The large intestine is mainly responsible for the formation, storage and excretion of feces, secretory functions, and maintaining the stability of the body’s normal internal environment. 1. Formation, storage and excretion of feces: the large intestine accepts food residues passed down from the small intestine, absorbs excess water, electrolytes and other substances (such as ammonia, bile acids, etc.), forms feces, and through peristalsis of the large intestine, transmits feces to the end of the large intestine, and excretes them through the anus. 2. Secretory function: cup cells secrete mucus in the mucus protein, protect the mucous membrane and lubricate feces, make feces easy to go down, protect the intestinal wall to prevent mechanical damage from bacterial erosion. 3. Maintaining the stability of the human body environment: bacteria contain a variety of enzymes, can make cellulose, sugar, fat and protein and other substances decomposition or fermentation, lactic acid, carbon dioxide, etc., to maintain the human body PH value and other physical and chemical properties and composition of relative stability.