What Does the Colon Do

The colon is a valuable part of the digestive tract. In a healthy adult, the colon is about 5 feet long and connects the small intestine to the rectum and anus.

The colons major function is to absorb water, nutrients, and salts from the partially digested food that enters from the small intestine. About 2 pints of partially digested liquid matter enter the colon from the small intestine each day, and about 1/3 of a pint of solid stool leaves the colon every day. The difference in volume is due to the colon’s absorption of material that is useful and valuable to the body, such as water, nutrients, and salts.

Colon motility (the contraction of the colon muscles and the movement of its contents) is controlled by hormones, nerves, and impulses in the colon muscles. These rhythmic contractions gradually shift the contents inside the colon toward the rectum. During this passage, water and nutrients are absorbed into the body, and what is left over is stool.

A few times each day, the contractions push the stool down to the end of the colon, resulting in a bowel movement. A normal bowel movement is one where the stool is firm, but not hard, contains no blood, and is passed without cramps or pain.
If the muscles of the colon do not contract in the right way, then the contents inside the colon do not move correctly, or move too quickly or too slowly, then overly watery stools or overly hard stools can result. When this happens, it causes abdominal pain, cramps, constipation, diarrhea, and a sense of incomplete stool movement.