Arising in the Parima mountains, the Orinoco River is a 1,500-mile long river that flows across Venezuela and into the Atlantic Ocean. Its main tributaries are Apure, Arauca, Atabaupa, Cauro, etc. Among the fish living in its waters is piranha. Croco

Origin of Amazon River

Published on 2013-03-11 23:02:00

The origin of Amazon River is the Lauricocha River, which springs from melting water from an Andes Range glacier at 5,800 m of altitude, northeast of Lima, Peru. Having run for 85 kilometers, Lauricocha River meets Nupe River to form Marañón River,

Baldwin 0-6-6-0 1000

Published on 2013-03-08 20:30:00

The Baldwin 0-6-6-0 1000 was a diesel-electric locomotive designed and manufactured by Baldwin Locomotive Works from 1945, for the Soviet State-owned Railways. It was powered by an 8-cylinder 1000 hp diesel engine that reached 60 mph (97km/h). It had

M62 Locomotive

Published on 2013-03-07 19:34:00

The M62 is a Russian V12 diesel engine locomotive, delivering 1,974 hp and capable of developing 62 miles per hour (100 km/h). It was made by the State-run Voroshilovgrad Locomotive Factory, from 1965 to 1994, to draw heavy freight trains on standard

Adler Steam Locomotive

Published on 2013-03-04 21:31:00

Designed by George and Robert Stephenson, the Adler was a British-made German steam locomotive, which entered service in 1835, running on standard gauge tracks, from Nurumberg to Früh and back, for the Bavarian Ludwig Railway. The firebox used coke

GWR 6800 Grange Class

Published on 2013-03-03 21:44:00

The GWR 6800 Grange Class was a steam locomotive model built by Great Western Railways between 1936 and 1939, used in England until the 1960s. It had a 4-6-0 configuration and drove on standard-gauge tracks (1.435 m). It used coal as fuel, running wi

Fire-tube Boiler

Published on 2013-03-01 21:56:00

A fire-tube boiler is a type of boiler used in steam locomotives in the 19th and first half of the 20th century. It consisted of a series of tubes running through water contained in a sealed vessel; hot gases from burning coal or wood in a firebox we

Anthracite

Published on 2013-02-28 13:33:00

Anthracite is a mineral coal which burns almost without flame. Black, hard and brittle, it has a high degree of metamorphism. It is used to heat water in boilers to produce steam to propel turbines in power plants. In the past anthracite was the powe

Helium

Published on 2013-02-26 20:46:00

Helium is an inert, very light, gaseous element, present in the Sun's atmosphere, some minerals, natural gas, etc. It also occurs as a radioactive decomposition product and is used as substitute for flammable gases in dirigible balloons. Symbol He; a

Very Large Telescope (VLT)

Published on 2013-02-25 20:11:00

The Very Large Telescope array is a astronomical optical system that is composed of four telescopes, which are combined into an astronomical interferometer, which probes the celestial bodies and structures of the universe with higher resolution by me

Archimedes' Principle

Published on 2013-02-24 17:27:00

The Archimedes' Principle is the law which establishes that a body immersed in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the body. This upward force which pushed up the body is called "buoyant force". The body will

Neon

Published on 2013-02-22 20:51:00

Neon is a chemically inert gaseous element, occurring in small amounts in the Earth's atmosphere. It is used mainly in orang-red tubular electrical discharge lamps. One liter of Neon, at 0ºC and at 760 millibars of pressure, weighs 0.9002 grams. Sym

Titanium

Published on 2013-02-21 20:44:00

Titanium is a dark-grey, very hard, light and corrosion-resistant metallic element, occurring combined with various minerals. It is used in metallurgy to remove oxygen and nitrogen from steel and to toughen it. Due to its lightness and hardness, tita

Harnessing the Energy from Coal withouth Burning it

Published on 2013-02-20 14:57:00

After more than 10 years of research, scientists of the Ohio State Universty have found a way to get energy from coal without burning it, avoiding and removing 99% of the pollution from this mineral through a process called coal-direct chemical loopi

Inertial Mass

Published on 2013-02-18 19:05:00

Inertial mass is the mass of a body as determined by Newton's Second Law of Motion (the body's momentum), which states that "the acceleration of a falling body is inversely proportional to its inertial mass but directly proportional to its gravitatio

Meteoroid

Published on 2013-02-16 09:03:00

A meteoroid is any of the small celestial rocky bodies that drift in outer space and that are smaller in size than an asteroid. They are often remnants of comets or any other celestial object that got fragmented upon collision and became spacial debr

Asteroid

Published on 2013-02-15 11:51:00

Also called minor planet, an asteroid is any of the thousands of small celestial bodies, measuring from 500 miles to less than one mile in diameter, that drift in outer space. In the Solar System, asteroids revolve about the Sun in orbits that lie mo

Metrology

Published on 2013-02-12 20:52:00

Metrology is the science of measures and weights. It establishes a ratio to another fixed quantity, length or weight called patron unit. For example, the meter is the patron unit of length in the metric system. Today, metrology is very important in s

Gallium

Published on 2013-02-09 08:59:00

Gallium is a rare, steely-gray, trivalent metallic element, which is used in high temperature thermometers because it has a high boiling point (1983ºC). Symbol Ga; atomic number 31; atomic weight 69.72.

Bacterium that Causes Gas Gangrene

Published on 2013-02-08 08:31:00

The bacterium that causes gas gangrene is the Clostridium perfringens, which is a Gram-negative rod-shaped anaerobic bacterium (bacillus). It is found widely in nature: humid soil, stagnant water, milk, and the human and animal intestinal tract. Cont

Origin of Mammals

Published on 2013-02-07 14:10:00

The origin of mammals go back to Protungulatum donnae, an ant-eating animal that had the size of a rat and that lived in the late Cretaceous, about 145 million years ago. The ancestor of mammals was an archaic warm-blooded ungulate with a long furry

Deer Fly

Published on 2013-02-06 19:37:00

The deer fly is a hematophagus (blood-sucking) fly of the genus Chrysops. It is found widely scattered in the tropical regions of West Africa. Most of the species of Chrysops are vectors that transmit the loa loa nematode parasite which causes a type

Beryllium

Published on 2013-02-05 19:14:00

Beryllium is a steel-grey, bivalent, hard, light metallic element, the salts of which are sweet. It is used in copper alloys for better fatigue endurance, in springs and in electrical contacts. Its melting point is 1,278º C. Symbol Be; atomic weight

Grampus griseus

Published on 2013-02-04 20:49:00

The Grampus griseus, commonly known as Risso's dolphin, is a cetacean of the dolphin family. It is widely found in northern seas, measuring up to 13 ft (4 m) long. It has a large dorsal fin and a round protruding head.

Spark Gap

Published on 2013-02-03 18:49:00

A spark gap is the space between to electrodes where sparks occur between them to ignite a combustion engine. At power substation there are big spark gaps, which are used to in high voltage switches.

Boron

Published on 2013-02-03 09:28:00

Boron is a non-metallic element, occurring naturally only in combination, as in borar, boric acid, etc. It is obtained in amorphous and crystalline form when reduced from its compounds. Symbol B; atomic weight10.812; atomic number 5.

Hymenoptera

Published on 2013-01-31 11:23:00

Hymenoptera is an order of insects comprising the wasps, bees, ants, and sawflies, whose legs and wings are attached to the thorax and are characterized by clearly differentiated head, thorax, and abdomen, and complete metamorphosis. They have two pa

Stator

Published on 2013-01-28 20:16:00

A stator is the part of an electric motor, generator, or turbine, which remains fixed with respect to a rotating part called rotor. In a motor and generator, it has insulated copper wire coils, which generate a magnetic field. A stator is composed of

Nickel

Published on 2013-01-27 09:45:00

Nickel is a hard silvery-white, ductile and malleable, metallic element, allied to iron and cobalt, not readily oxidized, and with a crystalline structure. It is used chiefly in alloys, in electroplating, and as catalyst in organic synthesis. Its mel

Lithium

Published on 2013-01-23 21:22:00

Lithium is a soft, silver-white, metallic element, which is the lightest of all metals, occurring combined in cerains minerals. With a melting point of 179º C, it is used in ceramics, alloys and optics. Symbol Li; atomic weight 6.94; atomic number 3

Electromagnet

Published on 2013-01-22 13:11:00

An electromagnet is a device consisting of an iron or steel core which is magnetized by electric current flowing through an enamel-insulated copper coil wound around it. The strength of the magnetic field thus produced will depend on the number loops

Radon

Published on 2013-01-20 19:47:00

Radon is a chemically inert, radioactive gaseous element, produced by the decay of radium. It is considered a serious health hazard. Symbol Rn; atomic weight 222; atomic number 86.

Fermium

Published on 2013-01-18 20:25:00

Fermium is a synthetic radioactive element, which has ten isotopes, produced by bombardment of plutonium or uranium. Symbol Fm; atomic number 100; valence 2 and 3. It was named after Enrico Fermi, the Italian physicist.

Dentary

Published on 2013-01-16 20:06:00

Dentary is one member of a pair of membrane bones that in lower vertebrates form the distal part of the lower jaws and in mammals comprise the mandible.

Rhodium

Published on 2013-01-15 20:08:00

Rhodium is a silvery-white metallic element of the platinum family, forming salts which give rose-colored solutions. It is used in electroplate microscope and instrument parts to prevent corrosion. Its melting point is 1964ºC. Symbol Rh; atomic weig

Ametropia

Published on 2013-01-14 17:56:00

Ametropia is an abnormal condition of the eye causing faulty refraction of light rays, as in astigmatism, miopia, etc. In this eye abnormality, images do not fall on the retina.

Ampere's Law

Published on 2013-01-12 19:39:00

The Ampere's law is the law that a magnetic field induced by an electric current is, at any point, directly proportional to the product of the current intensity and the length of the current conductor, inversely proportional to the square of the dist

Terbium

Published on 2013-01-12 19:28:00

Terbium is a rare-earth, metallic element present in certain minerals, such as gadolinite and monazite and yielding colorless salts. It has a melting point of 1356º C. Symbol Tb; atomic weight 158.92; atomic number 65; valence 3, 4.

Americium

Published on 2013-01-11 19:16:00

Americium is a radioactive metallic element, one of the products of high-energy helium bombardment of uranium and plutonium. It is used in smoke detectors and industrial gauges. Symbol Am; atomic number 95; atomic weight; valence 3, 4, 5, 6.

Yttrium

Published on 2013-01-10 17:33:00

Yttrium is a rare, trivalent, silvery, metallic element which is found in gadolinite and other minerals. It oxidizes when heated and reacts with water, but remains stable in air. Yttrium is used as a catalyst and in alloys. Symbol Y; atomic weight 88

Diphtheria

Published on 2013-01-09 20:14:00

Diphtheria is a febrile, infectious disease caused by a bacterium: Klebs-Löffler bacillus, or Corynebacterium diphtheriae, which produces toxins that destroy the cells of the body. It is marked by fever and the development of a false membrane or pat

Strontium

Published on 2013-01-08 16:54:00

Strontium is a bivalent, silvery metallic element whose compounds resemble those of calcium. It is found in nature only in the combined state, as in strontianite, which is used in fireworks, flares, and tracer bullets. Strontium melting point is 770

Zircon

Published on 2013-01-07 18:39:00

Zircon is a brown common mineral, ziconium silicate Zr2Si04, occurring in small tetragonal crystals or grains of various colors, usually opaque. It is found in ignious and metamorphic rocks in Brazil, Australia, the United States, etc.

Martial Eagle

Published on 2013-01-05 17:22:00

The martial eagle (Polemaetus bellicosus) is a bird of prey, which inhabits the open regions of sub-Saharan Africa. It is a large and heavy eagle, with a wingspan of up to 2.20 m and a weight of 6 kg (12.5 lb). Its head, wings, and back are black and

Crested Eagle

Published on 2013-01-04 19:06:00

The crested eagle is a tropical eagle of the genus Morphnus. It weighs between 4 and 6 pounds and has greyish white head and breast and black back and wings. It is found in Central and South America, from Guatemala to northern Argentina. The crested

Zirconium

Published on 2013-01-03 14:22:00

Zirconium is a metallic element found combined in zircon, baddeleyite, etc., resembling titanium chemically. It is used in steel metallurgy, as a refractory, as scavenger, and as opacifier in vitrous enamel. It has a melting point of 1,855ºC. Symbol

Palladium

Published on 2013-01-02 20:31:00

Palladium is a rare metallic element of the platinum group. It is silver-white, ductile, and malleable. Found in nickel and gold ores, it is used chiefly as catalyst and in dentistry, surgical instruments, and other alloys. It has a melting point of

Rubidium

Published on 2013-01-01 11:01:00

Rubidium is a silver-white, metallic, active element, which resembles potassium. It ignites in air and reacts with water. It is used in photoelectric cells and electronic vacuum tubes. Rubidium is found world wide in carnallite and pullocite. Symbol

Cadmium

Published on 2012-12-29 16:38:00

Cadmium is a white, ductile, divalent, metallic element which resembles tin in appearance. It is used in plating, in making alloys, and in rechargeable batteries. It is found in copper and zinc ores. Symbol Cd; atomic weight 112.41; atomic number 48;

Transverse cervical artery

Published on 2012-12-28 19:01:00

The transverse cervical artery is a blood vessel which arises from the thyrocervical trunk and travels backward across the base of the neck, giving off two branches; a superficial branch and a deep branch.

Polonium

Published on 2012-12-27 13:36:00

Polonium is a radioactive metallic element, discovered by M and Mme Curie in 1898. It is found in small quantities in uranium ores. The isotope polonium-210 is produced by bombarding bismuth with neutrons. It is used in the control of static electric

Platinum

Published on 2012-12-26 17:37:00

Platinum is a heavy, greyish-white, highly malleable and ductile metallic element. It is resistant to the majority of chemicals, practically unoxidizable, except by the presence of bases. It is fusable only to extremely high temperatures (melting poi

Barium

Published on 2012-12-23 17:06:00

Barium is a whitish malleable, metallic element. It is divalent, occurring in combination chiefly as barite and witherite. Symbol Ba; atomic weight 137.34; atomic number 56; valence 2. Barium has a boiling point of 1,140º. It is used in alloys with

Krypton

Published on 2012-12-22 17:39:00

Krypton is an inert, monatomic, oderless, gaseous element, present in very small amounts at high altitudes in the atmosphere. It has a melting point of -156.6º C. It is used in high-power tungsten-filament light bulbs. Symbol Kr, atomic weight 83.8,

Scheelite

Published on 2012-12-21 19:41:00

Scheelite is a calcium tungstate (mineral containing calcium and tungsten), usually occurring in tetragonal crystal. It is found in limestones intruded by granites. Its symbol is CaWO4.

Wolframite

Published on 2012-12-21 17:40:00

Wolframite is a mineral, iron manganese tungstate (Fe, Mn) WO4, which occurs in heavy greyish-black to brownish-black tabular or bladed crystals. Found in quartz veins, it is an important ore of tungsten.

Tungsten

Published on 2012-12-19 20:31:00

Tungsten is a rare metallic element having a bright-gray color. It is extremely hard and dense, has a metallic luster and a very high melting point of 3410º C. Found in wolframite, tungstite and other minerals, it is used in alloys of high speed cut

Radium

Published on 2012-12-18 16:50:00

Radium is a highly radiactive metallic element which produces radon and alpha rays when it disintegrates, with the latter being regarded a positively charged particles of helium. The disintegration of radium is understood to be a process by which an

Plutonium

Published on 2012-12-17 18:21:00

Plutonium (Pu) is a radioactive element, capable of self-maintained explosive fission. It was isolated from uranium 238 during research on the atomic bomb in 1940 by neutron bombardment. It has 13 isotopes, from which Pu 239 and Pu 244, with a half-l

Monazite

Published on 2012-12-15 18:47:00

Monazite is a reddish brown mineral, which is a phosphate of cerium and lanthanum, containing about 10% of thorium. Purified from other minerals, it is found in South Africa, North America, Brazil, and Australia.

Thorium

Published on 2012-12-14 19:24:00

Thorium is a greyish white, lustrous, malleable, radioactive, metallic element present in monazite. It is used as a source of nuclear energy, in vacuum tube filament coating, and in alloys. Symbol Th, its atomic number is 90, atomic weigh 232.038, an

Iridium

Published on 2012-12-13 19:16:00

Iridium is a hard metallic element resembling platinum. Dense and corrosion-resistant, it is used in platinum alloys, in bearings, surgical tools, and for the points of gold pens. It has valence 3, 4, an atomic weight 192.2, and an atomic number 77.

Osmium

Published on 2012-12-12 17:08:00

Osmium is a hard heavy metallic element, whose symbol is Os. It has the greatest density of the known chemical elements. It forms octavalent compounds, as OsO4. Osmium is used chiefly as a catalyst, in alloys, and in the manufacture of electric light

Class Stratification in the United States

Published on 2012-12-11 16:47:00

Like all state-organized societies, the United States is a stratified and has a complex system of classes, minorities and other hierarchical groups. Emic (subjective) versions of US stratification hierarchies differ from one class to another and bear

Bullet Cluster

Published on 2012-12-09 17:45:00

Also called Bullet Cluster, the Cluster 1E0657 is a group of individual galaxies lying at 3.4 billion light years away. The observation and studies of these colliding galaxies have provided evidence of the dark matter, which is a type of matter that

Mercury

Published on 2012-12-07 18:03:00

Mercury is a planet of the Solar System, lying at 36 million miles (57.9 million Km) away from the Sun; the closest, followed by Venus. It has a rotational period around the Sun of 88 days. The surface of Mercury is rough and full of craters; not onl

Remoras

Published on 2012-12-06 18:48:00

A remora is any of several species of elongated ocean fish which swim attached to bigger fish, such as swordfish, sharks, whales, marlins, etc., event to ships hulls. They feed on their host parasites. Aside from their 3 ft-long, elongated body, remo

Southern Cross

Published on 2012-12-05 18:03:00

The Southern Cross is a small constellation of bright stars lying in such a manner to form the shape of a cross (Crux in Latin). It is seen only from the Earth's southern hemisphere as one looks southward. Located in the Milky Way, close to Centaurus

Quantum Fluctuation

Published on 2012-12-04 19:55:00

Quantum fluctuation is a transient alteration in the amount of energy in a point in space, which leads to the creation of particle-antiparticle pairs of virtual particles. It is part of the uncertainty principle of German physicist Werner Heisenberg.

Comet

Published on 2012-12-03 16:27:00

A comet is a celestial object composed of water ice, frozen gases and small particles. It has nucleus or head, which is enveloped by ammonia and carbon dioxide gas that form a long tail-like beam called "coma". Comets orbit around the Sun in an ellip

Mars (Planet)

Published on 2012-12-02 20:12:00

Mars is a planet of the Solar System, the nearest to the Earth, occupying the fourth position in distance from the Sun at 229 million km away from it. With a diameter of 4,200 miles (6,800 km), Mars is about half the size of the Earth. It has ice cap

Comet Bennett

Published on 2012-12-01 10:01:00

The comet Bennett was a comet discovered by John Caister Bennett, from South Africa, on December 28, 1969, but was seen from Earth with the nake eye in March 1970, reaching periphelion on March 20. The commet head was wrapped up in a cloud of hydroge

Halley's Comet

Published on 2012-11-30 20:35:00

The Halley's comet is a comet which orbits elliptically around the sun and approaches to Earth every 76 years. It consists of water ice and stony minerals, with a nucleus measuring 5 x 10 miles. It was named after the British astronomer Edmund Halley

Lemon Shark

Published on 2012-11-29 17:40:00

Negaprion brevirostis, commonly known as the lemon shark, inhabits the tropical shallow waters of the Atlantic, from North Carolina to Brazil. It is 11 ft long. The female gives birth to its young every year, usually in shallow lagoons. Lemon sharks

Markarian's Chain

Published on 2012-11-27 16:28:00

Part of the Virgo Cluster, the Markarian's chain is a line of galaxies located about 72 million light years away. It was discovered by the Armenian astronomer Benik Jegischewitsch Markarjan in the 1970s.

Leo Triplet

Published on 2012-11-26 16:29:00

The Leo Triplet is a group of three galaxies composed of Messier 66, Messier 65, and MGC3628. It is approximately 36 million light years away. Messier 66 has a record of super nova explosions.

Nuclear Family

Published on 2012-11-25 17:14:00

Can a particular group be found in all domestic settings? Many anthropologists believe there is such a group, and refer to it as the nuclear family: husband, wife, and children. Ralph Linton held the view that father, mother, child are the "bedrock u

Bull Shark

Published on 2012-11-24 14:41:00

Carcharhinus leucas is commonly known as the bull shark, and is found in coastal shallow sea and river waters. Many bull shark attacks on swimmers have been recorded. It can weigh up to 500 lb (225 kg) and measures an average of 11 ft (3 m) in length

Great Hammerhead Shark

Published on 2012-11-22 19:55:00

The great hammerhead shark, scientifically known as Sphyma mokarran, is a large shark which is widely distributed around the globe, living in tropical ocean waters. It feeds on crustaceans, mollusks, bony fish, and other type of sharks. It reproduces

Ganciclovir

Published on 2012-11-20 10:20:00

A derivative of acyclovir, ganciclovir is an antiviral drug used in the treatment of viral retinitis, pneumonitis, and other viral infections. It works by stopping the development of a virus by inhibiting the DNA synthesis. Ganciclovir has antiviral

Acyclovir

Published on 2012-11-19 19:18:00

Acyclovir is anti-viral drug used in the treatment of viral infections, such as encephalitis, varicella zoster, herpes, and other viral diseases. Chemically, acyclovir is a synthetic purine nucleoside, which was first produced in the early 1980s by G

Encephalitis

Published on 2012-11-18 09:36:00

Encephalitis is an inflammatory disease of the brain, which could be caused by any of number of viruses, transmitted by mosquitoes, but it can also be caused by amoeba or bacteria. This inflammation of the brain has the following symptoms: nausea, vo

White Shark

Published on 2012-11-16 09:43:00

The white shark is a large agressive shark distributed world-wide in shallow and deep waters of tropical and temperate regions of the Atlantic and Pacific oceans. With a maximum length of 7 m (23ft) and a weight of 3,200 kg (7,100 lb), the white shar

Arbovirus

Published on 2012-11-15 20:39:00

An arbovirus is one of large group of spheroidal viruses, sheathed in a fatty membrane containing RNA. It is transmitted to human beings by mosquitoes and other blood-sucking insects. The arbovirus causes dengue, encephalitis, hemorrhagic fever, mild

Sandbar Shark

Published on 2012-11-14 21:22:00

The sandbar shark (Carcharhinus plumbeus) is a shallow-water shark which is found widely distributed, near coastal areas, from the Atlantic to the Indo-Pacific oceans. The adult can measure up to 2.5 m in length and has a high and prominent dorsal fi

Tiger Shark

Published on 2012-11-13 17:44:00

Galeocerdo cuvieri, commonly known as Tiger shark, is a large dangerous shark that lives in warm ocean waters. It has a long upper tail lobe and dorsal fin, and can measure up to 5 m (17 ft) in length. It is blue or grey in color with stripes on the

Dwarf Gulper Shark

Published on 2012-11-12 17:49:00

The Dwarf Gulper shark (Centrophorus atromarginatus) is a two-foot long shark that dwells in the Pacific and Indian ocean waters. It is a type of dogfish which feeds on deep water fish and shrimp.

Needle Dogfish

Published on 2012-11-11 17:01:00

Scientifically known as Centrophorus acus, the needle dogfish is a small type of shark that lives in deep sea waters. It has been sighted in the Pacific Ocean near Japan and in the Gulf of Mexico. Having two dorsal fins with spines, the adult needle

Great Wall of Galaxies

Published on 2012-11-10 07:48:00

The Great Wall (CfA2) is a layer of galaxies situated 250 million light years away, beyond the border of the Milky Way. It has a length of 500 million light years, and a width of 300 million light years. Its thickness or depth has not been determined

Stratum Basale

Published on 2012-11-09 09:12:00

The stratum basale is the innermost of five layers the epidermis is composed of. It consists of coboidal-shaped epithelial cells, constantly supplying new cells by mitotic division. These cells provided by the stratum basale go up to the surface of t

Keratinization

Published on 2012-11-08 14:41:00

Keratinization is the accumulation of keratin in epithelial cells, causing them to get hard and horny to form finger nails and hair. Keratin is a type of protein abundant in epithelial cells of epidermis. When the cells in the outer surface of the sk

Dermis

Published on 2012-11-07 19:26:00

Measuring between 0.05 and 0.3 cm thick, the dermis is the part of the skin which lies deep beneath the epidermis and consists of a layer of connective tissue. Within the dermis, there are organ of sensation, blood and lymph vessels, hair roots, nerv

Epidermis

Published on 2012-11-06 16:44:00

The epidermis is the exterior layer of squamous, overlapping, epithelial cells which constitute tha skin. The epidermis has no blood vessels and consists of five sub-layers of cells: 1) stratum basale, which is the deepest layer that is constantly pr

Epithelium

Published on 2012-11-04 19:43:00

The epithelium is a membranous tissue which covers the external part of the body, in the form of skin, and lines the internal cavities of body organs and vessels. Since it is closely packed in one or two layers, it has no blood vessels. It is made up

Endothelium

Published on 2012-11-03 20:54:00

Formed from the mesenchyme, the endothelium is a layer of specialized epithelial cells which lines the inner walls of blood vessels, heart cavities, and lymph vessels. The cells of the endothelium are flat and a basal membrane separates them from the

Thoracodorsal Artery

Published on 2012-11-02 22:17:00

The thoracodorsal artery originates from the subscapular artery, which, in turn, arises from the axillary artery. The thoracodorsal supplies the latissimus dorsi muscle with oxygenated blood.

Recurrent Fever

Published on 2012-10-31 21:24:00

Recurrent fever is an infectious disease caused by three different species of bacteria: Berrelia recurrentis, Bartonella quintana, and Rickettsia prowazeki, which are spirochetes (spiral-shaped) bacteria transmitted to man through the bite of blood-s

Arsenic Poisoning

Published on 2012-10-30 15:17:00

Usually, arsenic poisoning is a slow process that occurs over a long period of time by drinking underground water which runs through arsenic-rich rocks. Arsenic alters cellular metabolism, preventing the cells of the body from absorbing or using certain vitamins, such as thiamine (B1) and accelerating the death of vascular endothelial cells. Arsenic poisoning symptoms are cardiovascular episodes, increase of blood pressure, anemia, headaches, drowsiness, skin scaling, white lines on the fingerna [..]

Weil's Disease

Published on 2012-10-28 12:28:00

Also known as leptospirosis, Weil's disease is an infection caused by Leptospira interrogans, a spiral-shaped bacterium measuring about 12 micrometer long and 0.1 micrometer in diameter. The bacterium that causes Weil's disease is transmitted to man when urine or feces of contaminated domestic animals, such horses, sheep, and pigs gets in contact with a scratch or crack in his skin. The symptoms are high fever, liver inflammation, jaundice, headaches, etc. The disease can be fatal if there is bl [..]

Sandy Hurricane

Published on 2012-10-27 16:40:00

Sandy was upgraded to category 2 hurricane as it heads towards the eastern and northeastern coasts of the United States. Strong winds of more than 90 miles per hour has been recorded by meteorological service planes. Coastal flooding and torrential rains are being forecast as Sandy hugs along the coast from south to north. A lot of damage may be caused.

Anthrax

Published on 2012-10-26 20:14:00

Anthrax is a disease caused by Bacillus anthracis, a gram-positive, rod-shaped bacterium transmitted to man from cattle and sheep. Anthrax is extremely infectious and can be fatal if not treated. It is characterized by high fever, headache, weakness, and a skin ulcer or necrotic boil if the Bacillus anthracis enters the body through a small wound in the skin, with men who works with cattle and sheep being the most exposed. But the bacterium can also gets into the body by inhalation and ingestion [..]

Yellow Fever

Published on 2012-10-25 15:28:00

Yellow fever is a serious viral infection transmitted by the female of the Aedes aegypti mosquito, which is found in tropical regions of South and Central America and Africa. The virus which causes yellow fever is the flavivirus, which has nucleic acid and replicates in the cytoplasm of the host cells. This tropical disease breaks out after a 5-day incubation periods; the symptoms include jaundice, high fever, headache, chills, vomiting, and gastrointestinal bleeding.

Malaria

Published on 2012-10-24 13:24:00

Malaria is a world-wide infectious disease caused by four or more species of parasitic protozoans of the genus Plasmodium, which are transmitted or transferred to humans by mosquitoes of the genus Anopheles. The four known species of protozoans that trigger malaria are: Plasmodium vivax, Plasmodium malariae, Plasmodium falciparum, and Plasmodium ovale. Once in the blood stream, they occupy and destroy erythrocytes (red blood cells). The symptoms of malaria are: remittent chills and high fever, p [..]

External jugular vein

Published on 2012-10-23 12:05:00

The external jugular vein is one of two blood vessels, located each in one side of the neck. It collects oxygen-depleted blood from the retromandibular and auricular veins. The external jugular vein drains into the subclavian vein.

Psittacosis

Published on 2012-10-22 11:20:00

Also known as parrot fever, Psittacosis is an infectious disease triggered by Chlamydia psittaci, a small bacterium measuring 0.5 micrometers. It is transmitted to humans from parrots and other birds by inhalation or ingestion of tiny microdroplets of contaminated fluid. Psittacosis affects the lungs and bronchi, causing pneumonia. After a 5-to-14-day incubation period, the disease breaks out with the first symptoms, which include high fever, chills, diarrhea, conjunctivitis, arthralgias, diffic [..]

Cambrian

Published on 2012-10-21 22:37:00

The Cambrian is the first of seven geological periods into which the Paleozoic era is divided. It began approximately 600 million and ended 500 million years ago. The Cambrian is marked by the emergence and thriving of marine invertebrate animals, such as trilobites.

Ordovician

Published on 2012-10-20 18:35:00

Ordovician is the second period of the Paleozoic era. Preceded by the Cambrian and succeeded by the Silurian, the Ordovician began around 500 million and finished 440 million years ago. It is characterized by the abundance of marine and plant lives, such as conodonts, ostracods, algae, and seaweeds.

Stellar Populations

Published on 2012-10-19 21:53:00

Stellar populations are groups of stars classified by astronomers according to their metal content or metallicity. So, the first stars that appeared in the universe, having a low metal content, are categorized as Population III; they are pair-instability supernovae that have exhausted much of their energy. Population II are second generation of stars which also arose early in the history of a galaxy from hydrogen and helium; red giants belong to this group. The newest stars in a galaxy belong to [..]

Solar System

Published on 2012-10-18 20:42:00

The Solar System the group of celestial bodies, composed of the local star, called Sun, and nine planets which orbit around it in an elliptical pattern. The Solar System is part of the Milky Way galaxy. The Sun, which exerts a strong gravitational attraction on the planets and moons rotating around it, has seven hundred times the total mass of all the other celestial bodies of the system, including asteroids, comets and debris. The planets of the Solar System are: Mercury, Venus, Earth, Mars, Ju [..]

Polaris

Published on 2012-10-17 20:07:00

Also known as the North Star or Polaris, the Polar Star is a star of the second magnitude located close to the north pole of the heavens, in the Constellation Ursa Minor, near the end of the handle of the Little Dipper. It was useful to determine a geographic latitude of a particular place. The Polar Star has an amplitude of brightness variation of 0.14 stellar magnitude in a four day period.

Ganymede

Published on 2012-10-16 18:56:00

Discovered by Galileo Galilei in 1610, Ganymede is the largest moon of Jupiter, being the seventh in distance from the planet. With a liquid core rich in iron, Ganymede consists of silicate rock and water ice.

Anterior Perforated Substance

Published on 2012-10-15 21:39:00

The anterior perforated substance is a grey matter square area, composed of neuron bodies and is located between the olfactory trigone and the optic tract, at the base of the brain. It is pierced through by small branches of the anterior and middle cerebral arteries.

Basal Vein

Published on 2012-10-14 22:43:00

Originating at the anterior perforate substance, the basal vein is a large blood vessel which collects deoxygenated blood from three sources: the deep middle cerebral vein, the small anterior cerebral vein, and the inferior striate veins, and carries it into the internal cerebral vein.

Deep Middle Cerebral Vein

Published on 2012-10-13 20:40:00

The deep middle cerebral vein is a blood vessel in the brain which collects oxygen-depleted blood from smaller branches that come from the insular cortex as it drains it into the basal vein. The deep middle cerebral vein runs parallel to the middle cerebral artery that is located in the Sylvian fissure.

Gonadal Vein

Published on 2012-10-12 12:54:00

The gonadal vein is one of a pair of veins which receives deoxygenated blood from the testis or ovary, draining it to the inferior vena cava (the one on the right side) and to the renal vein (the one on the left side). In men, the gonadal vein is called testicular vein; in women, it is called ovarian vein.

Renal Veins

Published on 2012-10-11 20:07:00

The renal veins are the two blood vessels which collect oxygen-depleted blood from the two kidneys and drain it into the inferior vena cava. They run parallel to the renal arteries.

Hepatic Veins

Published on 2012-10-10 14:48:00

The hepatic veins form two groups of blood vessels which receives oxygen-depleted blood from the liver, draining it into the inferior vena cava. Although the amount of veins forming the upper and lower groups varies, the lower group has more veins than the upper one: usually three for the upper and up to 15 smaller veins for the lower group.

Inferior Vena Cava

Published on 2012-10-08 22:57:00

The inferior vena cava is a large-caliber blood vessel which collects deoxygenated blood from the legs and abdomen and carries it to the heart. It arises at the junction of the common iliac veins, runs up vertically and parallel to the abdominal aorta, and goes through the diaphragm, ending up at the right atrium of the heart, where the returning blood is pumped to the lungs by the right ventricle. Along its vertical course, the inferior vena cava is fed by the gonadal, renal, suprarenal, and he [..]

Internal Jugular Veins

Published on 2012-10-07 17:49:00

The left and right internal jugular veins are a pair of blood vessels located in each side of the neck, receiving deoxygenated blood from the face, neck, and brain. Each arises from the sigmoid sinus (S-shaped vein at the base of the head) and runs down the neck to meet the subclavian, forming the brachiocephalic vein.

Brachiocephalic Veins

Published on 2012-10-06 20:28:00

Also known as innominate veins, the brachiocephalic veins are a pair of blood vessels, one on each side of the upper chest, which begins at the union of the internal jugular and subclavian veins. The right and left brachiocephalic veins join together to form the superior vena cava that ends up at the right atrium of the heart. Each of the veins receives oxygen-depleted blood from the head and arm.

Superior Vena Cava

Published on 2012-10-05 23:12:00

Arising at the heart right atrium, the superior vena cava is a blood vessel which collects returning oxygen-depleted blood from the right and left brachiocephalic veins and internal jugular veins, draining it into the right atrium. This blood, which comes from the head, arms, and upper chest, then flows into the right ventricle through the tricuspid valve to be pumped into the lungs through the pulmonary artery.

Ovarian Artery

Published on 2012-10-04 20:32:00

The ovarian artery is an oxygen-rich blood vessel which originates from the abdominal aorta, at a point below the renal artery. It supplies blood to the ovaries, uterine tube, and ureter, giving off two branches: uretral and tubal arteries.

Middle Sacral Artery

Published on 2012-10-03 23:23:00

The middle sacral artery is a small branch that originates from the posterior part of the abdominal aorta. It supply oxigen-rich blood to the rectum back surface. The middle sacral anastomoses with a branch of the iliolumbar artery.

Inferior Mesenteric Artery

Published on 2012-10-02 23:26:00

The inferior mesenteric artery is an oxygen-rich blood vessel which comes off the abdominal aorta at a point before it forks into the common iliac arteries. It supplies the transverse colon and the rectum. Along the way, the inferior mesenteric artery gives off the colic, sigmoid, and superior rectal branches.

Radial Recurrent Artery

Published on 2012-10-01 22:23:00

The radial recurrent artery is a blood vessel which originates from the radial artery, just below the point where the arm and forearm fold. It runs up past the elbow to anastomose with the anterior branch of the deep brachial artery. The radial recurrent artery supplies arm muscles, bone and ligaments with oxygen-rich blood.

Synchrotron Radiation

Published on 2012-09-30 22:02:00

Synchrotron radiation is electromagnetic waves radiated by high-energy, charged particles which move in a circular fashion in a magnetic field. This radiation is polarized and continous. Synchrotron radiation was first observed in cyclic accelerators.

Kuiper Belt

Published on 2012-09-29 17:59:00

The Kuiper belt is a belt consisting of millions of small icy fragments, situated beyond Neptune orbit, surrounding the Solar System. It is believed to be made up of remnants, or debris, from the Solar System formation. These icy remnants are composed of frozen ammonia, water, and methane. Each one of these objects has an average diameter of 100 km. The Kuiper belt lies at 54 astronomical units from the Sun, with one astronomical unit being the equivalent of 93,000,000 miles. It is named after G [..]

Coronal Mass Ejection

Published on 2012-09-28 22:53:00

Coronal mass ejection is an exploding bubble of plasma, charged particles, and magnetic fields that expands out into space from the Sun's corona. During this bursting of bubble-shaped solar plasma, the charged particles are sent out at the speed of light. The ejected plasma is composed mainly of protons and electrons, as well as quantities of elements. This phenomenon usually causes disruption in satellites and magnetic storms on Earth. Coronal mass ejection is caused by magnetic reconnection, w [..]

Pluto (Planet)

Published on 2012-09-27 23:21:00

Pluto is a small planet that revolves around the Sun in the outermost orbit of the Solar System at 3.67 billion miles (5.907 billion km) away from this star, having the largest eccentricity. Located in the Kupier Belt, it takes this planet 248 years to complete an orbit around the Sun. Being the smallest in size of all the planets of the Solar System, Pluto has a diameter of 1,400 miles (2,300 km) and about 0.8 % of the Earth mass. It is composed of frozen gases, such as nitrogen and methane, an [..]

Uranus (Planet)

Published on 2012-09-26 23:35:00

Uranus is one of the largest planets of the Solar System. With twenty seven moons and a ring system, it orbits the Sun at a mean distance of 1.78 billion miles (2.87 billion km), between Saturn and Neptune, taking it 84.015 years to complete a revolution around the Sun. Uranus has a diameter of 31,800 miles (51,100 km) and a mass of 14.56 times that of planet Earth. Uranus is composed of a gaseous envelope, which contains hydrogen (H), helium (He), and methane (CH4), and a frozen water liquid co [..]

Neptune (Planet)

Published on 2012-09-25 19:46:00

Neptune is a gaseous planet of the Solar System. Orbiting at 2.8 billion miles away from the Sun, it is the eighth and last planet of the system. It takes Neptune 164.8 years to complete an orbit around the Sun. It has a diameter of 30.775 miles and more than 17 times the Earth's mass. Neptune is composed mainly of ammonia, methane, and ices, and has a weak magnetic field. This Solar System planet has thirteen moons and a ring of dust-size particles.

Jupiter (Planet)

Published on 2012-09-24 20:49:00

With a mass of 317.8 Earths, Jupiter is the biggest planet in the Solar System. It lies between Mars and Saturns, at 483.3 million miles away from the Sun, in the fifth position. It has a diameter of 888,815 miles and has more than sixty moons; the three largest and most observed and studied moons of Jupiter are Europa, Ganymede, and Callisto. With no solid surface, Jupiter is gaseous planet, which consists of helium, hydrogen, ammonia, methane, nitrogen, carbon, argon, and other elements. On th [..]

Trachea

Published on 2012-09-21 20:50:00

The trachea is a membranous tube that connects the larynx to the bronchi, functioning as an air passage during breathing. It consists of cartilaginous rings joined together by annular ligament. Commonly known as windpipe, the trachea measures about 10 cm in length and 1.5 cm in width, and divides into two branches: the right and left bronchi. Situated in front of the esophagus, a surgical incision (hole) made in the trachea, through the neck, just below Adam's apple, to rescue and save the life [..]

Bubonic Plague

Published on 2012-09-20 21:44:00

The bubonic plague is an infectious disease cause by Yersinia pestis, a rod-shaped bacterium. Man gets infected by this bacteria, through the bite of rat fleas. Before the discovery of antibiotics, bubonic plague used to be an extremely fatal and epidemic disease, whose symptoms are fever, chills, weakness, prostration, diarrhea, and the formation of painful lumps called buboes, which caused by the inflammation of lymph nodes, especially in the axillary and inguinal regions (armpits and groin).

Proterozoic Era

Published on 2012-09-19 22:56:00

The Proterozoic is the second geological era in the time spans of Earth history. It stretched from about 1,500 to 600 million years ago. Being part of the Precambrian times, the Proterozoic is characterized by the abundance of first aquatic life forms, such as bacteria, fungi, algae and other primitive multicellular organisms. The great amount of bacteria and algae contributed to the build-up of oxigen in the atmosphere.

Cenozoic Era

Published on 2012-09-19 00:21:00

Beginning 70 million years ago, the Cenozoic is the last of five geological eras in the Earth geological history, extending up to the present time. Divided into two periods, Tertiary and Quaternary, the Cenozoic era is marked by the orogenic movement that formed today's highest mountain ranges, such as the Himalayas and the Andes mountain ranges, widespread of glacial ice, and the emergence of birds and mammals. Man appeared on Earth during the Quaternary period of the Cenozoic era.

Mesozoic Era

Published on 2012-09-17 22:22:00

The Mesozoic is the fourth of five geological eras in the Earth history time spans. It stretched from 220 million to 70 million years ago and is divided into three periods; the Triassic, Jurassic, and Cretaceous. The Mesozoic era is characterized by intense volcanic activity, the presence of marine and land reptiles and dinosaurs, and the abundance of conifer trees. During this time, the continental drift took place as today's continents began to separate from one another.

Tundra

Published on 2012-09-16 09:33:00

The tundra is a subarctic biome characterized by a ground layer of grasses, mosses, and lichens, and a few perennials, but there are no trees. In tundra the ground is permanently frozen a few inches below the surface (permafrost). The snowshoe rabbit, arctic fox, and caribou are the most common animals found in the tundra.

Paleozoic Era

Published on 2012-09-15 12:12:00

Preceded by the Archeozoic and Proterozoic, the Paleozoic is the third era in the Earth geological history. It began about 600 million years ago and ended about 220 million years ago. The Paleozoic is divided into seven geological periods: Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, and Permian. From fish to reptiles, the Paleozoic is characterized by the consolidation of animal life as sea and land animals throve in warm moist weather, with marsh and swampy territory [..]

Newton's Third Law

Published on 2012-09-14 12:36:00

Also known as action-reaction law, Newton's third law states that for every action exerted on a body, there is an equal and opposite reaction, that is to say a force that goes in the opposite direction. This law is put in practice in rocket propulsion, when matter in gas form is forced out of the combustion chamber at very high speeds, it creates a reaction: an equal force that moves in the opposite direction, pushing the rocket upward.

How Many Bones is the Human Skull Made of?

Published on 2012-09-13 14:25:00

How many bones is the human skull made of? The skull or cranium is composed of eight cranial bones and fourteen facial bones, which are all fused together by sutures. The skull cranial bones protect the brain and they are: one frontal, two parietal, two sphenoid, two temporal, and one occipital bones. Dome of the skull is known as the skullcap and the lower part is called the base. The largest of the facial bones are the upper and lower jaws (maxilla and mandible). At the center of the base of t [..]

How Is Nuclear Energy Obtained?

Published on 2012-09-12 14:38:00

How is nuclear energy obtained? Nuclear power is obtained from the energy which can be released from the nucleus of an atom during fission or fusion. Until the 20th century man used water, wood, and the fossil fuels, such as coal, oil, and gas, as sources of energy. During the first quarter of the 20th century physicists investigated the structure of the atom. In 1919, Rutherford split the atom artificially. Thirteen years later, the neutron was discovered; a neutron is an atomic particle found [..]

Permian

Published on 2012-09-11 20:21:00

The Permian is the last of the seven geological periods of the Paleozoic era, beginning approximately 270 and ending 220 million years ago. The Permian is marked by the abundance of reptiles, the emergence of conifers, and deposit of sediment.

How Does a Rocket Motor Work?

Published on 2012-09-11 13:24:00

How does a rocket motor work? A rocket motor operates on the principle of action and reaction. Its upward thrust is the reaction to a downward force created by escaping gases. These gases are produced when two propellents burn inside the rocket. The two propellents, the fuel and the oxidant, are pumped by turbines into the combustion chamber. Here, the fuel is ignited. When the fuel burns, it releases energy in the form of hot gases. The gases escape through the exhaust at great speed, providing [..]

Jurassic (Geological Period)

Published on 2012-09-09 22:35:00

The Jurassic was the second geological period of the Mesozoic era, stretching from 180 to 135 million years ago, the others being the Triassic and Cretaceous. It is characterized by the presence of dinosaurs and conifers. The Jurassic is named after the French Jura region, rich in limestone and shale.

Myotonia Congenita

Published on 2012-09-08 14:38:00

The myotonia congenita, also known as Thomsen's disease, is a dominant hereditary muscle disorder characterized by muscle spasms and increase of muscular tone, which is exaggerated with physical effort, as relaxation or discontraction is difficult. The anatomical base for the myotonia congenita is a hypertrophy of the muscular tissue. The disease begins in childhood and early adolescence. Treatment: quinine is effective.

Body Tissue Repair

Published on 2012-09-07 23:10:00

The body tissue repair begins right after the acute inflammatory reaction as a result of tissue damage. It is the replacement of dead cells by new viable ones. These new cells may originate from the damaged parenchyma (an organ cellular structure) or from connective tissue in the damaged area. However, parenchymatous regeneration is very slow, since the cells that perform the organ main function are stable and it takes a long time for them to multiply, as is the case with hepatocytes, the cells [..]

Radiculitis (Medicine)

Published on 2012-09-06 22:28:00

Radiculitis is the inflammation of the anterior and posterior spinal nerve roots. It is characterized by intense pain, prickling sensation on the upper or lower limbs, superficial anesthesia, and paralysis when the anterior roots are affected; these symptoms are caused by inflammation and degeneration of nerve fibers. Depending on the type of spinal roots attacked, there can be lumbosacral, dorsal, and cervical radiculitis, which can be acute or chronic. Treatment is based on anti-inflammatory m [..]

Hematomyelia

Published on 2012-09-05 19:49:00

Hematomyelia is a disease characterized by intraspinal hemorrhage that affects the spinal cord grey matter. It is the equivalent to a cerebral hemorrhage, but it takes place in the spinal cord and it is rare. Hematomyelia is more frequently observed in young men. Although it is usually caused by a trauma, it can also be caused by vascular alteration, such as atherosclerosis and hypertension. This medical condition begins with paresthesia (burning or prickling sensation), followed by paralysis. D [..]

Myelitis

Published on 2012-09-04 18:59:00

Myelitis is an acute inflammatory process of the spinal cord which causes muscular weakness or paralysis; it could localized or diffused. This medical condition can be caused by bacterial or viral infection. From a pathological anatomy point of view, myelitis myelitis is characterized by loss of myelin and perivascular lymphocytic infiltrates, the presence of plasmocytes and macrophages. If the inflammatory process affects the whole diameter of the spinal cord, in a localized section, it is call [..]

Governments and Physical Coercion

Published on 2012-09-03 23:14:00

Thought control can be an effective supplementary means to maintaining political stability, but there are limits to the lies and deceptions that autocratic governments can get away with. If people are experiencing stagnant or declining standards of living, no amount of propaganda and false promises can prevent them from becoming restless and dissatisfied. As discontent mounts, the ruling elites of totalitarian regimes must either increase the use of direct force or make way for political changes [..]

Causes of Matrilocality

Published on 2012-09-02 18:32:00

A plausible theory in the causes of matrilocality is that it arises when males are obliged to absent themselves from their wives and homes for prolonged periods. This occurs when warfare, hunting, and trade change from quick short-distance forays to long-distance expeditions lasting several months. Matrilocality solves the problem of male absence structuring the domestic unit around a permanent core of resident mothers, daughters, and sisters who have been trained to cooperate with each other fr [..]

Causes of Patrilocality

Published on 2012-09-01 16:19:00

The causes for the prevalence of patrilocality among village societies is that cooperation among males is in some sense more crucial than cooperation among females. Men, for example, are more effective in hand to hand combat than women, and women are less mobile than men during pregnancy and when nursing infants. As a result, men generally monopolize the weapons of war and the hunt, leading the male control over trade and politics. The practice of intense small-scale warfare between neighboring [..]

Plant Ground Tissues

Published on 2012-08-30 20:53:00

Plant ground tissues consist of unspecialized cells; the most common kind is called parenchyma, which is composed of cells that are mainly of one kind and usually have thin walls. Frequently, stems contain two kinds of parenchyma. One, the cortex, occupies a peripheral position within the stem, just under the epidermis, whereas the other, the pith, is found in the center of many stems. In leaves parenchyma cells are filled with chloroplasts and do most of the photosynthesizing. Some parenchyma c [..]

Plant Surface Tissue

Published on 2012-08-29 22:09:00

Plant surface tissue forms the protective outer covering or skin of the plant body. Living epidermal cells are the main surface tissue of roots, stems, and leaves. Sometimes the epidermis secretes a waxy, water resistant cuticle which protects the plant from water-loss and injury. Frequently the epidermis produces hairlike structures, some which secrete sticky substances that protect the plant against attack by insects.

Plant Tissues

Published on 2012-08-28 21:27:00

Mature plants are made up of two basic kinds of tissues, meristematic tissues and mature tissues. These tissues are usually composed of cells of one type but sometimes consist of several different kinds. Meristematic tissues are composed of embryonic, undifferentiated cells which can divide indefinitely. Mature tissues are composed of cells which may undergo only a limited number of divisions during normal development and usually cease dividing entirely. Such mature tissues often have highly spe [..]

Pasteurella pestis

Published on 2012-08-27 22:06:00

Pasteurella pestis, also known as Yersin's bacillus, is a rod-shaped gramnegative bacterium which causes the plague. Its reproduction is slow in ordinary cultures and needs high humidity rates and oxigen to multiply, in 25-30º C temperatures. The Pasteurella pestis secrets endotoxins which attack either the lymphatic system or the lungs. It is transmitted to man through an insect vector: the rat's flea. It was discovered by Alexandre Yersin in 1894.

Hepatic Amebiasis

Published on 2012-08-26 21:23:00

Hepatic amebiasis is a medical condition in which the liver is infected or attacked by Entamoeba histolytica, a parasitic amoeba which enters the body through contaminated water and food. This amebic infection can lead to a liver abscess, which is an area of liquifaction necrosis that can have serious health implications. Hepatic amebiasis is the result of amebic dysentery, during which the Entamoeba histolytica spreads from the instestine to the liver, carried in the blood stream through the po [..]

Bushmaster (Snake)

Published on 2012-08-25 18:16:00

Scientifically known as Lachesis muta, the Bushmaster is a venomous pit viper snake. It is very large, with the adult reaching a length of up to 4 m, with an average length of 3 m. It is usually greyish light brown, with diamond-shaped black patterns on its back. The Bushmaster is distributed throughout Central and South America. Having a hemotoxic venom, the bite of the Lachesis snake is usually fatal.

Schilder's Disease

Published on 2012-08-24 20:59:00

Schilder's disease is a chronic disease characterized by loss of myelin, which is the white fatty subtance the wraps the nerve cell axons; when this happens nerve impulse transmission along the nervous fibers is hindered. This diffuse destruction of the myelin takes place in the cerebral cortex. Schilder's disease is progressive and symptoms are seizures, muscle weakness, speech impairment, loss of balance, mental weakness, etc. It is very similar to multiple sclerosis, but it attacks children a [..]

Osteomyelitis

Published on 2012-08-23 19:13:00

Osteomyelitis is a bone infection caused by bacteria (mainly Staphylococcus aureus), and can be the result of a bullet wound, an open bone fracture, untreated sinus infections, which can cause osteomyelitis of the skull. The symptoms of osteomyelitis is fever, chills, pain, abscess, etc. Treatment consists of antibiotics (local and general), anti-inflammatory medication, and surgery to clean infected area and drain the abscess.

Amebic Dysentery

Published on 2012-08-22 21:55:00

Also known as intestinal amebiasis, amebic dysentery is a severe infection of the intestine. It is characterized by diarrhea, intestinal bleeding with mucus. It is caused by Entamoeba histolytica, a parasitic amoeba which gets into the human bowels through contaminated water and food. Sometimes it spreads into liver and lungs.

Triassic

Published on 2012-08-21 08:14:00

The Triassic is the first period of the Mesozoic era, followed by the Jurassic and Cretaceous. Dating from 220 to 180 million years ago, the Triassic is characterized by volcanic activity, marine reptiles, dinosaurs, and the emergence of earliest mammals.

Pennsylvanian (Geological Period)

Published on 2012-08-19 23:07:00

Also known as Upper Carboniferous, the Pennsylvanian is a geological period of the Paleozoic era, which is divided into seven ones. The Pennsylvanian is marked by the existence of warm and moist weather, swampy lands, and the beginning of the evolution of large reptiles, as well as the formation of shale, limestone, and sandstone in America. The Pennsylvanian spans thirty million years, from 300,000,000 to 270,000,000 years ago.

Cretaceous

Published on 2012-08-18 21:27:00

The Cretaceous is one of the three periods into which the Mesozoic era is divided; the other two being the Triassic and Jurassic. The Cretaceous is characterized by the extinction of giant reptiles, advent of modern insects, and flowering plants. This period is usually subdivided into an Upper and Lower Cretaceous and comprises a time span between 135 and 70 million years ago. See Time Spans of Earth History

Quaternary (Geology)

Published on 2012-08-17 09:41:00

The Quaternary is a geological period of the Cenozoic era, beginning approximately 1.000.000 years ago. It is divided into the pliocene and present epochs and is characterized by the formation the great plains, the widespread of glacial ice, and the appearance of Homo sapiens (Neanderthal and Cro-magnon).

Pulmonary Amebiasis

Published on 2012-08-16 21:28:00

Pulmonary amebiasis is a lung infection caused by Entamoeba histolytica, a protozoan which gets into the human body through contaminated water and food. Usually, pulmonary amebiasis is the result of an amebic invasion of the lung pleura from the liver in an hepatic amebiasis case, which in turn is caused by intestinal amebiasis, with the amoeba infection spreading from the instestine to the liver and into the lungs through the diaphragm and pleural sacs. Symptoms are cough, pain in the chest, fe [..]

Tertiary (Geological Period)

Published on 2012-08-15 21:25:00

The Tertiary is a geological period of the Cenozoic era, beginning approximately 60 million years ago and spanning 30 million years. It divides into five epochs: the Paleocene, Eocene, Oligocene, Miocen, and Pliocene. The Tertiary marks the emergence of birds and mammals and the geological formation of the highest mountain chains on Earth, such as the Himalaya, the Andes, Rocky, and Alps mountain ranges.

Entamoeba histolytica

Published on 2012-08-14 17:52:00

The Entamoeba histolytica is a species of protozoan, which is parasitic and pathogenic to man. Once it has entered the human body, the Entamoeba histolytica lives in the large intestine, attacking its mucosa and causing amebic dysentery and lesions that can perforate the walls of the intestine. The active phase of the E histolytica is called trophozoite, which measures between 20 and 40 microns. It has pseudopod, which is formed from its ectoplasm. The parasite can end up in the liver, being tra [..]

Are We Still Evolving as Human Beings?

Published on 2012-08-14 00:31:00

Are we still evolving as humans? No, we are no longer evolving as human beings; with a volume of 1,425 cubic cm, our brain is not bigger in size than that of the Cro-Magnon or Neanderthal's, whose cerebrum ranged in volume between 1,500 and 1650 cc. On the contrary, the natural selection process that made possible human evolution is no longer selecting the smartest or fittest one, since we no longer have to fight for survival and women in the Western world do not have more than two children, if [..]

Amoeba

Published on 2012-08-12 22:06:00

An amoeba is a genus of protozoan (a one-celled microscopic organism), which consists of a mass of protoplasm, constantly changing in shape as it moves about and engulfs organic debris, cells or bacteria particles. They live in stagnant water in pools and ponds, but also as parasites in the blood and organs of the human body, causing diseases that are sometimes fatal. Most amoebas have one nucleus and reproduce asexually by cellular division.

Pneumonia

Published on 2012-08-11 13:32:00

Pneumonia is an inflammation of the lung caused by bacterial, viral, amoebic, and fungal infection. The symptoms are difficulty in breathing, chest pain, cough, high fever, and fatigue. Pneumonia is characterized by pyogenic edema (accumulation of liquid and pus) and excessive mucus which occludes (clogs up) the alveoli and bronchi. The infection in the lungs is usually caused by a bacterium called pneumococcus; before the discovery of antibiotics, bacterial pneumonia was fatal in 75% of the cas [..]

Trypanosoma cruzi

Published on 2012-08-10 12:29:00

The Trypanosoma cruzi is a protozoan which causes the Chagas disease. It is transmitted to man through the intervention of a blood-sucking insect which acts as a vector (kissing bug). The Trypanosoma cruzi is found in the flowing blood of infected persons and animals during the acute period of the disease. In this circulating phase of the parasite, the T cruzi is called trypomastigote, which is elongated, measuring approximately 20 microns, and has a thin undulating membrane that runs the full l [..]

Triatoma infestans

Published on 2012-08-09 23:27:00

The Triatoma infestans is a species of kissing bug found in northern Argentina, Brasil, and Peru. Being a blood-sucking insect, it is one of the main vectors of Tripanozoma Cruzi, a protozoan which causes the Chagas disease in man. The Triatoma lives in cracks in the walls of adobe houses as well as in thatched roofs, in poor country areas. Order: hemiptera; genus: Triatoma; species: infestans. It has brown wings, black abdomen with yellowish orange stripes, and a long proboscis.

Chagas Disease

Published on 2012-08-08 13:38:00

Also called American trypanosomiasis, the Chagas disease is an infectious illness caused by the Trypanosoma cruzi, a parasitic protozoan, which is transmitted by a hematophagus insect of the Reduviidae family. These blood-sucking insects, commonly called assassin bugs or kissing bugs, which act as vector of Chagas disease are scientifically identified as: Rhodnius prolixus, Triatoma infestans, and Panstrongylus geniculatus, which are found in Brasil, Argentina, Bolivia, Colombia, Peru and Venezu [..]

Protozoan

Published on 2012-08-06 23:26:00

A protozoan is a unicellular microorganism which live freely in water or as a parasitic entity in a multi-cellular organism. Some protozoa, like Trypanosoma gambiense and Trypanosoma cruzi, can cause dangerous diseases, such as the African trypanosomiasis (or sleeping sickness) and Chagas disease, respectively. Other protoza which cause diseases in men are Plasmodium (malaria), Entamoeba histolytica (dysentery), and Toxoplasma gondii (toxoplasmosis). Although they are single-celled organism, the [..]

What Makes Us Human?

Published on 2012-08-05 22:42:00

What makes us human? Aside from the longer lower limbs, opposing strong thumb, and the position of the foramen magnum at the center of the base of the skull, there are two other features, located in the central nervous system, which make us act differently from apes (chimps and gorillas). These are two myelinated fiber bundles, called fasciculus (pl fasciculi), linking different areas of the cerebral cortex; the arcuate fasciculus and the uncinate fasciculus. They are what makes us unique among [..]

Fer De Lance (Bothrops atrox)

Published on 2012-08-04 22:06:00

Scientifically known as the Bothrops atrox, the Fer De Lance is one of the most venomous snake in the American Continent. It has a potent cytotoxic and hemotoxic venom which destroy body tissues in the bitten area and red blood cells, causing necrosis. The bite of the Bothrops atrox can be fatal and, in severe cases, it is necessary the amputation of the affected member to save the patient's life. Found in South and Central America, the Fer De Lance is a pit viper that can measure up to 1.6 m lo [..]

What was the Key Element in Human Evolution?

Published on 2012-08-03 21:37:00

What was the key element in human evolution? The key chemical substance that contributed to the evolution of the human brain is vitamin B12, scientifically known as cyanocobalamin. It is an aminoacid of the B complex which plays a key role in the DNA synthesis and the myelination of axons, which is the long nerve cell process that transmits nerve impulses from the cell body to another neuron via the synaptic gap. Myelin is the fatty sheath that covers, protects, and feeds the axon. Another funct [..]

Common Interosseous Artery

Published on 2012-07-29 23:07:00

The common interosseous artery is a blood vessel that originates from upper part of the ulnar artery. It is about 1 cm in length and forks into two branches: dorsal interosseous and volar interosseous arteries.

Osteoporosis

Published on 2012-07-28 20:32:00

Osteoporosis is a disease in which the skeleton bones lose calcium and other minerals, giving way to porosity as they become frigile. Someone who suffers from osteoporosis has tendency of getting a broken bone, due to a decrease in bone mass. It affects older people (over 50), especially women who have had their menopause and their bodies no longer secrete estrogen (a type of hormone). Treatment: calcitonin, alendronate, and physical exercises; working out with light weight to tone up the muscle [..]

Endosteum

Published on 2012-07-27 15:38:00

The endosteum is a layer of connective tissue cells which covers the surface of a bone medullary cavity. It participates in the healing of broken bones.

Osteoarthritis

Published on 2012-07-26 23:19:00

Osteoarthritis is a chronic disease in which the joints cartilage is worn down progressively, causing inflammation and pain. It usually affects older people (over 50 years of age), with the knees and hips being the most common area affected by the disease. As a result of this gradual wearing away of the cartilage, the bone develops spurs. Osteoarthritis is usually caused by mechanical stress, such as misalignments of bones due to congenital causes; excessive weight and weak muscles can also caus [..]

Timber Rattlesnake

Published on 2012-07-25 14:29:00

The timber rattlesnake, scientifically known as Crotalus horridus, is a rattlesnake which inhabits the eastern region of the United States. It is one of the most venomous snake in North America, but it is not aggressive. The timber rattlesnake has long fangs through which it injects neurotoxic and cytotoxic venom that causes generalized muscle contraction, bleeding, and tissue destruction. It has a body length average of 1.30 m; it is brownish grey with keeled orange dorsal scales that run the l [..]

Western Diamondback Rattlesnake

Published on 2012-07-24 22:58:00

Known as the western diamondback rattlesnake, the Crotalus atrox is a species of rattlesnake found in the southwest of the United States and in northern Mexico. Among all the species of rattlesnakes, it is the most venomous as it has both hemotoxic and cytotoxic venom, which causes internal bleeding and tissue damage. Symptoms caused by the Crotalus atrox venom are abdominal pain, nausea, headache, and severe swelling followed by necrosis at site of the bite wound. So, the bite can be lethal if [..]

Osteocyte

Published on 2012-07-23 14:30:00

An osteocyte is a mature bone tissue cell which originates from an osteoblast. It is star-shaped and is set in the bone calcified matrix. Osteocytes have cytoplasmatic processes which juts out away from the cell body through the canaliculi, which are tiny channels through which an osteocyte obtains nutrients and release its waste products. Although they can live a very long time, throughout the life of the individual, osteocytes sometimes suffer from apoptosis, which the programmed cell death, d [..]

Periosteum

Published on 2012-07-20 13:57:00

The periosteum is a specialized connective tissue membrane which coats all the bones of the skeleton. It has bone-forming capabilities and serves as an anchoring surface for tendons and muscles. The periosteum is composed of two layers: 1) an outer layer, which is fibrous and contains blood vessels and fibroblasts that produce collagen; 2) an inner layer, called the cambium, which has progenitor cells that transform into osteoblasts, which in turn is responsible for bone formation.

Tiger Snake

Published on 2012-07-18 22:10:00

The Tiger snake is an extemely venomous elapid snake, which belongs to the genus Notechis. It inhabits southern Australia territory. The adult Tiger snake is 2 m long and is yellowish brown with dark ring patterns. It has neurotoxic venom and approximately 60% of the people bitten die in matter of hours when they are not treated; they die of cardiorespiratory paralysis.

Coral Snake

Published on 2012-07-15 10:37:00

The coral snake is a venomous snake which belongs to the genus Micrurus. Its glands secret a potent neurotoxic venom, which causes muscle paralysis and, hence, difficulty for breathing. It is found in southern United States and Mexico. The adult coral snake body measures an average of 1 m in length, and has yellow, red, and black rings or bands. If not treated, the victim could die of cardiorespiratory paralysis in a matter of hours.

Elapidae

Published on 2012-07-14 13:09:00

The elapidae is a family of highly venomous snakes, comprising Australian death adders, tiger snakes, brown snakes; African mambas; and Asian cobras. The elapidae members are characterized by having upper-jaw front fangs, which are short and grooved, smooth scales, and cylindrical tails. Their venom is generally neurotoxic.

Australian Brown Snake

Published on 2012-07-13 14:07:00

The brown snake is an extremely venomous elapid snake, which is found in Eastern Australia and belongs to the genus Pseudonaja. The adult is approximately 1.60 m long, brown, sometimes with different color spot or band patterns. It feeds on birds, rants, lizards, etc, and is active during the day. Being the second most venomous snake in the world (the taipan is firs), the Australian brown snake has a neurotoxic snake, which means its toxin affects the nervous system, blocking the nerve impulses [..]

Human Language and Consciousness

Published on 2012-07-12 14:36:00

Produced and understood by the Broca and Wernicke areas of the cerebral cortex, the human language is unique in possessing semantic universality, or the capacity to produce unlimited numbers of novel messages in the form of sentences, withouth loss of informational efficiency. Not only does human language have unrestricted power of productivity, but also gives a cultural structure or form to our consciousness. One of the most important means of achieving this productivity is the arbitrariness of [..]

Mojave Rattlesnake

Published on 2012-07-11 14:58:00

The rattlesnake is any of a kind of venomous snake belonging to the genera Crotalus and Sistrurus, widely distributed in the dry desert regions of the United States and Mexico. Its name derives from the interlocked keratin-ringed rattle which they have at the end of their tail, producing a buzzing sound when shaken. The Mojave rattlesnake (Crotalus scutulatus) has a heart-shaped head with vertically-elongated pupils, and an average bodily length of 1 m (3ft4in); it has brown and creamy white sca [..]

Saw-scaled Viper

Published on 2012-07-10 23:21:00

The saw-scaled viper is a species of a venomous snake which belongs to the genus Echis. With a pear-shaped head, the adult can reach a maximum body length of 1 m (3ft4in). The sub-species Echis carinatus sal of the saw-scaled viper is dark and light brown, with creamy white inverted "V" patterns along both sides of its body length and white spots on its dorsal scales which form serrated keels. This snake, which inhabits the warm and dry regions of northern Africa and Asia, feeds on lizards and r [..]

Boomslang Snake

Published on 2012-07-09 22:19:00

The boomslang, scientifically known as Dispholidus typus, is a colubrid snake of Africa. It is highly venomous and its fang glands secrete hemotoxin venom, which destroy the red blood cells, causing hemorrhage and intense fever; other symptoms are headache, nausea, and mental disorders. Although its fangs are situated toward the back of its upper jaw, the boomslang opens its mouth 90º when it bites. The adult boombslang has large eyes and can measure up to 1.60 m in length. Its body is green, w [..]

Malayan Krait

Published on 2012-07-08 14:57:00

The Malayan blue krait is one of the most venomous snake in the world. This elapid snake inhabits the warm regions of South East Asia. The Malayan krait has an average length of 1.50 m. Its body is either white or yellow, with dark blue or black rings. It has a powerful neurotoxic venom. Being a nocturnal reptile, the blue krait is very active during the night and more aggressive, feeding on mice and small birds.

Eastern Green Mamba

Published on 2012-07-07 15:27:00

The Dendroaspis agusticeps, commonly known as eastern green mamba, is an extremely venomous elapid snake found in eastern Africa, from Kenya to Zimbabwe. Green and with a 1.50m (5ft)-long body, it lives, mates, and feeds in the trees. In contrast with other venomous snakes, the green mamba of East Africa has round pupils, instead of the more common vertically-elongated pupils that resemble downward slits. Its eyes never blink because they have a transparent protective shield. Its venom contains [..]

King Cobra

Published on 2012-07-07 00:24:00

The king cobra is a highly venomous elapid snake, native of Asia (India, Pakistan, and Indonesia). Its scientific name is Ophiophagus hannah, which can measure up to 4.50 m in length. When threatened, the king cobra swells out its hood at the sides of its neck. The hood has two round spots on each side, which resembles eyes; the rest of the body is brown and creamy white. The king cobra has neurotoxic venom which affects the nervous system, causing paralysis, heart collapse, and renal failure.

Death Adder (Acanthopis)

Published on 2012-07-05 16:17:00

The acanthopis antarcticus, known as death adder, is an extremely venomous snake found in Australia and New Guinea. With a big arrow-shaped head, it has a short but thick body, measuring an average of 1.10 m in length; its bodily color patterns are brown and light grey rings. The death adder of Australia has neurotoxic vemom with a rate of 60% fatal bites from all the biting incidents reported in one year. The pacient dies of cardiorespiratory arrest, which means paralysis of the respiratory mus [..]

Optimal Foraging Theory

Published on 2012-07-04 13:22:00

To account for the selective behavior of hunters and gatherers (nomadic people), in regard to the selectiveness when they hunt, ecologists and anthropologists have developed a set of principles known as optimal foraging theory. This theory predicts that hunters or collectors will pursue or harvest only those species that maximize the rate of caloric return for the time they spend foraging. There will always be at least one species that will be taken on encounter, namely, the one with the highest [..]

Taipan (Snake)

Published on 2012-07-03 13:24:00

The coastal taipan (Oxyuranus scutellatus) is a large snake that inhabits the northeastern region of Australia. Although it is the most venomous land snake in the world, it is not as dangerous as other snakes, since it is shy and not aggressive; however it may attack when cornered. The coastal taipan is between dark brown and black in color, with the adult measuring an average of 1.30 m in length. It feeds on rodents, such as mice and rats, and birds. On every bite, the taipan can inject 120 mg [..]

Black Mamba

Published on 2012-07-03 01:03:00

The black mamba, whose scientific name is Dendroaspis polylepsis, is the fastest and most venomous snake in Africa. Its mouth is black and its body dark grey on the dorsal side and white on the ventral side. Inhabiting the eastern and southern portions of Africa, the adult black mamba has an average length of 3 m, with a maximum length of 4.20 m. What makes this African snake extremely deadly is the fact that it has its fangs located well forward in the front of its upper jaw; so, there is a muc [..]

Binary Contrasts and Myth

Published on 2012-07-01 18:36:00

Anthropologists have found considerable evidence suggesting that certain kinds of formal structures recur in widely different traditions of oral and written literature, including myths and folktales. These structures are characterized by binary contrasts, that is by two elements or themes that can be viewed as standing in diametric opposition to each other. Many example of recurring binary contrasts can be found in Western religion, literature, and mythology; good versus bad, up versus down, mal [..]

Bothrops alternatus

Published on 2012-06-30 14:40:00

The Bothrops alternatus, known as yarará in Argentina, is a species of snake from the warm and humid regions of South America, found in Brasil, Paraguay, and Argentina. It is a venomous snake whose glands secretes cytotoxic venom which destroy the tissue around the bitten area. There have been reported cases in which amputation of the hand or foot was required due to severely necrotized tissues (gangrene). The Bothrops alternatus is brown with white V-shaped alternating markings that border dar [..]

Heubner Recurrent Artery

Published on 2012-06-29 12:53:00

The Heubner recurrent artery is a brain artery which originates from the anterior cerebral artery between A1 and A2 segment. It supplies the anterior portion of the lentiform nucleus, the head of caudate, and part of the putamen. When the recurrent artery of Heubner gets blocked, or partially occluded, there is a high risk of infarction in the subcortical areas of the brain.

Eustachian Tube

Published on 2012-06-28 16:32:00

The eustachian tube is a duct which links the pharynx with the middle ear. Its function is to equalize the pressure between the middle ear and the outer world pressure by allowing air to enter the middle ear. When one has a cold, the eustachian tube become inflamed, blocking the entrance of air as hearing is decreased.

Ear

Published on 2012-06-27 16:49:00

The ear is the paired sensory organ of hearing and sense of balance, situated in each side of the head, below and in the temporal bone. It is composed of the external ear, the middle ear, and the inner ear. The external ear consists of the pinna and ear canal; the pinna is the funnel-like external visible organ that collects the acoustic vibrations. The middle ear is made up of the tympanic membrane (eardrum) and the auditory ossicles, which are three small bones called malleus (hammer), incus ( [..]

Reissner's Membrane

Published on 2012-06-26 14:50:00

Reissner's membrane is a thin flexible layer of epitheial tissue which separates the scala media (or cochlear duct) from the scala vestibuli of the cochlea in the inner ear. The Reissner's membrane is flexible enough to transmit the vibrating waves that go through the fluid-filled scala vestibuli down to the organ of Corti, stimulating the hair cells inside as the vibratory energy transforms into nerve impulses.

Modiolus

Published on 2012-06-25 10:07:00

Located in the inner ear, the modiolus is a conical-shaped bony core around which the cochlea winds (two and a half times). It contains the spiral ganglion, which is made up of nerve cells whose axons form the auditory nerve (or cochlear nerve). The spiral ganglion in the modiolus receives acoustic information from the hair cells in the organ of Corti situated in the cochlear duct (scala media) of the cochlea and then send it to the brain temporal lobe through the auditory nerve.

Spiral Lamina

Published on 2012-06-24 14:03:00

The spiral lamina is a double layer of bone which divides the cochlea into scala vestibuli and scala tympani. Being a projection of the modiolus, it winds around, following the spiral pattern of the cochlea.

How Acoustic Vibrations are Transmitted to the Brain

Published on 2012-06-23 14:36:00

You wonder how acoustic vibrations are transmitted to the brain? The acoustic vibrations, or sound, enter the ear through the auricle and ear canal. Then, the tympanic membrane (eardrum), located at the end of the ear canal, pick up these vibrations, passing them on to the auditory ossicles, which consist of three tiny bones called malleus (hammer), incus (anvil), and stapes (stirrup), that are joined together by ligaments. Then, the stapes, which is at the end of the auditory ossicles, transmit [..]

Rheumatic Fever

Published on 2012-06-22 14:06:00

Rheumatic fever is an inflammatory disease which is triggered by an Streptococci infection. It is the result of an strep throat which was untreated or not adequately treated. Rheumatic fever symptoms are high fever, pain, painful and swollen ankles, knees, and wrists; if not treated, this acute inflammatory disease may severely damage the heart valves. Treatment: antibiotics, such as penicillin-G, and anti-inflammatory medications, such as aspirin, ibuprofen, and corticosteroid.

Utricle

Published on 2012-06-19 13:01:00

Attached to the semicircular canals, the utricle is a membranous pouch located in the inner ear. Like the cochlea that has hair cells that convert vibrations into electrical impulses, the utricle also contain sensitive hair cells which detect the different degrees of tilting of the head, contributing to the sense of balance. The utricle and the saccule are both otolith organs contained in the inner ear.

Inner Ear

Published on 2012-06-18 15:33:00

The inner ear is the portion of the ear located in the temporal bone, consisting of the vestibule, the cochlea, and semicircular canals. The vestibule lies in the central part of the inner ear, between the cochlea and the semicircular canals. The cochlea is where the acoustic vibrations are converted into waves, which in turn stimulate the hair cells in the scala media (cochlear duct) of the cochlea, generating electrical impulses that travel to the temporal lobe of the cerebral cortex through t [..]

Middle Ear

Published on 2012-06-17 16:26:00

The middle ear is the part of the ear which includes the tympanic membrane (eardrum) and the auditory ossicles (malleus, incus, and stapes). The function of the middle ear is to transmit the acoustic vibrations, coming from the outer world through the outer ear, into the cochlea of the inner ear. It is also called tympanic cavity.

Endolymph

Published on 2012-06-16 12:52:00

Also known as Scarpa's fluid, the endolymph is the extracellular fluid enclosed within the cochlea and semicircular canals of the inner ear. Basically, the endolymph is composed of water, potassium, chloride, bicarbonate, and some amino acids, which are positively charged. The function of the endolymph is to act as a medium for the transmission of vibrations that come from the stapes; the endolymph makes it possible for the acoustic vibrations to flow in waves within the scala vestibuli, scala t [..]

Incus

Published on 2012-06-15 11:59:00

Also called anvil, the incus is one of the three small bones which constitute the ossicles. It is located between the malleus (hammer) and the stapes (stirrup). Having two processes called cruses, the incus is joined to the other two bones by ligaments. Vibrations picked up by the tympanic mambrane go through the malleus, incus, and stapes and into the cochlea through the fenestra ovalis (oval window).

Superior Olivary Complex

Published on 2012-06-14 12:51:00

The superior olivary complex is the clusters of neuron bodies, constituting nuclei of grey matter, which are located in the pons (brainstem). Nerve fibers from the cochlear nucleus projects to the superior olivary complex via the trapezoid body. It is the part of the pons where the auditory information coming from the right and left inner ears converge.

Scala Tympani

Published on 2012-06-13 14:32:00

The scala tympani is a spiraling fluid-filled tube lying below the scala media and scala vestibuli, from which it is separated by the basilar membrane and spiral lamina respectively, in the cochlea. When the tympanic membrane transmits the vibrations coming in from the outer world to the ossicles, the stapes transmits them in turn to the oval window, causing the liquid (perilymph) inside the scala tympani and scala vestibuli to move in waves. These vibratory waves of liquid inside the scala vest [..]

Scala Vestibuli

Published on 2012-06-12 12:39:00

The scala vestibuli is one of the three, fluid-filled, spiraling conduits into which the cochlea of the inner ear is divided. It is situated above the scala tympani and the scala media (cochlear duct), which is in between the first ones. The spiral lamina separates the scala vestibuli from the scala tympani, while Reissner's membrane separates it from the scala media.

Cochlear Duct

Published on 2012-06-11 13:46:00

The cochlear duct, also known as scala media, is a fluid-filled coiled up tube which is located in the cochlea bony canal and contains the organ of Corti. The cochlear duct lies between the scala vestibuli and the scala tympani, with the Reissner's membrane and the basilar membrane separating the three spiraling tubes that make up the cochlea.

Semicircular Canals

Published on 2012-06-10 14:47:00

The semicircular canals are the three fluid-filled tubes of the bony labyrinth, forming three loops; the superior semicircular canal, the posterior semicircular canal, and the horizontal semicircular canal. Being part of the vestibular system, they are involved with balance and equilibrium as they have motion sensors inside (sensory epithelium containing hair cells). The type of fluid each of the canals is filled with is endolymph.

Tympanic Membrane

Published on 2012-06-09 15:26:00

The tympanic membrane, or eardrum, is a thin conk-shaped membrane located at the entrance of the middle ear. The tympanic membrane vibrates in response to the sounds coming in through the outer ear from the outer world. Sounds of a lower pitch or frequency produce slower rate of vibration; sounds of lower volume or amplitude produce less dramatic vibrations; and higher frequency sounds produce faster vibrations. The tympanic membrane articulates with a chain of three bones called auditory ossicl [..]

Vestibular System

Published on 2012-06-08 15:05:00

The vestibular system is a sensory system of the inner ear which is associated with balance and equilibrium. It consists of two main structures: 1) the semicircular canals, which are three tiny fluid-filled semicircular tubes, located anteriorly, posteriorly, and horizontally; 2) the vestibule, which is in turn made up of the utricle and saccule. The vestibular system is connected to the vestibular ganglions through the vestibular nerves.

Fenestra Ovalis

Published on 2012-06-07 13:01:00

The fenestra ovalis (oval window) is a tiny aperture which links the middle ear with inner ear; covered by a vibrating membrane, the fenestra ovalis is a communicating door through which acoustic vibrations picked up by the tympanic membrane are transmitted from the ossicles to the cochlea. The stapes (stirrup), one of the three tiny bones that make up the ossicles, is attached to the fenestra ovalis.

Stapes

Published on 2012-06-06 13:25:00

Situated in the middle ear, the stapes, or stirrup, is one of the three small bones that constitute the auditory ossicles. The stapes receives vibratory impulses from the incus (anvil), to which it is attached, and transmit them to the cochlea through the fenestra ovalis (oval window).

Auditory Ossicles

Published on 2012-06-05 13:19:00

The auditory ossicles are the three small bones located in the middle ear, linking the tympanic membrane (eardrum) to the fenestra ovalis (oval window) of the vestibule of the inner ear. They are the malleus (hammer), the incus (anvil), and the stapes (stirrup).

Malleus

Published on 2012-06-04 14:34:00

Located in the middle ear, the malleus is a tiny bone which has the shape of a hammer. It is one of three small bones which constitute the auditory ossicles, articulating with the incus (anvil). The acoustic vibrations, coming from the outer world through the outer ear, vibrate the timpanic membrane (eardrum), setting in motion the malleus which strikes or shakes the incus, passing these vibrating waves onto the stapes (stirrup), which is in contact with the fenestra ovalis (oval window). Malleu [..]

Plant Vascular Tissue

Published on 2012-06-03 13:43:00

Vascular tissue is the distinguishing feature of higher plants. It is an intricate network of internal plumbing that runs continuously from the tips of the leaves and buds through the stem and main root down to the smallest root. It is visible in leaves as the familiar "veins". The two kinds of vascular tissue in plants are the xylem and phloem. Xylem transports water and dissolved minerals upward in the plant body and also supports the plant body; it is a complex tissue composed of several type [..]

Virion

Published on 2012-06-02 14:47:00

A virion is a virus in its extracellular stage. It contains nucleic acid which is surrounded and protected by a protein coat or capsid. All virions are extremely small, but there is a considerable range of sizes among them. One of the largest virions is that of the cowposx, which was used in vaccination against smallpox. The virion is a cube about 20 nanometers on a side. On the other hand, a small virion may be only 2 nanometers in diameter. Virions have very simple morphologies, since most of [..]

Pleurisy

Published on 2012-05-31 12:58:00

Pleurisy, also known as pleuritis, is the inflammation of the pleura, which is the thin double-layer membrane which surrounds the lungs. It is usually caused by either an infection of the lung or injury. Pleurisy is characterized by the build-up of fluids between the two layers that make up the pleura or between the pleura and the lung. This condition causes pain when breathing, and coughing. Treatment: drainage of fluids, and antibiotics to treat the infectious disease that has originated pleur [..]

Useful Bacteria

Published on 2012-05-30 10:26:00

In stressing the importance of antibiotics as harmful microbes killers, we may have narrowed our focus too sharply, creating the impression that the only import of bacteria to man lies in their relation to disease. However, a useful role looms large, "bacteria as manufacturers". Microbiologists, chemists, and engineers have pooled their talents to develop industrial processes in which microorganisms, and their enzymes, produce a variety of useful compounds. These techniques center about their fe [..]

Prontosil and Sulfonamides

Published on 2012-05-29 14:04:00

In 1935, Gerhard Domagk, a German bacteriologist, found that the dye Prontosil inhibited the growth of streptococci in man. However, although it was effective in treating infections, it was without effect on bacteria in vitro. It was soon discovered that Prontosil was degraded in the body and that its active antibacterial component in man was sulfanilamide. This discovery gave rise to a class of chemotherapeutic agents, the sulfonamides, which inhibit the growth of streptococci by preventing the [..]

Mesolithic

Published on 2012-05-28 15:10:00

The mesolithic, or Middle Stone Age, is a period between the Old Stone (Paleolithic) Age and the New Stone Age (Neolithic) in which men lived by hunting and gathering but tended toward a more "sttled in" existence. The mesolithic is characterized by the emergence of microlithic weapons and small-bladed stone tools which were attached to a haft. This middle period of the Stone Age began around 11,000 BC, extending until 4,000 year BC.

Bony Labyrinth

Published on 2012-05-27 18:37:00

The labyrinth is a bony cavity which is located in the petrous part of the temporal bone. Constituting the inner ear, the labyrinth is composed of the cochlea, canals, and vestibule. It contains the hair cells that pick up the acoustic vibrations coming into the ear from the outside world, transmitting it to the temporal lobe through the auditory nerve.

What Happened to the Neanderthals

Published on 2012-05-26 13:00:00

What happened to the Neanderthals? We cannot be certain, although anthropologists advance several interesting theories. Were they exterminated by invading bands of new men, who outnumbered them and wrested their hunting territories from them? Or did the Neanderthals die off by themselves before they ever came into contact with the invaders? Unable to cope with the new conditions of living as the climate in Europe began to change, were they carried off by malnutrition and disease? We know that pl [..]

Basilar Membrane

Published on 2012-05-25 13:52:00

Located in the inner ear, the basilar membrane is a thin elastic layer which forms the base for the organ of Corti, which contains the hair cells. It is composed of thin elastic fibers and epithelial cells, separating the two cochlear channels. The basilar membrane vibrates in waves.

Inner Hair Cells

Published on 2012-05-24 13:13:00

Arranged in a signle row in the organ of Corti, inner hair cells are the inner ear sensory cells that have hairlike processes. They convert acoustic vibration into nerve impulses transmitted to the brain via the auditory nerve.

First Stone Tools

Published on 2012-05-23 13:11:00

The first known stone tools came from Africa and date back beyond the Pleistocene, or Ice Age, more than one million years ago. These were the pebble tools used by the Australopithecines. They were made of crudely shaped lava or quartz pebbles a little larger than a man's fist. Sometimes the pebbles were broken or chipped on two sides to form a simple cutting or scraping instrument. If you came upon any of these early stone tools you might easily mistake them for bits of battered rock shaped by [..]

Organ of Corti

Published on 2012-05-22 09:24:00

The organ of Corti is a spiral-shaped structure located on the cochlea's basilar membrane. Named after the Italian anatomist Alberto Corti, it is composed of neuroepithelial hair cells as well as supporting cells. These neuroepithelial hair cells of the organ of Corti are receptors for hearing, transforming acoustic vibrations into nerve impulses that are sent to the brain temporal lobe.

Java Man, Peking Man and Fire Making

Published on 2012-05-21 13:44:00

About half a million years ago, a new type of man, probably descended from the Australopithecines, evolved in eastern Asia. Some of these early men lived in the jungle near the Solo River, central Java. In 1891, Dutch army doctor Eugene Dubois discovered the fosil remains of an ancient hominid that he called Pithecanthropus erectus, meaning the "Ape Man Who Stands Erect", who is simply known as the Java Man. What did he look like? He had a receding chin, a broad flat nose, projecting jaws, in wh [..]

Cochlea

Published on 2012-05-20 13:31:00

Located in the petrous portion of the temporal bone, the cochlea is a spiral tube which is a part of the inner ear, resembling a snail shell. The inner walls of the cochlea are lined with a fine layer of epithelium tissue as a thin membrane divides the spiralled tube along its length into two spaces which are filled with fluids. It contains the organ of Corti, which lies along the length of the membrane and is composed of neuroepithelial hair cells, which are special sensory receptor for hearing [..]

Hominid

Published on 2012-05-19 12:27:00

A hominid is any of the bipedal primates belonging to the Hominidae family, which includes all the species of the genera Australopithecus, as well as Homo erectus and Homo sapiens (Neanderthal and Cro-Magnon). The only surviving hominid today is Homo sapiens or modern man.

Differences Between Man and Apes

Published on 2012-05-18 13:14:00

Although they belong to the same order, primate, the physical differences between man and the present-day apes are so great that we cannot imagine a direct line of descent from one to the other. The evolutionary path taken by the apes does not lead to man. It is a detour. Like the lemur and the monkey, the ape occupies a side branch on our family tree. Our direct ancestor must have lived before the four present varieties of ape ever came on the scene.The ape's cranial capacity is between 400 and [..]

Ventral Spinocerebellar Tract

Published on 2012-05-17 14:36:00

The ventral spinocerebellar tract, also known as Gowers' column, is a bundle of myelinated axon fibers in the spinal cord which connects the body's periphery with the cerebellum, carrying sensory information. Running side by side with the dorsal spinocerebellar tract, along the spinal cord, Gowers' column lies on the anterior-lateral side of the spinal cord, being part of the white matter that surrounds the grey H-shaped grey matter.

Hands, Face, and Evolution

Published on 2012-05-16 13:53:00

The first primates, like most present day species, were arboreal, or tree-living. They were small, defenseless animals, and their survival depended on their ability to escape their enemies. Forelimbs ending in strong, flexible digits enabled them to get a secure grip on high branches where no big cat could follow. Thus, hands were an evolutionary adaptation to tree living. Among primate tree dwellers even the feet begin to look and function like hands. Some of lemurs, monkeys, and even the bulky [..]

Erb's Dystrophy

Published on 2012-05-15 13:19:00

Erb's dystrophy, or progressive muscular dystrophy, is a hereditary and familial disease which has a progressive and chronic evolution. It is characterized by muscular atrophies of facial, pelvic, and pectoral girdle muscles (of clavicle and scapula), sometimes accompanied by an excessive development of fatty tissue. The muscular atrophy is probably due to an alteration of muscular metabolism, by which the muscle fibers has difficulties in synthesizing phosphagens. Degenerative lesions in sympat [..]

Biological Classification of Man

Published on 2012-05-14 11:12:00

Man's biological classification reveals his relationship to simpler organisms. However in the smallest subdivision, species, man stands alone. But ultimately he is related even to the tiny ameba. Man is a vertebrate of the mammal class, of the pimate order, genus Homo, and species Sapiens. Being a primate means that he has stereoscopic, or three-dimensional, vision and a pair of hands with grasping fingers and flat fingernails. As a member of the genus Homo, he has an erect posture, with one str [..]

Voluntary Control of Breathing

Published on 2012-05-13 14:43:00

Despite the involuntary nature of most respiratory reflexes, it is quite obvious that there are also considerable voluntary control of breathing through respiratory muscle movements. Voluntary control is accomplished by descending pathways from the cerebral cortex to the motor neurons of the respiratory muscles. This voluntary control of respiration cannot be maintained when the involuntary stimuli, such as an elevated PCO2 or H+ concentration, become intense. An example is the inability to hold [..]

Sleep Apnea

Published on 2012-05-12 14:02:00

Sleep apnea is the periodic suspension of breathing during sleep. There are two general kinds of sleep apnea. Central sleep apnea is mainly caused by a decrease in neural output from the respiratory center in the medulla to the phrenic motor nerve output to the diaphragm. Obstructive sleep apnea is due to increased airway resistance because of narrowing or collapse of the upper airways (primarily pharynx) during inspiration. Obstructive sleep apnea may occur in as much as 4 percent of the adult [..]

Hypoxia

Published on 2012-05-11 12:35:00

Hypoxia is a decrease of oxygen supply to body organs and tissues. There are several causes of hypoxia, but they can be classed in four general categories: 1) hypoxic hypoxia (also termed hypoxemia), in which the arterial PO2 is reduced; 2) anemic or carbon monoxide hypoxia, in which the arterial PO2 is normal but the total oxygen content of the blood is reduced because of inadequate numbers of erythrocytes, deficient or abnormal hemoglobin, or competition for the hemoglobin molecule by carbon m [..]

Strümpell-Lorrain Familial Spasmodic Paraplegia

Published on 2012-05-10 12:31:00

The Strümpell-Lorrain's familial spasmodic paraplegia is a hereditary disease characterized by spastic paraplegia (abnormal muscle constraction and stiffness of the lower limbs), difficulty in lifting the feet off the ground when walking, with the toe dragging, muscle spasm, and sometimes speech disorders. Beginning before the age of 18, the symptoms of the Strümpell-Lorrain familial spasmodic paraplegia are caused by a systematic degeneration of the pyramidal tracts, which are composed of mot [..]

Funicular Myelosis

Published on 2012-05-09 13:01:00

Funicular Myelosis is central nervous system syndrome which consists in a demyelinating degeneration that affects several spinal tracts (funiculi) of the spinal cord, such as posterior and lateral tracts (combined degeneration). Funicular myelosis is linked to pernicious anemia and avitaminosis, such as lack of vitamin B12. It usually affects people older than forty years of age. The symptoms are tingling sensation and numbness of limbs, muscular weakness, paresis (impaired voluntary movement), [..]

Heimlich Maneuver

Published on 2012-05-08 10:50:00

The Heimlich maneuver is used to aid a person choking on a foreign body caught in and obstructing the upper airways. A sudden increase in abdominal pressure is produced as the rescuer’s fists, placed against the victim’s abdomen slightly above the navel and well below the tip of the sternum, are pressed into the abdomen with a quick upward thrust. The increased abdominal pressure forces the diaphragm upward into the thorax, reducing thoracic size and, by Boyle’s Law, increasing alveolar pr [..]

Asthma

Published on 2012-05-07 18:38:00

Asthma is a chronic disease characterized by intermittent episodes in which airway smooth muscle contracts strongly, markedly increasing airway resistance. The basic defect in asthma is chronic inflammation of the airways, the causes of which vary from person to person and include, among others, allergy, viral infections, and sensitivity to environmental factors. The important point is that the underlying inflammation causes the airway smooth muscle to be hyperresponsive and to contract strongly [..]

Werdnig-Hoffmann Disease

Published on 2012-05-06 14:12:00

The Werdnig-Hoffmann disease, also known as spinal muscular atrophy, is a hereditary and familial syndrome which affects children. It begins with atrophy of the pelvitrochanteric muscles (of the pelvis and hip joints); as a result, the patient is unable to sit or stand up. Reflexes are abolished, but there is no alteration of sensitivity. Over time, the atrophy extends to the upper limbs and thorax. The Werdnig-Hoffmann disease progresses slowly, eventually leading to death after six or seven ye [..]

Friedreich's Ataxia

Published on 2012-05-05 13:55:00

The Friedreich's ataxia is a hereditary, familial, and recessive syndrome which is anatomically characterized by degeneration of the posterior and spinocerebellar tracts of the spinal cord, causing lack of coordination of muscular movement, specially of limbs, when walking, which is called ataxia; other symptons are abolition of reflexes, dysarthria (speech problems), scoliosis, nistagmus, etc. Affecting more frecuently males than females, Friedreich's ataxia starts in early childhood and is chr [..]

Syringomyelia

Published on 2012-05-03 09:55:00

Syringomyelia is a disease characterized by the formation of longitudinal cavities in the grey matter of the spinal cord. These cavities are filled with fluid and may extend along the entire length of the spinal cord. Syringomyelia is extremely chronic and progressive, leading to paralysis. The cause is hereditary and affects adults, with the majority of the patients being males. The symptoms are limb anesthesia (the patient does not feel pain and heat), loss of muscular strength in hands, arms, [..]

Pneumothorax

Published on 2012-05-02 13:16:00

Pneumothorax is a lung anomaly in which rushing air fills in the pleural space when it is opened from the outside, causing a part of the lung to cave in. In this case the lung no longer follows movement of the thorax and the diaphragm (external pneumothorax). This also occurs if there is a tear in the lung and the visceral pleura and air is able to pass from the respiratory pathways into the pleural space (internal pneumothorax); in this case the mediastinum is pulled toward the healthy side dur [..]

Amyotrophic Lateral Sclerosis

Published on 2012-05-01 14:40:00

The amyotrophic lateral sclerosis, also known as Lou Gehrig's syndrome, is a disease characterized by the degeneration of the anterior horns of the spinal cord and medulla oblongata nuclei associated with degeneration of the direct pyramidal tracts. Amyotrophic lateral sclerosis causes spastic paraplegia (paralysis of the lower limbs) and muscular atrophy. The evolution of this disease is chronic, usually ending in death in a time span of 6 to 7 years. The cause of this syndrome is unkown.

Pleistocene

Published on 2012-04-30 12:41:00

The Pleistocene is one of two geological epochs into which the Quaternary period of the Cenozoic era is divided. It is the epoch in which all genera of Homo appeared on Earth, specially Homo sapiens (Neanderthal and Cro-magnon). The Pleistocene was characterized by global cooling and the ice ages, with very low temperature as two thirds of the planet was covered in ice during each of the four glacial ages. Mammoths, saber-toothed tigers, long-horn bisons and other big mammals also lived during t [..]

Order Chiroptera

Published on 2012-04-29 13:31:00

Chiroptera ("hand wings") is an order of mammals which includes all genera of bats. Chiroptera in turn comprise two groups: Microchiroptera, which are small bats that feed on insects and animal's blood; Megachiroptera, large-sized bats that eat fruit and small land animals. In order to detect their insect prey, most Chiroptera use echolocation.

Time Spans of Earth's History

Published on 2012-04-28 10:15:00

Scientists divide the Earth's history into five major time spans called eras: Archeozoic, Proterozoic, Paleozoic (the longest one), Mesozoic, and Cenozoic. The first two ones are the earliest, which cover the events from the beginning of the Earth to about 600 million years ago. Until recently it was believed that the Proterozoic was the era before life began, but it was discovered that certain forms of life, such as bacteria and algae existed even then.The Paleozoic ("ancient life") era covers [..]

First Land Plants

Published on 2012-04-27 10:49:00

Botanists generally agree that the first truly land plants can be identified from the third Paleozoic period, the Silurian. These were leafless plants that had the vascular conducting system typical of the most advanced plant phylum. This phylum produced ferns and then all the seed plants, such as trees, shrubs, and the flowering plants, including grasses. Green plants also evolved in another direction to produce mosses and liverworts which lack a vascular structure. Botanists do not know whethe [..]

Marsupial Embryological Development

Published on 2012-04-26 14:06:00

The marsupials, or marsupialia, are an order of pouched mammals, which include the kangaroos, koalas, and opposum, all inhabitants of Australia. The marsupial embryo stays in the utterus (womb) for only a short time. When the young are born they are little more than embryos. They crawl from the vagina into a pouch called marsupium on the mother's abdomen. The mother may lick a pathway through her fur to smooth their way. Once they are inside the pouch, the babies seek out a nipple which they gra [..]

Built-in Behavior in Insects

Published on 2012-04-25 12:57:00

Built-in behavior is the set of patterned repetitive activities done by insects. Let us analyze the female Aedes mosquito egg-laying behavior. The Aedes mosquitoes are orphaned by their parents as soon as the eggs are laid. After they hatch, each mosquito is strictly on its own. They have no opportunities to learn the special kind of egg-laying behavior; yet all Aedes female mosquitoes behave in this way: they lay their eggs just above the water line of a pond rather than in the water; second, t [..]

Fish Heart

Published on 2012-04-24 10:42:00

The design of the heart varies widely from class to class. For example, the fish heart, unlike that of birds, mammals, and reptiles, has only two chamber instead of four: an atrium and a ventricle. The atrium receives venous blood from the sinus venosus, which is a small sac or pouch that collects the carbon-dioxide-rich blood from the body tissues, and sends it to the ventricle, which pumps this blood to capillaries in the gills where it is oxygenated. From the gills it goes straight to capilla [..]

Insect Nervous System

Published on 2012-04-23 12:59:00

In insects the nervous system consists of a rudimentary brain and a nerve cord. This nerve cord, like that of most invertebrates, is double. It consists of a chain of ganglia, usually one in each body segment, which are connected to each other by two bundles of nerve fibers. The ganglia contain most of the nerve cell bodies. Each ganglion coordinates many of the responses in its own segment.There is a major difference between an insect's nervous system and that of vertebrates. In insects and mos [..]

Egg-laying Mammals

Published on 2012-04-22 12:38:00

Living mammals are placed into one of three major groups, depending on the way the animal completes its embryonic developement. One small group of mammals are the monotremes, which are egg-laying mammals. The monotremes include only three species, the duckbill platypus and two kinds of echidnas or spiny ant-eaters. All three are found only in Australia and New Zealand. These bizarre creatures differ from all other mammals because the female lays eggs, but when the young hatch she feeds them with [..]

Placental Mammals

Published on 2012-04-21 13:02:00

The most plentiful of most mammals are the placentals. Unlike the embryos of marsupials, the embryos of placental mammals are nourished within the mother's body by a special organ, the placenta, and are not born until development is well advanced. Placenta means "flat cake", which is the shape of this organ in humans; it is an evolutionary development of the membrane which in the reptilian ancestors of mammals enveloped the embryo within the eggs. In placental mammals these membranes have become [..]

Carnivora

Published on 2012-04-20 14:22:00

Carnivora is an order of mammals which comprises felines (cats, lions, tigers, leopards), canine (wolves, dogs), bears, weasels, raccoons, otters, etc. They have their bodies genetically built to hunt and feed on other animals; they have large fangs (canine teeth), two in the upper jaw and two in the lower jaw, and their premolar teeth are jagged and sharp, made for cutting meat and sinew, not for grinding like a ruminant's flat molars (back teeth). Other features are stronger jaws, paws with cl [..]

Pulmonary Abscess

Published on 2012-04-19 11:19:00

Pulmonary abscess is a collection of pus (dead leukocytes and cellular debris) in the lung caused by bacterial infection. The germs that produce abscess can reach the lungs through two ways: 1) bronqui, through which infection-causing bacterial, such as pneumococci and streptococci, get into the lung lobules, causing pneumonia that result in abscess; 2) circulating blood, which carries germs or contaminated clots that block the capillaries in the alveoli. Thus, pulmonary or lung abscess is the r [..]

Orders of Living Mammals

Published on 2012-04-18 11:42:00

The sixteen orders of living placental mammals are: 1) Artiodactyla (even-toed), which comprises even-toed hoofed animals, such as reindeer, camels, giraffes, cattle, sheep, pigs, hippopotamuses; 2) Carnivora (meat-eaters), which include bears, cats (felines), racoons, skunks, seals, otters, weasel; 3) Cetacea: whales, dolphin, porpoises; 4) Chiroptera: bats; 5) Dermoptera: flying lemurs; 6) Edentata (toothless): armadillos, sloths, and anteaters; 7) Primates: tree shrews, lemurs, monkeys, apes, [..]

Poikilotherm

Published on 2012-04-17 12:47:00

Poikilotherm is a cold-blooded animal; that is, an animal whose body temperature fluctuates with environmental temperature changes. An animal incapable of slef-regulation of body temperature. Fish, amphibians and reptiles are poikilotherms. Since these animals do not generate their own body temperature in the same way birds and mammals do, they depend entirely on an external source of heat; thus reptiles, such as snakes, crocodiles, and lizards need to bask in the sun for their body functions.

Rivers Ecosystems

Published on 2012-04-16 10:26:00

A river or stream is primarily a transport system between the land and the sea. Most of the nutrients in a river come from adjacent terrestrial ecosystems, and relatively little primary production occurs within the streams or rivers itself. The organisms that are characteristic of rivers and streams are especially adapted to feeding on organic ditritus. Some insect larvae, such as caddis flies, attach themselves to rocks and spin nets which catch food particles from the flowing waters. In slow-m [..]

Estuaries and Seashores Ecosystems

Published on 2012-04-15 12:25:00

At the junction of the oceans and the continents there is a narrow ribbon of ecosystems: the estuaries, which are among the most productive on earth. An estuary is an area near the mouth of a river or a bay where salinity is intermediate between fresh water and the salinity of the oceans. Estuaries, beaches, and the rocky shores of seacoasts are continuously subjected to the action of the tides that affect the plants and animals in this intertidal zone. Tides are the key to the high productivity [..]

Notochord

Published on 2012-04-14 12:32:00

The notochord is a longitudinal, rod-shaped structure that serves as a skeletal axis in the embryos of all chordates. In the vertebrates, it is replaced by the vertebral column as the organism develops.

Emphysema

Published on 2012-04-13 10:44:00

An emphysema is a pulmonary disease in which the alveoli contains an excessive amount of air, which causes distention of the affected areas. The air caught up in these tiny air sacs hinders the normal gas exchange (oxygen for carbon dioxide) that allow to oxygenate the blood. This abnormal expansion of the alveoli is usually irreversible and leads to the destruction of their epithelial walls. If the emphysema spreads throughout the lung, it becomes inflated with bluish grey color. The symptons a [..]

Bronchi

Published on 2012-04-12 10:38:00

The bronchi are the air passages into which the trachea divides, connecting it to the lungs. There are three kinds of bronchi: the primary bronchi, which are the main two branches (right and left) into which the trachea divides; the lobar bronchi, which are the secondary air passages given off by the primary bronchi; the tertiary bronchi are the smallest of the bronchial branches leading up to the bronchiole. Bronchi is plural of bronchus; so one branch is a bronchus, more than one are bronchi. [..]

Pleural Sac

Published on 2012-04-11 12:15:00

The pleural sac is a double-layered sac-like structure which completely surrounds each lung. It is made up of two layers: 1) an inner layer called the visceral pleura, which is firmly attached to the lung by connective tissue; 2) an outer layer, called the parietal pleura, is attached to and lines the interior thoracic wall and diaphragm. The two layers of pleura in each sac are so close to each other that normally they are always in virtual contact, but they are not attached to each other. Rath [..]

Lungs

Published on 2012-04-10 12:56:00

The lungs are a pair of sac-like respiratory organs which occupy the chest cavity. Gas exchange between inhaled air and the blood takes place in these organs. Thus, the function of the lungs is to oxygenated the blood and to expel out or exhale the carbon dioxide contained in the blood pumped into them by the heart right ventricle. The lungs incorporate the bronchial tree, which connects these organs to the trachea. Each lung is divided into lobes by deep clefts called interlobar fissures. The r [..]

Bronchiole

Published on 2012-04-08 13:56:00

A bronchiole is one of the tiny, thin-walled, tubular branches of the bronchi. There are three types of bronchioles: lobular, terminal, and respiratory one. Lobular bronchioles arise from a small bronchus, and from each lobular bronchiole four to five terminal bronchioles originates. Several respiratory bronchioles stem from a terminal one; the walls of these latter bronchioles are formed by a cuboidal epithelium. In turn, each respiratory bronchiole divides into several alveolar ducts, which en [..]

Alveoli

Published on 2012-04-07 13:07:00

Alveoli are tiny capillary-rich sacs located in the lungs. The thin epithelial walls and capillaries of each alveolus turn this balloon-like sac into a gas exchange chamber, where oxygen contained in the air we breathe is exchanged for the carbon dioxide contained in the venous blood circulating in the venous capillaries (blue) of each alveolus; these capillaries are tiny branches of the pulmonary artery; carbon dioxide-rich blood is pumped into the lungs by the right ventricle through the pulmo [..]

Refractory Period of the Heart

Published on 2012-04-06 12:27:00

Ventricular muscle, unlike skeletal muscle, is incapable of any significant degree of summation of contractions, and this is a very good thing. Imagine that cardiac muscle were able to undergo a prolonged tetanic contraction. During this period, no ventricular filling could occur since filling can occur only when the ventricular muscle is relaxed, and the heart would therefore cease to function as a pump. The inability of the heart to generate tetanic contractions is the result of the long absol [..]

Cardiac Muscle Innervation

Published on 2012-04-05 19:00:00

Approximately 1 percent of cardiac muscle cells do not function in contraction, but have specialized features that are essential for normal heart excitation. These cells constitute a network known as the conducting system of the heart and are in contact with the cardiac muscle cells via gap junctions. The conducting system initiates the heartbeat and helps spread the impulse rapidly throughout the heart. One final point about cardiac muscle is that certain cells in the atria secrete the family o [..]

Withdrawal Reflex

Published on 2012-04-04 21:15:00

In addition to the afferent information from the spindle stretch receptors and Golgi tendon organs of the activated muscle, other input is fed into the local motor control systems. For example, painful stimulation of the skin activates the ipsilateral flexor motor neurons and inhibits the ipsilateral extensor motor neurons, moving the body part away from the stimulus. This is called the withdrawal reflex. The same stimulus causes just the opposite response on the contralateral side of the body†[..]

Denervation Atrophy

Published on 2012-04-03 10:28:00

Denervation atrophy, also known as neurogenic atrophy, is the reduction in the diameter of muscle fibers and a decrease in the amount of contractile proteins they contain, due to the distruction of innervating motor neurons and/or their neuromuscular junctions, which causes discontinuation of the muscle nerve supply. Denervation atrophy is always accompanied by paralysis and is caused by several sindromes. A muscle can also atrophy with its nerve supply intact if the muscle is not used for a lon [..]

Tetanus

Published on 2012-04-02 13:10:00

Tetanus is an acute infectious disease characterized by rigid spasmodic contraction of several voluntary muscles, specially those of the neck, jaws, and trunk (muscles involved in expanding the chest in breathing). Tetanus is a neurological disorder that results from a decrease of the inhibitory input to alpha motor neurons. It occurs when spores of the soil bacterium Clostridium tetani (also known as Nicolaier's bacillus) invade a poorly oxygenated wound. Proliferation of the bacterium under an [..]

Hypocalcemic Tetany

Published on 2012-04-01 12:47:00

Hypocalcemic tetany is the involuntary tetanic contraction of skeletal muscles that occurs when the extracellular calcium concentration falls to about 40 percent of its normal value. This may seem surprising, since calcium is required for excitation-contraction coupling. However, we must bear in mind, that this calcium is sarcoplasmic reticulum calcium, not extracellular calcium. The effect of changes in extracellular calcium is exerted not on the sarcoplasmic reticulum calcium, but directly on [..]

Duchenne Muscular Dystrophy

Published on 2012-03-31 10:27:00

Duchenne muscular dystrophy is one of the most frequently encountered genetic diseases, affecting one in every 3500 males born in America, but much less commonly in females. Muscular dystrophy is associated with the progressive degeneration of skeletal and cardiac muscle fibers, weakening the muscles and leading ultimately to death from respiratory or cardiac failure. The symptoms become evident at about 2 to 6 years of age, and most affected individuals do not survive much beyond the age of 20. [..]

Types of Skeletal Muscle Fibers

Published on 2012-03-30 12:58:00

Skeletal muscle fibers do not all have the same mechanical and metabolic characteristics. Different types of fibers can be identified on the basis of their maximal velocities of shortening, fast or slow, and the major pathway used to form ATP—oxidative or glycolytic. Fast and slow fibers contain forms of myosin that differ in the maximal rates at which they split ATP. This, in turn, determines the maximal rate of crossbridge cycling and thus the maximal shortening velocity. Fibers containing m [..]

Neuromuscular Junction

Published on 2012-03-29 13:23:00

Neuromuscular junction is the junction of an axon terminal with the motor end plate, which in turn is the region of the muscle fiber plasma membrane that lies directly under the terminal portion of the axon. The axon terminals of a motor neuron contain vesicles similar to the vesicles found at synaptic junctions between two neurons. The events occurring at the neuromuscular junction are as follow: when an action potential in a motor neuron arrives at the axon terminal, it depolarizes the plasma [..]

Ecological Succession

Published on 2012-03-28 10:19:00

There are two types of ecological succession; primary and secondary. If a field that has been used to grow agricultural crops is abandoned, it will soon become overgrown with grasses, goldenrod, and other herbaceous plants. If this field was once a woodland, the weed field will be invaded in a few years by shrubs such as blackberry, sumac, and hawthorn. In time the field will support a woodland of hickory, maple, oaks or pines. This is not a haphazard process; it is an orderly sequence of change [..]

Prostaglandins

Published on 2012-03-27 16:49:00

The family of substances known as prostaglandins resemble other known hormones in many of their effects; chemically, however, they are a quite different class of compounds. Prostaglandins are fatty acids, variants of a 20-carbon carboxylic acid incorporating a five-member cyclopentane ring. They are synthesized in many tissue of the body from polyunsaturated fatty acids. The key to understanding prostaglandins and linking information about them to the rest of molecular biology is the fact that t [..]

Excitation-contraction Coupling

Published on 2012-03-26 09:41:00

Excitation-contraction coupling refers to the sequence of events by which an action potential in the plasma membrane of a muscle fiber leads to cross-bridge activity. The skeletal muscle plasma membrane is an excitable membrane capable of generating and propagating action potentials by mechanisms similar to those described for nerve cells. An action potential in a skeletal muscle fiber lasts 1 to 2 ms and is completed before any signs of mechanical activity begin. Once begun, the mechanical acti [..]

Sarcoplasmic Reticulum

Published on 2012-03-25 09:37:00

The sarcoplasmic reticulum in muscle is homologous to the endoplasmic reticulum found in most cells and forms a series of sleevelike segments around each myofibril. At the end of each segment there are two enlarged regions, known as lateral sacs, that are connected to each other by a series of smaller tubular elements. The lateral sacs store the calcium that is released following membrane excitation. A separate tubular structure, the transverse tubule (T-tubule), crosses the muscle fiber at the [..]

Tropomyosin

Published on 2012-03-23 12:06:00

Tropomyosin is a rod-shaped molecule composed of two intertwined polypeptides with a length approximately equal to that of seven actin molecules. Chains of tropomyosin molecules are arranged end to end along the actin thin filament. These tropomyosin molecules partially cover the myosin-binding site on each actin molecule, thereby preventing the cross-bridges from making contact with actin. Each tropomyosin molecule is held in this blocking position by troponin, a smaller, globular protein that [..]

Polar Molecule

Published on 2012-03-22 10:08:00

A polar molecule is a molecule on which the electrical charge is not evenly distributed. Polar molecules, like amino acids, tend to dissolve in water, whereas nonpolar molecules, like hydrocarbons, tend to dissolve in lipid solvents like alcohols or ethers.

Sensory System

Published on 2012-03-21 10:30:00

A sensory system is a part of the nervous system that consists of sensory recepor cells that receive stimuli from the external or internal environment, the neural pathways that conduct information from the receptors to the brain or spinal cord, and those parts of the brain that deal primarily with processing the information. Information processed by a sensory system may or may not lead to conscious awareness of the stimulus. Regardless of whether the information reaches consciousness, it is call [..]

Activation of the Postsynaptic Cell

Published on 2012-03-20 10:29:00

Once released from the presynaptic axon terminal, neurotransmitters diffuse across the cleft. A fraction of these molecules bind to receptors on the plasma membrane of the postsynaptic cell. The activated receptors themselves may contain an ion channel, or they may act indirectly, via a G protein, on separate ion channels. In either case, the result of the binding of neurotransmitter to receptor is the opening or closing of specific ion channels in the postsynaptic plasma membrane, which eventua [..]

Release of Neurotransmitter

Published on 2012-03-19 09:47:00

The release of neurotransmitter into the synaptic cleft is triggered when an action potential reaches the axon terminal. This is followed by movement of vesicles to the presynaptic membrane, fusion of the vesicle membrane with the plasma membrane of the presynaptic terminal, and exocytosis of the vesicle contents into the synaptic cleft. The process by which vesicles move to the terminal for exocytosis of neurotransmitter involves a complex set of proteins, called SNARE proteins, that are presen [..]

Types of synapses

Published on 2012-03-18 13:26:00

There are two types of synapses: electrical and chemical. At electrical synapses, the plasma membranes of the pre- and postsynaptic cells are joined by gap junctions. These allow the local currents resulting from arriving action potentials to flow directly across the junction through the connecting channels in either direction from one neuron to the neuron on the other side of the junction. This depolarizes the membrane of the second neuron to threshold, initiating an action potential. Communica [..]

Autonomic Nervous System

Published on 2012-03-17 21:28:00

The efferent innervation of tissues other than skeletal muscle is by way of the autonomic nervous system. It regulates involuntary action, such as the heart beat, smooth muscle movement or contraction (liver, intestines), and glands. The autonomic nervous system is made up of two neurons in series that connect the central nervous system and the effector cells. The first neuron has its cell body in the central nervous system. The synapse between the two neurons is outside the central nervous syst [..]

Ammonia Excretion in Vertebrates

Published on 2012-03-13 11:05:00

One of the breakdown products of nitrogen metabolism is ammonia. However, ammonia is very toxic to tissues, and it must be excreted or removed as rapidly as it is formed. This presents no problem to many aquatic non-vertebrate organisms which simply excrete the ammonia to the surrounding water as it is formed. Terrestrial animals cannot do this, obviously; they and the marine fish could flush out the ammonia with a large volumes of urine but they must conserve water. How do they solve this dilem [..]

Neuroeffector Junctions

Published on 2012-03-12 07:51:00

Many neurons of the peripheral nervous system end, however, not at synapses on other neurons but at neuroeffector junctions on muscle and gland cells. The neurotransmitters released by these efferent neurons’ terminals or varicosities provide the link by which electrical activity of the nervous system can regulate effector cell activity. The events that occur at neuroeffector junctions are similar to those at a synapse. The neurotransmitter is released from the efferent neuron upon the arrival [..]

Biogenic Amines

Published on 2012-03-11 09:59:00

The biogenic amines are small charged molecules that are synthesized from amino acids and contain an amino group (R–NH2). The most common biogenic amines are dopamine, norepinephrine, serotonin, and histamine. Epinephrine, another biogenic amine, is not a common neurotransmitter in the central nervous system but is the major hormone secreted by the adrenal medulla. Norepinephrine is an important neurotransmitter in both the central and peripheral components of the nervous system.

Heart Diseases by ischemia

Published on 2012-03-10 10:54:00

Most cases of heart disease are not "heart" diseases as such. They develop as a result of changes within the blood vessels that supply the myocardium. Skeletal muscles can contract in the absence of oxygen; cardiac muscle cannot. Cardiac muscle (myocardium) extracts about 80% of the oxygen brought to it by its own system of blood vessels, which include the coronaries arteries. Sometimes these vessels become constricted or blocked, which results in ischemia (insufficient blood flow). When they ar [..]

Neuropeptides

Published on 2012-03-09 10:56:00

The neuropeptides are composed of two or more amino acids linked together by peptide bonds. Some 85 neuropeptides have been found, but their physiological roles are often unknown. It seems that evolution has selected the same chemical messengers for use in widely differing circumstances, and many of the neuropeptides had been previously identified in nonneural tissue where they function as hormones or paracrine agents. They generally retain the name they were given when first discovered in the n [..]

Transfer RNA

Published on 2012-03-08 09:48:00

A transfer RNA (tRNA) is a small RNA (ribonucleic acid) molecule, about 80 nucleotides long that acts as a carrier of specific amino acids during protein synthesis. A molecule of transfer RNA, which is specific for a particular amino acid, binds to that amino acid. The sequence of three nucleotides that make up the anti-codon on the tRNA recognize and bind to the codon on the messenger RNA, which is complexed with a ribosome on which a polypetide chain developing. The amino acid is thus guided i [..]

Algal Symbioses

Published on 2012-03-07 10:05:00

One noteworthy feature of several sorts of green algae is the ease with which they form symbiotic relationships of various kinds with other organisms. Many fungi have green algae growing closely with them. The symbiotic organism composed of the alga and the fungus is called a lichen. In Addition, many green algea actually live inside de cells of other organisms, usually within a vacuole. More than a hundred different genera of invertebrates in eight different phyla have green algal symbionts gro [..]

Ionic Basis of the Action Potential

Published on 2012-03-06 11:36:00

The magnitude of the resting membrane and graded potentials depends upon the concentration gradients of and membrane permeabilities to different ions, particularly sodium and potassium. This is true for the action potential as well. The action potential is initiated by a transient change in membrane ion permeability, which allows sodium and potassium ions to move down their concentration gradients. In the resting state, the leak channels in the plasma membrane are predominantly those that are pe [..]

Generation of Action Potentials

Published on 2012-03-05 09:44:00

Stimuli bring the membrane to the threshold potential, and voltage-gated sodium channels trigger the all-or-none action potential. How is the threshold potential attained, and how are action potentials actually generated in various types of neurons? In afferent neurons, the initial depolarization to threshold is achieved by a graded potential—here called a receptor potential, which is generated in the sensory receptors at the peripheral ends of the neurons. These are the ends farthest from the [..]

Graded Potential

Published on 2012-03-04 09:49:00

Transient changes in the membrane potential from its resting level produce electrical signals. Such changes are the most important way that nerve cells process and transmit information. These signals occur in two forms: graded potentials and action potentials. Graded potentials are important in signaling over short distances; thus, the changes in membrane potential are confined to a relatively small region of the plasma membrane. They are usually produced by some specific change in the cell's en [..]

Receptor (Biology)

Published on 2012-03-02 10:43:00

In biology, a receptor is a specialized cell which makes close contact with sensory neurons. It responds to internal or external stimuli and sends nervous signals to these sensitive neurons, which in turn send nervous impulses to the animal's central nervous system. Receptors may be single cells or group of cells (sense organs).

Respiration in Insects

Published on 2012-03-01 12:11:00

Insects and most other land arthropods transport oxygen and carbon dioxide by means of tiny hollow tubes called tracheae, which open to the air by spiracles. The amount of air flowing into the tracheae is regulated in many insects by spiracular valves. Tracheae branch and rebranch, becoming smaller and smaller, finally ending in tracheoles; in many cases the tracheoles end within the cells that they supply. Diffusion accounts for most of the gas exchange. However, diffusion is a slow process and [..]

Resting Membrane Potential

Published on 2012-02-29 13:11:00

All cells under resting conditions have a potential difference across their plasma membranes with the inside of the cell negatively charged with respect to the outside. This potential is the resting membrane potential. By convention, extracellular fluid is assigned a voltage of zero, and the polarity (positive or negative) of the membrane potential is stated in terms of the sign of the excess charge on the inside of the cell. For example, if the intracellular fluid has an excess of negative char [..]

Neural Growth and Regeneration

Published on 2012-02-28 09:31:00

The elaborate networks of nerve cell processes that characterize the nervous system are remarkably similar in all human beings and depend upon the outgrowth of specific axons to specific targets. Development of the nervous system in the embryo begins with a series of divisions of undifferentiated precursor cells (stem cells) that can develop into neurons or glia. After the last cell division, each neuronal daughter cell differentiates, migrates to its final location, and sends out processes that [..]

Functional Classes of Neurons

Published on 2012-02-27 11:10:00

Neurons can be divided into three functional classes: afferent neurons, efferent neurons, and interneurons. Afferent neurons convey information from the tissues and organs of the body into the central nervous system. Efferent neurons convey information from the central nervous system out to effector cells (particularly muscle or gland cells or other neurons); the cell bodies and dendrites of efferent neurons are within the central nervous system, but the axons extend out into the periphery. Inte [..]

Procedural Memory

Published on 2012-02-26 09:13:00

Procedural memory can be thought of as the memory of how to do things. In other words, it is the memory for skilled behaviors independent of any conscious understanding, as for example, riding a bicycle. Individuals can suffer severe deficits in declarative memory but have intact procedural memory. One case study describes a pianist who learned a new piece to accompany a singer at a concert but had no recollection the following morning of having performed the composition. He could remember how t [..]

Declarative Memory

Published on 2012-02-25 09:30:00

Declarative memory is the retention and recall of conscious experiences that therefore can be put into words (declared). One example is the memory of having perceived an object or event and, therefore, recognizing it as familiar and maybe even knowing the specific time and place when the memory was instigated. A second example would be one’s general knowledge of the world such as names and facts. The hippocampus, amygdala, and diencephalon—all parts of the limbic system—are required for th [..]

Learning and Memory

Published on 2012-02-24 10:08:00

Learning is the acquisition of information and/or the internalization of a course of action in order to obtain the desired result or objective. Learning is a consequence of experience. It is measured by an increase in the likelihood of a particular behavioral response to a stimulus. Generally, rewards or punishments, as mentioned earlier, are crucial ingredients of learning, as are contact with and manipulation of the environment. Memory is the relatively permanent storage form of the learned in [..]

Cerebral Dominance and Language

Published on 2012-02-23 09:43:00

Although the two cerebral hemispheres appear to be nearly symmetrical, the left hemisphere has a dominance over the right in 90% of people with regard to language comprehension and motor production (Wernicke's and Broca's areas respectively), with each having anatomical, chemical, and functional specializations. Since the left cerebral hemisphere is highly specialized in language understanding, it is the side of the brain where the values or moral codes of a given culture is deeply internalized; [..]

Altered States of Consciousness

Published on 2012-02-22 09:38:00

States of consciousness may be different from the commonly experienced wakefulness, drowsiness, and so on. Other, more bizarre situations, such as those occurring with hypnosis, mind-altering drugs, and certain diseases, are referred to as altered states of consciousness. These altered states are also characteristic of psychiatric illnesses. One of the diseases that induces altered states of consciousness is schizophrenia, a disease in which information is not properly regulated in the brain. Th [..]

Limbic system Dysfunction

Published on 2012-02-21 08:42:00

In 1953, a young man known as H.M. received bilateral removal of the amygdala and large parts of the hippocampus as a treatment for persistent, untreatable epilepsy. Although his epileptic condition was improved after this surgery, he was now afflicted with a specific type of amnesia in which new memories could not be formed due to limbic system dysfunction, which was the result of the surgery. He still had a normal IQ and a normal working memory. He could retain information for minutes as long [..]

Coma

Published on 2012-02-20 15:04:00

The term coma describes a severe decrease in mental function due to structural, physiological, or metabolic impairment of the brain. A person in a coma exhibits a sustained loss of the capacity for arousal even in response to vigorous stimulation. There is no outward behavioral expression of any mental function, the eyes are closed, and sleep–wake cycles disappear. Coma can result from extensive damage to the cerebral cortex, damage to the brainstem arousal mechanisms, interruptions of the con [..]

Criteria for Brain Death

Published on 2012-02-20 09:07:00

Brain death is widely accepted by doctors and lawyers as the criterion for death, despite the viability of other organs. Brain death occurs when the brain no longer functions and has no possibility of functioning again. The problem now becomes practical. How do we know when a person (for example, someone in a coma) is considered brain dead? There is general agreement that the criteria listed below, if met, denote brain death.1) The nature and duration of the coma must be known.a. Known structura [..]

Mood Disorders

Published on 2012-02-19 09:22:00

The mood disorders are pervasive and sustained inner emotions that affect the person’s perception of the world. In addition to being part of the conscious experience of the person, it can be observed by others. In healthy people, moods can be normal, elated, or depressed, and people generally feel that they have some degree of control of their moods. That sense of control is lost, however, in the mood disorders, which include depressive disorders and bipolar disorders. Along with schizophrenia [..]

Selective Attention

Published on 2012-02-18 06:14:00

The term selective attention means the avoidance of distraction by irrelevant stimuli while seeking out and focusing on stimuli that are momentarily important. It is affected by both voluntary and reflex mechanisms. An example of voluntary control of directed attention familiar to students is ignoring distracting events in a busy library while studying there. An example of selective attention occurs with the presentation of a novel stimulus to a relaxed subject showing an alpha EEG pattern. This [..]

Primary Hyposecretion

Published on 2012-02-17 08:46:00

An endocrine gland may be secreting too little hormone because the gland cannot function normally. This is termed primary hyposecretion. Examples of primary hyposecretion include (1) destruction of the adrenal cortex, leading to decreased cortisol secretion, and (2) dietary deficiency of iodine leading to decreased secretion of thyroid hormones. There are many other causes— infections, toxic chemicals, and so on—all having the common denominator of damaging the endocrine gland.In contrast to [..]

Hypersecretion

Published on 2012-02-16 09:25:00

Hypersecretion is an excessive secretion of a hormone by a gland. A hormone can undergo either primary hypersecretion (the gland is secreting too much of the hormone on its own) or secondary hypersecretion (there is excessive stimulation of the gland by its tropic hormone). One of the most common causes of primary or secondary hypersecretion is the presence of a hormone-secreting endocrine-cell tumor. These tumors tend to produce their hormones continually at a high rate, even in the absence of [..]

Hydrogen Bonds

Published on 2012-02-15 08:39:00

The electrical attraction between the hydrogen atom in a polar bond in one molecule and an oxygen or nitrogen atom in a polar bond of another molecule forms a hydrogen bond. This type of bond is very weak, having only about 4 percent of the strength of the polar bonds linking the hydrogen and oxygen within a single water molecule (H2O). Hydrogen bonds are represented in diagrams by dashed or dotted lines to distinguish them from covalent bonds. Hydrogen bonds between and within molecules play an [..]

Free Radicals

Published on 2012-02-14 11:25:00

The electrons that revolve around the nucleus of an atom occupy regions known as orbitals, each of which can be occupied by one or more pairs of electrons, depending on the distance of the orbital from the nucleus. An atom is most stable when each orbital is occupied by its full complement of electrons. An atom containing a single (unpaired) electron in its outermost orbital is known as a free radical, as are molecules containing such atoms. Free radicals can react with other atoms, thereby fill [..]

Chordate Characteristics

Published on 2012-02-13 08:28:00

The chordates are animals which belong to the phylum Chordata. It includes the vertebrates (animals with spinal column) and animals that have notochord, such as tunicates and lancelets. This phylum gets its name from one of its three distinctive features or characteristics. The first one is the notochord; all chordates at some time during their lifetimes possess a flexible supporting rod along the back, called the notocord, which stiffens the animal's body. In most chordates, the notochord is lo [..]

Effects of Peptide hormones

Published on 2012-02-12 10:55:00

Peptide hormones and catecholamine effects are very important as they influence ion channels, enzyme activity, and the cytoplasmic JAK kinases activity. The receptors for peptide hormones and the catecholamine hormones are located on the outer surface of the target cell's plasma membrane. This location is important, since these hormones are too large and hydrophilic to diffuse through the plasma membrane. When activated by hormone binding, the receptors trigger one or more of the signal transduc [..]

Hormone Metabolism and Excretion

Published on 2012-02-11 09:41:00

Once a hormone has acted on the target tissue, the concentration of the hormone in the blood must be restored to normal. This is necessary to prevent excessive, possibly harmful actions of prolonged exposure of target cells to hormones. A hormone’s concentration in the plasma depends upon (1) its rate of secretion by the endocrine gland, and (2) its rate of removal from the blood. Removal, or "clearance," of the hormone occurs either by excretion or by metabolic transformation. The liver and t [..]

Hormone Receptors

Published on 2012-02-10 19:25:00

Because they are transported in the blood, hormones can reach virtually all tissues. Yet the response to a hormone is highly specific, involving only the target cells for that hormone. The ability to respond depends upon the presence on (or in) the target cells of specific receptors for those hormones. The receptors for peptide hormones and catecholamines are proteins located in the plasma membranes of the target cells. In contrast, the receptors for steroid hormones and the thyroid hormones are [..]

Peptide Hormones

Published on 2012-02-09 12:37:00

Most hormones are either peptides or proteins. They range in size from small peptides having only three amino acids to small proteins (some of which are glycoproteins). For convenience, it is sometimes referred to all these hormones as peptide hormones. They are water-soluble hormones which consist of a few amino acids that introduce a series of chemical reactions to change the cell's metabolism. Examples of peptide hormones include hormones of the pituitary gland and parathyroid glands.In many [..]

Lymph Flow Mechanism

Published on 2012-02-08 08:53:00

The lymphatic vessels beyond the lymphatic capillaries propel the lymph within them by their own contractions. The smooth muscle in the wall of the lymphatics exerts a pump-like action by inherent rhythmical contractions. Since the lymphatic vessels have valves similar to those in veins, these contractions produce a one-way flow toward the points at which the lymphatics enter the circulatory system. The lymphatic vessel smooth muscle is responsive to stretch, so when there is no accumulation of [..]

Bilateral Cingulotomy

Published on 2011-07-05 09:12:00

Bilateral cingulotomy is a brain surgical procedure which is used treat obsessive compulsive disorder, depression, and bipolar psychosis. In bilateral cingulotomy the supracallosal fibers of the cingulum bundle, which passes through the anterior cing

Dorsal Longitudinal Fasciculus

Published on 2011-07-04 09:07:00

Situated within the brain stem, the dorsal longitudinal fasciculus is a bundle of fibers which is composed of descending hypothalamic axons and ascending visceral sensory axons. The descending fibers of the dorsal longitudinal fasciculus arises from

Zaslon Radar

Published on 2011-07-03 10:39:00

The Zaslon radar is a multi-mode phased-array radar used on the Russian MiG-31 fighter aircraft. It was designed and developed by the Tikhomirov Scientific Research Institute of Instrument between 1975 and 1980. The Zaslon has the NATO codename Flash

Mass Spectrometry

Published on 2011-07-02 09:56:00

Mass spectrometry (MS) is an analytical technique which is used to determine the mass of ions (or charged particles). The technique has both qualitative and quantitative uses, which include identifying unknown compounds, determining the isotopic comp

Lacrimal Nerve

Published on 2011-07-01 10:22:00

The lacrimal nerve arises from ophthalmic nerve, which in turn originates from trigeminal nerve. It enters the orbit through the superior orbital fissure. As the lacrimal nerve enters the lacrimal gland, it gives off several filaments, supplying sens

Inferior Cervical Ganglion

Published on 2011-06-30 10:12:00

The inferior cervical ganglion is a group of bipolar neurons located behind the first part of subclavian artery, between the base of the transverse process of the last cervical vertebra and the neck of the first rib. It is frequently fused with the f

Spiral Ganglion

Published on 2011-06-29 12:46:00

The spiral ganglion is a ganglion made up of nerve cell bodies and is located in the modiolus of the cochlea. The neurons of the spiral ganglion are bipolar cells which sends axons to form the cochlear nerve which carries sensory acoustic information

Medial Longitudinal Fasciculus

Published on 2011-06-29 08:06:00

The medial longitudinal fasciculus is either of a pair of bundles of fibers that stretches along the brainstem, from the upper border of the mesencephalon to the cervical segments of the spinal cord. The medial longitudinal fasciculus consists of fib

Supraorbital Nerve

Published on 2011-06-28 09:59:00

The supraorbital nerve is a continuation of the frontal nerve, which arises from ophthalmic nerve. With a sensory distribution, it gives off the lateral and medial branches. The supraorbital nerve leaves orbit through supraorbital notch, and supplies

Nasociliary Nerve

Published on 2011-06-27 10:00:00

The nasociliary nerve branches off the ophthalmic nerve, which in turn originates from trigeminal. It is a sensory nerve that divides into the long ciliary, posterior ethmoidal, anterior ethmoidal, and infratrochlear nerves, and a communicating branc

Cardiac Plexus

Published on 2011-06-26 11:01:00

The cardiac plexus is the plexus of nerves located around the base of the heart, chiefly in the epicardium, formed by cardiac branches from the vagus nerves and the sympathetic trunks and ganglia. The cardiac plexus is divided into a superficial part

Endoscopic Brain Surgery (Endonasal)

Published on 2011-06-25 10:12:00

Endoscopic brain surgery is a minimally invasive procedure which involves using narrow endoscopes and surgical tools (often developed by the surgeons themselves) inserted through the nasal passage to remove tumors as large as baseballs. In endoscopic

Frontal Nerve

Published on 2011-06-24 19:11:00

The frontal nerve originates from ophthalmic branch of trigeminal nerve. It enters the orbit through the superior orbital fissure, providing sensory innervations for the skin of the forehead and scalp. Between the apex and base of the orbit, the fron

Supratrochlear Nerve

Published on 2011-06-24 09:17:00

The supratrochlear nerve is a sensory nerve which arises from the frontal nerve, which in turn is a branch of ophthalmic nerve. It leaves orbit at medial end of supraorbital margin and passes above the pulley of the superior oblique muscle, giving of

Inferior Cardiac Nerve

Published on 2011-06-23 10:11:00

Also called the cardiacus minor, the inferior cardiac nerve originates from either the inferior cervical ganglion or the first thoracic ganglion. It travels down along the front of the trachea and behind the subclavian artery to join the deep part of

Recurrent Laryngeal Nerve

Published on 2011-06-22 09:59:00

The recurrent laryngeal nerve is a branch of the vagus nerve (CN X). Running within the endoneurium, it innervates the laryngeal muscles in the neck and pick up sensory information from the larynx, which is where vocal cords are. The recurrent laryng

Anterior Vagal Trunk

Published on 2011-06-21 08:49:00

The anterior vagal trunk is a branch of the left vagus nerve (CN X) which innervates the ventral surface of the stomach. Although it is composed mainly of fibers from the left vagus, it also contains a few fibers from the right vagus. The anterior va

Great Auricular Nerve

Published on 2011-06-20 09:38:00

The great auricular nerve is a nerve arises from cervical plexus, which is made up of fibers from the second and third cervical nerves (C2, C3). It provides sensory innervation to the skin of the external ear, the adjacent portion of the scalp, cheek

Cochlear Nerve

Published on 2011-06-19 13:32:00

The cochlear nerve is one of the two branches of the vestibulocochlear nerve (CN VIII), the other being the vestibular nerve. It transmits information about hearing. The cochlear nerve consists of axons that arise from the bipolar cells in the spiral

Vestibular Nerve

Published on 2011-06-18 10:22:00

The vestibular nerve is one of the two branches of the Vestibulocochlear nerve. It is made up of axons of bipolar cells in the vestibular ganglion, ganglion of Scarpa, which is located in the upper part of the outer end of the internal auditory meatu

Trigeminal Ganglion

Published on 2011-06-17 09:48:00

Trigeminal ganglion is a flattened ganglion on the sensory root of the fifth cranial nerve (CN V: trigeminal nerve). It is located in a cleft in the dura mater on the anterior surface of the petrous part of the temporal bone, giving off the ophthalmi

Mandibular Nerve

Published on 2011-06-16 12:28:00

The mandibular nerve is one of the three branches of the trigeminal nerve (CN V). Composed of both sensory and motor fibers, the mandibular nerve supplies sensory fibers to the lower jaw, the floor of the mouth, the anterior two-thirds of the tongue,

Hertzsprung–Russell Diagram

Published on 2011-06-15 18:14:00

The Hertzsprung–Russell diagram is a stars scatter graph that shows the relationship between the stars' absolute magnitudes or luminosities versus their spectral types and effective temperatures. Hertzprung-Russell diagrams are not pictures or maps

Maxillary Nerve

Published on 2011-06-15 09:32:00

The maxillary nerve is one of the three major branches of cranial nerve V (CN V), or trigeminal nerve. It is composed of sensory fibers, carrying sensory information from the upper jaw (maxillary) and its teeth, the mucous membranes of the palate, na

Ophthalmic Nerve

Published on 2011-06-14 10:14:00

The ophthalmic nerve is composed of sensory fibers. It is one of the three branches of Cranial Nerve V (trigeminal nerve). The ophthalmic nerve travels through the wall of the cavernous sinus, entering the orbit via the superior orbital fissure. Once

Superior Colliculus

Published on 2011-06-13 10:34:00

The superior colliculus is a paired structure that forms a rostral lump on each side of the dorsal part of the midbrain. It is a highly layered structure which functions as a visual, motor, and sensory reflex center. The two superior colliculi sit be

SU Radar

Published on 2011-06-12 09:49:00

The SU was a World War II vintage surface search radar and was fitted aboard PRESTONIAN class frigates. Known for its good surface clutter rejection, it also had an A-scan for use as a gunnery spotting radar for the 4" gun and the maximum range mark

AN/SPS-6C

Published on 2011-06-11 16:14:00

The AN/SPS-6C was a shipborne, long range, air and surface search radar, which was designed to supply target bearing and range data to its 5-inch A-scope indicator. In addition, as many as four, external, PPI indicators of the Radar Indicating Equipm

AN SPQ-2D

Published on 2011-06-10 08:44:00

The AN/SPQ-2D was a surface search radar that could transmit both short and long pulses at the same time. It was designed and manufactured by the Italian firm Signalamento Marittemo eo Aero of Florence Italy. The AN/SPQ-2D alternated the long and sho

Confocal Microscopy

Published on 2011-06-09 07:40:00

Confocal microscopy is an optical imaging technique which is used to increase optical resolution and contrast of a micrograph by using point illumination and a spatial pinhole to eliminate out-of-focus light in specimens that are thicker than the foc

Periodic Table: New Elements Added

Published on 2011-06-08 22:35:00

NEW YORK — Two new elements have been added to the periodic table. The elements were recognized by an international committee of chemists and physicists. They're called elements 114 and 116 for now — permanent names and symbols will be chosen lat

P-70 Lena-M Radar

Published on 2011-06-08 09:02:00

The P-70, known as "Lena-M", was a static 2D very high frequency radar developed and used by the former Soviet Union. The P-70 radar was designed as a static structure mounted on a two story building which housed the radar and power supply equipment

Polarimetric Radar

Published on 2011-06-07 10:59:00

A polarimetric radar, also called dual-polarization radar, transmits radio wave pulses that have both horizontal and vertical orientations. The horizontal pulses essentially give a measure of the horizontal dimension of cloud and precipitation (snow,

Puyehue Volcano

Published on 2011-06-06 20:48:00

Puyehue is a volcanic complex composed of two coalesced vents which make up a major mountain massif in the Andes, in Puyehue National Park of Ranco Province, Chile. The volcanic complex has shaped the local landscape and produced a huge variety of vo

Kasta 2E-1

Published on 2011-06-06 10:20:00

The Kasta 2E-1 is a Russian, UHF band acquisition, surveillance radar which was designed to detect fixed-wing aircraft, helicopters, and cruise missiles. The Kasta 2E-1 is a mobile solid-state lowaltitude radar which consists of an electronic equipme

Dagger Radar

Published on 2011-06-05 09:07:00

The Dagger is a target acquisition and surveillance radar which operates in J-Band, with scan rate of 60 or 30 rpm. Manufactured by Alenia Marconi Systems, the Dagger is also a multi-beam high resolution 3D radar, which means it provides three-dimens

Synthetic Aperture Radar

Published on 2011-06-04 09:26:00

Synthetic aperture radar (SAR) uses the relative motion between an antenna and its target region to provide distinctive long-term coherent-signal variations which are exploited to obtain finer spatial resolution than is possible with conventional bea

Pulse Repetition Frequency

Published on 2011-06-03 09:27:00

Pulse repetition frequency (PRF) is the number of pulses per second in a system transmission. Pulse repetition frequency should not be confused with transmission frequency, which is determined by the rate at which cycles are repeated within the trans

Magnetron

Published on 2011-06-02 11:11:00

The magnetron is a high-powered vacuum tube which generates microwaves using the interaction of a stream of electrons with a magnetic field. A cavity magnetron is composed of a hot cathode with a high continuous or pulsed negative potential by a high

Sampson Multifunction Radar

Published on 2011-06-02 08:56:00

The Sampson is an active phased array radar developed by BAE Systems Integrated System Technologies. The Sampson is a multifunction S-band radar which operates in the 2-4 GHz frequency. The Sampson radar is capable of simultaneously detect and track

ARTHUR Radar

Published on 2011-06-01 10:40:00

The ARTHUR is a field artillery acquisition radar, which was developed by Ericsson for the primary role as the core element of a brigade or division level counter battery sensor system. The ARTHUR is capable of detecting hostile artillery by tracking

WSR-88D

Published on 2011-05-31 12:57:00

The WSR-88D (Weather Surveilance Radar - 88 Doppler) is a doppler weather radar developed by the NEXRAD program, which is a joint effort between the Dept. of Commerce, Dept. of Defense, and Dept. of Transportation. The WSR-88D operates in two basic m

AN/MPN-11

Published on 2011-05-30 11:12:00

The AN/MPN-11 was a mobile Ground-controlled approach radar. It was a mobile trailer-mounted version of the AN/CPN-4 GCA unit (CPN stands for Cargo-transportable Radar Navigation). The AN/MPN-11 contained newer, more powerful radars, better radios in

Superior Mesenteric Artery

Published on 2011-05-29 14:09:00

The superior mesenteric artery originates at the anterior surface of the abdominal aorta, supplying oxygenated blood to the intestine from the lower part of the duodenum through two-thirds of the transverse colon, and the pancreas to the left colic f

Splenic Artery

Published on 2011-05-29 10:27:00

The splenic artery is an artery which arises from the celiac trunk and supplies oxygen-rich blood to the spleen, running superior to the pancreas. Along its course, before reaching the spleen, the splenic artery gives off branches to the stomach, pan

Femoral Artery Aneurysm

Published on 2011-05-28 13:01:00

A femoral artery aneurysm is a bulging or ballooning of the femoral artery due to a weakness in the walls of the artery. The femoral artery is located in the groin region, arising from the external iliac artery; and an aneurysm is a localized, blood-

Superficial Femoral Artery

Published on 2011-05-24 15:55:00

The superficial femoral artery is one of the two main branches of the common femoral artery. It travels down parallel to the femur, supplying the thigh muscles. The superficial femoral artery connects to the popliteal artery at the opening of adducto

Deep Femoral Artery

Published on 2011-05-20 10:51:00

The deep femoral artery is a branch of the femoral artery which runs posteriorly (more deeply) down the thigh, closer to the femur than the rest of the femoral artery. Also known as the profunda femoris artery, the deep femoral artery comes off the f

Internal Iliac Artery (Hypogastric)

Published on 2011-05-19 10:04:00

Also known as hypogastric artery, the internal iliac artery is a short and thick blood vessel which originates at the bifurcation of the common iliac, opposite the lumbosacral articulation, and, passing downward to the upper margin of the greater sci

External Iliac Artery

Published on 2011-05-18 08:46:00

The external iliac artery is a large blood vessel which originates from the bifurcation of the common iliac artery. Then the external iliac runs down obliquely outwards, giving off two branches along its way: the inferior epigastric artery and the de

Femoral Artery

Published on 2011-05-17 13:52:00

The femoral artery is a large blood vessel of the thigh, supplying oxygen-rich blood to the thigh. It arises from the external iliac artery which comes off from the common iliac artery, and this in turn from the abdominal aorta. Passing fairly close

Common Iliac Artery

Published on 2011-05-17 09:19:00

The common iliac artery is either of two large arteries which arises from the end of the abdominal aorta, being a bifurcation of this blood vessel. Supplying oxygenated blood to the pelvis, the common iliac arteries run obliquely towards the sides, t

Celiac Artery

Published on 2011-05-16 10:48:00

Also known as the celiac trunk, the celiac artery is a blood vessel which branches off the abdominal aorta, anterior to the T12 vertebra, and then travels to the left. The celiac artery supplies oxygenated blood to the liver, stomach, abdominal esoph

Pericardial Arteries

Published on 2011-05-16 08:28:00

The pericardial arteries are small blood vessels which arise from the thoracic aorta. They supply oxygenated blood to the dorsal surface of the pericardium. The pericardial arteries are paired branches.

Superior Phrenic Arteries

Published on 2011-05-16 07:31:00

The superior phrenic arteries are blood vessels that arise from the lower part of the thoracic aorta and supply the diaphragm. They are distributed to the posterior part of the upper surface of the diaphragm, and anastomose with the musculophrenic an

Juxtaglomerular Apparatus

Published on 2011-05-15 09:18:00

The juxtaglomerular apparatus is an anatomical unit located between the vascular pole of the renal corpuscle and the returning distal convoluted tubule of the same nephron. Named for its proximity to the glomerulus, the juxtaglomerular apparatus is a

Renal Artery Stenosis

Published on 2011-05-14 11:28:00

Renal artery stenosis is the narrowing of one of the arteries that supply oxygen-rich blood to the kidneys. Since this constriction of the renal artery can hinder the blood flow that target the kidney, renal artery stenosis may result in hypertension

Bronchial Arteries

Published on 2011-05-14 08:50:00

Arising directly from the aorta, the bronchial arteries supply the lungs with oxygenated blood. There are usually two bronchial arteries which travel to the left lung, and one to the right lung as they ramify with the bronchial tree in relation to th

Abdominal Aortic Aneurysm

Published on 2011-05-13 20:24:00

Abdominal aortic aneurysm is the ballooning of the aorta artery in its last section in the abdomen. Originating in the left ventricle of the heart, the aorta is a major blood vessel which supply the body with oxygen-rich blood. In abdominal aortic an

Esophageal Arteries

Published on 2011-05-13 13:36:00

Esophageal arteries are a group of arteries which carry oxygen-rich blood from the aorta, supplying the esophagus. They come off from different sources, which in turn have their origin in the aorta artery. 1) The four esophageal arteries which arise

Abdominal Aorta

Published on 2011-05-11 09:08:00

Beginning at the level of the diaphragm, the abdominal aorta is a the third and final section of the aorta artery, which is the largest blood vessel of the body. It is a direct continuation of the thoracic aorta, running down the posterior wall of th

Right Common Carotid Artery

Published on 2011-05-10 10:50:00

The right common carotid artery originates from the brachiocephalic trunk, which in turn arises from the arch of the aorta. Running upward into the right side of the neck, it divides into the external and internal carotid arteries. The right common c

Right Subclavian Artery

Published on 2011-05-10 07:30:00

The right subclavian artery is one of the two branches into which the brachiocephalic artery divides, the other being the right common carotid artery. Extending from the brachiocephalic artery to the right side of the body, the right subclavian arter

Left Subclavian Artery

Published on 2011-05-09 19:35:00

The left subclavian artery is an oxygen-rich blood vessel which branches off the aortic arch of the aorta, beside the left common carotid artery, supplying the left arm, spinal cord, ear, and brain. To facilitate the description, the left subclavian

Aortic Arch Syndrome

Published on 2011-05-09 12:23:00

Aortic arch syndrome is a group of signs and symptoms which are caused by structural abnormalities in the blood vessels that branch off the arch of the aorta, which is the top portion of this main artery carrying blood away from the heart. The three

Left Common Carotid Artery

Published on 2011-05-09 10:19:00

Springing directly from the aorta, the left common carotid artery arises from the highest part of the aortic arch, between the brachiocephalic artery and the left subclavian artery. The left common carotid artery has a substantial presence in the tho

Thoracic Aorta

Published on 2011-05-09 08:24:00

Contained in the posterior mediastinal cavity, the thoracic aorta is the section of the aorta artery which begins right after the aortic arch and descends to the diaphragm, which is the muscle that separates the chest from the abdomen. At the startin

Brachiocephalic Artery

Published on 2011-05-07 13:42:00

The brachiocephalic artery is a short branch that comes off the aortic arch of the aorta. It goes obliquely upward to the right, to a point near the junction of the sternum (breast bone) and the right clavicle (collarbone); then it goes slightly back

Coarctation of the Aorta

Published on 2011-05-07 09:56:00

Coarctation of the aorta is a constriction of the aorta artery due to a congenital defect, preventing the free flow of blood and sometimes causing the heart to abnormally enlarge. The aorta is the main blood vessel that carries oxygen-rich blood from

Aorta Artery

Published on 2011-05-06 17:42:00

The aorta is the major blood vessel of the human body. It is an artery which carries oxygenated blood from the heart to the rest of the body. The walls of the aorta are composed of three layers of connective tissue and elastic fibers. These layers ar

Descending Aorta

Published on 2011-05-06 12:14:00

The descending aorta is the part of the aorta which begins at the aortic arch and then runs down through the chest and abdomen. The descending aorta extends to a point in the lower abdomen where it splits into the common iliac arteries which supply t

Ascending Aorta

Published on 2011-05-06 09:42:00

The ascending aorta is the first part of the aorta artery. Beginning at the aortic annulus, it arises from the heart left ventricle and extends to the aortic arch, which is the second part. The ascending aorta gives off two branches: the right and le

1974 Tornado Outbreak

Published on 2011-05-05 13:37:00

The 1974 tornado outbreak was a large number of tornadoes that broke out in the central States, USA, on April 3-4, 1974. During a 16-hour period, 148 tornadoes occurred from Illinois and Indiana into Michigan and Ohio southward through the Tennessee

Aortic Arch

Published on 2011-05-05 11:18:00

The aortic arch is the part of the aorta artery which forms a bend or curve as it ascends, turns back and then down, forming an inverted U. The aortic arch lies within the mediastinum, which is the central compartment of the thoracic cavity. Being th

Hypereosinophilic Syndrome

Published on 2011-05-04 10:31:00

Hypereosinophilic syndrome (HES) is a rare blood disease in which the body produces too many of a particular type of leukocyte (white blood cell) called eosinophils. Eosinophils normally help the body fight allergies and certain types of infections.

Atrioventricular Block

Published on 2011-05-03 13:16:00

An atrioventricular block (AV block) is the impairment, or delay, of the electrical conduction between the atria and ventricles of the heart. Strong vagal stimulation may produce atrioventricular block. The cholinergic receptor types affected are the

Heart Block

Published on 2011-05-03 08:48:00

A heart block is a condition in which the electrical system of the heart is impaired as the electrical signal cannot travel down through the special pathways. In a heart block, the electrical impulses that cause the heart to beat are delayed. Heart b

Kearns-Sayre Syndrome

Published on 2011-05-02 13:01:00

Kearns–Sayre syndrome (KSS) is a rare neuromuscular disease with onset usually before 20 years of age. Kearns–Sayre syndrome occurs spontaneously in the majority of cases. In some cases it has been shown to be inherited through mitochondrial, aut

Myxomatous Degeneration

Published on 2011-05-01 20:42:00

Myxomatous degeneration is a pathological weakening of connective tissue. Since it occurs in conjunction with an accumulation of dermatan sulfate, a glycosaminoglycan, within the connective tissue matrix of the mitral valve, myxomatous degeneration i

Marfan Syndrome

Published on 2011-05-01 13:22:00

Marfan syndrome is a genetic condition that affects the connective tissue. In the Marfan syndrome, the chemical structure of the connective tissue is abnormally altered, and as a consequence many of these structures are not as stiff as they should be

Mitochondrial Diseases

Published on 2011-04-30 13:40:00

Mitochondrial diseases are a group of disorders caused by damage to cell mitochondria, which are small structures or organelles located in human cells. Mitochondrial diseases result from failures of the mitochondria to convert food to energy. The res

Myasthenia Gravis

Published on 2011-04-30 09:28:00

Myasthenia gravis is a neuromuscular disease which affects the muscles and the nerves that control them. It is characterized by weakness and fatigability of skeletal muscles. Myasthenia gravis is an autoimmune disorder in which immune cells, which no

Cardiac Skeleton

Published on 2011-04-29 12:32:00

The cardiac skeleton is the structure of dense connective tissue in the heart which electrically isolates the atria from the ventricles, forming four fibrous rings that surround the ostia of the valves, a right and left fibrous trigone, formed by con

Acute Cardiogenic Pulmonary Edema

Published on 2011-04-29 08:55:00

Acute cardiogenic pulmonary edema results from an acute left ventricular insufficiency, itself resulting from systolic or diastolic dysfunction, with myocardial infarction being the main etiology. Treatment is based on oxygen, diuretics and nitrates.

Left Ventricular Noncompaction Cardiomyopathy

Published on 2011-04-28 17:35:00

Left ventricular noncompaction cardiomyopathy is a heart condition in which the muscular wall of the left ventricle appears to be spongy and non-compacted, consisting of a meshwork of numerous muscle bands called trabeculations. Left ventricular non-

Fibrous Rings of the Heart

Published on 2011-04-28 10:59:00

The fibrous rings of the heart (anulus fibrosus cordis) are the dense fibrous rings of connective tissue which surround the right and left atrioventricular (tricuspid and mitral) orifices and arterial (aortic and pulmonary) orifices to which are atta

Diabetic Cardiomyopathy

Published on 2011-04-28 08:56:00

Diabetic cardiomyopathy is a disease process which affects the myocardium (heart muscle) in diabetic patients, causing a wide range of structural abnormalities and eventually leading to left ventricular hypertrophy and diastolic and systolic dysfunct

Ventricular Tachycardia

Published on 2011-04-27 09:48:00

Ventricular tachycardia is a frequent, post-infarction and perioperative arrhythmia with a fast heart beat that starts in one of the ventricles of the heart. There is a ventricular tachycardia when the pulse rate is more than 100 beats per minute, wi

Endocardial Resection

Published on 2011-04-27 07:22:00

Endocardial resection procedure (ERP) is a surgical removal of a portion of left ventricular endocardium and underlying myocardium containing an arrhythmogenic area from the base of an aneurysm or infarction in order to relieve ventricular tachycardi

Noncompaction Cardiomyopathy

Published on 2011-04-26 13:47:00

Noncompaction cardiomyopathy (NCC) is a congenital cardiomyopathy which is characterized by a spongy structure of the heart muscle (myocardium), which is the reason it is also called spongiform cardiomyopathy. This condition affects both children and

Cardiomyopathy

Published on 2011-04-26 10:45:00

Cardiomyopathy is a disease of the myocardium (heart muscle), making it larger, thicker, and more rigid than normal, and in rare cases, scar tissue replaces the muscle tissue. In a cardiomyopathy, the heart loses its capacity of pumping blood efficie

Plasmapheresis

Published on 2011-04-26 09:27:00

Also known as therapeutic plasma exchange, plasmapheresis is a blood purification procedure used to treat several autoimmune diseases. It is the removal of plasma from withdrawn blood, with retransfusion of the formed elements into the donor; general

Mitochondrial Myopathy

Published on 2011-04-25 13:11:00

Mitochondrial myopathy is neuromuscular disease which is caused by damage to the mitochondrion of the cell, which is an energy-producing cell organelle (structure), serving as a power plant within the cell. Since both nerve cells in the brain and mus

Endomyocardial Fibrosis

Published on 2011-04-23 16:53:00

Endomyocardial fibrosis (EMF) is a heart condition which is characterized by fibrosis and thickening of the apical endocardium of the right and left ventricles. The clinical manifestations are largely related to the consequences of restrictive ventri

Loeffler Endocarditis

Published on 2011-04-23 12:05:00

Loeffler endocarditis is a restricive cardiomyopathy which is characterized by fibrous thickening of the endocardium, leading to apical obliteration and restrictive cardiomyopathy, resulting in heart failure, thromboembolic events, or atrial fibrilla

Endocardial Cushion Defect

Published on 2011-04-23 09:11:00

Endocardial cushion defect (ECD) is a congenital heart disease in which the walls that separates the atria and ventricles (heart chambers) are poorly formed or absent. Essentially, the middle part of the heart is missing. Endocardial cushion defect o

Endocardial Fibroelastosis

Published on 2011-04-22 21:28:00

Endocardial fibroelastosis (EFE) is a congenital heart disease which is characterized by thickening of the inner lining of the left ventricle, thickening and malformation of the cardiac valves, and hypertrophy of the heart. Put in another words, endo

Myocardial Necrosis

Published on 2011-04-22 20:52:00

Myocardial necrosis is a focal or massive and subsequent scarring and tissue death in the myocardium (heart muscle). It is caused by deficient or total lack of blood supply to the heart muscle, and by infection, such as Histophilus somni, the encepha

Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)

Published on 2011-04-22 09:58:00

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a type of nonischemic cardiomyopathy that involves primarily the right ventricle. It is characterized by hypokinetic areas involving the free wall of the right ventricle, with fibrofatty repla

Restrictive Cardiomyopathy

Published on 2011-04-21 15:32:00

Restrictive cardiomyopathy (RCM) is a heart condition in which the walls of the ventricles stiffen and lose their flexibility due to infiltration by abnormal tissue. As a result, the heart cannot fill adequately with blood and eventually loses its ab

Nonischemic Cardiomyopathy

Published on 2011-04-21 09:21:00

Nonischemic cardiomyopathy is damage to the myocardium (heart muscle) which is not associated with interruption to the heart's blood supply. In ischemic cardiomyopathy, the heart muscle is damaged because there is a restriction or interruption of oxy

Tricuspid Regurgitation

Published on 2011-04-20 21:38:00

Also known as tricuspid insufficiency, tricuspid regurgitation is a heart condition in which the tricuspid valve does not close properly during systole (heart contraction), causing blood to flow backward (leak) into the right atrium when the right ve

Basilar Artery Angioplasty

Published on 2011-04-20 13:48:00

Basilar artery angioplasty is a mechanical procedure to treat basilar artery stenosis (narrowing of the artery). The basilar artery is an important artery in the brain as it brings blood to some of its most critical parts such as the the breathing ce

Renal Artery Angioplasty

Published on 2011-04-20 12:32:00

Renal artery angioplasty (percutaneous transluminal renal angioplasty, PTRA) is used to treat atherosclerotic obstruction of the renal artery. Renal artery stenosis can lead to hypertension and loss of renal function. Percutaneous transluminal angiop

Implantable Cardioverter Defibrillator

Published on 2011-04-20 08:18:00

An implantable cardioverter defibrillator (ICD) is a small battery-powered device which is implanted in the patient's chest, when he is at risk of sudden cardiac arrest due to ventricular fibrillation. When an implantable cardioverter defibrillator d

Dilated Cardiomyopathy

Published on 2011-04-19 16:46:00

Dilated cardiomyopathy is a the enlargement of the myocardium, rendering the heart unable to pump blood efficiently. Over time, the decreased heart function can affect the lungs, liver, and other body systems. In dilated cardiomyopathy, it is the hea

Tricuspid Valve Repair (Video)

Published on 2011-04-19 12:52:00

Tricuspid valve repair is done when a tricuspid valve leaflet is floppy and prolapses. The tricuspid valve repair procedure involves surgically separating, cutting out a section, or pleating a valve leaflet. When the tricuspid valve does not function

Tricuspid Valve Stenosis

Published on 2011-04-19 09:21:00

Tricuspid valve stenosis is an abnormal narrowing of the opening in the valve. When this occurs, there is an increased resistance to blood flow through the valve. Situated between the right atrium and the right ventricle of the heart, the tricuspid v

Hypertrophic Cardiomyopathy

Published on 2011-04-18 17:37:00

Hypertrophic cardiomyopathy is a heart condition in which a portion of the myocardium is abnormally enlarged without any obvious cause. This hypertrophy of the heart muscle makes it harder for the heart to pump blood into the arteries. Hypertrophic c

Epinephrine

Published on 2011-04-18 15:09:00

Also called adrenaline, epinephrine is a hormone produced by the adrenal medulla and released into the bloodstream in response to physical or mental stress, as from fear or injury. Epinephrine initiates many bodily responses, including the stimulatio

Cardiogenic Shock

Published on 2011-04-18 13:29:00

Cardiogenic shock is the inability of the heart to pump enough blood to the organs of the body due to damage to the heart muscle, most often from a large myocardial infarction. Other causes of cardiogenic shock include cardiomyopathy, cardiac valve p

Ventricular Fibrillation

Published on 2011-04-18 10:38:00

Ventricular fibrillation is the chaotic asynchronous contraction of the ventricular myocardium (heart muscle). To put it in other words, it is a turbulent, disorganized electrical activity of the heart that makes the myocardium quivers rather than co

Pericardial Cavity

Published on 2011-04-17 08:55:00

The pericardial cavity is the space between the visceral pericardium and the parietal pericardium. This cavity is filled with pericardial fluid which serves as a shock absorber by reducing friction between the pericardial membranes. The pericardium i

Cor Pulmonale

Published on 2011-04-16 19:31:00

Cor pulmonale is a heart condition in which the right ventricle cannot pump blood to the lungs due to hypertrophy (enlargement) of the right side caused by prolonged high blood pressure in the pulmonary arteries. This incapability of the right ventri

Angioplasty

Published on 2011-04-16 17:29:00

Angioplasty is a mechanical procedure to open arteries or veins, which have become extremely narrowed or blocked as a result of atherosclerosis. To perform an angioplasty an deflated balloon on a guide wire, known as a balloon catheter, is passed int

Mitral Valve Replacement (Video)

Published on 2011-04-16 15:39:00

Mitral valve replacement is a surgical procedure in which a heart mitral valve is replaced by a mechanical or a biological tissue valve. Mitral valve replacement is typically performed robotically or manually, when the valve becomes too tight (mitral

Alcoholic Cardiomyopathy

Published on 2011-04-16 12:45:00

Alcoholic cardiomyopathy is a heart condition in which excessive, habitual use of alcohol weakens the myocardium, leading to heart failure; blood cannot be pumped efficiently, and this in turn affects the lungs, liver, brain, and other body systems.

Transcatheter Pulmonary Valve Replacement

Published on 2011-04-16 07:37:00

Transcatheter pulmonary valve replacement is a minimally invasive procedure, which involves the implantation of the first-ever catheter-based pulmonary valve, is currently performed by interventional cardiologists at Morgan Stanley Children's Hospita

Pulmonary Valve Stenosis

Published on 2011-04-15 10:38:00

Pulmonary valve stenosis is a heart condition that affects the pulmonary valve, which can not open wide enough due to narrowing. As a result, less deoxygenated blood flows from right ventricle to the pulmonary artery and to the lungs. While the most

Heart Valve Dysplasia

Published on 2011-04-15 08:32:00

Heart valve dysplasia is a congenital heart defect which affects the aortic, pulmonary, mitral, and tricuspid heart valves. Heart valve dysplasia is an error in the development of any of the heart valves, and a common cause of congenital heart defect

Myocardial Infarction

Published on 2011-04-14 09:27:00

Myocardial infarction (MI) is the the irreversible necrosis of the myocardium (heart muscle) due to interruption of blood supply to the heart. This condition results from an imbalance of oxygen supply and demand. Also known as heart attack, myocardia

Aortic Dissection

Published on 2011-04-13 20:58:00

Aortic dissection is a life-threatening condition in which the innermost layer of the aorta artery wall splits open (dissects), causing blood to flow in between the layers of the aorta wall. If the blood bursts through all three layers of the aorta a

Percutaneous Coronary Angioplasty

Published on 2011-04-13 12:35:00

Percutaneous coronary angioplasty is a therapeutic procedure to open a narrowed or blocked artery which supply blood to the heart. Percutaneous coronary angioplasty is used when the buildup of plaque which blocks the flow of blood in an artery wall o

Ischemic Cardiomyopathy

Published on 2011-04-13 08:36:00

Ischemic cardiomyopathy is a weakness of the myocardium (heart muscle) due to inadequate oxygen delivery to the myocardium with coronary artery disease being the most common cause. Not supported by current cardiomyopathies classification schemes. "Is

Mitral Valve Clip Repair (Surgery)

Published on 2011-04-12 13:16:00

Mitral valve repair is a surgical procedure to repair a defective heart mitral valve. The techniques of mitral valve repair include inserting a cloth-covered ring around the valve to bring the leaflets into contact with each other (annuloplasty), rem

Heart Valvular Disease (Video)

Published on 2011-04-12 08:53:00

Valvular disease is a condition in which the valves of the heart do not function properly due to damage or a defect in one, two or all four heart valves, which are the tricuspid, pulmonary, mitral, and aortic. The former two are situated on the right

Aortic Annulus

Published on 2011-04-11 21:02:00

The aortic annulus is a fibrous ring of the heart surrounding the aortic orifice. It serves for the attachment of the aorta artery, which a major vessel carrying oxygenated blood from the heart to the body. Accurate preoperative assessment of the aor

Annuloaortic Ectasia

Published on 2011-04-11 20:05:00

Annuloaortic ectasia is a dilatation of the proximal aorta and the fibrous ring of the heart at the aortic orifice. It may cause aortic regurgitation, and, when severe, also dissecting aneurysm. It is associated with Marfan's syndrome. The proximal a

Intra-aortic Balloon Pump

Published on 2011-04-11 18:50:00

The intra-aortic balloon pump (IABP) is a mechanical device which reduces cardiac workload by decreasing afterload. It also increases coronary blood flow. The intra-aortic balloon consists of a cylindrical polyethylene balloon which is attached to th

Left Ventricular Hypertrophy

Published on 2011-04-11 08:26:00

Left ventricular hypertrophy (LVH) is the enlargement of the left ventricle of the heart. It can develops in response to some factor, such as high blood pressure, that requires the left ventricle to work harder. As the workload increases, the myocard

Ventricular Systole

Published on 2011-04-10 08:22:00

Ventricular systole is the contraction of the muscles (myocardia) of the left and right ventricles by which blood is forced into the aorta and pulmonary artery during the cardiac cycle. However, the term usually describes the phase of left ventricle

Aortic Insufficiency

Published on 2011-04-09 11:06:00

Also known as aortic regurgitation, aortic insufficiency is a heart condition in which the aortic valve does not close tightly enough to avoid leakage, allowing some of the blood that has just been pumped out of left ventricle into the aorta to flow

Aortic Valve Replacement (Video)

Published on 2011-04-09 09:52:00

Aortic valve replacement is a surgical procedure to replace a malfunctioning aortic valve. It is a complex surgery that requires the use of a heart lung machine in order to temporarily stop the heart for the surgeons to be able to replace the defecti

Computer Cursor Moved by Thoughts

Published on 2011-04-08 22:37:00

A cursor on a computer screen can be moved using thoughts about a range of vowel sounds, research has found. Brain signals have been translated into motion or even pictures before, but the current research showcases a nascent technique called electro

Pericardial Effusion

Published on 2011-04-08 11:01:00

Pericardial effusion is an abnormal accumulation of excess fluid between the pericardium and the heart; this space is called pericardial cavity. Normal levels of pericardial fluid are from 15 to 50 ml. Because of the limited amount of space in the pe

Aortic Vestibule

Published on 2011-04-08 08:39:00

The aortic vestibule is the superior part of the heart left ventricle, situated immediately below the aortic orifice, allowing room for segments of the closed aortic valve and leading into the root of the aorta. Forming part of the outflow tract of t

Transposition of the Great Arteries

Published on 2011-04-07 18:16:00

Transposition of the great arteries (TGA) is a congenital heart condition in which the pulmonary artery and the aorta are swapped, arising from the wrong ventricle. It is said that they are transposed (switched), which means that they do not originat

Hypoplastic Left Heart Syndrome

Published on 2011-04-07 10:54:00

Hypoplastic left heart syndrome (HLHS) is a congenital malformation of the left side of the heart, affecting the aortic valve, mitral valve, left ventricle, and aorta. In babies with hypoplastic left heart syndrome, the aorta and left ventricle are v

Aortic Valvuloplasty

Published on 2011-04-06 17:26:00

Aortic valvuloplasty is the repair of a narrowed aortic valve (aortic stenosis) using a balloon catheter inside the valve to open it up. Balloon aortic valvuloplasty is a procedure in which a catheter (thin tube) that has a small deflated balloon at

Physicists Found New Particle

Published on 2011-04-06 17:05:00

Physicists at the Fermi National Accelerator Laboratory are planning to announce Wednesday that they have found a suspicious bump in their data that could be evidence of a new elementary particle or even, some say, a new force of nature. The results,

Pantent Ductus Arteriosus

Published on 2011-04-06 09:17:00

Patent ductus arteriosus is a heart condition in which the ductus arteriosus, which is a blood vessel that allows blood to bypass the baby's lungs before birth, fails to close after birth. During fetal development, the ductus arteriosus is a normal s

Myocardial Rupture

Published on 2011-04-05 17:47:00

Myocardial rupture is a laceration of the walls of the heart chambers (ventricles or atria), of the papillary muscles or chordae tendineae, of the interatrial or interventricular septum, or of one of the valves of the heart. Myocardial rupture occurs

Truncus Arteriosus

Published on 2011-04-05 12:46:00

Truncus arteriosus is a congenital heart condition in which the embryological structure known as the truncus arteriosus never fully divides into two independent blood vessels: the pulmonary artery and aorta. In the heart of a healthy person, the aort

Aortic Stenosis (Surgery)

Published on 2011-04-05 09:36:00

Aortic stenosis is the narrowing or occlusion of the heart's aortic valve, which prevents it from opening properly and does not let oxygenated blood flow completely out of the left ventricle into the aortic artery, causing this heart chamber to becom

Tetralogy of Fallot

Published on 2011-04-04 11:11:00

Tetralogy of Fallot is a congenital cardiac malformation in which the heart has four anatomical defects, which change the normal flow of blood through the heart. In tetralogy of Fallot the left ventricle pumps poor-oxygen blood to the rest of the bod

Pericardial Tamponade

Published on 2011-04-03 13:30:00

Pericardial tamponade is the compression of the heart that occurs when blood or fluid builds up in the space between the myocardium and the pericardium, which is the outer covering sac of the heart. If the fluid significantly elevates the pressure on

Hyperviscosity Syndrome

Published on 2011-04-03 12:29:00

Hyperviscosity syndrome is a serious condition caused by an increase in the viscosity of the blood, which in turn is caused by increased circulating serum immunoglobulins and can be seen in diseases, such as immunoglobulin myeloma (plasma cells cance

Takotsubo Cardiomyopathy

Published on 2011-04-02 09:06:00

Takotsubo cardiomyopathy is a heart condition in which there is a sudden temporary weakening of the myocardium, which is the muscle of the heart, triggered by emotional stress. Since the stressful situations that cause Takotsubo cardiomyopathy usuall

Congestive Heart Failure

Published on 2011-04-01 08:25:00

Congestive heart failure is a condition in which the heart can no longer pump enough blood to the rest of the body. It usually affects only the right side or only the left side of the heart. These are called right-sided heart failure or left-sided he

Eisenmenger Syndrome (treatment)

Published on 2011-03-31 12:42:00

Eisenmenger syndrome is a heart condition in which abnormal left-to-right atrial or ventricular shunt causes pulmonary hypertension, which in turn, causes increased pressures in the right side of the heart and reversal of the shunt into a right-to-le

Cardiomyocytes

Published on 2011-03-30 09:02:00

Also known as myocardiocyte, the cardiomyocyte is the muscular fiber of the myocardium, which is the heart muscle. A cardiomyocyte is a cell that contains myofibrils, which are long chains of sarcomeres, which in turn is the contractile units of the

Ventricular Septal Defect

Published on 2011-03-30 06:54:00

The ventricular septal defect is a congenital heart condition in which there is one or more holes in the interventricular septum, which the muscular wall separating the right ventricle from the left. Faults with NKX2.5 gene can cause ventricular sept

Balloon Mitral Valvuloplasty

Published on 2011-03-29 17:47:00

Balloon mitral valvuloplasty is a minimally invasive therapeutic procedure to correct a mitral stenosis by dilating the valve using a balloon. For treatment of symptomatic mitral valve stenosis, balloon valvuloplasty has emerged as an alternative to

Constrictive Pericarditis

Published on 2011-03-29 09:23:00

Constrictive pericarditis is a chronic inflammation of the pericardium, which is a two-layered sac that wraps the heart and contains the roots of the great vessels. Constrictive pericarditis occurs when a fibrotic, thickened, and adherent pericardium

Idiopathic

Published on 2011-03-29 08:35:00

Idiopathic means arising spontaneously or from an obscure or unknown cause. It is an adjective used primarily in the science of medicine. Idiopathic is a term from nosology, the classification of diseases. For some medical conditions, one or more cau

Amyloidosis

Published on 2011-03-28 16:39:00

Amyloidosis is an abnormal accumulation of amyloid proteins in the body organs or tissues. Amyloids are insoluble fibrous protein aggregates sharing specific structural traits. Amyloidosis may play a role in various degenerative diseases. Although de

Myxoma

Published on 2011-03-28 08:34:00

Myxoma is a benign tumor of the heart. Usually located in either the left or right atrium, a myxoma is an abnormal growth which consists of a stalk-shaped mass of primitive connective tissue which grows on the wall of the interatrial septum. Approxim

Left Ventricle

Published on 2011-03-27 12:35:00

Lined with endocardium, the left ventricle is one of the four chambers of the heart. It lies below the left atrium, and beside the right ventricle, from which it is separated by the interatrial septum. The left ventricle receives oxygenated blood fro

Interatrial septum

Published on 2011-03-26 18:17:00

The interatrial septum is the wall of cardiac tissue that separates the right atrium from the left atrium. Due to its obliquity, right atrium mainly lies anterior to left atrium. The interatrial septum begins to take shape during the first and second

Left Atrium

Published on 2011-03-26 14:51:00

The left atrium is one of the four chambers of the heart. It is situated above the left ventricle, with which it is communicated by the mitral valve, and beside the right atrium, from which it is separated by the interatrial septum. The left atrium g

Atrial Septal Defect

Published on 2011-03-26 09:37:00

Atrial septal defect (ASD) is a congenital heart condition in which the interatrial septum that separates the left and right atria allows blood to seep or flow from one atrium into the other. In a healthy person the interatrial septum is water tight

Scotoma

Published on 2011-03-24 10:49:00

A scotoma is an area of diminished vision within the visual field or degenerated visual acuity which is surrounded by a field of normal vision. Scotomas may be central, if caused by a disease which affects the macula or optic nerve, or peripheral if

Pancreatic Pseudocyst

Published on 2011-03-24 08:28:00

A pancreatic pseudocyst is a localized collection of tissue, fluid, debris, pancreatic enzymes, and blood in the abdomen. The prefix "pseudo-" means "false", which distinguishes them from true cysts, which are lined by epithelium. Thus, a pseudocysts

Hemosuccus Pancreaticus

Published on 2011-03-23 16:41:00

Hemosuccus pancreaticus is a rare cause of gastrointestinal bleeding. It is caused by a bleeding source in the pancreas, pancreatic duct, or structures adjacent to the pancreas, such as the splenic artery, that bleed into the pancreatic duct, which i

Achromatopsia

Published on 2011-03-23 12:15:00

Also known as rod monochromatism, achromatopsia is a recessive inherited eye condition which is associated with color blindness, extreme light sensitivity, and visual acuity loss. It affects approximately 1 in every 33,000 Americans. Achromatopsia me

Anisometropia

Published on 2011-03-22 17:08:00

Anisometropia is the condition in which each eye has different refractive power. This means that one eye can be mildly nearsighted (myopic) while the other very nearsighted; or one eye is nearsighted and the other eye is farsighted. Anisometropia cau

Usher Syndrome

Published on 2011-03-22 15:36:00

Usher syndrome is a genetic disorder which causes hearing and vision loss. The hearing loss is associated with a defective inner ear, whereas the vision loss is associated with retinitis pigmentosa (RP), a degeneration of the retinal cells. Usher syn

Choroiditis

Published on 2011-03-22 11:18:00

Choroiditis is an inflammation of the choroid, which is the middle vascular layer of the eye that supplies the retina. Usually the symptoms include blurred vision, photophobia, and eye pain. When the inflammation occurs on its entirety, it is called

Mycotic Keratitis

Published on 2011-03-22 10:12:00

Mycotic keratitis is an inflammation of the cornea caused by fungi. It is a mycotic infection of the eye cornea, which the transparent frontal part of the globe. This type of keratitis is usually caused by three types of fungi: Fusarium spp, Aspergil

Choroideremia

Published on 2011-03-21 17:45:00

Choroideremia is an inherited, retinal degenerative disorder that causes progressive loss of vision, affecting both the choroid and retina of the eye. Choroideremia leads to the degeneration of the choriocapillaris, the retinal pigment epithelium, an

Electroretinography

Published on 2011-03-21 16:26:00

Electroretinography is an ophthalmological test to measure the electrical activity of the cells that make up the retina of the eye; rods, cones, bipolar, amacrine, and ganglion cells. The retina is a sensitive inner layer of the eyeball on which the

Leber's Congenital Amaurosis

Published on 2011-03-21 08:12:00

Leber's congenital amaurosis (LCA) is an inherited retinal disease which occurs at birth and is characterized by loss of vision. It is an autosomal recessive disorder caused by abnormal development of photoreceptor cells (cones and rods of the retina

Microphthalmia

Published on 2011-03-21 06:23:00

Microphthalmia is a condition in which one or both globes (eyeballs) are abnormally small. Microphthalmia is defined as a globe with a total axial length (TAL) that is at least two standard deviations below the mean for age. Severe microphthalmia ref

Optic Disc Drusen

Published on 2011-03-20 15:47:00

Optic disc drusen is an eye condition in which small spherical mass of mucoproteins and mucopolysaccharides progressively calcify in the optic disc. These beads of mucoproteins are remnants of the axonal transport system of degenerated retinal gangli

Lysosomal Storage Disease

Published on 2011-03-20 09:50:00

Lysosomal storage disease is a metabolic disorder arising from defects in lysosomal function. It results when the lysosome, which is an organelle found in the body's cells, malfunctions. The lysosome is the cell’s recycling center because it proces

Sjögren's Syndrome

Published on 2011-03-19 09:18:00

Sjögren's syndrome is a systemic autoimmune disorder in which immune cells attack and destroy the exocrine glands that produce tears and saliva. This disorder causes dryness in your mouth and eyes. It can also lead to dryness in other places that ne

Cone-rod Dystrophy

Published on 2011-03-18 20:23:00

Cone-rod dystrophy (CRD) is a genetical progressive disease which causes deterioration and death of the retina's cone and rod photoreceptor cells. This eye condition usually leads to early impairment of vision, and blindness in the last stages of the

Neurotrophic Keratitis

Published on 2011-03-18 08:20:00

Neurotrophic keratitis is a degenerative corneal disease which is caused by reduced corneal innervation due to an impairment of trigeminal nerve. The most common causes of reduced corneal innervation are viral infection, such as herpes simplex and he

Scleral Lens

Published on 2011-03-17 15:59:00

A scleral lens is a type of contact lens that rests on the sclera of the eyeball, creating a tear-filled vault over the cornea. Custom-made for each eye, a scleral lens is large and has a diameter between 18 and 20mm. It is designed to rest on the sc

Chorioretinitis

Published on 2011-03-17 08:12:00

Chorioretinitis is an inflammatory process of the choroid which is caused by toxoplasmosis and cytomegalovirus infections. This eye condition affects young children or immunocompromised subjects, such as people with AIDS. Congenital toxoplasmosis via

How Brain Neurons Work

Published on 2011-03-16 22:14:00

Neurons work using chemicals, known as neurotransmitters, which help them to communicate with one another through synaptic gaps. These neurotransmitters concentrates in the synaptic vesicles located at the tip of the teledendron of a neuron axon. The

Keratitis

Published on 2011-03-16 14:44:00

Keratitis is inflammation of the cornea of the eye. The cornea is the curved transparent layer in front of the eye. Keratitis can be provoked by diferent causes, one of which is viral keratitis, which is an infection of a herpes simplex virus seconda

Keratoconus

Published on 2011-03-16 10:01:00

Keratoconus is an eye condition in which there is a gradual deterioration of the structure of the cornea, causing it to thin and bulge out. Usually discovered during adolescence, this degenerative disorder of the eye causes decreased visual acuity (s

Corneal Keratocyte (Fibroblasts)

Published on 2011-03-15 10:39:00

Corneal keratocytes, also known as corneal fibroblasts, are specialized cells which reside in the stroma of the eye cornea. The function of keratocytes is to keep the stroma transparent, healing its wounds, and synthesizing its components. Another im

Ocular Immune System (Privilege)

Published on 2011-03-14 08:55:00

The ocular immune system is the immunological defense system which protects the eye from infection, regulating healing processes following injuries. Although the interior of the eye lacks lymph vessels, it is highly vascularized, and many immune cell

Amaurosis Fugax

Published on 2011-03-13 10:54:00

Amaurosis fugax is a pathological condition which is characterized by a transient loss of vision in one eye owing to a temporary lack of blood circulation to the retina. Vision loss lasts from a few seconds to several minutes before recovering the vi

Sattler's Layer

Published on 2011-03-12 18:04:00

Sattler's layer is the choroid middle layer, which consists of medium diameter blood vessels. Sattler's layer supplies oxygen and nourishment to the outer layers of the retina.

Memory Booster Research

Published on 2011-03-12 13:12:00

Through intensive research, scientists have been trying for many years to obtain a genuine memory booster, a drug that could tune the brain’s biological search engine so that it’s better at retrieving not only recently learned facts, like last ni

Retinoschisis

Published on 2011-03-12 09:16:00

Retinoschisis is an eye condition in which the sensitive layer of the retina splits gradually into different layers, affecting the retinal photosensitive cells in the macula (cones and rods). It results in loss of vision in the corresponding visual f

Retinal Hemorrhage

Published on 2011-03-11 08:10:00

Retinal hemorrhage is an abnormal bleeding onto the surface of the retina due to a burst in one or several blood vessels located on its surface. This rupture in a tiny artery or vein in the retina is usually caused by hypertension, retinal vein occlu

Retinal Circulation

Published on 2011-03-10 08:43:00

The retinal circulation derives its circulation from the central retinal artery, which is a branch of the ophthalmic artery, but passing in conjunction with the optic nerve. This artery runs inferior to the optic nerve within its dural sheath to the

Uveal Circulation

Published on 2011-03-10 07:33:00

The uveal circulation consists of arteries entering the globe outside the optic nerve, these supply the uvea and outer and middle layers of the retina. The arteries of the uveal circulation, supplying the uvea and outer and middle layers of the retin

Corneal Epithelial Neoplasm

Published on 2011-03-09 06:52:00

Corneal epithelial neoplasm is an abnormal mass of tissue, or tumor, on the corneal epithelium of the eye. The neoplasm may be benign or malignant and can be corrected with laser surgery or corneal transplant, depending on the type of tumor. The word

Retinitis Pigmentosa

Published on 2011-03-08 17:23:00

Retinitis pigmentosa (RP) is an eye disease that leads to incurable blindness, which is caused by a progressive degeneration of the retina which affects night vision and peripheral vision. Retinitis pigmentosa is a genetic disorder which can be cause

Blood-ocular Barrier

Published on 2011-03-08 08:37:00

The blood-ocular barrier is a physical barrier between the local blood vessels and most parts of the eyeball. It prevents many foreign substances from going through it. The blood-ocular barrier is composed of two barriers: 1) the blood-aqueous barrie

Descemet's Membrane

Published on 2011-03-07 13:52:00

Descemet's membrane, or posterior limiting membrane, is the basement membrane located between the corneal stroma, and the endothelial layer of the cornea. It is a thin acellular layer which serves as the modified basement membrane of the corneal endo

Brain-derived Neurotrophic Factor

Published on 2011-03-07 06:49:00

The brain-derived neurotrophic factor (BDNF) is a protein molecule which belongs to the neurotrophin family of growth factors. It encourages the growth and differentiation of new neurons and synapses, helping to support the survival of existing neuro

Nerve Growth Factor

Published on 2011-03-06 09:45:00

The nerve growth factor (NGF) is a type of protein molecule that stimulates the growth and maintenance of sympathetic and sensory neurons and is essential for their survival. The nerve growth factor consists of three types of polypeptide chains: alph

Neurotrophins

Published on 2011-03-05 06:36:00

Also known as neurotrophic factors, neurotrophins are a family of related polypeptides (proteins) which induce the survival, development, and function of neurons. Produced by the nervous system, neurotrophins are critical to neuronal growth, regenera

Olfactory Sulcus

Published on 2011-03-04 11:38:00

The olfactory sulcus is a groove that runs anterior-posteriorly (from front to back) in the inferior surface of the frontal lobe, separating the straight gyrus (gyrus rectus) from the medial orbital gyrus.Depth of Olfactory Sulcus and SchizophreniaAb

Medial Frontal Gyrus

Published on 2011-03-03 18:29:00

The medial frontal gyrus is located on the upper part of the medial, or inner, surface of the brain hemisphere. It is a continuation of the superior frontal gyrus. The medial frontal gyrus is separated from the cingulate gyrus by the cingulate sulcus

Orbital Gyri

Published on 2011-03-02 15:45:00

The orbital gyri are small, irregular convolutions on the inferior surface of the frontal lobe in each cerebral hemisphere. The orbital gyri comprises the medial, anterior, lateral, and posterior orbital gyri, all of them lying on the inferior concav

Exocrine Pancreas

Published on 2011-03-02 09:29:00

The exocrine pancreas is the part of the pancreas that secrets digestive enzymes in inactive form, such as trypsinogen and chymotrypsinogen, which are activated in the duodenum into trypsin and chymotrypsin that convert proteins to amino acids. Pancr

Trypsinogen

Published on 2011-03-01 20:33:00

Trypsinogen is a precursor enzyme, or zymogen, secreted by the exocrine part of the pancreas, moving to the small intestine after secretion. In the duodenum, it is activated into the enzyme trypsin by enteropeptidase, which is found in the intestinal

Medial Orbital Gyrus

Published on 2011-03-01 19:46:00

The medial orbital gyrus is a small cerebral convolution situated on the inferior surface of the frontal lobe, lying between the straight gyrus (gyrus rectus) and the anterior and posterior gyri. It is continuous with the middle frontal gyrus. The me

Anterior Orbital Gyrus

Published on 2011-03-01 11:58:00

The anterior orbital gyrus is located on the inferior surface of the frontal lobe of each cerebral hemisphere. Lying anteriorly to the posterior orbital gyrus, it is a continuation of the middle frontal gyrus. The anterior orbital gyrus is separated

Straight Gyrus

Published on 2011-02-28 16:14:00

Also called gyrus rectus in Latin, the straight gyrus is the portion of the frontal lobe lying alongside the medial orbital gyrus in each cerebral hemisphere. Bounded laterally by the olfactory sulcus, the straight gyrus is continuous with the superi

Posterior Orbital Gyrus

Published on 2011-02-27 13:26:00

The posterior orbital gyrus is located in the inferior surface, or orbital surface, of the frontal lobe. It is bounded anteriorly by one of the orbital sulci that runs crosswise or obliquely, separating it from the anterior orbital gyrus. The posteri

Tinnitus

Published on 2011-02-26 15:56:00

Tinnitus is an auditory phantom sensation with ringing or hissing sounds. Up to 17% of the adult population experience tinnitus at least occasionally, and as many as 10% report unremitting tinnitus. However, the underlying pathomechanism has not yet

Heschl's Gyrus

Published on 2011-02-26 15:08:00

The Heschl's gyrus is any of three small gyri which are located in the superior temporal gyrus of the brain temporal lobe. Occupying Brodmann areas 41 and 42, the Heschl's gyri run transversely on the surface of the temporal lobe, bordering on the Sy

Medial Temporal Lobe

Published on 2011-02-26 11:59:00

The medial temporal lobe is a region of the temporal lobe which is located on the inferior surface of both cerebral hemisphere. It is composed of the fusiform gyrus, parahippocampal gyrus, and hippocampal region (Ammon's horn, dentate gyrus, and subi

Neurogenesis

Published on 2011-02-24 08:45:00

Etimologically, neurogenesis means "birth of neurons". It is the process by which neurons are generated, especially during embryological and fetal development. Neurogenesis is responsible for populating the growing brain of a fetus with neurons. Alth

Granule Cells (Development)

Published on 2011-02-23 09:26:00

The granule cells are a type of neuron found in the granular layer of the cerebellum and dentate gyrus of the hippocampus, in the olfactory bulb, and layer IV of the cerebral cortex. Granule cells in different brain regions are both functionally and

Visual Pathway

Published on 2011-02-22 07:59:00

The visual pathway begins at the retina with the ganglion cells converging at the optic disc to form the optic nerve. Then the nerves enter the cranial cavity through the optic foramina and get together to form the optic chiasm. Fibers from the contr

Meyer's Loop

Published on 2011-02-21 09:44:00

Meyer's loop is the most anterior extension of the optic radiation which sweeps back on its self into the temporal lobe. The last relay of the visual pathway corresponds to fibers from the lateral geniculate nucleus which project to the occipital cor

Gliosis

Published on 2011-02-20 09:33:00

Gliosis is the multiplication of astrocytes in the brain due to enjury or damage, often leading to the formation of glial scar. Astrocytes are glial cells, which perform a supporting rol in the CNS. When neurons die, they are replaced by astrocytes,

Hippocampal Sclerosis

Published on 2011-02-19 09:46:00

Hippocampal sclerosis is the loss of neurons in the field CA1 of Ammon's horn in the hippocampus due to temporal lobe epilepsy. The typical magnetic resonance imaging (MRI) features of hippocampal sclerosis are unilateral volume loss and increased si

Hippocampal Sulcus

Published on 2011-02-18 14:57:00

The hippocampal sulcus is a fissure that separates the dentate gyrus from the subiculum and the CA1 field of Ammon's horn in the hippocampus, extending from the splenium of the corpus callosum almost to the tip of the temporal lobe. Enlargement of th

Subiculum

Published on 2011-02-18 08:34:00

The subiculum is the most inferior region of the hippocampus, lying between field CA1 of Ammon's horn and the parahippocampal gyrus. Located ventrally and medially to the dentate gyrus, it is a ventral continuation of the hippocampus. The subiculum i

Perforant Pathway

Published on 2011-02-17 12:59:46

The perforant pathway is a pathway of neuron axons which arises from layers II, III, V, and VI of the entorhinal cortex, establishing connections with the dentate gyrus and the Ammon's horn in the hippocampus as it perforates the subiculum. The perfo

Cortical Dysplasia

Published on 2011-02-16 09:28:34

Cortical dysplasia is a malformation of the cerebral cortex due to a congenital disorder where the neurons in a region of the cerebrum did not migrate in the proper cortical order during development of the embryo and fetus. Put it in other words, cor

Schaffer Collaterals

Published on 2011-02-15 13:42:00

Schaffer collaterals are axon branches which are given off by Ammon's horn CA3 pyramidal neurons in the hippocampus. Schaffer collaterals project to area CA1 of the hippocampus and are an integral part of memory formation and the emotional network of

Ammon's Horn (Anatomy)

Published on 2011-02-15 07:48:00

Also called cornu ammonis, the Ammon's horn is one of the two interlocking gyri which make up the hippocampus of the brain; the other is the dentate gyrus. In anatomy "Ammon's horns" is abbreviated CA (for Cornu Ammonis). It is differentiated into fo

Dentate Gyrus

Published on 2011-02-14 10:08:00

The dentate gyrus is one of the two gyri that constitute the hyppocampus; the other is the Ammon's horn. The dentate gyrus is composed of three layers of neurons: molecular, granular, and polymorphic. The middle layer is most prominent and contains g

Parahippocampal Gyrus

Published on 2011-02-13 13:19:00

The parahippocampal gyrus is a cortical region of the cerebrum, located on the inferior surface of the temporal lobe, on each cerebral hemisphere, lying between the hippocampal and collateral sulci. It envelops the hippocampus. The parahippocampal gy

Fiber Tractography

Published on 2011-02-12 12:44:00

Fiber tractography is the neurological procedure to study neuron axons tracts in a human brain using magnetic resonance imaging techniques and computer-based image analysis. A fiber tractography test can be shown in either two dimensional or three di

Fusiform Gyrus

Published on 2011-02-11 09:26:00

Also known as occipitotemporal gyrus, the fusiform gyrus is located between the inferior temporal gyrus and parahippocampal gyrus, on the inferior surface of each cerebral hemisphere. It is situated in Brodmann Area 37. Among the functions performed

Inferior Longitudinal fasciculus

Published on 2011-02-10 09:39:00

The inferior longitudinal fasciculus is a bundle of myelinated axons which connects the occipital lobe with the temporal lobe in each hemisphere of the cerebrum. It runs parallel to the lateral walls of the inferior and posterior cornua of the latera

Superior Longitudinal Fasciculus

Published on 2011-02-09 17:27:00

The superior longitudinal fasciculus is a thick and long bundle of myelinated axons which links the frontal lobe to the occipital, and part of the parietal and temporal lobes of each cerebral hemisphere. The association fibers that constitute the sup

Occipitofrontal Fasciculus

Published on 2011-02-09 06:09:00

The occipitofrontal fasciculus is a bundle of association fibers which connects the frontal lobe with the occipital lobe of each brain hemisphere. The myelanated fibers that make up the occipitofrontal fasciculus radiate in a fan-like manner, extendi

Uncinate Fasciculus

Published on 2011-02-08 12:45:00

The uncinate fasciculus is a band of cortical neuron myelinated axons in the human brain that connects the inferior part of the frontal lobe with the anterior temporal lobe and parts of the limbic system, such as the hippocampus and amygdala that are

Arcuate Fasciculus

Published on 2011-02-07 10:05:00

The arcuate fasciculus is the thick bundle of myelinated axons which links the Broca's area to the Wernicke's area, which are the two language centers of the brain. Thus, the arcuate fasciculus fibers go from the inferior frontal gyrus of the frontal

Hypoglossal Nerve (CN XII)

Published on 2011-02-06 12:18:00

Also known as CN XII, the hypoglossal nerve is the twelfth of twelve paired cranial nerves. The CN XII innervates the muscles of the tongue. It is a somatomotor nerve whose fibers originate in the hypoglossal nucleus neurons situated in the dorsal me

Accessory Nerve (CN XI)

Published on 2011-02-05 10:26:00

The accessory nerve is the eleventh of the twelve paired cranial nerves. It is also known as cranial nerve XI (CN XI). It is called accessory since it receives an accessory root from the upper part of the spinal cord as it emerges from the skull. The

Vagus Nerve (CN X)

Published on 2011-02-04 10:03:00

Also known as cranial nerve X (CN X), the vagus nerve is one of the twelve paired cranial nerves. Consisting of both motor and sensory fibers, the vagus nerve emerges from the medulla oblongata in the groove between the olive and the inferior peduncl

Glossopharyngeal Nerve (CN IX)

Published on 2011-02-03 15:17:00

The Glossopharyngeal nerve is the ninth cranial nerve (CN IX). It consists of both motor and sensory fibers and emerges from the brain stem as the most rostral of a series of nerve rootlets that protrude between the olive and inferior cerebellar pedu

Vestibulocochlear Nerve (CN VIII)

Published on 2011-02-02 13:05:00

The vestibulocochlear nerve, also known as cranial nerve VIII (CN VIII), is composed of sensory fibers which carry two types of sensory information to the brain: balance and hearing. It is the 8th of the twelve cranial nerves. The vestibulocochlear n

Facial Nerve (CN VII)

Published on 2011-02-01 09:58:00

The facial nerve is the seventh cranial nerve (CN VII). It is a paired nerve with both motor and sensory functions, providing motor innervation to the muscles of facial expression and sensory information of taste sensations from the anterior two-thir

Abducens Nerve (CN VI)

Published on 2011-01-31 12:09:00

The abducens nerve, also known as cranial nerve VI (CN VI), is one of the twelve paired cranial nerves. It is made up of motor axons and innervate the lateral rectus muscle of the eyeball. The CN VI originates in the abducens nucleus which is located

Trigeminal Nerve (CN V)

Published on 2011-01-30 08:39:00

The trigeminal nerve, also known as cranial nerve V (CN V), is both a sensory and motor nerve which emerges from the side of the pons, near its upper border, by a large sensory and a small motor root. The sensory fibers of CN V carries sensory inform

Trochlear Nerve (CN IV)

Published on 2011-01-29 13:54:00

The trochlear nerve, which is also called cranial nerve IV (CN IV), is the motor nerve which innervates the superior oblique muscle of the eyeball. The trochlear nerve is composed of axons of neurons situated in the trochlear nucleus, in the ventral

Oculomotor Nerve (CN III)

Published on 2011-01-28 12:22:00

The oculomotor nerve, or cranial nerve III, is the third of twelve paired cranial nerves. It is responsible of eyelid and eyeball movement. The cranial nerve III (CN III) originates in the oculomotor nucleus situated in the superior colliculus of the

Olfactory Nerve (CN I)

Published on 2011-01-27 16:46:00

The olfactory nerve is one of the twelve cranial nerves that emerge directly from the base of the brain. Also called cranial nerve I (CN I), it is the first and shortest of the twelve. The olfactory nerve is formed by axons from specialized olfactory

CAPTOR Radar

Published on 2011-01-26 09:56:00

The Euroradar CAPTOR, also known as ECR-90, is a multi-mode pulse-doppler radar used in the Eurofighter Typhoon aircraft. The radar was developed from the BAE Systems Blue Vixen, which had been designed for the BAE Sea Harrier, by Euroradar. The ECR-

AN/SPS-73(V)12

Published on 2011-01-25 11:00:00

The AN/SPS-73(V)12 is a two-dimensional, surface-search/navigation radar. It provides contact range, bearing information, and improved signal processing and automatic target detection capability. The radar has its own display indicator, which is capa

AN/SPS-10B

Published on 2011-01-24 09:20:00

The AN/SPS-10B was a medium range, C-band, surface warning radar with a limited air capability. In the Canadian Forces, this type was used in pre-DELEX steamers and training facilities. The AN/SPS-10B was used for the detection, ranging and tracking

AN/SPA-4 Range-Azimuth Indicator

Published on 2011-01-22 12:03:00

The AN/SPA-4 was a self-contained range-azimuth indicator which was designed for operation with any naval search radar system having a pulse repetition frequency between 140 and 3,000 pps. This indicator was capable of receiving radar information fro

Sperry 127E

Published on 2011-01-21 15:11:00

Sperry 127E was a solid state navigation radar which utilized integrated circuit (IC) technology and was first fitted aboard DDH 280 class. It was fitted with a 12 inch CRT and was designed on the precepts of the Radio Law, Safety Agreement of Life a

Sperry Marine Radar MK 2

Published on 2011-01-20 13:22:00

The Sperry Marine Radar MK 2 was a medium range, surface search radar which was designated High Definition Warning Surface (HDWS) set. From the early 1950's, until well into the 1970's, almost every ship in the Royal Canadian Navy was fitted with the

4356M Bottle Transmitter

Published on 2011-01-19 13:58:00

The 4356M bottle transmitter (B.T.) did not emit any radio frequencies. This device was used to provide transmission to a group of repeater motors, such as those in a radar installation, or to step up the number of repeaters that can be controlled fr

AN/SPG-34

Published on 2011-01-18 11:45:00

The AN/SPG-34 was an X-band fire control radar for AA guns. The antenna was a 40 inch diameter dish that could produce a 2.4 degree beam. Designed for surface vessels of the Canadian Navy, AN/SPG-34 had a power output from 25 to 30 Kw and a range of

AN/SPS-12

Published on 2011-01-17 16:04:00

The AN/SPS-12 was an L-band, medium surveillance radar which was developed to detect aircraft and surface vessels. It was primarily an air search radar which was fitted on the original Canadian DDE class destroyers. Target range of the AN/SPS-12 was

AN/SPS-33

Published on 2011-01-16 15:03:00

The AN/SPS-33 was a vertical, 3-dimensional target-tracking radar developed by the firm Hughes for the American Navy. It operated in combination with the AN/SPS-32 to form the SCANFAR system. The AN/SPS-33 was phased array and was frequency scanned i

AN/SPS-32

Published on 2011-01-15 11:56:00

The AN/SPS-32 was a long-range air search and target acquisition radar developed by Hughes for the US Navy. The AN/SPS-32 operated together with the AN/SPS-33, which was the square array used for 3D tracking, into one system known as SCANFAR. It 

AN/APQ-180

Published on 2011-01-14 07:57:00

The AN/APQ-180 is an all-weather, multi-mode radar which was developed by Raytheon from the APG-70 for the AC-130U Specter gunship aircraft. This X-band pulse-doppler radar is designed for both air-air and air-ground missions; they are able to look u

Doppler Effect

Published on 2011-01-13 09:38:00

The Doppler effect is the change in frequency of a wave for an observer moving relative to the source of the wave. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. The received frequency i

AN/TPS-58 MTLR

Published on 2011-01-12 07:26:00

The AN/TPS-58 Moving-Target-Locating Radar (MTLR) is a coherent Doppler radar developed by Raytheon for the US Army. It is used for general surveillance and artillery burst detection. The AN/TPS-58 is a transportable (vehicle-mounted) radar which wei

AN/SPY-3

Published on 2011-01-11 13:51:00

The AN/SPY-3 is an X-band, active phased array radar which has been developed by Raytheon for the US Navy to be used for both blue-water and littoral operations. It can combine the functions of up to five radars and ten antennas. AN/SPY-3 is the firs

RT-34/APS-13

Published on 2011-01-10 11:18:00

The RT-34/APS-13 was a low power UHF tail warning radar transmitter/receiver which was used in Allied aircraft such as the P51 Mustang and also the P-38L, P-47D, P-61, P-63, P-82D in the later stages of the war. The APS-13 operated at 420 MHz with a

AN/TPQ-36 Firefinder radar

Published on 2011-01-09 08:56:00

The AN/TPQ-36 Firefinder is a light weight, weapon locating, I-band radar developed by Northrop Grumman for the US Army. The radar was designed to detect and track artillery projectiles to find out the exact point from which they have been fired. Wit

AN/SPY-1

Published on 2011-01-08 09:04:00

The AN/SPY-1 is a ship-based, passive phased array radar developed by Lockheed Martin for the US Navy. Using four complementary antennas in order to provide full 360 degree coverage, the AN/SPY-1 is an important component of the Aegis Combat System,

AN/MPQ-64 Sentinel

Published on 2011-01-07 10:13:00

Using an X-band range-gated, pulse-doppler system, the AN/MPQ-64 Sentinel is an acquisition and tracking surveillance three-dimensional radar which is used to alert and queue Short Range Air Defense (SHORAD) weapons to the locations of hostile target

AN/MPN-14

Published on 2011-01-06 09:48:00

The AN/MPN-14 was a Mobile Ground Approach System which could be configured as a complete Radar Approach Control (RAPCON) or Ground Controlled Approach (GCA) facility. The AN/MPN-14 radar was used by air traffic controllers to identify, sequence, and

AN/MPQ-14

Published on 2011-01-05 08:59:00

The AN/MPQ-14 was a height and direction-finding radar which was used for Ground Directed Bombing (GDB), during the Korean and Vietnam War. The AN/MPQ-14 was employed to guide attack aircraft at night or during adverse weather conditions. It was the

AN/SPN-46

Published on 2011-01-04 14:55:00

The AN/SPN-46 is a precision aproach and landing radar system developed by Textron Systems for the US Navy aircraft carriers. The AN/SPN-46 utilizes an X-band coherent transmitter and receiver using monopulse tracking and doppler processing on receiv

AN/SPG-53

Published on 2011-01-04 08:06:00

The AN/SPG-53 was a ship-based fire control radar developed in the 1960s by Western Electric for the US Navy and manufactured by AT&T. It was designed for controlling the Mark 42 5"/54 caliber gun on the Belknap class cruisers, Mitscher class des

AN/MPN-1

Published on 2011-01-03 09:06:00

The AN/MPN-1 was a mobile ground-controlled approach radar first used during the Second World War. This radar was employed to assist the process of directing aircraft over a predetermined glide path for safe approach to an airdrome runway under condi

AN/SPS-49

Published on 2011-01-02 09:22:00

The AN/SPS-49 was a ship-based, L-band, air search radar developed by Raytheon for the US Navy. The first SPS-49 prototype was installed on board the destroyer USS Gyatt in 1965 for a test period, effectively entering service with the Navy in 1976 on

AN/SPS-48

Published on 2011-01-01 11:45:00

The AN/SPS-48 was a long-range, 3-dimensional, air search radar which operated in the E band and F band (2 to 4 GHz) frequencies. Manufactured by ITT Corporation, the AN/SPS-48 entered service with the US Navy in 1965, installed in the USS Worden. Th

AN/SPS-43

Published on 2010-12-31 08:20:00

The AN/SPS-43 was a ship-based, 2-dimensional, air-search radar developed and manufactured by the American firm Westinghouse. The AN/SPS-43 was capable of providing bearing and distance information, but no altitude information. With an antenna that l