Nutrition is a process necessary to ensure the vital activity of the human body. The stomach plays one of the main roles in this process. The functions of the stomach are the accumulation of food mass, its partial processing and further promotion to the intestine, where the absorption of nutrients takes place. All these processes take place in the gastrointestinal tract.
Stomach: structure and functions
It is a muscular hollow organ of the digestive system, which is located between the esophagus and the duodenum 12.
Next, we will find out what function the stomach performs and analyze its structure.
It consists of the following conditional departments:
- Cardiac (inlet) part. Its projection is at the level of the 7th rib on the left.
- The arch or bottom, the projection of which is located on the left at the level of the 5th rib, more precisely, its cartilage.
- The bodies of the stomach.
- Pyloric or pyloric department. At the outlet of the stomach is the pyloric sphincter, which separates the stomach from the duodenum 12. The pylorus projection isanteriorly opposite the 8th rib to the right of the midline and posteriorly between the 12th thoracic and 1st lumbar vertebra.
The shape of this organ looks like a hook. This is especially noticeable on x-rays. The stomach has a small curvature that faces the liver and a large one that faces the spleen.
The wall of the organ consists of four layers, one of which is external, it is a serous membrane. The other three layers are inner:
- Muscular.
- Submucosal.
- Slimy.
Due to the rigid muscle layer and the submucosal layer lying on it, the mucosa has numerous folds. In the region of the body and fundus of the stomach, these folds have an oblique, longitudinal and transverse direction, and in the region of the lesser curvature - only longitudinal. Due to this structure, the surface of the gastric mucosa is significantly increased. This makes the food bolus easier to digest.
Functions
What is the function of the stomach? A lot of them. Let's list the main ones.
- Motor.
- Secretory.
- Suction.
- Excretory.
- Protective.
- Endocrine.
Each of these functions plays an important role in the process of digestion. Next, we will consider the functions of the stomach in more detail. It is known that the process of digestion begins in the oral cavity, from there food enters the stomach through the esophagus.
Motor function
Further digestion of food takes place in the stomach. The motor function of the stomach consists in the accumulation of food mass, its mechanical processing and further movement into the intestine.
During a meal and in the first minutes after that, the stomach is relaxed, which contributes to the accumulation of food in it and ensures the secretion. Next, contractile movements begin, which are provided by the muscle layer. In this case, the food mass is mixed with gastric juice.
The following types of movements are characteristic of the musculature of an organ:
- Perist altic (wave-like).
- Systolic - occur in the pyloric region.
- Tonic - helps to reduce the size of the stomach cavity (its bottom and body).
After eating, the perist altic waves are weak at first. By the end of the first hour after a meal, they intensify, which helps to move the food bolus to the exit from the stomach. The pressure in the pylorus of the stomach increases. The pyloric sphincter opens and part of the food mass enters the duodenum. The remainder of this mass returns to the pyloric region. The evacuation function of the stomach is inseparable from the motor function. They provide grinding and homogenization of the food mass and thus contribute to better absorption of nutrients in the intestines.
Secretory function. Gastric glands
The secretory function of the stomach is the chemical processing of the food bolus with the help of the produced secret. For a day, an adult produces from one to one and a half liters of gastric juice. In histhe composition includes hydrochloric acid and a number of enzymes: pepsin, lipase and chymosin.
Glands are located on the entire surface of the mucosa. They are endocrine glands that produce gastric juice. The functions of the stomach are directly related to this secret. The glands are divided into several varieties:
- Cardiac. They are located in the region of the cardia near the entrance to this organ. These glands produce a mucoid mucus-like secretion. It performs a protective function and serves to protect the stomach from self-digestion.
- Main or fundic glands. They are located in the fundus and body of the stomach. They produce gastric juice containing pepsin. Due to the produced juice, the food mass is digested.
- Intermediary glands. Located in a narrow intermediate zone of the stomach between the body and the pylorus. These glands produce a viscous mucoid secret that is alkaline and protects the stomach from the aggressive effects of gastric juice. It also contains hydrochloric acid.
- Pyloric glands. Located in the pyloric part. The secret produced by them also plays a protective role against the acidic environment of gastric juice.
The secretory function of the stomach is provided by three types of cells: cardiac, fundal, or main, and pyloric.
Suction function
This activity of the body is rather of a secondary role, since the main absorption of processed nutrients occurs in the intestines, where foodthe mass is brought to a state in which the body can easily use all the substances necessary for life that come with food from the outside.
Excretory function
It lies in the fact that some substances enter the stomach cavity from the lymph and blood through its wall, namely:
- Amino acids.
- Proteins.
- Uric acid.
- Urea.
- Electrolytes.
If the concentration of these substances in the blood increases, then their intake into the stomach increases.
The excretory function of the stomach is especially important during fasting. The protein in the blood cannot be used by the cells of the body. They are only able to assimilate the end product of protein breakdown - amino acids. Getting from the blood to the stomach, the protein undergoes further processing under the action of enzymes and breaks down into amino acids, which are further utilized by the tissues of the body and its vital organs.
Protection function
This function is provided by the secret that the organ produces. Infected pathogens die from exposure to gastric juice, more precisely, from hydrochloric acid, which is in its composition.
In addition, the stomach is designed in such a way that when poor-quality food enters it, it is able to ensure its return and prevent dangerous substances from entering the intestines. Thus, this process will prevent poisoning.
Endocrine function
This function is implementedendocrine cells of the stomach, which are located in its mucous layer. These cells produce more than 10 hormones that are able to regulate the work of the stomach itself and the digestive system, as well as the whole organism. These hormones include:
- Gastrin - produced by G-cells of the stomach itself. It regulates the acidity of gastric juice, responsible for the synthesis of hydrochloric acid, and also affects motor function.
- Gastron - inhibits the production of hydrochloric acid.
- Somatostatin - inhibits the synthesis of insulin and glucagon.
- Bombezin - this hormone is synthesized both by the stomach itself and by the proximal small intestine. Under its influence, the release of gastrin is activated. It also affects the contractions of the gallbladder and the enzymatic function of the pancreas.
- Bulbogastron - inhibits the secretory and motor function of the stomach itself.
- Duocrinine - stimulates duodenal secretion.
- Vasoactive intestinal peptide (VIP). This hormone is synthesized in all parts of the gastrointestinal tract. It inhibits the synthesis of pepsin and hydrochloric acid and relaxes the smooth muscles of the gallbladder.
We found out that the stomach plays an important role in the process of digestion and life support of the organism. Its structure and functions are also indicated.
Functional disorders
Diseases of the gastrointestinal tract, as a rule, are associated with a violation of any of its structures. Violation of the function of the stomach in this case is observed quite often. We can talk about such pathologies only if the patient has not been diagnosed during the examination.no organic lesions of this organ.
Disorders of the secretory or motor function of the stomach can occur with pain and dyspepsia. But with the right treatment, these changes are often reversible.
