The secretion of the stomach can be observed when not only nutrients but also foreign bodies (rubber rings, hard objects, etc.) are injected into it, but the secretion in this case will not be food, but rejected. It may be accompanied by a nauseous state, the occurrence of anti-peristaltic movements and end with vomiting.
The motor activity of the stomach ensures the mixing of the food mass and the evacuation of the contents from the stomach. At first, after eating, the motor activity of the stomach is weakened, but as the food mass is soaked with gastric juice, it begins to increase and manifests itself in periodically arising peristaltic waves and one after the other, which are more often completed with the opening of the pyloric sphincter. As a result, small portions of the contents of the stomach pass into the intestine. Sphincter opening also contributes to irritation of the sphincter area from the stomach, whereas irritation of the sphincter with the same acidic contents from the intestine causes the sphincter to immediately close and remains in this state until the food mass in the intestine is completely neutralized.
When food is eaten, a large amount of water often enters the stomach or water can be separated from the food product, as is the case, for example, when currying milk in the stomach under the influence of the enzyme chymosin . The presence of excess water can dilute the gastric juice and thus impede the digestion process. To prevent this, there is a special water chute in the stomach, located on the lesser curvature, along which excess water is removed into the intestine.Go
The contents of the stomach in portions enters the duodenum, where it undergoes further digestion. This digestion is carried out under the influence of pancreatic and intestinal juice enzymes . The secretion of the pancreas occurs under the influence of both the nervous mechanism and the specific hormone secretin, which is formed in the mucous membrane of the duodenum under the influence of hydrochloric acid , which enters together with the contents from the stomach. In the mucous membrane of the duodenum also forms a hormone that affects the formation of pancreatic enzymes - pancreozymin. Protein fragments that enter the intestine as peptones undergo further digestion under the influence of the enzyme pancreatic juice, trypsin (enterokinase-activated intestinal juice), as well as the intestinal juice enzyme, erepsin, and are brought to amino acids. Carbohydrates also continue to be digested here in a weakly alkaline environment under the influence of amylase, maltase, lactase and other enzymes of intestinal juice and pancreatic juice.
Fats are also digested in the intestine under the influence of the enzyme lipase , intestinal juice and pancreatic juice. At the same time, bile is involved in the digestion and absorption of fat digestion products. Bile also refers to digestive juices. It begins to stand out in the intestine through the common bile duct after 20 minutes after taking milk and 30–40–50 min. after taking bread and meat. At the same time, biliary excretion is not associated with food intake, but with the onset of chyme coming from the stomach into the intestine due to the reflex influence from the intestinal surface on the sphincter of the bile duct (Oddi's sphincter) and contraction of the muscles of the gallbladder wall. The effect of bile is expressed in the fact that it emulsifies fats, activates lipase and promotes the dissolution of fatty acids.
Currently confirmed the existence in the intestine of a special, so-called parietal, digestion. The essence of this process lies in the fact that due to the presence of villi, and therefore a huge surface, favorable conditions arise for the adsorption of the enzyme (amylase) by the intestinal wall and to enhance the enzymatic reaction in this area.
In the small intestine, digestion is completed by the absorption of nutrients (see Absorption). As the intestinal contents are further absorbed and transported, the spent slag substances enter the colon; this is where water is absorbed and feces form. The final formation of feces is completed in the rectum , and the filling of its ampoule causes a corresponding irritation and urge to act to defecate.