Human stomach

The stomach is a hollow muscle organ that is part of the digestive tract, located between the esophagus and the duodenum .

In the stomach, the input - cardiac part (pars cardiaca) is distinguished, to the left of which the stomach expands, forming the bottom (arch) of the stomach (fundus (fornix) ventriculi), which then goes down and to the right directly into the body of the stomach (corpus ventriculi). The left (lower) convex edge of the stomach forms a large curvature (cutvatura major), and the right concave upper forms a small curvature (curvatura minor). In the upper left part of the lesser curvature is the cardiac opening (ostium cardiacum) - the place where the esophagus passes into the stomach.

The right narrowed part of the stomach is called pyloric (pars pylorica). In its composition, a wider part, called the pyloric cave (antrum pyloricum), and a narrower channel of the pylorus (canalis pyloricus) are distinguished. The latter passes into the duodenum. The boundary between the pylorus and the duodenum is a circular groove - the pylorus (pylorus), which corresponds to the opening of the pyloric canal. It is equipped with a sphincter (ring muscle). The human stomach has two walls - the front (paries anterior), which is facing forward, somewhat up and to the right, and the back (paries posterior), facing back, down and left. The front and back walls pass one into another along the greater and lesser curvature of the stomach.

The shape of the stomach is subject to changes depending on the amount of food eaten, the position of the human body, and some other factors. The length of an empty stomach is usually about 18-20 cm, the distance between the large and small curvature is 7-8 cm. A moderately filled stomach has a length of 24-26 cm, the maximum distance between the curvatures increases to 10-12 cm, between the front and back walls - 8-9 cm. The volume of the stomach in an adult can vary depending on the amount of food and fluid taken. The volume of an empty stomach is about 0.5 liters. After eating, it stretches from 1.5 to 4 liters.

The peritoneal ligaments of the stomach from the side of lesser curvature belong to the lesser omentum .

Hepatic-gastric ligament, lig. hepatogastricum , which is a continuation to the left of the hepato -duodenal ligament, approaches the pyloric part and the lesser curvature of the stomach from the side of the liver portal. Here, its front and back leaves pass to the corresponding walls of the stomach.

From the side of the greater curvature of the stomach are the ligaments that make up the greater omentum.

Gastric phrenic ligament, lig. gastrophrenicum , passes from the diaphragm to the bottom of the stomach.

Gastro-splenic ligament, lig. gastrosplenicum from the top of the greater curvature approaches the gates of the spleen.

Gastrointestinal ligament, lig. gastrocolicum , connects the greater curvature of the stomach with the transverse colon from the pylorus to the lower pole of the spleen. It is loosely connected with the front wall of the transverse colon, which allows bloodless to separate the greater curvature of the stomach, together with the greater omentum, from the transverse colon when the stomach is resected for cancer.

The listed ligaments of the stomach are often called superficial.

The stomach serves as a reservoir for swallowed food, which is mixed in it and begins to be digested under the influence of gastric juice , which contains pepsin , chymosin , lipase , hydrochloric acid , mucus and other active compounds. In addition to chemical food processing, the stomach also performs an endocrine function by secretion of a number of biologically active substances - histamine , motilin , gastrin , substance P , serotonin , etc., as well as the absorption function - it absorbs sugars, alcohol, water, salt. An antianemic factor is formed in the mucous membrane of the stomach, which contributes to the absorption of vitamin B12 from food.

1. accumulation of food mass, its mechanical processing and promotion into the intestine;
2. Castle's anti-anemic factor secretion (in the middle of the 20th century it was noticed that anemia occurs after resection of the stomach ), which promotes the absorption of vitamin B12 from food;
3. excretory (aggravated by renal failure);
4. protective (bactericidal) - due to hydrochloric acid;

It develops from the anterior torso of the anterior intestine.

At 5-6 weeks, a differentiation of the intestinal tube occurs: a spindle-shaped expansion appears, which is suspended on the ventral and dorsal mesentery. The stuffing bag begins to form. In the area of ​​great curvature, an increased growth of the dorsal mesentery occurs.

At 7-8 weeks, the anterior intestine in the region of the stomach (caudal end) makes rotations: around the vertical axis from left to right (the right wall becomes posterior, the left wall becomes anterior) and around the sagittal axis from bottom to top (small curvature points up, large curvature points down). The ventral and dorsal mesentery atrophy.

At 9-10 weeks, the tissues of the stomach differentiate, and at the end of 3 months, the stomach is formed.

Gastric Topography

Three quarters of the stomach is located in the left hypochondrium and one quarter in the epigastric region. The cardiac opening is located to the left of the stomach at the level of X-XI thoracic vertebrae. The pylorus hole is located at the right edge of the spinal column at the level of the XII thoracic - I lumbar vertebrae. The cardiac part, the bottom and the body of the stomach are adjacent to the diaphragm , the small curvature is in contact with the visceral surface of the left lobe of the liver. To the anterior abdominal wall, a small portion of the body of the stomach is triangular in shape. The gland bag located behind the stomach separates it from the organs located retroperitoneally. In the area of ​​great curvature, the posterior surface of the stomach is adjacent to the transverse colon and its mesentery , the bottom of the stomach is to the spleen . Behind the body of the stomach in the retroperitoneal space are the pancreas , as well as the upper pole of the left kidney and left adrenal gland .

Skeletotopia of the stomach

• cardiac department, lat. pars cardiaca - at level VII of the rib on the left;
• the bottom of the stomach (arch), lat. fundus (fornix) ventricul - at the level of the cartilage of the V rib on the left;
• the body of the stomach, lat. corpus ventriculi - between the bottom of the stomach and the pyloric department, respectively;
• pyloric department (pyloric), lat. pars pylorica - at the level of the Th12-L1 vertebra on the right.

The bottom of the stomach is adjacent to the ribs, the pyloric department - to the spinal column.

Syntopia of the stomach

Adjacent to the stomach:

• in front - the left lobe of the liver ;
• back, left, top - spleen ;
• behind - a pancreas ;
• below - loops of the small (skinny) intestine .

Holotopia of the stomach

Covered with peritoneum on all sides (intraperitoneally), projected into the epigastrium (regio epigastrica).

Histologically, only 3 sections of the stomach are distinguished, since the mucous membrane of the bottom and body of the stomach have a similar structure and are considered as a whole.

The wall of the stomach is formed by four membranes: the mucosa, submucosa, muscle and serous.

Mucous membrane

The relief of the mucous membrane (CO) of the stomach is characterized by longitudinal folds, fields, dimples. It consists of three layers: epithelial, intrinsic and muscular lamina.

Epithelium

A single-layer highly prismatic (columnar) glandular enterodermal type, lining the gastric fossa, is the same in all parts of the stomach. All its cells secrete a special mucous secretion on the surface of CO, covering CO with a continuous layer of 0.5 mm thickness. Bicarbonate , diffusing into the mucus, neutralizes hydrochloric acid. For the secretion of enzymes and hydrochloric acid into the lumen of the stomach, temporary channels are formed in the mucus layer. Mucus forms a protective barrier that prevents mechanical damage to CO and its digestion by gastric juice. This barrier is damaged by alcohol and non-steroidal anti-inflammatory drugs .

The integumentary epithelium is completely renewed within 1-3 days.

Own record

It is formed by loose fibrous unformed connective tissue with a large number of blood and lymph vessels, contains diffuse accumulations of lymphoid tissue and individual lymph nodes. In the form of thin layers passes between the glands of the stomach, which occupy the bulk of this layer.

Glands of the stomach

The number of glands is about 15 million - simple, tubular, branched and unbranched (in the bottom of the stomach; they are divided into cardiac, intrinsic (fundal) and pyloric.

• cardial - tubular, with highly branched end sections, often having a wide clearance. They are located in the cardial part of the stomach, similar to the cardiac glands of the esophagus. They contain mucous cells (with a light CPU, flattened core, lying basally) that produce mucoid secretions, bicarbonates and potassium and sodium chlorides. There are also individual main, parietal and endocrine cells (see below).
• own (fundamental) glands are unbranched, located in the body and the bottom of the stomach and numerically prevail over other types of glands. Groups of 3–7 fall into small gastric fossae. They emit a narrowed neck, an elongated body and bottom. They consist of 5 types of cells: main, parietal (parietal), cervical, additional mucous membranes and endocrine.
  • main cells are the most numerous in the area of ​​the body and the bottom of the gland. They have a pyramidal or cylindrical shape and a large core located basally. CP - basophilic, granular, in the basal part of the cell and around the nucleus contains a lot of graPS, a well-developed KG, in which large secretory zymogenic granules are formed (contain pepsinogen and other proenzymes) that accumulate in the apical part of the cell and secreted into the gland lumen. Under the influence of hydrochloric acid, pepsinogen is converted into active pepsin in the lumen of the stomach.
  • parietal (parietal) cells - prevail in the area of ​​the body of the gland. Larger than the main ones. They have a rounded shape with a narrow apex facing the lumen of the gland, which they protrude between the main cells, located outside of them. The nucleus lies in the center of the cell. In the oxyphilic CPU there are many large MTXs with developed cristae and special intracellular secretory tubules in the form of narrow slits, in which numerous microwaves are turned.
  • On the periphery of the tubules there is a tubulo-vesicular complex - a system of membrane vesicles and tubes (reserve membrane containing ion pumps), which merge with the tubules with active secretion.
    Parietal cells secrete hydrogen and chlorine ions through the apical pole, which, in their entirety, represent hydrochloric acid, which creates an acidic (pH <2) medium in the lumen of the stomach. The latter provides:
    • protein breakdown;
    • conversion of pepsinogen to pepsin and optimum pH for the activity of the latter;
    • inhibition of the growth of pathogenic microorganisms.
      

Through the basal plasmalemma, the parietal cell releases bicarbonate ions, which are brought by capillaries of their own plate to the basal surface of the integumentary cells, transporting them to the mucus, where they neutralize hydrochloric acid.
Parietal cells also synthesize and secrete an antianemic factor, which, having formed a complex with vitamin B12, is absorbed in the ileum and is necessary for normal blood formation. With the failure of this factor (as a result of autoimmune damage to parietal cells or after removal of the stomach), malignant anemia develops.
The secretion of parietal cells is stimulated by histamine, gastrin and acetylcholine.

• mucous cervical cells - not numerous, located in the neck. Small size. The cytoplasm is weakly basophilic, granular, contains moderately developed graPS and a large supranuclear CG, from which large mucous granules accumulate at the apical pole are separated. These cells often divide and are considered as cambial elements of the epithelium of the glands and integumentary epithelium of the stomach, where they, differentiating, migrate. Cell renewal in the glands is much slower than in the integumentary epithelium. The mucus produced by the cervical cells probably protects them from damage.
• additional mucous cells - are located in the body of its own glands and have a densified nucleus in the basal part of the cells. In the apical part of these cells, many round and oval granules, a small amount of Mx and KG were found.
• endocrine cells - located in the bottom of the glands. Light, the form is diverse (triangular, oval or polygonal). The apical pole contains the nucleus; it does not always reach the lumen of the gland. In the basal pole are dense secretory granules secreted into the blood. The granules are coated with a membrane, stained with silver and chromium salts and contain peptide hormones and amines.
  Relate to DES and APUD-system, divided into EC-, ECL- and G-cells. They produce hormones that affect the secretory activity and motility of the digestive tract:
  

• D: somatostatin (body, pyloric department) - inhibits the secretion of HEP cells and gastric glands;
• EC: serotonin, motilin, substance P (body, pyloric department) - enhances intestinal motility;
• ECL: histamine (body) - enhances the secretion of hydrochloric acid by the stomach;

• pyloric glands are tubular, with highly branched and convoluted end sections. They are located in the pyloric department. Fall into very deep gastric fossae. Formed by mucous cells, the secret of which protects CO from acidic gastric juice. Most glands do not contain parietal cells. They are mainly represented by endocrine cells (see above):
  

• D: somatostatin (body, pyloric department) - inhibits the secretion of HEP cells and gastric glands;
• EC: serotonin, motilin, substance P (body, pyloric department) - enhances intestinal motility;
• G: gastrin (pyloric department) - enhances the secretion of hydrochloric acid and pepsinogen by the stomach;
• L: enteroglucagon (pyloric department) - stimulates glycogenolysis in the liver.

Muscle plate

Muscle plate CO - is formed by three layers of smooth muscle cells (inner and outer circular and middle longitudinal). From it, thin bundles of smooth muscle cells are sent between the glands.

Submucosa

The submucosa of the stomach is well developed. It is formed by loose fibrous unformed connective tissue, which is rich in its structure with elastic fibers, blood and lymph vessels (arterial, venous and lymphatic plexuses) and nerves (submucosal plexus). The submucosa is involved in the formation of gastric folds.

Muscle sheath

The muscular membrane of the stomach is formed by smooth muscle tissue that forms 3 layers: the outer - longitudinal, the middle - circular, the inner - oblique. The first two of them are a continuation of the eponymous layers of the muscular membrane of the esophagus. Longitudinal muscle bundles are located mainly near the small and large curvature of the stomach. Individual muscle bundles are more developed in the pyloric region.

The circular layer is maximally developed in the pyloric department, where its fibers form the pyloric compressor (sphincter) (thickness 3-5 mm). When it is reduced, the exit from the stomach is closed. Obliquely oriented muscle fibers in the structure of the walls of the digestive canal are present only in the stomach. They “spill over” through the cardial part of the stomach to the left of the cardiac opening and then go down and to the right in the thickness of the walls of the stomach towards large curvature. Between the muscle layers is the muscular nerve plexus.

Serous membrane

The outer serous membrane is represented by the peritoneum. It is formed by a layer of mesothelium and underlying connective tissue. Only narrow strips of the walls of the stomach located on the small and large curvature are devoid of serous cover. In these places, blood vessels and nerves approach the stomach. The serous membrane is separated from the muscle by a thin subserous base.

The glands of the gastric mucosa secrete gastric juice containing digestive enzymes pepsin , chymosin and lipase , as well as hydrochloric acid and other substances. Gastric juice breaks down proteins and partially fats , has a bactericidal effect.

Due to the muscle layer, the stomach mixes food and gastric juice, forming chyme - a liquid slurry that is removed in separate portions from the stomach through the pyloric canal. Depending on the consistency of the food received, it lingers in the stomach from 20 minutes (fruit juices, as well as vegetable juices and broths) to 6 hours (pork).

In addition, the wall of the stomach absorbs carbohydrates , ethanol , water and some salts.

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