The stomach and its functions. The structure of the stomach: sections, layers

Nutrition is a complexly coordinated process aimed at replenishing the energy of a living organism through processing, digestion, splitting, and absorption of nutrients. All these and some other functions are performed by the gastrointestinal tract, which consists of many important elements combined into a single system. Each of its mechanisms is capable of performing a variety of actions, but when one element suffers, the operation of the entire structure is disrupted.

This is due to the fact that food, entering our body, undergoes multi-stage processing, these are not only the familiar processes of digestion in the stomach and absorption in the intestines. Digestion also includes the absorption of those same substances by the body. Thus, the diagram of the human digestive system takes on a broader picture. Pictures with captions will help visualize the topic of the article.

In the digestive system, it is customary to distinguish the organs of the gastrointestinal tract and additional organs called glands. The organs of the digestive tract include:

A visual arrangement of the organs of the gastrointestinal tract depicts the figure below. After reviewing the basics, it is worth considering the structure of the organs of the human digestive system in more detail.

The initial section of the gastrointestinal tract is oral cavity. Here, under the influence of teeth, mechanical processing of incoming food is performed. Human teeth have a variety of shapes, which means that their functions are also different: incisors are cut, fangs are torn, premolars and molars are crushed.

In addition to mechanical processing, chemical processing also begins in the oral cavity. This happens under the influence of saliva, or rather, its enzymes that break down some carbohydrates. Of course, the full breakdown of carbohydrates cannot occur here due to the short stay of the food bolus in the mouth. But the enzymes impregnate the lump, and the astringent components of the saliva hold it together, making it easy to move towards the throat.

Pharynx- this is a tube consisting of several cartilages, performs the function of carrying the food bolus to the esophagus. In addition to carrying food, the pharynx is also a respiratory organ, 3 sections are placed here: the oropharynx, nasopharynx and laryngopharynx - the last two belong to the upper respiratory tract.

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From the pharynx, food enters esophagus- a long muscular tube, which also performs the function of carrying food already to the stomach. A feature of the structure of the esophagus are 3 physiological narrowing. The esophagus is characterized by peristaltic movements.

The lower end of the esophagus opens into the stomach cavity. The stomach has a rather complex structure, since its mucous membrane is rich in a large number of tissue glands, a variety of cells that produce gastric juice. Food stays in the stomach from 3 to 10 hours, it depends on the nature of the food taken. The stomach digests it, impregnates it with enzymes, turns into chyme, then the "food gruel" in portions enters the duodenum.

The duodenum belongs to the small intestine, but it is worth focusing on it, since it is here that one of the most important elements of the digestive process comes in - these are intestinal and pancreatic juices and bile. Bile is an enzyme-rich fluid produced by the liver. Distinguish between cystic and hepatic bile, they differ somewhat in composition, but perform the same functions. Pancreatic juice, together with bile, intestinal juice, constitute the most important enzymatic factor of digestion, which consists in the almost complete breakdown of substances. The mucous membrane of the duodenum has special villi that can capture large lipid molecules, which, due to their size, are not able to be absorbed by blood vessels.

Next, the chyme passes into the jejunum, then into the ileum. The small intestine is followed by the large intestine, beginning with the caecum, which is best known as the appendix. The appendix does not carry any special properties during digestion, as it is a rudimentary organ, that is, an organ that has lost its functions. The large intestine is represented by the caecum, colon and rectum. It performs functions such as water absorption, secretion of specific substances, the formation of feces and, finally, an excretory function. The peculiarity of the large intestine is the presence of microflora, which determines the normal functioning of the entire human body as a whole.

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Digestive glands are organs capable of producing enzymes that enter the digestive tract and carry out the digestion of nutrients.

Large salivary glands. These are paired glands, distinguish:

Parotid salivary glands (located in front of and below the auricle)
Submandibular and sublingual (located under the diaphragm of the mouth)

They produce saliva - a mixture of the secrets of all the salivary glands. It is a viscous transparent liquid consisting of water (98.5%) and dry residue (1.5%). The dry residue includes mucin, lysozyme, enzymes that break down carbohydrates, salts, etc. Saliva enters the oral cavity through the excretory ducts of the glands during meals or during visual, olfactory and auditory irritation.

Liver. This unpaired parenchymal organ, located in the right hypochondrium, is the largest gland of the human body, its weight in an adult can be approximately 1.5-2 kg. In shape, the liver resembles an irregularly shaped wedge, with the help of ligaments it is divided into 2 lobes. The liver produces bile that is golden in color. It consists of water (97.5%) and dry residue (2.5%). The dry residue is represented by bile acids (cholic acid), pigments (bilirubin, biliverdin) and cholesterol, as well as enzymes, vitamins, and inorganic salts. In addition to digestive activity, bile also performs an excretory function, that is, it is able to remove metabolic products from the body, for example, bilirubin already mentioned above (a breakdown product of hemoglobin).

Hepatocytes are specific cells of the lobules of the liver, it is from them that the tissue of the organ consists. They serve as filters for toxins that come with the blood, therefore, the liver has the ability to protect the body from poisonous poisons.

The gallbladder is located under the liver and adjacent to it. It is a kind of reservoir for hepatic bile, which enters it through the excretory ducts. Here, bile accumulates and enters the intestines through the bile ducts. This bile is now called gallbladder and is dark olive in color.

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Skeletonopia of the stomach
The structure and functions of the stomach
- The structure of the mucosa of the organ
- What you need to know about the structural features of the stomach?
X-ray anatomy and physiology of the stomach
Endoscopy of the organ in question

What is the structure of the stomach and what does this organ look like? The stomach is an extension of the digestive tract in the form of a bag. In this organ, food accumulates after moving it through the esophagus, the initial stages of digestion go through, when the solid components of the food must turn into a liquid composition or porridge.

The food that has entered the body undergoes further digestion, which began in the oral cavity.

Skeletonopia of the stomach

The abdomen has an anterior and a posterior wall. The bent, directed upwards and to the right, the extreme part of the organ is called the lesser curvature. The convex, oriented downwards and to the left, the extreme part of the organ is called the greater curvature. On the slight curvature, near the exit end, a notch can be seen where several sections of slight curvature meet at an acute angle.

The sections of the human stomach are presented in the following form:

digestion bag (digestorius);
physiological sphincter;
element in the form of a dome (bottom of the stomach);
the entry point of the esophagus, which is located near the heart (ostium cardiacum);
exit point;
proximal stomach;
exit hole;
adjacent part of the body;
organ body;
area that is located next to the body;
canal of the stomach;
a narrow tube-shaped part (canalis pyloricus), which is located near the pylorus.

Syntopy, holotopy, skeletotopy, the structure of its walls - all this adds up to the topographic anatomy of the stomach.

This organ is located in the epigastrium. Most of the organ is located to the left of the middle of the plane. The large curvature of the organ, if filled, will be located in the regio umbilicalis. The fornix of the stomach can reach the lower part of the 5th rib. Ostium cardiacum is located on the left side of the spine, at a distance of 2-3 cm from the extreme part of the sternum.

The syntopy of the stomach is as follows: the pylorus in the case of an empty organ will lie in the midline or to the right of it. In the case of a full state, the abdomen in the upper part will be in contact with the lower base of the left side of the liver. In the back, the organ comes into contact with the upper pole of the left kidney and the adrenal gland, with the anterior base of the pancreas.

When the stomach is not full, due to the contraction of the walls, the organ will go into the depth, and the vacated space will be occupied by the transverse colon. The latter can be located in front of the stomach, under the diaphragm. The size of the body can vary. In the case of an average level of stretching, the length of the element is approximately 20-25 cm. The dimensions of the stomach of the newborn are small (length is 5 cm). The capacity of the organ will largely depend on the dietary habits of the subject, the value is most often in the range of 1-3 liters.

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The structure and functions of the stomach

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The structure of the mucosa of the organ

The wall consists of several shells:

Tunica serosa is the serous muscular membrane of the stomach.
Tunica mucosa - mucous membrane. It has a developed submucosa. Designed to perform the main function of the stomach, namely the processing of food consumed. In the mucosa there are several glands that produce gastric juice. This substance contains hydrochloric acid.
Tunica muscularis - muscular membrane. It is represented by myocytes and muscle tissues. In the form of bags, they are placed in three layers. The middle layer is more pronounced than the longitudinal one. The circular layer of the stomach will thicken closer to the exit.

The perverse flap in the case of contraction of the pyloric constrictor will completely separate the abdominal cavity from the duodenal cavity. There is also a device that regulates the entry of food from the stomach into the intestine and prevents its return. Otherwise, neutralization of the acidic environment of the stomach could occur.

Gland classification:

Cardinal.
Pyloric, which consist exclusively of basic cells.
Gastric. There are quite a lot of them in the body. They are located in the area of the arch and body of the organ. There are various cells in the composition: main and parietal.

The pancreas is located behind the organ in question.

In some places, single follicles are scattered in the mucosa.

Impregnation of food with gastric juice can be achieved due to the ability of the mucous membrane to form folds. This can be provided by the presence of a loose submucosa that contains vessels and nerves and allows the mucosa to be combined into various folds. The blood supply to the stomach is due to the vessels that surround it. Along a slight curvature, the folds of the stomach, the structure of which is being considered, will have a longitudinal direction and form a path, which, in the event of muscle contraction, will become a channel through which food fluids will pass from the esophagus to the pylorus, bypassing the fundus element. The abdominal ligaments of the stomach on the side of a slight curvature belong to the small omentum.

In addition to folds, the mucosa may have rounded elevations called margins. On their basis, small pits can be detected. Glands will open into these pits. At the entrance of the esophagus under a microscope, one can see a clear border between the epithelium of the stomach and esophagus. In the region of the opening of the pylorus, a circular fold is located, which delimits the acidic environment from the alkaline one.

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What you need to know about the structural features of the stomach?

Oblique muscle fibers are connected into bundles that fit on the left side of the ostium cardiacum and create a loop for support.

The structure of the ruminant stomach is distinguished by a complex digestive system.

The outer layer of the wall will be formed by a serous film, which is an element of the peritoneum. The serous film will connect to the stomach in all places except for two curvatures. Vessels will be located between several sheets of the peritoneum. There is a small area at the base of the stomach on the left side of the ostium cardiacum, which is not covered by the peritoneum. In this place, the organ is in contact with the diaphragm.

Despite its relatively simple form, the human stomach, controlled by an innervation device, is a perfect organ that allows a person to easily adapt to various eating patterns.

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X-ray anatomy and physiology of the stomach

Such a diagnosis of this organ in sick people makes it possible to identify the dimensions, shape, location of the stomach and the image of the folds of its mucous membrane. In this case, the tone of the muscle shell matters. The human stomach will not retain x-ray beams and therefore will not cast shadows on the x-ray image. You can only find enlightenment, which corresponds to the gas bubble: air penetrating with food and gases rising to the roof of the stomach.

To prepare the stomach for diagnosis, barium sulfate contrast should be used. On the contrast image, you can see that the cardiac sphincter, fornix and body of the organ will form the descending part of the shadow. The pyloric part of the stomach forms the ascending part of the shadow. The ratios of such parts can be individual in each case. The most commonly observed types and positions of the body:

An organ in the form of a horn. The body of the stomach is located almost across, the pyloric part of the stomach narrows slightly. The pylorus is located on the right side of the extreme part of the spinal column and is the lowest point of the organ. As a result, there will be no angle between the parts of the stomach. The entire organ is located almost transversely.
Hook organ. The descending part is located obliquely or almost vertically down. The ascending part is placed obliquely. The pylorus is located near the right edge of the spinal column. An angle is formed between these parts, which is slightly less than a right one. In general, the stomach is placed obliquely.
Organ in the form of a stocking. It looks like an organ in the form of a hook. The only difference is that the descending part of the organ is longer and descends vertically. The ascending part rises sharply. In this case, the resulting angle will be approximately 35-40°.

The stomach is located on the left side of the midline and slightly passes beyond it in some places. The organ is placed vertically. A correlation can be noted between the shape and placement of the stomach: the organ in the form of a horn in most cases has a transverse position, the organ in the form of a hook is oblique, and the elongated organ is vertical.

The shape of the organ is more associated with the type of physique.

In patients with a brachymorphic body type and a small body, a horn-shaped stomach can often be found. The organ is located transversely, the lowest part is 3-5 cm above the line that connects the iliac crests.

In patients with a dolichomorphic physique and an elongated torso of small width, one can often find an elongated organ with a vertical arrangement. Almost the entire stomach is located to the left of the spinal column. The pylorus will be projected on the spine, the lower line of the organ in question will fall below the linea biiliaca.

In patients with a transitional physique, you can find the shape of the organ in the form of a hook. The stomach is placed obliquely. This shape and position is the most common.

Muscle tone also affects the shape. On an empty stomach, the body is in a collapsed state. If food enters it, then the stomach will begin to stretch to cover its contents.

The meridian of the stomach starts from the wing of the nose and rises to the inner corner of the eye, where it connects with the meridian of the bladder.

The mucosal glands will secrete a juice that contains digestive pigments as well as hydrochloric acid. Such juice will have a bactericidal effect.

Anatomy of the gastrointestinal tract is a complex of organs that ensure the vital activity of the body. The scheme of the structure of the gastrointestinal tract is the human organs sequentially located, and depicted as cavities. The hollow spaces are interconnected and form a single channel for accepting, changing the qualitative structure, and removing food. The length of the entire channel is about 8.5 - 10 meters. Each hollow (empty from the inside) organ is surrounded by shells (walls) that are identical to each other in structure.

The walls of the gastrointestinal tract

Shells of hollow channels have the following structure:

From the inside, the walls of the gastrointestinal tract are lined with epithelium - a layer of mucosal cells that are in direct contact with food. The mucosa performs three tasks:

protection from damage (physical or toxic effects);
enzymatic breakdown of nutrients, vitamins, minerals (parietal digestion, carried out in the small intestine);
the transfer of fluid into the blood (absorption).

After the mucous membrane is the submucosal layer, consisting of connective tissue. The tissue itself does not have a functional component, it contains numerous venous, lymphoid and nerve clusters.
The muscular membrane, which follows, has an uneven thickness in different areas of the gastrointestinal tract. It is endowed with the function of moving food through the digestive tube.
The outer layer of the walls is represented by the peritoneum (or serous membrane), which protects the organs from external damage.

Major organs of the gastrointestinal tract

The anatomy of the human gastrointestinal tract is an integration of the digestive tract and glands that synthesize the digestive secret.

The departments of the gastrointestinal tract include the following organs:

The initial site is the oral fissure (oral cavity).
Muscular tube in the form of a cylinder (pharynx).
Muscular canal that connects the stomach sac and the pharynx (esophagus).
Hollow food processing tank (stomach).
A thin tube about 5 meters long (small intestine). Consists of the initial section (duodenum), middle (jejunum), and lower (ileum).
The lower (final) part of the gastrointestinal tract (large intestine). It consists of: the initial sac-like department or the caecum with the process of the appendix, the colon system (ascending, transverse, descending, sigmoid) and the final department - the rectum.

All parts of the gastrointestinal tract are endowed with certain functions that make up the whole process of digestion, which is the initial one in a complex metabolic mechanism.

Oral cavity

The primary gastrointestinal tract includes:

musculoskeletal organ (lips);
mucous membrane lining the cavity (gums);
two rows of bone formations (teeth);
mobile muscular organ with a fold going to the gums (tongue);
a pharynx bounded by a hard and soft palate;
salivary glands.

Functional purposes of the department:

mechanical grinding, chemical processing and differentiation of food taste;
formation of sounds;
breath;
protection from pathogens.

The tongue and soft palate are involved in the process of swallowing.

Pharynx

It has the shape of a funnel, localized in front of the 6th and 7th cervical vertebrae. By structure, it consists of the upper, middle and lower parts (nasopharynx, oropharynx, laryngopharynx, respectively).

Connects the oral cavity with the muscular canal of the esophagus. Takes part in the processes:

breathing;
speech formation;
reflex contraction and relaxation of muscles to promote food (swallowing);

The pharynx is equipped with a mechanism of protection against external negative factors.

Esophagus

A flattened muscular canal up to 30 cm in length, consisting of the cervical, thoracic and abdominal parts, ending in a cardiac valve (sphincter). The valve closes off the stomach to prevent backflow of food and acid (into the esophagus). The main task of the body is to move food towards the stomach for its further processing (digestion).

Stomach

The scheme of the stomach includes four main zones, divided among themselves conditionally:

Cardiac (supracardial and subcardial) zone. It is located at the junction of the stomach and esophagus, equipped with a closing sphincter (valve).
Upper section or vault. It is placed on the left side under the diaphragm. It is supplied with glands that synthesize gastric juice.
Organ body. It is localized below the arch, has the largest volume of all organs of the gastrointestinal tract, is intended for temporary storage of food coming from the muscle canal, and its splitting.
Pyloric or pyloric zone. It is located at the bottom of the system, connecting the stomach and intestines through the pyloric (outlet) valve.

hydrochloric (HCl) acid;
enzymes (pepsin, gastrixin, chymosin);
protein (mucin);
enzyme with bactericidal properties (lysozyme);
mineral salts and water.

Functionally, the stomach is designed to store and process food, absorb liquids and salts.

Digestion of food occurs under the action of gastric juice and muscle contractions of the body. When the stomach is empty, juice production stops. The resulting semi-solid substance (chyme) is sent to the duodenum with the help of the vagus (vagus nerve).

Small intestine

It performs the main work on food processing (abdominal and parietal digestion), acid neutralization, as well as the function of absorption (absorption) of useful substances to deliver them to the bloodstream.

Consists of three zones:

Duodenum. Responsible for the work of the output pulp (its timely and regular reduction). It is supplied with gastric, pancreatic, intestinal juice and bile. The alkaline secret is synthesized by glands located in the walls of the organ. Under the influence of these liquids, the process of digestion of chyme occurs.
T small intestine. Smooth muscle organ involved in the digestive process. Without clear boundaries, it passes into the next zone - the ileum.
Ileum. Anatomically covered by the peritoneum on all sides, takes an active part in the breakdown of nutrients and other substances. It ends with the ileocecal sphincter that separates the large and small intestines.

The process of breaking down food is completed in the small intestine.

Colon

The lower zone of the gastrointestinal tract, endowed with the function of absorbing fluid, and the formation of excrement. The organ does not secrete juice, it produces a mucous substance for the excrement-forming process.

Divided into several zones:

Cecum. It is equipped with a process that does not play a big role in the body - the appendix.
The colon system consists of four organic zones (ascending, transverse, descending, sigmoid) that are not involved in the process of food processing. The functional purpose is the absorption of nutrients, the activation of the movement of processed products, the formation, maturation and excretion of excrement.
Rectum. The final zone of the digestive tract. Designed for the accumulation of fecal formations. The structure has a strong muscular valve (anal sphincter). The main function is the dynamic release of the intestine from accumulated excrement through the anus.

The complex structure of the human gastrointestinal tract requires careful attention. Malfunctions in the work of one of the organs inevitably lead to disturbances in the work of the entire digestive system.

The residence time of the contents (digestible food) in the stomach is normal - about 1 hour.

Anatomy of the stomach

Anatomically, the stomach is divided into four parts:

cardiac(lat. pars cardiaca) adjacent to the esophagus;
pyloric or gatekeeper (lat. pars pylorica), adjacent to the duodenum;
body of the stomach(lat. corpus ventriculi), located between the cardiac and pyloric parts;
fundus of the stomach(lat. fundus ventriculi), located above and to the left of the cardial part.

In the pyloric region, they secrete gatekeeper's cave(lat. antrum pyloricum), synonyms antrum or anthurm and channel gatekeeper(lat. canalis pyloricus).

The figure on the right shows: 1. The body of the stomach. 2. Fundus of the stomach. 3. Anterior wall of the stomach. 4. Large curvature. 5. Small curvature. 6. Lower esophageal sphincter (cardia). 9. Pyloric sphincter. 10. Antrum. 11. Pyloric canal. 12. Corner cut. 13. A furrow that forms during digestion between the longitudinal folds of the mucosa along the lesser curvature. 14. Folds of the mucous membrane.

The following anatomical structures are also distinguished in the stomach:

anterior wall of the stomach(lat. paries anterior);
posterior wall of the stomach(lat. paries posterior);
lesser curvature of the stomach(lat. curvatura ventriculi minor);
greater curvature of the stomach(lat. curvatura ventriculi major).

The stomach is separated from the esophagus by the lower esophageal sphincter and from the duodenum by the pyloric sphincter.

The shape of the stomach depends on the position of the body, the fullness of food, the functional state of the person. With an average filling, the length of the stomach is 14–30 cm, the width is 10–16 cm, the length of the lesser curvature is 10.5 cm, the greater curvature is 32–64 cm, the wall thickness in the cardia is 2–3 mm (up to 6 mm), in the antrum 3 -4 mm (up to 8 mm). The capacity of the stomach is from 1.5 to 2.5 liters (the male stomach is larger than the female one). The mass of the stomach of a “conditional person” (with a body weight of 70 kg) is normal - 150 g.

The wall of the stomach consists of four main layers (listed starting from the inner surface of the wall to the outer):

mucosa covered by a single layer of columnar epithelium
submucosa
muscular layer, consisting of three sublayers of smooth muscles:

inner sublayer of oblique muscles
middle sublayer of circular muscles
outer sublayer of longitudinal muscles

serous membrane.

Between the submucosa and the muscular layer is the nervous Meissner (synonymous with submucosal; lat. plexus submucosus) a plexus that regulates the secretory function of epithelial cells between the circular and longitudinal muscles - Auerbach's (synonymous with intermuscular; lat. plexus myentericus) plexus.

The mucous membrane of the stomach

The mucous membrane of the stomach is formed by a single-layer cylindrical epithelium, its own layer and muscular plate, which forms folds (the relief of the mucous membrane), gastric fields and gastric pits, where the excretory ducts of the gastric glands are localized. In its own layer of the mucous membrane are tubular gastric glands, consisting of parietal cellsproducing hydrochloric acid; chief cellsproducing the pepsin proenzyme pepsinogen, and additional (mucous) cells that secrete mucus. In addition, mucus is synthesized by mucous cells located in the layer of the superficial (integumentary) epithelium of the stomach.

The surface of the gastric mucosa is covered with a continuous thin layer of mucous gel, consisting of glycoproteins, and under it is a layer of bicarbonates adjacent to the surface epithelium of the mucous membrane. Together they form a mucobicarbonate barrier of the stomach, protecting epitheliocytes from the aggression of the acid-peptic factor (Zimmerman Ya.S.). The composition of the mucus includes immunoglobulin A (IgA), lysozyme, lactoferrin and other components with antimicrobial activity.

The surface of the mucous membrane of the body of the stomach has a pit structure, which creates conditions for minimal contact of the epithelium with the aggressive intracavitary environment of the stomach, which is also facilitated by a powerful layer of mucous gel. Therefore, the acidity on the surface of the epithelium is close to neutral. The mucous membrane of the body of the stomach is characterized by a relatively short path for the movement of hydrochloric acid from the parietal cells into the lumen of the stomach, since they are located mainly in the upper half of the glands, and the main cells are in the basal part. An important contribution to the mechanism of protection of the gastric mucosa from the aggression of gastric juice is made by the extremely rapid nature of the secretion of the glands, due to the work of the muscle fibers of the gastric mucosa. The mucous membrane of the antral region of the stomach (see the figure on the right), on the contrary, is characterized by a “villous” structure of the surface of the mucous membrane, which is formed by short villi or convoluted ridges 125–350 µm high (Lysikov Yu.A. et al.).

Children's stomach

In children, the shape of the stomach is unstable, depending on the constitution of the child's body, age and diet. In newborns, the stomach has a round shape, by the beginning of the first year it becomes oblong. By the age of 7–11, the shape of a child's stomach does not differ from that of an adult. In infants, the stomach is located horizontally, but as soon as the child begins to walk, he assumes a more vertical position.

By the time the child is born, the fundus and cardial section of the stomach are not sufficiently developed, and the pyloric section is much better, which explains frequent regurgitation. Regurgitation is also facilitated by swallowing air during sucking (aerophagia), with improper feeding technique, a short frenulum of the tongue, greedy sucking, too rapid release of milk from the mother's breast.

Gastric juice

The main components of gastric juice are: hydrochloric acid secreted by the parietal (parietal) cells, proteolytic, produced by chief cells and non-proteolytic enzymes, mucus and bicarbonates (secreted by additional cells), internal Castle factor (production of parietal cells).

The gastric juice of a healthy person is practically colorless, odorless and contains a small amount of mucus.

Basal, not stimulated by food or otherwise, secretion in men is: gastric juice 80-100 ml / h, hydrochloric acid - 2.5-5.0 mmol / h, pepsin - 20-35 mg / h. Women have 25-30% less. About 2 liters of gastric juice are produced in the stomach of an adult per day.

The gastric juice of an infant contains the same ingredients as the gastric juice of an adult: rennet, hydrochloric acid, pepsin, lipase, but their content is reduced, especially in newborns, and increases gradually. Pepsin breaks down proteins into albumins and peptones. Lipase breaks down neutral fats into fatty acids and glycerol. Rennet (the most active of the enzymes in infants) curdles milk (Bokonbaeva SD and others).

Stomach acidity

The main contribution to the total acidity of gastric juice is made by hydrochloric acid produced by the parietal cells of the fundic glands of the stomach, located mainly in the fundus and body of the stomach. The concentration of hydrochloric acid secreted by the parietal cells is the same and equal to 160 mmol / l, but the acidity of the secreted gastric juice varies due to a change in the number of functioning parietal cells and neutralization of hydrochloric acid by the alkaline components of gastric juice.

Normal acidity in the lumen of the body of the stomach on an empty stomach is 1.5-2.0 pH. The acidity on the surface of the epithelial layer facing the lumen of the stomach is 1.5–2.0 pH. Acidity in the depth of the epithelial layer of the stomach is about 7.0 pH. Normal acidity in the antrum of the stomach is 1.3–7.4 pH.

Currently, the only reliable method for measuring the acidity of the stomach is considered to be intragastric pH-metryperformed using special devices - acidogastrometersequipped with pH probes with several pH sensors, which allows you to measure acidity simultaneously in different areas of the gastrointestinal tract.

The acidity of the stomach in conditionally healthy people (who do not have any subjective sensations in gastroenterological terms) changes cyclically during the day. Daily fluctuations in acidity are greater in the antrum than in the body of the stomach. The main reason for such changes in acidity is the longer duration of nocturnal duodenogastric refluxes (DGR) compared to daytime ones, which throw duodenal contents into the stomach and, thereby, reduce acidity in the stomach lumen (increase pH). The table below shows the average values of acidity in the antrum and body of the stomach in apparently healthy patients (Kolesnikova I.Yu., 2009):

The total acidity of gastric juice in children of the first year of life is 2.5–3 times lower than in adults. Free hydrochloric acid is determined during breastfeeding after 1-1.5 hours, and with artificial - after 2.5-3 hours after feeding. The acidity of gastric juice is subject to significant fluctuations depending on the nature and diet, the state of the gastrointestinal tract.

Motility of the stomach

With regard to motor activity, the stomach can be divided into two zones: proximal (upper) and distal (lower). There are no rhythmic contractions and peristalsis in the proximal zone. The tone of this zone depends on the fullness of the stomach. When food is received, the tone of the muscular membrane of the stomach decreases and the stomach reflexively relaxes.

Motor activity of various parts of the stomach and duodenum (Gorban V.V. et al.)

The figure on the right shows a diagram of the fundic gland (Dubinskaya T.K.):

1 - layer of mucus-bicarbonate
2 - surface epithelium
3 - mucous cells of the neck of the glands
4 - parietal (parietal) cells
5 - endocrine cells
6 - chief (zymogenic) cells
7 - fundic gland
8 - gastric fossa

Microflora of the stomach

Until recently, it was believed that due to the bactericidal action of gastric juice, the microflora that penetrated the stomach dies within 30 minutes. However, modern methods of microbiological research have shown that this is not the case. The amount of various mucosal microflora in the stomach in healthy people is 10 3 -10 4 / ml (3 lg CFU / g), including 44.4% of cases revealed Helicobacter pylori(5.3 lg CFU / g), in 55.5% - streptococci (4 lg CFU / g), in 61.1% - staphylococci (3.7 lg CFU / g), in 50% - lactobacilli (3, 2 lg CFU / g), in 22.2% - fungi of the genus Candida(3.5 lg cfu/g). In addition, bacteroids, corynebacteria, micrococci, etc. were sown in the amount of 2.7–3.7 lg CFU/g. It should be noted that Helicobacter pylori were determined only in association with other bacteria. The environment in the stomach turned out to be sterile in healthy people only in 10% of cases. By origin, the microflora of the stomach is conditionally divided into oral-respiratory and fecal. In 2005, in the stomach of healthy people, strains of lactobacilli were found that adapted (like Helicobacter pylori) to exist in the sharply acidic environment of the stomach: Lactobacillus gastricus, Lactobacillus antri, Lactobacillus kalixensis, Lactobacillus ultunensis. In various diseases (chronic gastritis, peptic ulcer, stomach cancer), the number and diversity of bacteria colonizing the stomach increase significantly. In chronic gastritis, the greatest amount of mucosal microflora was found in the antrum, in peptic ulcer - in the periulcerous zone (in the inflammatory ridge). Moreover, often the dominant position is occupied by Helicobacter pylori, and streptococci, staphylococci,

The stomach is a sac-shaped organ of the digestive system, which is located between the duodenum and the esophagus.

It is customary to distinguish the front wall of the organ, which is directed anteriorly and upwards, and the back, facing downwards and backwards. In the place where both walls converge, an upper concave edge is formed, called a small curvature, which is directed to the right and up, and a lower convex edge, or a large curvature, directed to the left and down.

The structure of the stomach involves the division of the body into several sections, including:

the cardial part, beginning with a cardiac opening connecting the stomach to the esophagus;
the body of the organ, located to the left of the inlet section;
the fundus of the stomach, located under the left dome of the diaphragm and separated from the cardia by a notch;
the pyloric part, adjacent to the pylorus opening, through which the duodenum and stomach are connected.

The structure of the stomach wall

The wall of the organ is formed by such 3 shells as:

Serous, external, which covers the stomach from almost all sides;
Muscular, middle, which is well developed and represented in turn by three layers:
- outer longitudinal;
- middle circular;
- internal, from oblique fibers;
Mucous, internal, which is covered with a cylindrical epithelium, consisting of a single layer.

The connective tissue basis of the mucosa contains lymphatic, venous and arterial vessels, single lymphoid nodules and nerves.

Glands of the stomach

The entire surface of the mucosa has small elevations called gastric fields, on which there are gastric pits, which are the mouths of numerous - up to 35 million - gastric glands. Their functions include the production of gastric juice, which contains digestive enzymes, which are designed for chemical processing of the food bolus.

There are several types of gastric glands.

All of them have both similar functions and structural features, as well as certain differences and features:

the cardiac glands are distributed in the mucosa in the area of the entrance to the organ;
the main ones are in the mucous membrane of the body and fundus of the stomach;
intermediate - in the mucous membrane of the intermediate region of the organ, between the body and the antrum;
priloric - in the mucous membrane of the pylorus.

All glands are tubular and have 5 main cell types:

mucoid, or additional, secreting mucus;
main, or zymogenic, secreting, reserving and excreting proenzymes;
parietal, or parietal, producing hydrochloric acid and protein;
endocrine G- and D-cells secreting the hormones gastrin and somatostatin, respectively.

The shape and size of the stomach

Normally, the filled organ has a length of 25-26 cm, the distance separating the greater and lesser curvature varies within limits not exceeding 12 cm, and the posterior and anterior surfaces are separated from each other by a distance of about 9 cm. An empty stomach has a length not exceeding 20 cm, both walls are in contact, and the distance between the greater and lesser curvature is about 8 cm. The volume of the stomach of an adult is about 3 liters and can vary from 1.5 to 4.5 liters, depending on the amount of food in it , muscle tone and body type.

Depending on the physique of a person, 3 main forms of the stomach are distinguished, including in the form of:

Horns, or cone (brachymorphic physique), with an almost transverse arrangement of the organ;
Fish hook (mesomorphic physique), while the body is located almost vertically, then sharply bending to the right side, forms an open acute angle between the evacuation channel and the digestive sac;
Stocking (dolichomorphic physique), when the descending section is lowered low, and the pyloric part rises steeply, being located along the midline or slightly away from it.

These forms of the stomach are inherent in the body, which is in a vertical position. If a person lies on his side or on his back, the shape of the organ changes. In addition, it also depends on gender and age - in children and the elderly, the stomach is most often found in the form of a horn, in women - an elongated hook.

Ligament apparatus

The diagram of the ligamentous apparatus highlights the superficial, located in the frontal plane, and deep, horizontally located, ligaments of the stomach, including:

Gastrocolic, which is the transition of 2 sheets of the visceral peritoneum from the greater curvature to the transverse colon and extending from the pyloric zone to the lower pole of the spleen, representing the upper part of the greater omentum. Between these sheets of the ligament are 2 gastroepiploic arteries, connecting one to the other.
Gastro-splenic, connecting the greater curvature and the hilum of the spleen and covering its vascular pedicle. It contains short arteries.
Diaphragmatic-esophageal, which is the transition of the parietal peritoneum from the diaphragm to the cardial part of the stomach and esophagus.
Gastro-diaphragmatic, serving as the transition of the parietal peritoneum from the diaphragm to the anterior surface of the bottom and partly the cardia.
Hepatogastric, coming from the gate of the liver in the form of a trapezoid with a base on the lesser curvature, where it is divided into 2 leaves passing into the visceral peritoneum of the anterior and posterior walls of the stomach. The right and left gastric arteries run in the tissue of the lesser curvature. Deep ligaments can be identified after dissection of the gastrocolic ligament.
Gastro-pancreas, which serves as the transition of the parietal peritoneum from the upper edge of the pancreas to the posterior surface of the cardia and body of the stomach. In the ligament are the celiac branch and the left gastric vessels.
Pyloric-pancreas, located between the right side of the pancreas and the pylorus.

secretion of the stomach

The process of digestion of food directly depends on its secretion. Gastric juice is an aggressive environment, and the secretion regulation system ensures that the secret of gastric acids does not harm the body, but performs its functions. The central nervous system also takes part in this process.

The stomach is not a simple reservoir for storing and digesting food, but a complex system that uses the mechanisms of self-regulation of the secretion of gastric juice, which act due to hormone-like substances produced by the tissues of not only the stomach, but also the pancreas, as well as the duodenum.

As a result of exposure to aggressive enzymes and an increased level of acidity, gastric juice has an antiseptic effect and has the ability to destroy most bacteria. The mucous membrane of the organ is protected from self-digestion due to the constant self-renewal of the cellular composition, the presence of a layer of mucus on the surface of the inner membrane and abundant blood supply. Violation of any function leads to the development of diseases such as ulcers and gastritis.

Hormones

The regulation of the secretory work of the digestive glands is carried out due to humoral and nervous mechanisms. The main nerve fibers that stimulate secretion are parasympathetic, which are the axons of postganglionic neurons. Nerve sympathetic fibers, on the contrary, inhibit the secretion of the digestive glands, exerting trophic influences on them and enhancing the synthesis of secretion components.

Gastrointestinal regulatory peptides such as:

somatostatin, which inhibits the release of glucagon, insulin and most gastrointestinal hormones;
a vasoactive peptide that inhibits the secretion of hydrochloric acid and pepsin by the stomach, and also relaxes the muscles of blood vessels;
gastrin, which stimulates the secretion of pepsin and stimulates the motility of the relaxed duodenum and stomach;
deli and bulbogastron, which reduce the volume of gastric secretion and the concentration of hydrochloric acid;
bombesin, which stimulates the release of gastrin.

Physiology of the stomach

The stomach is the main organ of the human digestive system. Food enters it after it passes through the mouth and esophagus. The glands of the mucous membrane of the organ secrete gastric juice, which, thanks to the digestive enzymes lipase, pepsin, chymosin, hydrochloric acid and other active substances contained in it, not only breaks down proteins and fats, but also has a powerful bactericidal effect.

Thanks to the muscular layer, the stomach mixes food with gastric juice, forming a liquid slurry, or chyme, which is excreted in separate portions from the stomach into the duodenum through the pyloric sphincter. Depending on the consistency, the incoming food lump lingers in the stomach from a quarter of an hour (broths, vegetable and fruit juices) to 6 hours (pork meat). In addition, the walls of the body absorb ethanol, water, carbohydrates, sugar and some salts.

In order to understand the principles of proper nutrition, long-term health and longevity, you must understand the basic processes of digestion and know how nutrients are absorbed by the body. By regulating the intake of food and controlling its quantity and quality, you can achieve good results on the path of your own recovery.