liver fluke: see fluke.

liver, largest glandular organ of the body, weighing about 3 lb (1.36 kg). It is reddish brown in color and is divided into four lobes of unequal size and shape. The liver lies on the right side of the abdominal cavity beneath the diaphragm. Blood is carried to the liver via two large vessels: the hepatic artery carries oxygen-rich blood from the aorta, and the portal vein carries blood containing digested food from the small intestine. These blood vessels subdivide in the liver repeatedly, terminating in minute capillaries. Each capillary leads to a lobule. Liver tissue is composed of thousands of lobules, and each lobule is made up of hepatic cells, the basic metabolic cells of the liver. One of the liver's major functions is the manufacture and secretion of bile, which is stored in the gall bladder and released in the small intestine. Bile salts emulsify fats, a process that prepares the latter for digestion by the intestinal enzymes (see digestive system). The hepatic cells assimilate carbohydrates, fats, and proteins. They convert glucose to its stored form, glycogen, which is reconverted into glucose as the body requires it for energy. The ability of the liver to maintain the proper level of glucose in the blood is called its glucose buffer function. The end products of fat digestion, fatty acids, are used to synthesize cholesterol and other substances needed by the body. Excess carbohydrates and protein are also converted into fat by the liver. Digested proteins in the form of amino acids are broken down further in the liver by deamination. Part of the amino acid molecule is converted into glycogen and other compounds. Urea, a waste product of protein breakdown, is produced by the liver, a process which removes poisonous ammonia from the body fluids. The liver is also capable of synthesizing certain amino acids (the so-called nonessential amino acids) from other amino acids in a process called transamination. Some essential components of blood are manufactured by the liver, including about 95% of the plasma proteins and the blood-clotting substances (fibrinogen, prothrombin, and other coagulation factors). The liver also filters harmful substances from the blood. Phagocytic cells in the liver, called Kupffer cells, remove large amounts of debris and bacteria. In addition, the liver stores important vitamins and minerals, including vitamins A, D, K, and B₁₂. Several diseases states can affect the liver, such as hepatitis (an inflammation of the liver) and cirrhosis (a chronic inflammation that progresses ultimately to organ failure). Alcohol alters the metabolism of the liver, which can have overall detrimental effects over long periods of abuse. In 1994, a bioartificial liver, part machine, part cloned living liver cells, was used for the first time. Functioning somewhat like a kidney dialysis machine, the bioartificial liver can support patients with acute liver failure until their own livers regenerate, or it can be used by patients while waiting for a liver transplant.

cod-liver oil, yellowish oil obtained from the liver of the codfish. The oil is rich in vitamin A and vitamin D (calciferol). It was long used as a preventive and cure for rickets in Baltic and Scandinavian countries, where fish is a dietary staple. However, it was not until the 1920s that doctors in the U.S. finally recognized its therapeutic usefulness. More palatable synthetic vitamins have largely replaced cod-liver oil as dietary supplements, and almost all the milk sold in the United States and Europe now contains added vitamins A and D. See vitamin.

Largest gland in the body, with several lobes. It secretes bile; metabolizes proteins, carbohydrates, and fats; stores glycogen, vitamins, and other substances; synthesizes coagulation factors; removes wastes and toxic matter from the blood; regulates blood volume; and destroys old red blood cells. The portal vein carries blood from the gastrointestinal tract, gallbladder, pancreas, and spleen to the liver to be processed. A duct system carries bile from the liver to the duodenum and the gallbladder. Liver tissue consists of a mass of cells tunneled with bile ducts and blood vessels. About 60percnt are hepatic cells, which have more metabolic functions than any other cells. A second type, Kupffer cells, play a role in blood-cell formation, antibody production, and ingestion of foreign particles and cell debris. The liver manufactures plasma proteins, including albumin and clotting factors, and synthesizes enzymes that modify substances such as nutrients and toxins, filtered from the blood. Liver disorders include jaundice, hepatitis, cirrhosis, tumours, vascular obstruction, abscess, and glycogen-storage diseases.

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Oil obtained primarily from the liver of the Atlantic cod and related fish. It is principally a mixture of the glycerides (see glycerol) of many fatty acids, but its minor constituents, the fat-soluble vitamin A and vitamin D, give it its importance. It was once used to treat and prevent rickets, but the widespread fortification of milk with vitamin D in the United States and Europe beginning in the 1930s eliminated rickets as a significant public health problem. It is still used as a remedy for joint pain caused by arthritis and as a preventive of cardiovascular disease, although these benefits have not been proven scientifically. It is also used in feeds for poultry and other animals.

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(born May 10, 1902, Pittsburgh, Pa., U.S.—died June 22, 1965, Hollywood, Calif.) U.S. film producer. He trained with his father, a movie executive, before moving to Hollywood in 1926. Working for MGM, RKO, and other studios, he produced films such as Dinner at Eight (1933), King Kong (1933), David Copperfield (1935), and A Tale of Two Cities (1935). He formed his own company, Selznick International, in 1936 and produced hits such as A Star Is Born (1937). He was essential to the enormous success of Gone with the Wind (1939), overseeing its entire production with detailed memos about every aspect of the movie. He brought Alfred Hitchcock to the U.S. and produced Rebecca (1940) and Spellbound (1945). He also produced Duel in the Sun (1946), The Third Man (1949), and A Farewell to Arms (1957), which starred his second wife, Jennifer Jones.

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(born Dec. 18, 1912, Washington, D.C., U.S.—died July 4, 2002, Washington, D.C.) U.S. pilot and administrator, the first African American general in the U.S. Air Force. He graduated from West Point and in 1941 was admitted to the Army Air Corps. He organized the 99th Fighter Squadron, the first all-black air unit, and in 1943 he organized and commanded the Tuskegee Airmen. He flew 60 combat missions. In 1948 Davis helped plan the desegregation of the Air Force, and he later commanded a fighter wing in the Korean War. After retiring as lieutenant general in 1970, he was named director of civil aviation security in the U.S. Department of Transportation (1971–75). In 1998 he was awarded his fourth general's star, attaining the highest order in the U.S. military.

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