Structure and function of the stomach

Patient complains to the doctor for stomach pain. And ask more, so he does not even know where the stomach is, from which side, below or above the abdomen. Therefore, doctors adhere to the rule of asking questions about the place where it hurts.

And what body is relevant to the problem, you can understand, knowing the anatomical and physiological features of the gastrointestinal tract and digestion of a person as a whole. To find out how the stomach hurts, we will return to the school volume of knowledge about its anatomical structure, analyze the device and add a little about the features of the work.

Where is the stomach?

From the course of anatomy it is known that the stomach is located in the uppermost part of the abdominal cavity in the "border" area to the diaphragm. Its projection on the abdomen allows us to distinguish the epigastrium zone for the apex( the middle region where the lower ribs connect), the lower sections are opposite the navel.

The stomach of the person in relation to the median line at ¾ is to the left and to the right lies ¼ of the organ. The shape and capacity of the organ may vary. But there is always an opportunity to select a bend from the left along the contour-a small curvature, and on the right-a large curvature. The location of the stomach is often directed slightly at an angle to the middle down and to the left.

Dimensions and shape

The size of the stomach of an adult person depends on its shape, fullness, individual characteristics. The form is supported by:

• muscle tone;
• height of the dome of the diaphragm;
• by intra-abdominal pressure;
• is the effect of the intestine.

It is capable of changing under the action of the contents, with a change in the position of the body, depending on the condition of neighboring organs, in pathology. For example, when cicatrizing the ulcer, it is possible to form an "hourglass", with ascites and tumors the stomach looks like a "horn".Gastroptosis( omission of the stomach) causes a lowering of the lower border to the level of the small pelvis, and the shape is lengthened.

Radiologically the upper limit is 0.5 to 2.5 cm below the contour of the diaphragm, the lower - 2-4 cm above the ilium, the variants of the

form are visible in the study. The dimensions of the stomach at moderate filling are:

• in a length of 15-18 cm, width of 12-14 cm;
• wall thickness is 2-3 mm.

Average capacity in the male body is 1.5-2.5 liters, in women it is slightly less. Depending on the slope of the longitudinal axis, the position of the organ is fixed as vertical, horizontal or oblique. For tall, lean asthenics, the vertical position is more typical, for the short-legged undersized hypersthenics - horizontal, with a normostenic physique, an oblique direction is observed.

Neighborhood organs

Anatomy of the human stomach is inextricably linked to the condition of neighboring organs. Therefore, it is important for a doctor to know the topography, you can call it a "3D vision" of connections with neighboring bodies. The anterior surface of the stomach is partially attached to the diaphragm, to the abdominal wall and the lower edge of the liver.

The posterior surface touches the pancreas, aorta, spleen, upper part of the left kidney with the adrenal gland, in part - with the transverse colon. Dense "neighborhood" is supported by nutrition from some arterial branches, joint venous and lymphatic drainage. Therefore, the structure of the human stomach is susceptible to changes in pathological conditions of other internal organs.

We should not forget that behind the stomach around the superior mesenteric artery lies the solar plexus, which receives impulses from all the major organs of the

. Departments and their anatomy

The entrance( cardiac) hole connects the stomach to the esophagus. Through it comes swallowed food. The output( gateway) channel ensures the transfer of the processed contents to the initial section of the small intestine-the duodenum. At the borders there are muscular pulpit( sphincters).Their timely work depends on the timing of digestion.

Conditionally in the stomach are 4 parts:

• cardiac( input) - connects to the esophagus;
• bottom - next to the cardial part forms the arch;
• body is the main department;
• gatekeeper( pyloric) - forms the output.

In the gateway zone, an antrum( cave) and the canal are isolated. The departments of the stomach perform their tasks. For this, they have a special structure at the cellular level.

The structure of the stomach wall

The exterior of the body is covered with a serous membrane from a loose connective tissue tissue and flat epithelium. From the inside, the wall divides:

• into the mucosa;
• submucosal layer;
• muscle layer.

An important feature is the absence of nerve pain receptors in the mucosa. They are found only in deeper layers. Therefore, a person feels pain when the work of muscles is broken( spastic contraction or hyperextension) or pathological process, bypassing the mucous membrane has passed into the depth( with erosions, ulcers).

Due to the muscle tone from the inside, folds are retained, which, if necessary, increase the volume of the human stomach( function of depositing)

Which cells provide the function of digesting food?

The structure of the mucosa is studied by histologists in the diagnosis of the pathological process. Normally, it includes:

• cells of single-layered cylindrical epithelium;
• layer, called "own", from loose connective tissue;
• muscular plate.

In the second layer there are own glands, having a tubular structure. They are subdivided into 3 subspecies:

• main ones - produce pepsinogen and chymosin( digestive enzymes, in acid medium they turn into proteolytic enzymes);
• parietal( obkladochnye) - synthesize hydrochloric acid and gastromukoprotein;
• additional - form slime.

Among the glands of the pyloric zone there are G-cells that release the gastric hormonal substance - gastrin. Additional cells, except for mucus, synthesize the substance necessary for the assimilation of vitamin B12 and hematopoiesis in the bone marrow( Castle factor).The entire surface of the mucosa in the deep layers contains cells synthesizing the precursor of serotonin.

Gastric glands are arranged in groups, so under the microscope from the inside, the mucosa has a granular appearance with small pits and flat irregularly shaped fields. Attention is paid to the good adaptability of a healthy mucosa. It is capable of rapid recovery: the epithelium on the surface is replaced less than every 2 days, and the glandular - in 2-3 days. A balance is maintained between the old cells being rejected and the newly educated.

In diseases of the stomach, hypertrophy of glands, inflammation and cell death occurs, dystrophic and atrophic disorders are accompanied by a failure of production of the necessary substances, scarring replaces the active tissue with dysfunctional fibroblasts. Malignant cells are transformed into atypical cells. Begin to expand and release toxic substances that poison the body.

The secretory activity of the stomach is controlled by nervous and humoral mechanisms. The main influence on the work of the organ is provided by the branches of the sympathetic and vagus nerves. Sensitivity is provided by the receptor apparatus of the wall and spinal nerves.

How is the food transported?

The structure of the stomach provides for the transportation of food from the esophagus with its simultaneous treatment. The muscular wall shell includes 3 layers of smooth muscles:

• from the outside - longitudinal;
• in the middle - circular( circular);
• from the inside - oblique.

When the muscle groups contract, the stomach works like a "concrete mixer".At the same time, rhythmic contractions occur in segments, pendulum movements, and tonic contractions.
Thanks to this, the food continues to be crushed, well mixed with gastric juice, gradually moves to the pyloric department.

Several factors affect the passage of the food lump from the stomach into the intestine:

• mass of the contents;
• supports the difference in pressure between the gastric outlet and the duodenal bulb;
• Sufficiency of pulverization of gastric contents;
• osmotic pressure of the processed food composition( chemical composition);
• temperature and acidity.

Gastric juice provides "processing" of the food lump

Peristalsis is strengthened under the influence of the vagus nerve, oppressed by sympathetic innervation. The bottom and body of the stomach provide food storage, the effect of proteolytic substances on it. The antral part is responsible for the evacuation process.

How is the stomach protected?

In the anatomy of the stomach, it is impossible not to mention the ability of the body to self-defense. A thin layer of mucus is represented by a mucoid secret, produced by a cylindrical epithelium. Its composition includes polysaccharides, proteins, proteoglycans, glycoproteins. Slime is insoluble. Has a slightly alkaline reaction, is able to partially neutralize excess hydrochloric acid. In acidic medium it turns into a thick gel, covers the entire inner surface of the stomach.

Stimulate the production of mucus insulin, serotonin, secretin, nerve receptors of the sympathetic nerve, prostaglandins. The opposite inhibitory effect( which corresponds to the violation of the protective barrier) is provided by medications( for example, Aspirin groups).Insolvency protection leads to an inflammatory reaction of the gastric mucosa.

Anatomico-physiological features( AFO) in children and the elderly

In the fourth week of pregnancy, the embryo develops from the anterior pharynx of the pharynx, esophagus, stomach and partly othersorgans of digestion. The newborn stomach is horizontal. When the kid gets to his feet and starts walking the axis moves to a vertical position.

The volume of physiological capacity does not immediately correspond to the size of the organ:

• in the newborn it is only 7 ml;
• on the fifth day - 50 ml;
• for the tenth - 80 ml.

In the period of newborns, the cardial department and the bottom are most poorly developed. The cardiac sphincter functions insufficiently compared to the pyloric sphincter, so the baby often belches. In the mucous membrane there are still few secretory glands, it is functionally ready to receive only the mother's milk. Gastric juice has the same composition as in an adult, but its acidity and enzyme activity is much lower.

Stomach's stomach produces basic enzymes:

• chymosin( rennet enzyme) - is necessary for the assimilation and curtailing of milk;
• lipase - for the splitting of fats, but it is still not enough.

Peristalsis of the muscle layer is slowed down. The period of evacuation of food in the intestines depends on the type of feeding: the artificial animals are delayed for a longer period. The development of the total mass of the gastric glands is affected by the transition to complementary feeding and further expansion of nutrition. By adolescence, the number of glands increases a thousand times. In old age, the position of the stomach again returns to the horizontal, often there is an omission.

Dimensions are reduced. The muscle layer gradually atrophies and loses its tone. Therefore peristalsis is sharply slowed down, food is delayed for a long time. Simultaneously, the cells of the mucous membrane are depleted and atrophied, the amount of secreting glands decreases. This is expressed in a decrease in the production of pepsin, mucus, a decrease in acidity. In elderly people, due to the pronounced atherosclerotic process in the mesenteric arteries, the nutrition of the organ wall is disrupted, which provokes the formation of ulcers.

Scheme of departments and their functional purpose

Functions

Anatomical structure of the stomach is adapted to perform the body of the basic functional duties:

• formation of acid and pepsin for digestion;
• mechanical and chemical processing of food by gastric juice, enzymes;
• the deposition of the food lump for the time necessary for proper digestion;
• evacuation to the duodenum;
• development of Kastla's internal factor for the assimilation of vitamin B12, which the body needs as a coenzyme in the biochemical energy production process;
• participation in the metabolism by the synthesis of serotonin, prostaglandins;
• synthesis of mucus to protect the surface, gastrointestinal hormones involved in various stages in the digestive process.

Different degree of disruption of functions leads to pathology not only of the stomach, but also of other digestive organs. The goal of therapy of diseases in gastroenterological practice is the restoration of function and anatomical structures.