(See also Overview of the Digestive System.)
The liver is a large organ with several functions (see also Liver), only some of which are related to digestion.
The nutrients of food are absorbed into the intestinal wall, which is supplied with many tiny blood vessels (capillaries). The capillaries carry the absorbed nutrients into veins that join larger veins and eventually enter the liver as the portal vein.
Blood from the portal vein is processed in two ways:
The liver does the necessary processing at high speed and passes the blood, full of nutrients, into the general circulation.
The liver manufactures about half of the body's cholesterol. The rest comes from food. About 80% of the cholesterol made by the liver is used to make bile. The liver secretes bile, which is stored in the gallbladder until it is needed.