The stomach is an enlarged part of the digestive tract. The inner mucous membrane of the stomach forms folds and contains a large number of glands that secrete gastric juice. One type of gland produces the digestive enzyme pepsin, which breaks down proteins into amino acids. Other glands produce hydrochloric acid, which is necessary to activate pepsin and kill microorganisms. Some of the glands produce mucus that protects the walls of the stomach from self-digestion.
In the stomach, food lingers for 2–8 hours, and then enters the small intestine, which is 5–6 meters long. In the first section of the small intestine – the duodenum – the ducts of the liver and pancreas open.
The liver is the largest organ in the human body. The liver is located in the abdominal cavity on the right under the diaphragm. It does not form digestive enzymes, but it has a number of important functions:
- secretes bile into the intestinal cavity, which is necessary for emulsification and breakdown of fats;
- creates an alkaline environment in the intestines and stimulates the pancreas;
- serves as a barrier to toxic substances resulting from the digestion of food;
- converts glucose to glycogen, and when blood sugar levels drop, breaks down glycogen and releases glucose.
The pancreas is located on the left under the stomach. This is a gland of mixed secretion. Its function in digestion is to release pancreatic (pancreatic) juice, which is rich in digestive enzymes. Under the action of pancreatic juice enzymes in the small intestine, the final breakdown of proteins to amino acids, carbohydrates to glucose, and fats to fatty acids and glycerol occurs.
The most important function of the small intestine is the absorption of digestive products. The mucous membrane of the small intestine has a special structure. It forms numerous villi that multiply the suction surface.
The large intestine is 1.5–2 meters long. In it, the cecum with appendix, colon and rectum are isolated. In the large intestine, water, fiber digestion products are absorbed and feces are formed. Undigested residues accumulate in the rectum and are removed through the anus.