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, enzyme s 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 (see diverticulum ), polyp s, and tumour s.