Chyme passes from the stomach to the small intestine where most nutrients are absorbed. After passing through the small intestine, the remaining chyme enters the large intestine. The large intestine is responsible for absorbing remaining water and electrolytes (sodium, potassium, and chloride). It also forms and excretes feces.

The large intestine includes the colon, the rectum, and the anus.

The large intestine consists of the colon, the rectum, and the anus. The colon can be further divided into the cecum (hence the -cecal in ileocecal valve, ileo- refers to ileum), ascending colon, transverse colon, descending colon, and sigmoid colon.

Digestion continues when chyme moves from the ileum into the cecum. Peristalsis in the ileum forces chyme into the cecum.  Once the chyme enters the cecum, colon movements begin.

Mechanical Digestion

Mechanical digestion in the large intestine includes a combination of three types of movements. The presence of food residues in the colon stimulates a slow-moving, sluggish contraction which pushes the material into the ascending colon.  These movements also churn the food residue which helps the large intestine absorb water.  The removal of water from the chyme is the process that causes the formation of feces.

The second type of movement is peristalsis which is the method of moving material throughout the entire digestive system.  The following animation shows peristaltic movement in the large intestine.

The third type is a mass movement. These strong waves start midway through the transverse colon and quickly force the contents (the feces) toward the rectum. Mass movements usually occur three or four times per day either while one eats or immediately afterward.

Food residue leaving the colon enters the rectum and passes to the anal canal. The anal canal opens to the exterior body at the anus where defecation occurs.