Function of the large intestine: The mucosa of the large intestine does not have villi. The intestinal glands only secrete mucus that protects the mucosa and eases the passage of intestinal contents. It does not contain digestive enzymes, so digestion cannot be carried out in the large intestine. The large intestine mainly absorbs water, some minerals and vitamins, turning the semi-liquid contents into feces.

In addition, under normal circumstances, there are also coliforms and many other bacteria in the large intestine. These bacteria can putrefy food that has not been fully absorbed and digested in the small intestine, decompose it through fermentation and produce gas, and produce various vitamins, such as folic acid, vitamin K, niacin, vitamin B and pantothenic acid.

Most of the gas produced in the intestines due to bacterial action is absorbed by the blood vessels in the intestinal wall, and part of it is excreted from the body.