In animals, the tube through which food passes; it extends from the mouth to the anus. It is a complex organ, adapted for digestion. In human adults, it is about 9 m/30 ft long, consisting of the mouth cavity, pharynx, esophagus, stomach, and the small and large intestines.
A constant stream of enzymes from the canal wall and from the pancreas assists the breakdown of food molecules into smaller, soluble nutrient molecules, which are absorbed through the canal wall into the bloodstream and carried to individual cells. The muscles of the alimentary canal keep the incoming food moving, mix it with the enzymes and other juices, and slowly push it in the direction of the anus, a process known as peristalsis. The wall of the canal receives an excellent supply of blood and is folded so as to increase its surface area. These two adaptations ensure efficient absorption of nutrient molecules.
Or 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, cecum, and rectum, has a variety of functions, including cellulose digestion, water absorption, and storage of feces. From the gut nutrients are carried to the liver via the hepatic portal vein, ready for assimilation by the cells.
Tubular passage of mucous membrane and muscle extending about 8.3 meters from mouth to anus; functions in digestion and elimination; SYN. alimentary tract, digestive tube, digestive tract, gastrointestinal tract, GI tract.
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