Large intestine - Definition and Overview

In anatomy of the digestive system, the colon is the part of the intestine from the cecum to the rectum. Its primary purpose is to extract water from feces. In mammals, it consists of the ascending colon on the right side, the transverse colon, the descending colon on the left side, the sigmoid colon, and the rectum.

Diseases of the colon

• angiodysplasia of the colon
• colon cancer
• Crohns disease
• diarrhea
• diverticulitis
• Hirschsprung's disease (aganglionosis)
• colitis
• polyposis (see also Polyp)
• pseudomembranous colitis
• ulcerative colitis and toxic megacolon
• irritable bowel syndrome (spastic colon)

Role in digestion

The large intestine comes after the small intestine in the digestive tract and measures approximately 1.5m in length. Although there are differences in the large intestine between different organisms, the large intestine is mainly responsible for storing waste, reclaiming water and maintaining the water balance.

By the time the chyme has reached this tube, almost all nutrients have been absorbed by the body and only water and some electrolytes like sodium and chloride are left. As the chyme moves though the large intestine, water is removed, while the chyme is mixed with mucus and bacteria, and becomes feces. It is important to know that the large intestine produces no digestive enzymes and that the chemical digestion is completed in the small intestine before the chyme reaches the large intestine. The pH in the colon varies between 5.5 and 7 (neutral or slightly acidic).