The human digestive system includes the mouth, pharynx, esophagus, stomach, duodenum and pancreas, and liver. The digestive system consists of two major parts: the alimentary canal and the digestive glands. The digestive glands include small digestive glands scattered in the walls of the digestive tract and large digestive glands such as the sublingual gland, submandibular gland, liver and pancreas. The alimentary canal includes the upper digestive tract such as the oral cavity, pharynx, esophagus, stomach, duodenum and the lower digestive tract such as the jejunum, ileum, cecum, appendix, colon, sigmoid colon and rectum, anal canal. The basic physiological functions of the digestive system are ingestion, transportation, digestion of food and absorption of nutrients, excretion of waste. The completion of these physiological functions facilitates the coordinated physiological activities of the entire gastrointestinal tract. The digestive process consists of two functions, physical (mechanical) digestion and chemical digestion, both of which are carried out simultaneously and work together to complete the digestive process. The digestive system is one of the eight systems of the human body, in addition to digestion and absorption functions, but also has endocrine and immune functions.