gut

In the digestive system, the part of an animal responsible for processing food and preparing it for entry into the blood.

The gut consists of a tube divided into segments specialized to perform different functions. The front end (the mouth) is adapted for food intake and for the first stages of digestion. The stomach is a storage area, although digestion of protein by the enzyme pepsin starts here; in many herbivorous mammals this is also the site of cellulose digestion. The small intestine follows the stomach and is specialized for digestion and for absorption. The large intestine, consisting of the colon, caecum, and rectum, has a variety of functions, including cellulose digestion, water absorption, and storage of faeces. From the gut nutrients are carried to the liver via the hepatic portal vein, ready for assimilation by the cells.

French researchers analysing human faeces discovered in 1999 that of the 98 species of gut bacteria identified, 78 were new to science. Most gut bacteria are harmless.