The digestive system is a set of organs, which provide mechanical and chemical processing of food, extracting nutrients from it and their absorption

Structure of the digestive system

The digestive system is a set of organs, which provide mechanical and chemical processing of food, extracting nutrients from it and their absorption and excretion of undigested food and undigested residues from the body.

The digestive system consists of the gastrointestinal tract and digestive glands — salivary, pancreatic and liver, which produce secrets needed for digestion. The gastrointestinal tract is designed so that food can move it in one direction (from the mouth to the anus), and so a person can eat and even eaten earlier food is still digesting.

The gastrointestinal tract has a curved tube with an expansion (stomach) and loops (intestine) with a total length of 6-9 m. It begins with oral cavity, then pharynx, esophagus, stomach, small and large intestines; it ends with anus (see Diagram 80). Esophagus, stomach and intestines have a tubular structure. Their walls are composed of four layers (membranes) (diagram 81). Inner layer — mucosa — performs the following functions: secretion (mucus, digestive enzymes), absorption and the production of digestive hormones. The next layer — submucosa contains a lot of blood and lymph vessels and nerves. Together with the mucosa, it forms folds, which increases the suction and secretory surfaces of gastrointestinal tract. Muscular coat is formed by smooth muscles, which provide food machining — milling, mixing, passing through the gastrointestinal tract and the excretion of undigested residues. Taken from http://worldofschool.org

Diagram 80. The general structure of the digestive system: 1 — mouth; 2 — tongue; 3 — throat; 4 — esophagus; 5 — stomach; 6 — duodenum; 7 — small intestine; 8 — the ileum; 9 — ascending colon; 10 — transverse colon; 11 — descending colon; 12 — sigmoid colon; 13 — rectum; 14 — cecum; 15 — appendix cecum — appendix
Diagram 81. The structure of the gastrointestinal tract walls: a) stomach wall: 1 — mucosa 2 — submucosal layer, 3 — tunica muscularis, 4 — serosa; b) small intestine wall: 5 — intestinal villi, 6 — mucosa, 7 — submucosal layer, 8 — serous membrane, 9 — muscular layer, 10 — blood vessels; c) colon wall: 11 — mucosa, 12 — submucosal layer, 13 — muscular shell, 14 — serosa

The external layer of the pharynx and esophagus is the serosa, the outer shell of the stomach and intestine is called the peritoneum. It also has several layers and not only covers the internal organs from the outside, but also connects them with each other and with the abdominal wall, as if a strong frame.

Questions:
  • Describe the general structure of the digestive tract.