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End section of the intestine. It is about 5 ft (1.5 m) long, is wider than the small intestine, and has a smooth inner wall. In the first half, enzymes from the small intestine complete digestion, and bacteria produce many B vitamins and vitamin K. Over 24–30 hours, churning movements break down tough cellulose fibres and expose chyme to the colon's walls, which absorb water and electrolytes; absorption is its main function, along with storing fecal matter for expulsion. The more vigorous mass movement (gastrocolic reflex) occurs only two or three times a day to propel waste material toward the anal canal. Common afflictions include ulcerative colitis, diverticulosis (seediverticulum), polyps, and tumours.
This entry comes from Encyclopædia Britannica Concise. For the full entry on large intestine, visit Britannica.com.