Intestine, small: The tubelike organ that receives the products of digestion from the stomach. It has three parts, the duodenum, the jejunum, and the ileum. The duodenum is rich in glands that produce digestive enzymes, and also receives bile from the liver. Digested material moves from the duodenum to the ileum through the jejunum. The ileum ends with the ileocecal valve, which prevents food passed into the large intestine from traveling back into the small intestine. The walls of the small intestine are muscular, and contract to move digested food along its length. The intestinal tube is lined with a mucus-like tissue that sends forth tiny, finger-like projections called villi. The villi increase the surface available for absorbing nutrients from digested food.
See also intestine, large.