The human digestive system consists of two parts: the digestive tract and the digestive glands connected to it. The digestive tract includes the mouth, pharynx, esophagus, stomach, small intestine and large intestine. The small digestive glands are mainly located in the walls of the digestive tract, while the large digestive glands include the salivary glands, the liver and the pancreas. The digestive glands mainly secrete digestive juices, which can total 6 to 8 liters per day. The basic physiological function of the digestive system is to take in, transfer and digest food, absorb nutrients, and provide material and energy sources for the body’s metabolism, while food residues that are not digested and absorbed are eventually eliminated from the body in the form of feces. The stomach can accommodate a large amount of ingested food, and through mechanical and chemical digestion, chyme is formed and gradually discharged into the small intestine with the movement of the stomach. The small intestine is the main site of digestion and absorption. After food enters the small intestine, it is chemically digested by pancreatic juice, bile and small intestine fluid and mechanically digested by small intestine peristalsis to form small molecules, which are absorbed into the blood and lymphatic fluid through the epithelial cells of the digestive tract mucosa. Most nutrients are absorbed in the small intestine, and food residues that are difficult to digest and absorb enter the large intestine. The large intestine has only certain absorption functions, mainly absorbing water and electrolytes, as well as forming, storing and excreting feces.