Where does the gastrointestinal tract begin
Stomach structure and function
The stomach is in the upper part of the abdomen, slightly to the left of the center of the body. Its shape and size varies from person to person and depends on the filling level, body position and age. With moderate filling, it is 20-30 centimeters long and can hold 1.2-1.6 liters.
The stomach is divided into several sections. The mouth of the stomach is located at the entry point of the esophagus into the stomach. This is followed by the actual stomach as a sack-like enlargement of the digestive tube. The shape and size of the stomach depends on the filling conditions. When standing, it is roughly hooked and its lowest point is slightly below the navel.
The mouth of the stomach is first followed by a blind sack-like enlargement, the Bottom of stomach, and finally the Stomach body. The transition to the small intestine follows. It begins with a wide anteroom and is also the deepest part of the stomach. The anteroom goes into the Porter canal (Pylorus or gatekeeper), which forms a natural constriction. In this area, the muscles of the stomach wall are heavily thickened and therefore very strong. This creates a narrow, final transition from the stomach to the duodenum (duodenum).
Compared to other sections of the digestive tract, the stomach is characterized by a particularly thick mucous membrane. It covers the entire surface of the stomach and contains many glands.
The stomach wall is made up of strong muscle layers made up of longitudinal, ring-shaped and inclined muscle fibers. They generate wave-like movements (peristalsis) and serve to mix and transport the food to the small intestine.
The main task of the stomach is to store the food temporarily in order to then pass it on evenly in small amounts to the intestines for further digestion. The stomach makes it possible to meet the nutritional needs with a few larger meals. Without a stomach, people would have to eat the food in many small portions throughout the day. How long the chyme stays in the stomach depends on the composition of the food: Easily digestible, such as B. fruits and vegetables, only about 1-2 hours, difficult to digest, fatty food about 5-8 hours.
The muscle movements of the stomach mix the chyme and finally transport it further into the intestines. You can also make yourself noticeable externally by chuckling and rumbling ("stomach growling").
In addition, the stomach kills pathogens. To do so, form so-called Parietal cells hydrochloric acid in the stomach wall, which lowers the pH value to a value between 2 and 3 and makes most bacteria harmless. So that the stomach does not digest itself through the hydrochloric acid Adjoining cells a layer of mucus that covers the mucous membrane and protects it from the acid.
The body not only stores and disinfects in the stomach, it also starts digesting there. For this purpose, the Main cells the enzyme pepsin is formed, which breaks down the proteins ingested through food into digestible pieces. Carbohydrates and fats, on the other hand, pass through the stomach almost unhindered.
Together, the glandular system of main, secondary and secondary cells forms around 2 liters of hydrochloric acid and pepsin a day, which together form gastric juice. The production of gastric juice begins as soon as the food comes into contact with the mucous membrane and stretches the stomach. But also stimuli before eating, such as B. The smell of food can already stimulate gastric juice formation.
Once the food has reached the stomach, the expansion of the base of the stomach and digested proteins lead to an increased release of gastric juice. The amount depends on the composition of the food: Spicy foods, alcohol, nicotine and caffeine promote the release. Once part of the food has reached the small intestine, gastric acid production is reduced again.
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