Anatomy of the stomach. Structure and function of the human stomach

The human stomach is the main reservoir for storing the food of the body. If the body did not have the same capacity as the stomach, we would eat constantly, not just a few times a day. It also releases a mixture of acid, mucus and digestive enzymes that help digest and disinfect our food while it is being stored.

Macroscopic anatomy

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

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

The stomach is an enlarged part of the gastrointestinal tract, which has the shape of a crescent. Its inner layer is full of wrinkles, known to us as wrinkles (or creases). It is these folds that allow it to stretch out so that large portions of food can be placed in it, which subsequently moves calmly in the process of digestion.

In form 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. It is a narrow, pipe-like part that goes into a wider cavity - the body of the stomach. Cardia consists of the lower sphincter of the esophagus, as well as a group of muscle tissue that shrinks to keep food and acid in the stomach.

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

3. A little above the body is a domed area known as its bottom.

4. Below the body is a 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 the mucosa, which is a simple epithelial tissue with a variety of exocrine cells. Small pores, called gastric pits, contain many exocrine cells that produce digestive enzymes and hydrochloric acid in the stomach. Mucous cells located throughout the mucous membrane and gastric fossa 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 can not be said for the mucosa of other organs of the gastrointestinal tract.

In the depth of the mucous membrane there is a thin layer of smooth muscles - the muscular plate. It forms folds and increases the contact of the mucosa with the contents of the stomach.

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

Muscular layer

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

Serous membrane

The outer layer of the stomach surrounding the muscle tissue is called the serosa, which is made from simple squamous epithelial and loose connective tissues. The serous layer has a smooth, slippery surface and secretes a liquid, watery secret known as serous fluid. The smooth, wet surface of the serous membrane helps protect the stomach from friction, during its constant expansion and constriction.

The anatomy of the human stomach is now more or less clear. All that is described above, we will consider a little later on the diagrams. But first we will understand what the functions of the human stomach.

Storage

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

The volume of the human stomach can vary, but on average, it can contain 1-2 liters of food and liquids, which helps digestion. When the stomach is stretched by a large amount of food, it can store up to 3-4 liters. Stretched stomach makes digestion difficult. Since the cavity can not easily contract to mix food properly, it leads to a feeling of discomfort. The volume of the human stomach also depends on the age and condition of the body.

After the cavity of the stomach was filled with food, it remains for another 1-2 hours. At this time, the stomach continues the digestive process, which began in the mouth, and allows the intestines, pancreas, gall bladder 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. As a rule, it usually closes to keep food and stomach secretion. Once the chyme is ready to leave the stomach, the gatekeeper's sphincter opens to allow a small amount of digested food to pass into the duodenum. Within 1-2 hours this process is slowly repeated until all the digested food leaves the stomach. The slow rate of release of chyme helps to decompose it into components and to maximize digestion and absorption of nutrients in the intestine.

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 located 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 mixed with food in the stomach to promote digestion.

Specialized exocrine cells of the mucosa - mucous cells, retain mucus in the folds and pits of the stomach. This mucus spreads through the surface of the mucous membrane to cover the lining of the stomach with a thick, acid and enzyme-resistant barrier. The mucus of the stomach is also rich in bicarbonate ions, which neutralize the pH factor of the acid of the gastric juice.

The parietal cells located in the pits of the stomach produce 2 important substances: the internal factor of Castle and hydrochloric acid. The internal factor is a glycoprotein that binds to vitamin B12 in the stomach and helps it to be absorbed by the small intestine. Vitamin B12 is an essential nutrient for the formation of red blood cells.

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

The main cells, also in the pits of the stomach, produce two digestive enzymes: pepsinogen and gastric lipase. Pepsinogen is a precursor molecule of a very powerful, digestive protein enzyme - pepsin. Since pepsin would destroy the main cells, which produce it, it hid in the form of pepsinogen, where it is not dangerous. When pepsinogen is contacted with an acidic pH factor that is contained in the stomach acid, it changes shape and becomes an active enzyme of pepsin, which turns proteins into amino acids.

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

G-cells of the stomach - endocrine cells located at the base of the pits of the stomach. G cells synthesize the hormone gastrin in 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 the walls of the stomach during meals. Gastrin passes through the blood to various receptor cells throughout the stomach, and its main task is stimulation of the gland and muscles of the stomach. The effect of gastrin on the gland leads to an increase in the secretion of gastric juice, which improves digestion. Stimulation of smooth muscles by gastrin promotes more severe 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 gall bladder, where it increases the secretion of juice and bile.

As you can see, enzymes of 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 a physical division of the mass of food into smaller portions, and chemical digestion is the conversion of larger molecules into smaller molecules.

• Mechanical digestion is due to the mixing action of the walls of the stomach. His smooth muscles contract, so that portions of food are mixed with gastric juice, which leads to the formation of a thick liquid - chyme.

• While food is physically mixed with gastric juice, the enzymes present in it are chemically splitting large molecules into smaller subunits. Gastric lipase cleaves triglyceride fats for fatty acids and diglycerides. Pepsin breaks down proteins into smaller amino acids. The chemical decomposition begun in the stomach does not end until the chyme enters the intestine.

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, increases its activity, stimulating an increase in the amount of produced gastric juice, muscle contraction and gastric emptying through the sphincter of the pylorus.

• Cholecystokinin (CCK) is produced by the mucosa of the duodenum. It is a hormone that slows down the emptying of the stomach by reducing the pyloric sphincter. SCS is released in response to a meal rich in proteins and fats, which are very difficult to digest by our body. SSC allows food to be stored in the stomach longer for more thorough digestion and gives time to the pancreas and gall bladder to release enzymes and bile that improve digestion in the duodenum.

• Secretin - another hormone produced by the mucosa of the duodenum, reacts to the acidity of the chyme entering the intestine from the stomach. Secretin passes 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 the acid. The purpose of secretin is to protect the intestines from the harmful effects of chyme acid.

Stomach: building

Formally, we have already familiarized ourselves with the anatomy and functions of the human stomach. Let's use the illustrations to see where the human stomach is and what it consists of.

Picture 1:

This figure depicts the stomach of a person whose structure can be considered in more detail. Here are denoted:

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

Figure 2:

In this image, the anatomy of the stomach is clearly visible. The figures are:

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

Figure 3:

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

1 - the upper group of lymph nodes; 2 - pancreatic group of nodes; 3 - pyloric group; 4 - the bottom group of pyloric knots.

Figure 4:

This image shows the structure of the wall of the stomach. Here are marked:

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

Figure 5:

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

This image is quite interesting. It does not depict the anatomy of the human stomach or something like that, although some of its parts can still be considered. This figure shows what is heartburn and what happens with it.

1 - esophagus; 2 - lower esophageal sphincter; 3 - stomach contractions; 4 - gastric acid together with its contents rises in 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 stomach of a person, the pictures of which were presented above, is a very important organ in our body. Without it you can live, but this life is unlikely to replace a full one. Fortunately, in our time, many problems can be avoided simply by periodically visiting a gastroenterologist. Timely diagnosis of the disease will help to get rid of it more quickly. The main thing is not to delay the trip to the doctor, and if something hurts, then you should immediately contact this specialist with a problem.