Nutrition is the process necessary to ensure the vital functions of the human body. The stomach plays a major role in this process. The functions of the stomach are the accumulation of food mass, its partial processing and further advancement into the intestine, where nutrients are absorbed. All these processes occur 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:
- Cardial (input) part. Its projection is at the level of 7 ribs on the left.
- The arch or the bottom, the projection of which is located on the left at the level of the 5th rib, more precisely, its cartilage.
- The body of the stomach.
- Pyloric or pyloric department. At the exit from the stomach is the pyloric sphincter, which separates the stomach from the duodenum 12. The projection of the pylorus is located in front opposite the 8th rib to the right of the midline and behind between the 12th thoracic and 1st lumbar vertebra.
The shape of this organ looks like a hook. This is especially noticeable in x-rays. The stomach has a small curvature that faces the liver, and a large curvature that faces the spleen.
The organ wall consists of four layers, one of which is external, it represents the serous membrane. Three other layers are internal:
- Muscular.
- Submucosa.
- Slimy.
Due to the rigid muscle layer and the submucosa lying on it, the mucosa has numerous folds. In the area of the body and the bottom of the stomach, these folds have an oblique, longitudinal and transverse direction, and in the region of lesser curvature - only longitudinal. Due to this structure, the surface of the gastric mucosa is significantly increased. This facilitates the digestion of the food lump.
Functions
What function does the stomach perform? A lot of them. We list the main ones.
- Motor.
- Secretory.
- Suction.
- Excretory.
- Protective.
- Endocrine.
Each of these functions in the digestive process plays an important role. Next, we consider the functions of the stomach in more detail. It is known that the digestion process begins even in the oral cavity, from where food passes through the esophagus into the stomach.
Motor function
Further digestion of food occurs in the stomach . The motor function of the stomach is the accumulation of food mass, its mechanical processing and further advancement into the intestine.
During meals and in the first minutes after this, the stomach is relaxed, which contributes to the accumulation of food in it and provides secretion. Next, contractile movements that provide the muscle layer begin. In this case, the food mass is mixed with gastric juice.
The following types of movements are characteristic of the musculature of an organ:
- Peristaltic (wave-like).
- Systolic - occur in the pyloric department.
- Tonic - help reduce the size of the cavity of the stomach (its bottom and body).
After eating, peristaltic waves are weak at first. By the end of the first hour after the meal, they intensify, which helps to move the food lump to the exit from the stomach. The pressure in the pyloric region of the stomach increases. The pyloric sphincter opens and part of the food mass enters the duodenum 12. The remaining large part of this mass returns to the pyloric department. The evacuation function of the stomach is inseparable from the motor. They provide grinding and homogenization of the food mass and thereby contribute to better absorption of nutrients in the intestine.
Secretory function. Glands of the stomach
The secretory function of the stomach is to chemically treat the food lump with the help of the secretion produced. One to one and a half liters of gastric juice is produced per day in an adult. It consists of hydrochloric acid and a number of enzymes: pepsin, lipase and chymosin.
Glands are located on the entire surface of the mucosa. They are glands of external secretion 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 area of the cardia near the entrance to this body. These glands produce mucoid mucus-like secretions. It performs a protective function and serves to protect the stomach; it is self-digesting.
- The main or fundus glands. They are located in the bottom and body of the stomach. They produce gastric juice containing pepsin. Due to the produced juice, digestion of the food mass occurs.
- Intermediary glands. Located in a narrow intermediate zone of the stomach between the body and the pylorus. These glands produce a viscous mucoid secretion, which has an alkaline reaction and protects the stomach from the aggressive effects of gastric juice. It also includes hydrochloric acid.
- Pyloric glands. Located in the pyloric part. The secret they produce 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 organ, rather, has a secondary role, because the main absorption of processed nutrients occurs in the intestine, where the food mass is brought to a state in which the body can easily use all the substances necessary for life, coming from outside from food.
Excretory function
It consists in the fact that some substances come from the lymph and blood into the cavity of the stomach through its wall, namely:
- Amino acids.
- Squirrels.
- Uric acid.
- Urea.
- Electrolytes.
If the concentration in the blood of these substances increases, then their entry into the stomach increases.
Excretory function of the stomach is especially important during fasting. Protein in the blood cannot be used by the cells of the body. They can only assimilate the final 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 then utilized by the body’s tissues and its vital organs.
Protective function
This function is provided by the secret that the body produces. Caught pathogens die from exposure to gastric juice, more precisely, from hydrochloric acid in its composition.
In addition, the stomach is designed in such a way that when poor-quality food gets into it, it is able to ensure its return and prevent the entry of hazardous substances into the intestines. Thus, this process will prevent poisoning.
Endocrine function
This function is carried out by the endocrine cells of the stomach, which are located in its mucous layer. These cells produce more than 10 hormones that are able to regulate the functioning of the stomach and digestive system, as well as the whole organism. These hormones include:
- Gastrin - is 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.
- Bombesin - this hormone is synthesized both by the stomach itself and by the proximal part of the 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.
- Duocrinin - stimulates the secretion of the duodenum 12.
- 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 muscles of the gallbladder.
We found out that in the process of digestion and ensuring the vital functions of the body, the stomach plays an important role. The structure and functions of it are also indicated.
Functional disorders
Gastrointestinal diseases, as a rule, are associated with a violation of any of its structure. Violation of the function of the stomach is observed quite often. You can talk about such pathologies only if the patient during the examination did not reveal any organic lesions of this organ.
Disorders of the secretory or motor function of the stomach can occur with pain and dyspepsia. But with proper treatment, these changes are often reversible.