What is Large Intestine in human biology?

Food undigested in the small intestine is passed on by peristalsis into the large intestine, or colon. The intestine is composed of circular muscles that contract in rhythmic waves to push the food down the intestinal tube. The undigested mass generally contains large amounts of cellulose, which retains water and minerals. Its bulk triggers the peristaltic waves that propel the mass through the colon. Water and ions are gradually reabsorbed by the colon, producing the semisolid feces from undigestible materials.

The wall of the colon produces a mucus lining to neutralize acids produced by intestinal organisms and to facilitate the passage of feces. Many types of bacteria, some parasites, and yeast normally live in the colon of healthy persons. In fact, the populations of bacteria that reside in the colon are referred to as the "intestinal flora." Vitamin K and biotin are synthesized by some of these bacteria, and can be absorbed across the colon wall. For this reason, taking of antibiotics over a long period of time can lead to a deficiency in these vitamins, because the normal "good" intestinal bacterial flora producing the vitamins are killed along with disease-causing organisms.

The colon is usually studied as sections, and these are identified by name: the ascending, transverse, and descending colon are named according to their position. The descending colon leads to the shorter, wider sigmoid colon, and on to the short rectum and anal canal. Eventually feces are eliminated from the colon by peristalsis and relaxation of the sphincter muscles of the anus.