Functions of the stomach and structure
Nutrition is the process necessary to ensure the vital activity of the human body. Stomach in this process plays a major role. Functions of the stomach consist in the accumulation of the food mass, its partial processing and further progression to the intestine, where nutrient absorption takes place. All these processes occur in the gastrointestinal tract.
Stomach: structure and function
It is a muscular hollow organ of the digestive system, which is located between the esophagus and the 12-duodenum.
Next, we will find out what function the stomach does and analyze its structure.
It consists of the following conditional divisions:
- The cardiac (entrance) part. Its projection is at the level of the 7 edge on the left.
- The vault or bottom, the projection of which is located on the left at the level of the 5 rib, or rather, its cartilage.
- The body of the stomach.
- Doorkeeper or pyloric department. At the exit from the stomach is located the sphincter of the gatekeeper, which separates the stomach from the 12-duodenum. The projection of the gatekeeper is in front of the 8 rib right of the middle line and behind the 12 thoracic and 1 lumbar vertebrae.
The shape of this organ looks like a hook. This is especially noticeable on X-ray images. The stomach has a small curvature that faces the liver, and a large one, facing the spleen.
The wall of the body consists of four layers, one of which is external, it is a serous membrane. Three other layers are internal:
Due to the rigid muscular layer and the submucosal lying on it, the mucosa has numerous folds. In the region of the body and bottom of the stomach these folds have oblique, longitudinal and transverse direction, and in the region of small curvature - only longitudinal. Due to this structure, the surface of the gastric mucosa is significantly increased. This makes it easier to digest the food lump.
What is the function of the stomach? A lot of them. Let's list the main ones.
Each of these functions in the process of digestion plays its important role. Next, we 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 through the esophagus enters the stomach.
In the stomach, further digestion of food occurs. The motor function of the stomach is in the accumulation of food mass, its mechanical processing and further movement into the intestine.
During food intake and in the first minutes after that the stomach is relaxed, which promotes the accumulation of food in it and secures secretion. Then the contractile movements that the muscle layer provides begin. In this case, mixing of the food mass with gastric juice occurs.
The following types of movements are characteristic of the musculature of an organ:
- Peristaltic (wavy).
- Systolic - occur in the pyloric department.
- Tonic - contribute to a decrease in the size of the stomach cavity (its bottom and body).
After eating, peristaltic waves are initially weak. By the end of the first hour after the meal, they are intensified, which helps to move the food lump to the exit from the stomach. The pressure in the gatekeeper's stomach increases. The sphincter of the pylorus is opened and part of the food mass enters the 12-colon. The remaining bulk of this mass is returned to the pyloric department. Evacuation function of the stomach is inseparable from the motor. They provide grinding and homogenization of the food mass and thus contribute to a better absorption of nutrients in the intestine.
Secretory function. Glands of the stomach
The secretory function of the stomach is the chemical processing of the food lump with the help of secreted secret. For a day an adult develops from one to one and a half liters of gastric juice. It includes hydrochloric acid and a number of enzymes: pepsin, lipase and chymosin.
On the entire surface of the mucosa are the glands. They are glands of external secretion, which produce gastric juice. The functions of the stomach are directly related to this secret. The glands are divided into several varieties:
- Cardiac. Located in the cardia area near the entrance to this organ. These glands produce mucoid mucous secretion. It performs a protective function and serves to protect the stomach it is self-digesting.
- Major or fundal glands. Located in the bottom and body of the stomach. They produce gastric juice, containing pepsin. Due to the juice produced, digestion of the food mass occurs.
- Intermediary glands. Located in a narrow intermediate zone of the stomach between the body and the gatekeeper. These glands produce a viscous mucoid secret that has an alkaline reaction and protects the stomach from the corrosive effects of gastric juice. In its composition, including, includes hydrochloric acid.
- Pyloric glands. Located in the gatekeeper. The secret they produce also plays a protective role against the acidic environment of the gastric juice.
The secretory function of the stomach is provided by three types of cells: cardiac, base, or main, and pyloric.
This activity of the organ, rather, has a secondary role, since the main absorption of the processed nutrients takes place in the intestine, where the food mass is brought to a state in which the body can easily use all substances necessary for life activity, coming from food from the outside.
It consists in the fact that some substances come from the lymph and blood into the stomach cavity through its wall, namely:
- Amino acids.
- Uric acid.
If the concentration in the blood of these substances increases, then their intake into the stomach increases.
Excretory function of the stomach is especially important in fasting. The protein found in the blood can not be used by the cells of the body. They are only able to assimilate the final product of the breakdown of the protein - the amino acid. Getting from the blood into the stomach, the protein is subjected to further processing under the action of enzymes and breaks down into amino acids, which are later utilized by the tissues of the body and its vital organs.
This function is provided at the expense of the secret that the organ produces. The infected pathogens die from the action of gastric juice on them, more precisely, from the hydrochloric acid in its composition.
In addition, the stomach is designed in such a way that if it gets into it poor quality food, it is able to ensure its return and prevent the ingress of dangerous substances into the intestine. Thus, this process will prevent poisoning.
This function is carried out by the endocrine cells of the stomach, which are located in its mucous layer. These cells produce more 10 hormones, which are able to regulate the work of the stomach and digestive system, as well as the whole organism. Such hormones include:
- Gastrin is produced by the G-cells of the stomach itself. It regulates the acidity of gastric juice, responsible for the synthesis of hydrochloric acid, and also affects the motor function.
- Gastron - inhibits the production of hydrochloric acid.
- Somatostatin - inhibits the synthesis of insulin and glucagon.
- Bombesin - this hormone is synthesized both by the stomach and 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 secretory and motor function of the stomach itself.
- Duocrinin - stimulates the secretion of the 12-duodenum.
- Vasoactive intestinal peptide (VIP). This hormone is synthesized in all parts of the digestive tract. It inhibits the synthesis of pepsin and hydrochloric acid and relaxes the smooth muscle of the gallbladder.
We found out that in the process of digestion and maintenance of vital functions of the body, the stomach plays an important role. The structure and its functions are also indicated.
Diseases of the gastrointestinal tract, as a rule, are associated with a violation of any of its structures. Dysfunction of the stomach is observed quite often. One can speak about such pathologies only if the patient during the examination did not reveal any organic lesions of this organ.
Violations 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.