liver

n.

the largest gland of the body, weighing 1200–1600 g. Situated in the top right portion of the abdominal cavity, the liver is divided by fissures (fossae) into four lobes: the right (the largest lobe), left, quadrate, and caudate lobes. It is connected to the diaphragm and abdominal walls by five ligaments: the membranous falciform (which separates the right and left lobes), coronary, and right and left triangular ligaments and the fibrous round ligament, which is derived from the embryonic umbilical vein. Venous blood containing digested food is brought to the liver in the hepatic portal vein (see portal system). Branches of this vein pass in between the lobules and terminate in the sinusoids .

Oxygenated blood is supplied in the hepatic artery. The blood leaves the liver via a central vein in each lobule, which drains into the hepatic vein. The liver is supplied by parasympathetic nerve fibres from the vagus nerve, and by sympathetic fibres from the solar plexus. The liver has a number of important functions. It synthesizes bile, which drains into the gall bladder before being released into the duodenum. The liver is an important site of metabolism of carbohydrates, proteins, and fats. It regulates the amount of blood sugar, converting excess glucose to glycogen; it removes excess amino acids by breaking them down into ammonia and finally urea; and it stores and metabolizes fats. The liver also synthesizes fibrinogen and prothrombin (essential blood-clotting substances) and heparin, an anticoagulant. It forms red blood cells in the fetus and is the site of production of plasma proteins. It has an important role in the detoxification of poisonous substances and it breaks down worn out red cells and other unwanted substances, such as excess oestrogen in the male (see also Kupffer cells). The liver is also the site of vitamin A synthesis; this vitamin is stored in the liver, together with vitamins B₁₂, D, and K.

The liver is the site of many important diseases, including hepatitis, cirrhosis, amoebic dysentery, hydatid disease, and hepatomas.