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External structure of the stomach. Structure of the stomach: sections, layers

Stomach wall consists of three shells:
1) tunica mucosa - mucous membrane with a highly developed submucosa, tela submucosa;
2) tunica muscularis - muscular coat;
3) tunica serosa - serous membrane.

Tunica mucosa built according to the main function of the stomach - chemical processing of food in an acidic environment.

In this regard, in the mucous membrane there are special gastric glands that produce gastric juice, succus gastricus, containing hydrochloric acid.

There are three types of glands:
1) cardiac glands, glandulae cardiacae;
2) gastric glands, glandulae gastricae(propriae); they are numerous (approximately 100 per 1 mm 2 surface), located in the fornix and body of the stomach and contain two types of cells: main cells (secrete pepsinogen) and parietal cells (secrete hydrochloric acid);
3) pyloric glands, glandulae pyloricae, consist only of chief cells.

In some places, single lymphatic follicles, folliculi lymphatici gastrici.

Close contact of food with the mucous membrane and better saturation with gastric juice is achieved due to the ability of the mucous membrane to collect in folds, plicae gastricae, which is ensured by the contraction of the mucosal mucosa’s own muscles (lamina muscularis mucosae) and the presence of a loose submucosa, tela submucosa, containing vessels and nerves and allowing the mucous membrane to smooth out and gather into folds in different directions.

Along the lesser curvature, the folds have a longitudinal direction and form a “gastric track”, which, with contraction of the stomach muscles, can now become a channel through which liquid parts of food (water, saline solutions) can pass from the esophagus to the pylorus, bypassing the cardiac part of the stomach.

In addition to folds, the mucous membrane has roundish elevations (1 - 6 mm in diameter), called gastric fields, areae gastricae, on the surface of which numerous small (0.2 mm in diameter) openings of the gastric pits, foveolae gastricae, are visible. The glands of the stomach open into these pits.

In fresh condition tunica mucosa reddish-gray in color, and at the entrance to the esophagus, a sharp boundary between the squamous epithelium of the esophagus (skin-type epithelium) and the columnar epithelium of the stomach (intestinal-type epithelium) is macroscopically noticeable.

In the area pyloric holes, ostium pyloricum, there is a circular fold of the mucous membrane that separates the acidic environment of the stomach from the alkaline environment of the intestine; it's called valvula pylorica.


Tunica muscularis represented by myocytes, non-striated muscle tissue, which help mix and move food; according to the shape of the stomach in the form of a bag, they are located not in two layers, as in the esophageal tube, but in three: outer - longitudinal, stratum longitudindle; average - circular, stratum circulare, and internal - oblique, fibrae oblique. Longitudinal fibers are a continuation of the same fibers of the esophagus.

Stratum circularе more pronounced longitudinally; it is a continuation of the circular fibers of the esophagus. Towards the exit of the stomach, the circular layer thickens and forms a ring of muscle tissue at the border between the pylorus and the duodenum, m. sphincter pylori - pyloric constrictor.

Corresponding to the sphincter pyloric valve, valvula pylorica, with contraction of the pyloric constrictor, it completely separates the cavity of the stomach from the cavity of the duodenum.

Sphincter pylori and valvula pylorica constitute a special device that regulates the passage of food from the stomach to the intestine and prevents its reverse flow, which would entail neutralization of the acidic environment of the stomach.


Fibrae obliquae, oblique muscle fibers, are folded into bundles, which, wrapping in a loop on the left ostium cardiacum, form "support loop", serving as a punctum fixum for the oblique muscles. The latter descend obliquely along the anterior and posterior surfaces of the stomach and, during their contraction, pull the greater curvature towards the ostium cardiacum.

The outermost layer of the stomach wall is formed serous membrane, tunica serosa, which is part of the peritoneum; The serous cover closely fuses with the stomach along its entire length, with the exception of both curvatures, where large blood vessels pass between the two layers of the peritoneum.

On the posterior surface of the stomach to the left of the ostium cardiacum there is a small area not covered by the peritoneum (about 5 cm wide), where the stomach is in direct contact with the diaphragm, and sometimes with the upper pole of the left kidney and the adrenal gland. Despite its relatively simple shape, the human stomach, controlled by a complex innervation apparatus, is a very advanced organ that allows a person to quite easily adapt to various dietary regimes.

>> what is a stomach?

(lat. ventriculus, gaster) is a hollow organ of the digestive tract in which accumulation and partial digestion of food occurs.

Anatomical characteristics of the stomach
The entire gastrointestinal tract can be imagined as a pipe approximately 7-8 m long. The upper sections of the digestive tract are represented by the oral cavity, pharynx, esophagus, stomach and the initial section of the small intestine (duodenum), the lower sections are a continuation of the small intestine (jejunum and ileum ), as well as the large intestine with its end section - the rectum. As food passes through the various sections of this tube, it undergoes various changes - digestion and absorption. The stomach is a pouch-shaped extension of the digestive tube located between the esophagus and duodenum. Food from the mouth enters the stomach through the esophagus. From the stomach, partially digested food masses are excreted into the duodenum (the initial section of the small intestine).

The site provides reference information for informational purposes only. Diagnosis and treatment of diseases must be carried out under the supervision of a specialist. All drugs have contraindications. Consultation with a specialist is required!

Mucosa of the stomach consists of three layers: epithelium (E), lamina propria (LP) and lamina muscularis (MP) of the mucous membrane.


Surface mucous membrane forms a variable pattern of grooves, ridges, funnel-shaped recesses communicating with the openings of the gastric pits (GD). The pits are lined with a single-layer highly prismatic epithelium consisting of superficial mucous cells. At the bottom of the fossa, from 3 to 5 gastric glands (PG) open. To show them better, the group of glands in the figure is highlighted.


 Stomach glands- purely tubular glands, lined with a single-layer cubic or prismatic epithelium, consisting of several types of cells, therefore the production of gastric glands is a mixture of the secretions of these cells. In such cases, some authors talk about heterocrine glands. The glands are long and consist of a base, body and neck, which opens into the gastric cavity (pit). The glands occupy most of the thickness mucous membrane. Sometimes they branch into two branches. The native glands of the stomach run perpendicular to the muscular plate of the mucous membrane, reaching it with their bases. In total there are about 15 million own gastric glands.


The glands are surrounded by well-vascularized loose interglandular connective tissue - the lamina propria (LP).


The muscular plate of the mucous membrane is relatively thick and is divided into two layers - the inner circular and outer longitudinal.


The submucosa (SU) is formed by loose connective tissue with many arteries (A) and veins (B) of the muscular type. Lymphatic vessels (not shown) and the submucosal nerve plexus (NS) are also present here.


Blood supply to the mucous membrane occurs as follows: the arteries of the submucosal base give off two types of branches - short and long arterioles, which pass through the muscular plate of the mucosa and reach the interglandular lamina propria. Short arterioles (SAR) branch to form a basal capillary network that supplies the base and body of the glands. Long arterioles (LARs) pass without branching along the glands and then form the superficial capillary network (SCR) just below the surface of the epithelium. This capillary network surrounds the gastric pits and ensures their good vascularization. The same network supplies blood to the necks of the glands, anastomosing with capillaries formed by short arterioles.

Both capillary systems are drained by common venules (Vn), which descend along the glands and empty into the veins of the submucosa.


This system blood supply to the mucous membrane body of the stomach provides excellent oxygenation.

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The stomach (gaster) is a sac-like expansion of the lower part of the esophagus, localized in the peritoneum, most of it is located on the left side of the hypochondrium (3/4), ¼ is located in the epigastric region.

The shape, size, position and volume of the organ are changeable, the parameters depend on the tone of the muscles of the stomach, its filling with gases, food, physique, size and location of neighboring organs.

Topography and structure

The stomach is located in the epigastrium between the esophagus and duodenum (duodenum), under the diaphragm and liver. The volume of an organ in an adult is 1–3 liters, the length of an empty organ is 18–20 cm, and the length of a filled organ is 22–26 cm.

The stomach consists of the following parts:

  • The cardiac part, which is adjacent to the area where the esophagus enters the stomach;
  • Bottom (vault);
  • Body;
  • The pyloric part consists of the vestibule and the canal (pylorus);
  • Minor and major curvature (walls).

The wall of the stomach consists of the following layers: the muscular layer, the serous layer and the mucous layer.

Muscularis, which includes:

  • The outer layer is the rectus muscles (lesser and greater curvature);
  • Middle - circular muscles (sphincter - a valve that prevents the exit of the food bolus);
  • Internal - oblique muscles (give the stomach its shape).

The muscular layer is responsible for the activity of contractions (peristalsis) of the organ and the advancement of the food bolus.

Serous layer, which is separated from the muscle by a thin subserosal layer, it is responsible for nutrition and innervation (supply of nerve endings) of the organ. This layer covers the stomach completely, provides shape and fixes the organ. The layer contains lymphatic, blood vessels and Meissner's nerve plexuses.

Mucous layer– forms folds that increase the surface area of ​​the stomach for more efficient digestion. In addition to the folds, the layer contains gastric fields (round elevations), on their surface the ducts of the endocrine glands open, which produce gastric juice.

The organ is supplied with blood through the celiac trunk, the left and right omental arteries of the stomach and small intragastric arteries. Lymphatic drainage occurs through the hepatic lymph node, the innervation of the organ is carried out by the submucosal, subserosal and intermuscular plexuses (intramural nerve plexuses), and the vagus and sympathetic nerves are also involved.

Stomach glands

The glands of the organ look like tubes with an expanded end. The narrow part is necessary for secreting various chemical substances, the wide part of the gland is intended for removing the resulting substance. There are pits located on the inside of the organ; they are the excretory ducts of the glands.

Exocrine (external) glands They have drainage ducts through which the resulting secretion is discharged out. Depending on the location, the following types of glands are distinguished:

  • Cardiac - the number is 1–2 million, localized at the entrance to the stomach, their function is to soften the bolus of food and prepare it for digestion;
  • Own - the number is about 35 million, each gland consists of 3 types of cells: main, mucous and parietal. The main ones contribute to the breakdown of milk protein, produce chymosin and pepsin, which digests all remaining proteins. The mucous membranes produce mucus, and hydrochloric acid is synthesized in the parietal membranes;
  • Pyloric - number 3.5 million, localized in the transition of the stomach to the small intestine, consist of mucous and endocrine cells. Mucous cells produce mucus, which dilutes gastric juice and partially neutralizes hydrochloric acid. Endocrines take part in the formation of gastric juice.

Endocrine glands are localized in the tissues of the organ, these include the following gland cells:

  • Somatostotin – inhibits the activity of the organ;
  • Gastrin – stimulates the functioning of the stomach;
  • Bombesin – activates the synthesis of hydrochloric acid and the functioning of the gallbladder;
  • Melatonin – is responsible for the daily cyclicity of the organ;
  • Enkephalin – has an analgesic effect;
  • Histamine – activates the synthesis of hydrochloric acid, affects blood vessels;
  • Vasointestinal peptide - dilates vascular walls, activates the activity of the pancreas.

The functioning of the organ occurs according to the following scheme:

  • The sight, smell of food, irritation of taste buds activate gastric secretion;
  • The cardiac glands produce mucus to soften the food mass and protect the organ from self-digestion;
  • Own glands produce hydrochloric acid and digestive enzymes. Hydrochloric acid disinfects food, breaks it down, enzymes contribute to chemical processing.

Functions of the organ

The stomach performs the following functions:


The human stomach is the body's main food storage reservoir. If the body did not have such a capacity as the stomach, we would eat constantly, and not just several times a day. It also secretes a mixture of acid, mucus and digestive enzymes that help digest and sanitize our food while it is stored.

Macroscopic anatomy

What kind of stomach does a person have? It is a round, hollow organ. Where is a person's stomach? It is located below the diaphragm on the left side of the abdominal cavity.

The structure of human organs is such that the stomach is located between the esophagus and the duodenum.

The stomach is an expanded tract, shaped like a crescent. Its inner layer is full of wrinkles, known to us as wrinkles (or folds). It is these folds that allow it to stretch to accommodate large portions of food, which subsequently quietly moves during the digestion process.

Based on shape and function, the human stomach can be divided into four parts:

1. The esophagus connects to the stomach in a small area called the cardia. This is a narrow, tube-like part that passes into a wider cavity - the body of the stomach. The cardia consists of the lower esophageal sphincter, as well as a group of muscle tissue that contracts to hold food and acid in the stomach.

2. The cardiac section passes into the body of the stomach, which forms its central and largest part.

3. Slightly above the body is a dome-shaped area known as the floor.

4. Below the body is the pylorus. This part connects the stomach to the duodenum and contains the pyloric sphincter, which controls the flow of partially digested food (chyme) from the stomach and into the duodenum.

Microscopic anatomy of the stomach

Microscopic analysis of the structure of the stomach shows that it is made of several separate layers of tissue: mucous, submucosal, muscular and serous.

Mucous membrane

The inner layer of the stomach consists entirely of simple epithelial tissue with many exocrine cells. Small pores called gastric pits contain many exocrine cells that produce digestive enzymes and mucous cells, located throughout the mucosa and gastric pits, secrete mucus to protect the stomach from its own digestive secretions. Due to the depth of the gastric pits, the mucous membrane can thicken, which cannot be said about the mucous membrane of other organs of the gastrointestinal tract.

Deep in the mucous membrane there is a thin layer of smooth muscle - the muscular plate. It is she who forms folds and increases contact of the mucous membrane with the contents of the stomach.

Around the mucous membrane there is another layer - the submucosa. It consists of connective tissue, blood vessels and nerves. Connective tissues support the structure of the mucous membrane and connect it to the muscle layer. The blood supply to the submucosa ensures the supply of nutrients to the walls of the stomach. Nerve tissue in the submucosa controls the contents of the stomach and controls smooth muscle and the secretion of digestive substances.

Muscle layer

The muscular layer of the stomach surrounds the submucosa and makes up most of the gastric mass. The muscle plate consists of 3 layers of smooth muscle tissue. These layers of smooth muscle allow the stomach to contract to mix food and move it through the digestive tract.

Serosa

The outer layer of the stomach surrounding the muscle tissue is called the serosa, which is made of simple squamous epithelial and loose connective tissue. The serosa has a smooth, slippery surface and secretes a thin, watery secretion known as the serosa. The smooth, wet surface of the serosa helps protect the stomach from friction as it continually expands and contracts.

The anatomy of the human stomach is now more or less clear. We will consider everything described above a little later in the diagrams. But first, let's figure out what the functions of the human stomach are.

Storage

In the mouth, we chew and moisten solid food until it becomes a homogeneous mass, shaped like a small ball. As we swallow each pellet, it slowly passes through the esophagus to the stomach, where it is stored along with the rest of the food.

The volume of a person's stomach can vary, but on average it can hold 1-2 liters of food and liquid to aid digestion. When the stomach is stretched by a large amount of food, it can store up to 3-4 liters. A distended stomach makes digestion difficult. Since the cavity cannot easily contract to mix food properly, it results in a feeling of discomfort. The volume of a person’s stomach also depends on the age and condition of the body.

After the stomach cavity has been filled with food, it is stored for another 1-2 hours. At this time, the stomach continues the digestive process that began in the mouth, and allows the intestines, pancreas, gallbladder and liver to prepare to complete the procedure begun.

At the end of the stomach, the pyloric sphincter controls the movement of food into the intestines. Typically, it is usually closed to contain food and stomach secretions. Once the chyme is ready to leave the stomach, the pyloric sphincter opens to allow a small amount of digested food to pass into the duodenum. Over the course of 1-2 hours, this process is slowly repeated until all digested food leaves the stomach. The slow rate of release of chyme helps break it down into its components and maximize digestion and absorption of nutrients in the intestines.

Secretion

The stomach produces and stores several important substances to control the digestion of food. Each of them is produced by exocrine or endocrine cells found in the mucous membrane.

The main exocrine product of the stomach is gastric juice - a mixture of mucus, hydrochloric acid and digestive enzymes. Gastric juice mixes with food in the stomach to aid digestion.

Specialized exocrine cells of the mucous membrane - mucous cells - store mucus in the folds and pits of the stomach. This mucus spreads across the mucosal surface to coat the lining of the abdomen with a thick, acid- and enzyme-resistant barrier. Stomach mucus is also rich in bicarbonate ions, which neutralize the pH of stomach acid.

Located in the pits of the stomach, they produce 2 important substances: intrinsic Castle factor and hydrochloric acid. Intrinsic factor is a glycoprotein that binds to vitamin B12 in the stomach and helps it be absorbed by the small intestine. is an essential nutrient for the formation of red blood cells.

The acid in the human stomach protects our body by killing pathogenic bacteria that are present in food. It also helps digest proteins, turning them into an expanded form that is more easily processed by enzymes. Pepsin is an enzyme that is activated only under the influence of hydrochloric acid in the stomach.

Chief cells, also found in the pits of the stomach, produce two digestive enzymes: pepsinogen and gastric lipase. Pepsinogen is the precursor molecule to the very powerful protein-digesting enzyme pepsin. Since pepsin would destroy the main cells that produce it, it hides in the form of pepsinogen, where it is harmless. When pepsinogen comes into contact with the acidic pH found in stomach acid, it changes shape and becomes the active enzyme pepsin, which converts proteins into amino acids.

Gastric lipase is an enzyme that digests fats by removing the fatty acid from the triglyceride molecule.

Gastric G cells are endocrine cells found at the base of the gastric pits. G cells synthesize the hormone gastrin into the bloodstream in response to many stimuli, such as signals from the vagus nerve, the presence of amino acids in the stomach from digested proteins, or stretching of the stomach walls during eating. Gastrin travels through the blood to various receptor cells throughout the stomach, and its main task is to stimulate the glands and muscles of the stomach. The effect of gastrin on the glands leads to an increase in the secretion of gastric juice, which improves digestion. Gastrin's stimulation of smooth muscle promotes stronger contractions of the stomach and the opening of the pyloric sphincter to move food into the duodenum. Gastrin can also stimulate cells in the pancreas and gallbladder, where it increases the secretion of juices and bile.

As you can see, human stomach enzymes perform very important functions in digestion.

Digestion

Digestion in the stomach can be divided into two classes: mechanical and chemical digestion. Mechanical digestion is nothing more than the physical division of a mass of food into smaller portions, while chemical digestion is the transformation of larger molecules into smaller molecules.

Mechanical digestion occurs due to the mixing actions of the stomach walls. Its smooth muscles contract, causing portions of food to mix with gastric juice, which leads to the formation of a thick liquid - chyme.

While food is physically mixed with gastric juice, enzymes present in it chemically break down large molecules into smaller subunits. Gastric lipase breaks down triglyceride fats into fatty acids and diglycerides. Pepsin breaks down proteins into smaller amino acids. Chemical decomposition, begun in the stomach, is not completed until the chyme enters the intestines.

But the functions of the human stomach are not limited to digestion.

Hormones

The activity of the stomach is controlled by a number of hormones that regulate the production of stomach acid and the release of food into the duodenum.

Gastrin, produced by the G cells of the stomach itself, increases its activity by stimulating an increase in the amount of gastric juice produced, muscle contraction and emptying of the stomach through the pyloric sphincter.

Cholecystokinin (CCK) is produced by the duodenal mucosa. It is a hormone that slows down gastric emptying by contracting the pyloric sphincter. CCK is released in response to meals rich in proteins and fats, which are very difficult for our body to digest. CSC allows food to be stored in the stomach longer for more thorough digestion and gives time to the pancreas and gallbladder to release enzymes and bile that improve the digestion process in the duodenum.

Secretin, another hormone produced by the duodenal mucosa, responds to the acidity of the chyme entering the intestine from the stomach. Secretin travels through the blood to the stomach, where it slows the production of gastric juice by the exocrine glands of the mucous membrane. Secretin also stimulates the production of pancreatic juice and bile, which contain bicarbonate ions that neutralize acid. The purpose of secretin is to protect the intestines from the harmful effects of chyme acid.

Human stomach: structure

Formally, we have already become familiar with the anatomy and functions of the human stomach. Let's use illustrations to look at where the human stomach is located and what it consists of.

Figure 1:

This figure shows the human stomach, the structure of which can be examined in more detail. Here are indicated:

1 - esophagus; 2 - lower esophageal sphincter; 3 - cardia; 4- body of the stomach; 5 - bottom of the stomach; 6 - serous membrane; 7 - longitudinal layer; 8 - circular layer; 9 - oblique layer; 10 - greater curvature; 11 - folds of the mucous membrane; 12 - cavity of the pylorus of the stomach; 13 - canal of the pylorus of the stomach; 14 - pyloric sphincter; 15 - duodenum; 16 - gatekeeper; 17 - small curvature.

Figure 2:

This image clearly shows the anatomy of the stomach. The numbers indicate:

1 - esophagus; 2 - bottom of the stomach; 3 - body of the stomach; 4 - greater curvature; 5 - cavity; 6 - gatekeeper; 7 - duodenum; 8 - small curvature; 9 - cardia; 10 - gastroesophageal junction.

Figure 3:

It shows the anatomy of the stomach and the location of its lymph nodes. The numbers correspond to:

1 - upper group of lymph nodes; 2 - pancreatic group of nodes; 3 - pyloric group; 4 - lower group of pyloric nodes.

Figure 4:

This image shows the structure of the stomach wall. Marked here:

1 - serous membrane; 2 - longitudinal muscle layer; 3 - circular muscle layer; 4 - mucous membrane; 5 - longitudinal muscular layer of the mucous membrane; 6 - circular muscular layer of the mucous membrane; 7 - glandular epithelium of the mucous membrane; 8 - blood vessels; 9 - gastric gland.

Figure 5:

Of course, the structure of human organs is not visible in the last figure, but the approximate position of the stomach in the body can be seen.

This image is quite interesting. It doesn't show the anatomy of the human stomach or anything like that, although you can still see some parts of it. This picture shows what heartburn is and what happens when it occurs.

1 - esophagus; 2 - lower esophageal sphincter; 3 - stomach contractions; 4 - stomach acid along with its contents rises into the esophagus; 5 - burning sensation in the chest and throat.

In principle, the picture clearly shows what happens with heartburn and no additional explanation is required.

The human stomach, the pictures of which were presented above, is a very important organ in our body. You can live without it, but this life is unlikely to replace a full one. Fortunately, nowadays you can avoid many problems simply by periodically visiting a gastroenterologist. Timely diagnosis of the disease will help you get rid of it faster. The main thing is not to delay going to the doctor, and if something hurts, then you should immediately contact a specialist about this problem.