The digestive tract is composed of two parts: the upper digestive tract and the lower digestive tract. The upper digestive tract includes the mouth, pharynx, esophagus, stomach and duodenum, and the lower digestive tract includes the jejunum, ileum and large intestine. In the oral cavity, through chewing and salivary enzymes, food is initially decomposed and digested, and the food mass with saliva enters the stomach through the esophagus through swallowing action; 2, pharynx: the pharynx can be divided into nasopharynx, oropharynx and laryngopharynx, which can mainly complete the reflex action of swallowing; 3, esophagus: it mainly plays the role of transporting food; 4, stomach: the stomach is the organ for storing food. Food into the stomach, the stomach through regular peristalsis, the food and digestive enzymes fully integrated to achieve the role of initial digestion of food; 5, duodenum: duodenum is the part that connects the stomach and small intestine, duodenum has the role of secreting mucus, stimulating the pancreas to secrete digestive enzymes, as well as stimulating the gallbladder to secrete bile. Second, the lower digestive tract: 1, jejunum, ileum: they do not have obvious physiological boundaries, mainly to play the role of digestion and absorption of food; 2, large intestine: including the cecum, appendix, colon, rectum, anal canal, the main function of the large intestine is to absorb water and inorganic salts, but also to provide a temporary storage place for digested and absorbed food residues, and will be transformed into feces and excreted out of the body.