The gastric mucosa consists of what epithelium. Structure of the stomach: sections, layers

The patient complains to the doctor about stomach pain. And if you ask in more detail, he doesn’t even know where the stomach is, on which side, at the bottom or at the top of the stomach. Therefore, doctors adhere to the rule of asking questions about the place where it hurts.

And which organ is related to the problem can be figured out by knowing the anatomical and physiological characteristics of the gastrointestinal tract and human digestion as a whole. To find out how the stomach hurts, we will return to the school body of knowledge about its anatomical structure, disassemble the device and add a little about the features of its operation.

Where is the stomach?

From the anatomy course we know that the stomach is located in the uppermost part of the abdominal cavity in the “border” region to the diaphragm. Its projection onto the abdomen allows us to highlight the epigastric zone for the apex (the middle region where the lower ribs connect), the lower sections are located opposite the navel.

In relation to the midline, the human stomach is ¾ to the left and ¼ of the organ is to the right. The shape and capacity of the organ may vary. But it is always possible to select a bend along the contour on the left - a small curvature, and on the right - a large one. The location of the stomach is most often directed slightly at an angle towards the middle, down and to the left.

Dimensions and shape

The size of an adult’s stomach depends on its shape, fullness, and individual characteristics. Form supported:

• muscle tone;
• height of the diaphragm dome;
• intra-abdominal pressure;
• influence of the intestines.

It is capable of changing under the influence of the contents, with changes in body position, depending on the condition of neighboring organs, and with pathology. For example, with scarring of an ulcer, an “hourglass” may form; with ascites and a tumor, the stomach looks like a “horn”. Gastroptosis (prolapse of the stomach) causes the lower border to decrease to the level of the pelvis, and the shape lengthens.

Radiologically, the upper limit is considered to be a point 0.5–2.5 cm below the contour of the diaphragm, the lower limit is considered to be 2–4 cm above the ilium; upon examination, variations in shape are visible

The dimensions of the stomach with moderate filling are:

• 15–18 cm in length, 12–14 cm in width;
• wall thickness 2–3 mm.

Due to the elasticity of the wall and internal folds, the volume of an adult’s stomach can increase to 4 liters.

The average capacity in the male body is 1.5–2.5 liters, in women it is slightly less. Depending on the inclination of the longitudinal axis, the position of the organ is fixed as vertical, horizontal or oblique. For tall, thin asthenics, a vertical position is more typical; for broad-shouldered, short-stature hypersthenics, a horizontal position is more typical; with a normosthenic physique, an oblique direction is observed.

Neighboring organs

The anatomy of the human stomach is inextricably linked with the condition of neighboring organs. Therefore, it is important for a doctor to know the topography; we can call it a “3D vision” of connections with neighboring organs. The anterior surface of the stomach is partially adjacent to the diaphragm, the abdominal wall and the lower edge of the liver.

The posterior surface is in contact with the pancreas, aorta, spleen, the upper part of the left kidney with the adrenal gland, and partially with the transverse colon. The dense “neighborhood” is reinforced by nutrition from the same arterial branches, joint venous and lymphatic drainage. Therefore, the structure of the human stomach is subject 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 most important organs

Divisions and their anatomy

The inlet (cardial) opening connects the stomach to the esophagus. Swallowed food passes through it. The exit (pyloric) canal ensures the movement of the processed contents into the initial section of the small intestine - the duodenum. At the borders there are muscle sphincters (sphincters). The timeliness of digestion depends on their proper functioning.

Conventionally, the stomach is divided into 4 parts:

• cardiac (entrance) - connects to the esophagus;
• bottom - forms a vault next to the cardiac part;
• body - main section;
• pyloric (pyloric) - forms an exit.

In the gateway zone there is an antrum (cave) and the canal itself. Each section of the stomach performs its own tasks. For this purpose they have a special structure at the cellular level.

The structure of the stomach wall

On the outside, the organ is covered with a serous membrane made of a loose connective tissue base and squamous epithelium. From the inside the wall is divided:

• on the mucous membrane;
• submucosal layer;
• muscle layer.

An important feature is the absence of nerve pain receptors in the mucous membrane. They are present only in deeper layers. Therefore, a person feels pain when muscle function is disrupted (spastic contraction or overstretching) or the pathological process, bypassing the mucous membrane, moves into the depths (with erosions, ulcers).

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

What cells provide the function of digesting food?

The structure of the mucous membrane is studied by histologists when diagnosing a pathological process. Normally it includes:

• cells of single-layer columnar epithelium;
• a layer called “intrinsic”, made of loose connective tissue;
• muscle plate.

The second layer contains its own glands, which have a tubular structure. They are divided into 3 subspecies:

• the main ones produce pepsinogen and chymosin (digestive enzymes, in an acidic environment they turn into proteolytic enzymes);
• parietal (lining) - synthesize hydrochloric acid and gastromucoprotein;
• additional - form mucus.

Among the glands of the pyloric zone are G-cells that secrete the gastric hormonal substance gastrin. Accessory cells, in addition to mucus, synthesize a substance necessary for the absorption of vitamin B 12 and hematopoiesis in the bone marrow (Castle factor). The entire surface of the mucosa in the deep layers contains cells that synthesize the precursor of serotonin.

The gastric glands are located in groups, so under a microscope, from the inside, the mucous membrane has a granular appearance with small pits and flat, irregularly shaped fields. The good adaptability of the healthy mucous membrane is noteworthy. It is capable of rapid recovery: the epithelium on the surface is replaced less than every 2 days, and the glandular one - in 2–3 days. A balance is maintained between old cells being rejected and newly formed ones.

In diseases of the stomach, hypertrophy of the glands, inflammation and cell death occur, dystrophic and atrophic disorders are accompanied by a failure in the production of necessary substances, scarring replaces the functioning tissue with non-functioning fibrocytes. Malignant cells transform into atypical ones. They begin to grow 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 functioning of the organ is exerted by the branches of the sympathetic and vagus nerves. Sensitivity is provided by the receptor apparatus of the wall and spinal nerves.

How is food transported?

The structure of the stomach provides for the transportation of food coming from the esophagus and its simultaneous processing. The muscular layer of the wall includes 3 layers of smooth muscle:

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

When muscle groups contract, the stomach acts like a “concrete mixer.” At the same time, rhythmic contractions occur in the segments, pendulum-like movements, and tonic contractions.
Thanks to this, the food continues to be crushed, mixes well with gastric juice, and gradually moves to the pyloric region.

The transition of a bolus of food from the stomach to the intestines is influenced by several factors:

• weight of content;
• maintaining the difference in pressure between the outlet of the stomach and the duodenal bulb;
• sufficiency of grinding of gastric contents;
• osmotic pressure of processed food composition (chemical composition);
• temperature and acidity.

Gastric juice ensures the “processing” of the food bolus

Peristalsis is enhanced by the vagus nerve and inhibited by sympathetic innervation. The fundus and body of the stomach ensure the deposition of food and the effect of proteolytic substances on it. The antrum is responsible for the evacuation process.

How is the stomach protected?

In the anatomy of the stomach, it is impossible not to note the organ’s ability to protect itself. A thin layer of mucus is represented by mucoid secretion produced by columnar epithelium. Its composition includes polysaccharides, proteins, proteoglycans, and glycoproteins. Mucus is insoluble. It has a slightly alkaline reaction and is able to partially neutralize excess hydrochloric acid. In an acidic environment it turns into a thick gel, covering the entire inner surface of the stomach.

Insulin, serotonin, secretin, nerve receptors of the sympathetic nerve, and prostaglandins stimulate mucus production. The opposite inhibitory effect (which corresponds to a violation of the protective barrier) is exerted by drugs (for example, the Aspirin group). Failure of protection leads to an inflammatory reaction of the gastric mucosa.

Anatomical and physiological characteristics (APF) in children and the elderly

In the fourth week of pregnancy, the embryo begins to form the pharynx, esophagus, stomach and partially other digestive organs from the foregut. In newborns, the stomach is located horizontally. When the baby gets on his feet and begins to walk, the axis moves to a vertical position.

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

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

For a one-year-old child, a volume of 250 ml is considered normal. By three years it increases to 600 ml, by twelve - to 1.5 liters.

In the neonatal period, the cardia and fundus are the most poorly developed. The cardiac sphincter does not function sufficiently compared to the pyloric sphincter, so the baby often burps. There are still few secretory glands in the mucous membrane; functionally it is ready to receive only mother's milk. Gastric juice has the same composition as that of an adult, but its acidity and enzyme activity are much lower.

The baby's stomach produces the main enzymes:

• chymosin (rennet enzyme) - necessary for the digestion and curdling of milk;
• lipase - for the breakdown of fats, but it is still small.

Peristalsis of the muscle layer is slowed down. The time it takes for food to be evacuated into the intestines depends on the type of feeding: in artificial babies it is delayed for a longer period. The development of the total mass of the gastric glands is influenced 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 returns to horizontal again, and prolapse often occurs.

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

Diagram of departments and their functional purpose

Functions

The anatomical structure of the stomach is adapted for the organ to perform its main functional duties:

• formation of acid and pepsin for digestion;
• mechanical and chemical processing of food by gastric juice, enzymes;
• depositing a bolus of food for the time necessary for proper digestion;
• evacuation to the duodenum;
• production of internal Castle factor for the absorption of vitamin B 12, necessary for the body as a coenzyme in the biochemical process of obtaining energy;
• participation in metabolism through the synthesis of serotonin, prostaglandins;
• synthesis of mucus to protect the surface, gastrointestinal hormones involved at different stages in the digestive process.

Varying degrees of dysfunction lead to pathology not only of the stomach, but also of other digestive organs. The goal of disease therapy in gastroenterological practice is to restore function and anatomical structures.

The stomach (ventriculus s. gaster) serves as a container for food and prepares it for digestion. Under the influence of gastric juice, food particles are loosened and saturated with digestive enzymes. Many microorganisms that enter the stomach cavity die under the influence of gastric juice. When the muscles of the stomach contract, the food gruel is subjected to mechanical processing and then evacuated to the next sections of the digestive system. It has been established that the mucous membrane produces a special substance that stimulates hematopoiesis (Castle factor).

The stomach is divided into the cardiac part, the fundus, the body and the pyloric part (Fig. 230).

The cardiac part (pars cardiaca) is relatively small, located at the entry of the esophagus into the stomach, and corresponds to the XI thoracic vertebra. When the esophagus flows into the stomach, there is a cardiac opening (ostium cardiacum). The cardiac part on the left is delimited from the vault of the stomach by the notch (incisura cardiaca).

The fundus ventriculi is the highest part of the stomach and is located on the left under the diaphragm. There is always an accumulation of air in it.

The body of the stomach (corpus ventriculi) occupies its middle part.

The pyloric part (pars pylorica) starts from the angular notch (incisura angularis), located on the lesser curvature, and ends with the pyloric sphincter (m. sphincter pylori). In the pyloric part, three sections are distinguished: the vestibule (vestibulum pylori), the cave (antrum pyloricum), and the canal (canalis pyloricus). Vestibulum pylori is located in the initial section of the pyloric part, and then passes into the antrum pyloricum, which is the narrowed part; canalis pyloricus is located in the sphincter area. Knowledge of these parts is important for describing the localization of many pathological changes in gastric diseases. The pylorus of the stomach (pylorus) leads into the opening (ostium pyloricum), which opens into the cavity of the duodenum.

All parts of the stomach have anterior and posterior walls (paries ventriculi anterior et posterior), which are connected into the lesser curvature of the stomach (curvatura ventriculi minor), concave to the right, and the greater curvature (curvatura ventriculi major), convex to the left.

Stomach shape. In a corpse, the stomach has the shape of a retort, which is caused by the loss of tone of the muscular layer and the muscular layer of the mucous membrane. Under pressure from gases, the stomach stretches and enlarges. In a living person, an empty stomach resembles an intestine and only expands when filled with food. The shape of the stomach largely depends on the human constitution.

Horn shaped stomach. It occurs more often in people of brachymorphic build. It is located with a long axis from left to right (Fig. 231).

Fishhook shaped stomach. The body of the stomach descends. At the junction of the body and the pyloric part there is an angle (Fig. 232). The pyloric sphincter is located slightly above the lower pole of the stomach. A stomach of a similar shape is found in normosthenics - people of average height and build.

Stocking shaped stomach. To some extent, it resembles a fishhook-shaped stomach. A distinctive feature is that the lower pole of the stomach is located significantly lower than the sphincter of the pyloric part (Fig. 233). In this regard, the pyloric part of the stomach has an ascending direction. This form is more common in people with dolichomorphic build.

Topography of the stomach. The stomach is located in the abdominal cavity in the regio epigastrica. The longitudinal axis of the stomach is projected to the left of the spine. The place where the esophagus enters the stomach on the left side corresponds to the body of the XI thoracic vertebra, and the pyloric sphincter is located to the right of the XII thoracic, sometimes I lumbar vertebra. The vault of the stomach is in contact with the left dome of the diaphragm. In this case, the upper border corresponds to the fifth left rib along the midclavicular line. An empty stomach does not go below the linea biiliaca (the line between the crests of the iliac bones). The anterior wall of the stomach in the cardiac and pyloric parts along the lesser curvature is covered with the liver. The anterior wall of the body of the stomach is in contact with the parietal peritoneum of the anterior abdominal wall (Fig. 234). The posterior wall in the area of ​​the arch and greater curvature is in contact with the spleen, adrenal gland, upper pole of the kidney and pancreas, and in the area of ​​the lower 2/3 of the greater curvature - with the transverse colon.

Stomach wall. It consists of a mucous membrane (tunica mucosa) with a submucosal layer (tela submucosa), a muscular layer (tunica muscularis) and a serous membrane (tunica serosa).

The mucous membrane is covered with single-layer prismatic epithelium (intestinal type), which has the property of secreting mucoid secretion (mucus) with its apical end (facing the stomach cavity). Mucus protects the stomach wall from the action of pepsin and hydrochloric acid, preventing self-digestion of the mucous membrane. In addition, mucus serves as a protective layer for the mucous membrane when exposed to rough food. The gastric epithelium is located on the connective tissue lamina propria of the mucous membrane, consisting of elastic fibers, loose connective tissue and formed elements (fibroblasts, lymphocytes, leukocytes). In the submucosal layer there are nodules of lymphatic tissue (folliculi lymphatici gastrici). At the border with it there is a muscle layer (lamina muscularis mucosae). The contraction of these muscles causes the formation of folds (plicae gastricae) in the mucous membrane (Fig. 235). These folds in the area of ​​the arch and the greater curvature are located without a specific order, and along the lesser curvature they are oriented longitudinally. They are clearly visible when x-raying an empty stomach. On the mucous membrane, in addition to folds, there are fields and pits. The gastric areas (areae gastricae) are outlined by small grooves that divide the surface of the mucous membrane into areas where the mouths of the digestive glands are located (Fig. 236). Gastric pits (foveolae gastricae) are retractions of the epithelium into the own layer of the mucous membrane. At the bottom of the pits, the ducts of the digestive glands open.

236. The surface of the gastric mucosa, photographed in incident light. ×200

Glands. There are three types of glands: cardiac (gll. cardiacae), fundic (gll. gastricae) and pyloric (gll. pyloricae). Cardiac glands are simple tubular. Their secretory sections are localized in their own layer of the mucous membrane. They produce a mucus-like secretion mixed with the enzyme dipeptidase, which can break down proteins into amino acids, a glycolytic enzyme for the breakdown of carbohydrates, and also a secretion of an alkaline reaction. All glands of the stomach can be excited by the action of nutrients or nerve impulses of the autonomic nervous system.

The fundic glands are in the form of branched tubes that open into the gastric pits, lined with gastric epithelium. The glands are formed by chief, parietal and accessory cells. The chief and parietal cells secrete gastric juice containing hydrochloric acid. Accessory cells are located near the isthmus of the glands and secrete mucus of an alkaline reaction, reminiscent of the mucus secreted by the prismatic epithelium of the gastric mucosa.

The pyloric glands are more branched than the cardiac and fundic glands. The pyloric glands are formed by various cells that produce pepsin and mucous secretions.

The submucosal layer of the stomach is well developed, consisting of loose connective tissue with dense vascular and nerve plexuses. The muscular layer is conventionally divided into three layers: the outer longitudinal (stratum longitudinale), the middle circular (stratum circulare) and the inner (stratum internum), consisting of oblique fibers (librae obliquae) (Fig. 237). The circular and longitudinal layers are best developed in the pyloric part, worse in the fornix and upper part of the body of the stomach. The longitudinal layer is clearly visible on the lesser and greater curvature of the stomach. It starts from the esophagus and ends at the pyloric part. When the longitudinal layer contracts, the stomach shortens and the shape of the greater and lesser curvature changes. The inner muscular layer from the cardiac part passes along the lesser curvature, giving portions to the body of the anterior and posterior walls, the greater curvature of the stomach. When it contracts, the notch of the cardiac part increases, and the greater curvature is tightened. Circular muscle fibers surround the stomach, starting from the esophageal opening and ending with the pyloric sphincter, which is also a derivative of this muscle layer. The pyloric sphincter (m. sphincter pylori) has the shape of a ring 4-5 mm thick.

The mucous membrane, due to the contraction of the lamina muscularis mucosae, tightly covers the food bolus. The muscular lining of the stomach wall also has its own tone. In the stomach, the pressure rises to 40 mm, and in the pyloric part - up to 150 mm Hg. Art. It is necessary to distinguish between tonic and periodic types of contraction of the stomach muscle. With tonic contraction, it is constantly contracted and the wall of the stomach actively adapts to the food bolus. Periodic contractions occur approximately every 18-22 s. in the vault area and gradually spread towards the pyloric sphincter. The food gruel is in close contact with the wall of the stomach. Periodic waves of the circular layer remove a layer of digested gruel from the surface of the food bolus and collect it in the pyloric part. The pyloric sphincter is almost always closed. It opens when alkalization of the contents occurs in the pyloric part. In this case, a portion of semi-liquid gruel is released into the duodenum. As soon as the acidic portion of food reaches the initial part of the duodenum, the sphincter closes until the gastric juice is neutralized. Solid food stays in the stomach for a long time, while liquid food enters the intestines faster.

The serous membrane covers the stomach on all sides, i.e. intraperitoneally. The peritoneum externally contains mesothelium, located on a connective tissue base having six layers.

Gastric ligaments. The ligaments of the stomach and other organs of the digestive system are not the same ligaments that are found in the musculoskeletal system, but are thickened layers of the peritoneum.

The diaphragmatic-esophageal ligament (lig. phrenicoesophageum) is a piece of peritoneum that passes from the diaphragm to the esophagus and the cardial notch of the stomach. The esophageal arterial branch from the left gastric artery passes through the thickness of the ligament.

The diaphragmatic-gastric ligament (lig. phrenicogastricum), like the previous one, is a piece of the diaphragmatic peritoneum, which, descending from the diaphragm, is attached to the vault of the stomach.

Gastrosplenic ligament (lig. gastrolienale): it consists of two layers of peritoneum, passing from the anterior and posterior walls in the upper part of the greater curvature of the stomach to the visceral surface of the spleen. In the thickness of the ligament, vessels pass to the bottom of the stomach.

The gastrocolic ligament (lig. gastrocolicum) connects 2/3 of the greater curvature of the stomach with the transverse colon. It represents the leaves of the upper part of the greater omentum fused together. The right and left gastroepiploic arteries and vein of the stomach pass through the ligament.

The hepatogastric ligament (lig. hepatogastricum) is a two-layer sheet stretched between the hilum of the liver and the lesser curvature of the stomach. The ligament is a transformed ventral mesentery that existed in the embryonic period of development. In the upper part the ligament is thin and transparent, and closer to the pyloric sphincter it is thicker and more tense.

The gastropancreatic ligament (lig. gastropancreaticum) and the pyloric-pancreatic ligament (lig. pyloropancreaticum), formed by one layer of the peritoneum, are visible when dissecting the lig. gastrocolicum. This releases the greater curvature of the stomach, which can be raised and then penetrated into the omental bursa (bursa omentalis).

In a newborn, the long stomach is oriented vertically. The arch and body are expanded, and the pyloric part is narrowed. The pyloric part is relatively longer in relation to other parts of the stomach. The volume of a newborn's stomach is 30 ml; under the influence of food it increases over the course of a year to 300 ml. By puberty, the volume of the stomach reaches 1700 ml. Babies have more cells that produce lipase and lactase, which help break down the nutrients in milk.

X-rays of the stomach

X-ray examination of the stomach is a common procedure in clinics and clinics. Most often, contrast is carried out with barium mass, air in combination with parietography (injection of gas into the peritoneal cavity) in the form of overview and targeted images.

The overview image reveals the general contours and shape of the stomach. It shows the fornix containing a gas bubble, the cardiac part, the body, and the pyloric part. The contours of the stomach, which reflect the internal relief, are of great importance. During peristalsis of the stomach, circular retractions are formed on the greater and lesser curvature due to muscle contraction. In case of changes in the cardiac part and the vault of the stomach, it is necessary to determine the relationship to the diaphragm, the width and depth of the angle between the esophagus and the vault of the stomach. It is very important to trace the medial contour of the gastric vault and the wall of the esophagus facing it, and then the cardiac part. Normally, these sections have a smooth surface.

The sphincter canal has a length of 1 cm, a diameter of 2-3 mm and opens in the central part of the duodenal bulb.

When the stomach is slightly filled, especially with a liquid suspension of barium mass, it is distributed mainly between the folds; in the body of the stomach there are 4-5 folds 3-5 mm wide. In the area of ​​the fornix and pyloric part they have an oblique position. A targeted image reveals any detail of the structure of the stomach, for example, the state of the folds of its body. These images are very valuable for x-ray diagnostics.

Parietograms can only be performed by contrasting the abdominal cavity and stomach with air. This method is very effective; it helps to identify the external and internal relief of the stomach wall. Pictures are taken in anterior projection.

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 stomach's 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, enzymes in the human stomach 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 the food is physically mixed with the gastric juice, the enzymes present in it chemically break down the large molecules into their 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.

Picture 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.

Comments:

• What is the wall made of?
  • Superficial pitted epithelium of the mucosa
  • Muscular plate
  • Submucosal layer
  • Muscularis
  • Serosa

The stomach is an organ of the digestive tract that serves as a storage facility for food and its subsequent processing. The anterior and posterior walls of the stomach pass into each other along the greater and lesser curvature. This organ also has cardiac and pyloric parts, a body and a fundus. Let's take a closer look at the structure of the stomach wall.

What is the wall made of?

• mucous membrane;
• submucosal layer;
• muscularis propria;
• serous membrane.

The mucous membrane includes:

• single-layer, single-row epithelium;
• muscle plate;
• basal membrane plate.

The gastric mucosa is a continuation of the esophageal mucosa. Where the esophagus passes into the stomach, there is a serrated strip separating the mucous epithelium, which consists of many layers, and the microcylindrical tissue, which is a single layer. On top, the cellular tissues are impregnated with a mucous substance produced by mucocytes.

The mucous membrane is divided into small convex areas called gastric fields, which are thickened from 1 to 6 millimeters. They have a polygonal shape and are separated from each other by grooves. They contain connective tissue layers. They contain superficial veins.

These fields have special funnels - gastric dimples (approximately 0.2 mm wide), which lie surrounded by villi folds. Near the pylorus, the folds are most noticeable. In all pits there are rudiments of one or two ducts of the glands of the organ.

The average thickness of this shell is normally 0.25-1.5 millimeters, and the area is from 500 to 8510 cm². The number of glands varies from 5 to 25 million. Up to 50 gastric pits can be located on an area of ​​1 cm². Each of them has 4-6 glands. 65-67% of the total blood flow in the organ is occupied by the circulatory system. Of these, 13% belong to the submucosal layer and 15% to the muscular layer.

The mucous membrane creates folds with various inclinations in the sections: along the shallow curvature there are longitudinal folds, in the area of ​​the bottom and body of the organ - oblique, transverse and longitudinal. They significantly expand the size of the stomach, increase the interaction between food and mucous membranes and lead to a more efficient digestion process.

There are 3 zones in the mucous membrane:

• cardiac;
• fundal;
• pyloric.

Their boundaries are blurry, and they smoothly transform from one to another. The diameter of the intermediate zones is 1 cm. They practically merge with the anatomical sections, but still not absolutely. Each zone contains the following types of glands:

• in the cardia zone there are cardiac glands;
• in the area of ​​the body and bottom - the main ones;
• in the mucous membrane (intermediate territory of the organ) - intermediate glands;
• in the pyloric mucosa there is a pyloric gland.

Return to contents

Superficial pitted epithelium of the mucosa

It is a cylindrical epithelial mucocytic cell arranged in a single layer. The surface pit layer contains:

1. Cells of the APUD system, synthesizing biogens-amines and hormones-peptides. Depending on the quality and quantity of food, they adjust the secretory and motor functions of the digestive organs.
2. Intraepithelial lymphocytes that have a cytotoxic effect against bacteria that come with the food a person eats. These lymphocytes collect and transmit information about certain food components to other structures in the immune system.

Return to contents

Muscular plate

The submucosal layer, together with the muscular plate, forms multiple folds in the mucous layer.

The basal membrane looks like loose tissue with vessels (lymphatic and blood) flowing through it. These vessels cause the formation of the microcirculatory duct, arteriole-venular shunts, fenestrated capillaries, gastric glands and cellular substance (which consists of reticular, precollagen and collagen fibers and a large number of cells):

1. Lymphoid cells (reticulars, fibroblasts, plasma, mast cells). Uniting into a reticulum, they can be single or group follicles.
2. Migrating blood granulocytes and lymphocytes, providing antibacterial and antitoxic effects. In addition, they appear in leukopidesis of the digestive system.

In the lamina propria, the volume of neutrophils, basophils, lymphocytes and eosinophils increases during digestion. Basophils at this moment produce substances that increase vascular permeability. Neutrophils secrete enzymes: lysozyme and lactoferrin. They have an anti-inflammatory function. Eosinophils and lymphocytes eliminate toxic elements during immune reactions.

The lamina proper performs a number of significant functions:

1. Mechanical function (by maintaining the structure of the epithelium).
2. Trophic-transport (by ensuring diffusion from epithelial cells into the blood in various compounds).
3. Digestive function (leukopidesis).

Lymphoid tissue in the lamina propria establishes serious antigenic protection, protecting organs from viruses, bacteria and toxins that can enter the body with food, and also conducts phagocytosis and synthesizes immunoglobulins.

Return to contents

Submucosal layer

The wall of the stomach consists of a submucosal layer, which is a fibrous, loose and shapeless tissue. This tissue has many collagen bundles and elastic fibers. In addition, in the submucosal layer there are venous and arterial trunks, which form the submucosal plexus, lymphatic plexus and Meiner's nerve plexus.

The submucosal layer forms folds and helps the wall stretch. It is the most durable.

The human stomach is a hollow, muscular digestive organ that has a complex structure and performs many important functions. The gastric mucosa is its inner layer, which is formed by the epithelium and, together with bicarbonates, protects the muscle wall from the aggressive influence of hydrochloric acid. Its integrity and healthy condition ensures comfortable digestion and complete absorption of water.

What is the mucous layer of the stomach wall?

The inner surface of the organ is completely covered with mucus. It looks embossed, has folds, pits, villi and “fields”. Each of these formations performs its own function. In its thickness there are stomach glands and blood vessels. The mucous membrane covering the organ from the inside is a continuation of the same one in the esophagus, but differs in color. Here its color is more intense, the vessels are visible only in atrophic conditions. Normal thickness is 1.5-2 mm. Together with bicarbonates, it forms unique barriers, the so-called protective factors.

What elements does the mucous membrane consist of?

The walls have a complex structure.

The inner layer of the stomach consists of a single layer of epithelium, which secretes mucus and bicarbonates and is located on a plate of loose connective tissue. The pits present on it are the exit openings of the glands located in the submucosal layer. They are formed by chief, accessory and parietal cells that secrete secretions. It consists of hydrochloric acid, pepsin and other biologically active substances necessary for digestion. Anatomically, glands are divided into the following types:

• Cardiac. They are simple tubular in structure. Dipeptidases and glycolytic enzymes are isolated.
• The main ones. Branched tubes, the main secretion of which is hydrochloric acid. The middle part and fornix of the stomach have the greatest concentration.
• Pyloric. The secretion they secrete contains pepsin and mucus.

Folds are formed due to their own layer of muscle fibers. They are located in three layers, the inner and outer of which are circulatory, and the middle one is longitudinal. They have different directions in different parts of the organ. For example, along the lesser curvature - longitudinal, and in the area of ​​the pylorus - circulatory. Thanks to them, the total surface of the mucous membrane and the area of ​​its contact with food increases. Under the inner layer there is a submucosal layer containing capillaries and nerve endings.

The lamina propria, intercellular substance, reticular and collagen fibers, as well as blood and lymphatic vessels are components of the stroma of the mucous membrane.

Functions of the inner layer of the stomach

The mucous membrane creates a barrier protection against the aggressive effects of gastric juice.

When food enters the stomach, it is tightly grasped by the mucous membrane and moistened with the secretion secreted by its glands. The content of enzymes in it ensures the breakdown of large molecules into smaller ones. The most important function of the mucous membrane is protective. It protects the organ from the aggression of hydrochloric acid, medications, mechanical and thermal irritants. The function of the stomach in the regulation of hematopoietic processes is also ensured by its mucous membrane, since its glands produce erythropoietin and the antianemic Castle factor. Violation of its functional activity, inflammatory or infectious processes cause gastropathy and digestive disorders, which are difficult to cure.

Diseases of the gastric mucosa

The mucous microflora of the organ contains various types of bacteria, including Helicobacter pylori. In the absence of a provoking factor, they do not cause diseases of the stomach and intestines. But if the protective functions of the organ are impaired, and the mucous layer lining it is damaged, then the diversity of bacteria and the number of their colonies increases sharply, leading to pathologies. The most frequently diagnosed among them are:

• gastritis;
• ulcerative or erosive lesions;
• phlebeurysm;
• benign or malignant tumors;
• injuries;
• chemical burns of the gastric mucosa;
• mucosal metaplasia or enterolization;
• congenital defects, for example, ectopia in the esophagus.

Causes and symptoms of the main pathologies of the stomach

The lack of a balanced diet provokes dangerous pathologies of the gastrointestinal tract.

The number of diseases of the gastrointestinal tract is increasing all the time. They affect both women and men of different ages. Provoking factors are:

• Irregular meals or snacks on the go;
• binge eating;
• eating food that is too hot or cold;
• stress;
• infectious and autoimmune processes;
• alcohol and smoking;
• long-term medication use.

Almost every gastric pathology is accompanied by pain in the epigastric region, belching, nausea and vomiting. In the acute phase of the disease, fever, pale skin, and bloating are possible. A characteristic white or grayish coating appears on the tongue, worsening the patient’s sense of taste.

Diagnosis of stomach diseases

The study will determine with high accuracy the degree of damage to the mucous membrane.

• Fibrogastroscopy. During the examination, hemorrhagic mucous membrane, its swelling, and loss of integrity are observed. A pyloric ulcer is accompanied by pyloric stenosis, and epithelial proliferation is possible. With gastritis, the wall of the organ is lined with mucous membrane, which has a bright red or greenish color. It is small-lumpy with hemorrhages and areas of atrophy.
• Gastric metaplasia requires a histological examination to determine the presence of malignant cells. This diagnostic method can reveal the intestinal epithelium and structural changes in glands and cells.
• Blood tests.
• X-ray examination.
• pH-metry.
• Breath test for the presence of Helicobacter pylori.
• Fecal occult blood test.

A timely, complete examination of a patient with gastropathology, including instrumental and laboratory methods, makes it possible to make an accurate diagnosis and begin treatment on time, preventing the development of complications or the transition of the disease to a chronic form.