liver

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In vertebrates, large organ with many regulatory and storage functions. The human liver is situated in the upper abdomen, and weighs about 2 kg/4.5 lb. It is divided into four lobes. The liver receives the products of digestion (food absorbed from the gut and carried to the liver by the bloodstream), converts glucose to glycogen (a long-chain carbohydrate used for storage), and then back to glucose when needed. In this way the liver regulates the level of glucose in the blood (see homeostasis). This is partly controlled by a hormone, insulin. The liver removes excess amino acids from the blood, converting them to urea, which is excreted by the kidneys. The liver also synthesizes vitamins, produces bile and blood-clotting factors, and removes damaged red cells and toxins such as alcohol from the blood.

If more protein is eaten than is needed to make different proteins for the body, the excess is broken down. This breakdown takes place in the liver. One product of this breakdown is urea and this has to be lost from the body in the urine. The liver also stores some vitamins, produces bile, and breaks down red blood cells.

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