The secretion of gastric juice occurs through the work of the gastric mucosa. It is a colorless, odorless liquid with small lumps of mucus. Any deviations from this norm, for example, a change in color and density, indicate the presence of problems with the gastrointestinal tract. The composition of gastric juice is complex, since it is produced by various cells of the gastric mucosa. Its main component is which, in turn, is distinguished by its concentrated composition.

Gastric juice composition

In addition to hydrochloric acid, gastric juice contains the following components

1. Bicarbonates (they neutralize the destructive effect of hydrochloric acid on the stomach walls).
2. Pepsinogen, which turns into pepsin (the latter is involved in the breakdown of proteins). Pepsin is divided into another family of enzymes, each of which has its own functions.
3. Mucus (it also protects the mucous membrane from destruction).
4. Castle Factor (an enzyme that assists in the absorption of B 12).

However, the main component of gastric juice is still hydrochloric acid. We will talk about it.

What is hydrochloric acid?

It is produced by the parietal cells of the stomach glands located on the body and the bottom of the organ. In essence, the mucous membrane is divided into several zones: one produces hydrochloric acid, the other releases bicarbonates that neutralize it. It is noteworthy that in men there are several times more parietal cells than in women.

Hydrochloric acid in the stomach has a strict concentration level - it is 0.3-0.5% (or 160 mmol / l). Its composition is so concentrated that if there were no protective substances in the gastric juice and mucous membrane, it would burn out its own stomach. That is why, with insufficient production of mucus by the stomach, a person has gastritis or duodenal ulcer. Acid is constantly present in the stomach, but in response to food intake, its amount increases. Basal secretion of hydrochloric acid (that is, morning) is 5-7 mmol / hour.

A healthy stomach produces up to 2.5 liters of hydrochloric acid per day!

The secretion of hydrochloric acid has 3 phases.

1. Reaction to the taste and smell of food. It is triggered and transmitted from the central nervous system to gastric cells through nerve endings.
2. After food enters the body, a more significant phase begins. Gastrin acts on parient cells, stimulating the production of hydrochloric acid.
3. The final phase begins after chyme (already digested food) enters the duodenum. Due to the increase in hydrochloric acid, the stomach produces somatostatin, its blocker.

What functions does hydrochloric acid perform in the stomach?

First of all, it improves digestion, destroys most of the bacteria that enter the stomach with food, which slows down or even interferes with the putrefactive process.

What are the functions of hydrochloric acid in the stomach? Below is a list detailing this issue.

• Protein denaturation (this is the destruction of their molecular structure) and their swelling.
• Activation of pepsinogen, which turns into pepsin, is one of the most important
• Creation in conditions of which enzymatic digestion is much easier.
• Evacuation of food from the stomach into the duodenum, where digestion continues.
• Antibacterial action - many bacteria cannot live in such an aggressive environment.
• Excitation of the secretion of pancreatic juice.

The role of hydrochloric acid in the breakdown of proteins deserves special attention. The importance of proteins in the body is enormous. This issue has been studied by scientists for many decades. It has been established that hydrochloric acid in the stomach stimulates the production of pepsin, creating a favorable environment for its activity, promotes partial denaturation and swelling of proteins. In the duodenum, hydrochloric acid stimulates the production of secretin, improves iron absorption and has a bactericidal effect.

Proteins and acidity of gastric juice

The role of hydrochloric acid in is still unclear. However, it has been established that in inflammatory diseases of the stomach, its secretion is disturbed and, as a consequence, the digestion of proteins.

The value of proteins in our body can hardly be overestimated. This group is divided into many subgroups, each of which does its own thing. So, proteins-hormones control life processes (growth and reproduction), proteins-enzymes provide chemical processes (respiration, digestion, metabolism), hemoglobin saturates cells with oxygen.

Denaturation of proteins (this facilitates the process of their subsequent breakdown) enables the body to use their properties to the maximum. Each protein is made up of amino acids. Most of them are synthesized by our body, but there is a group of so-called essential amino acids that enter the body only from the outside.

Gastric acidity

Such an important aspect as the pH of the stomach directly depends on hydrochloric acid. And if there is a deviation from the norm, gastritis, dyspeptic disorders and other unpleasant conditions occur. The acidity in the stomach can be low, normal and high.

Despite the "popularity" of elevated pH, people often experience lower or normal acidity. The latter ranges from 0.8 to 1.5.

Decreased stomach acidity

Low acidity occurs with constant stress and inflammatory diseases. This happens due to the excitation of the sympathetic nervous system, which directly affects the production of gastric juice. A decrease in acidity entails a deterioration in food digestion and stomach cramps. Food remains in the cavity, begins to rot, increasing the multiplication of pathogenic bacteria. The person suffers from flatulence and nausea. The latter is a response to stomach cramps. Moreover, the process of absorption of all nutrients contained in our food is actively disrupted, which leads to disruption of the work of the whole organism. By the way, it is on the basis of a natural decrease in pH after 40 years that a person begins to age rapidly. That is, the hydrochloric acid in the stomach actually affects the health of the whole organism.

The stomach, surprised by the excessive multiplication of bacteria, begins to turn on the protective function, resulting in inflammation. He is treated with drugs that further inhibit the production of hydrochloric acid - and the circle closes. A person is forced to constantly visit a doctor.

Increased acidity of the stomach

Despite the opinion of many gastroenterologists, high acidity is much less common with low acidity. The danger is that with prolonged juice, ulcers of the esophagus and stomach appear. The patient is worried about heartburn and pain. This is where proton pump inhibitors - "Omez" and its analogues will be useful. Symptoms are removed with the help of antacids - "Gaviscon", "Fosfalugel", etc.

To diagnose high acidity, they must be used because, according to the symptoms, it is easy to confuse it with reduced secretion.

Types of determination of stomach acidity

Hydrochloric acid in the stomach (that is, its level) is determined by several methods.

1. Sounding. It is done using a special tube through which the contents of the stomach are sucked out.
2. Intragastric pH-metry. Sensors measure acidity directly in the stomach.

The second method is considered the most informative.

Stomach acidity is something that most doctors do not pay attention to, but in fact it is extremely important for the diagnosis and treatment of gastrointestinal diseases.

In an adult, about 2-2.5 l gastric juice.

Gastric juice contains enzymes (pepsin, gelatinase, chymosin, etc.), hydrochloric acid (0.4-0.6%), gastromucoprotein, mucus, minerals, water.

Paramount among enzymes It has pepsin.Pepsin only works in an acidic environment. It breaks down proteins to albumosis and peptones. Enzymatic activity gastrixin close to the activity of pepsin. Chymosin causes milk curdling.

Also found in gastric juice non-proteolytic enzymes. One of these enzymes is lysozymeproviding bactericidal properties of gastric juice.

The role of gastric acid hydrochloric acid.

- under its influence proteins swell, which facilitates their digestion;

Softens bones;

It has a bactericidal effect;

Participates in the evacuation of food into the duodenum;

Activates pepsin of gastric juice;

Converts prosecretin of intestinal juice into secretin, which stimulates pancreatic secretion.

Protects milk;

Creates an acidic environment necessary for the work of gastric acid enzymes.

Influence of food composition on gastric secretion.

The glands of the stomach, outside the digestion process, secrete only mucus and pyloric juice. After food enters the oral cavity or at the sight of food, its smell and the effect of other food-related irritants on the body, secretion of juice in the stomach begins. Concentration begins 5-9 minutes after a person or animal has begun to eat.

The duration of the secretory process, the quantity and quality of gastric juice are strictly dependent on the nature of the food.

The onset of secretion with any food irritant is always associated with the situation preceding and accompanying food intake, as well as the reflex effect from the receptors of the oral cavity and pharynx on the glandular apparatus of the stomach. As a result, in the 1st hour, the quantity and quality of gastric juice released from eating bread and meat did not depend on the chemical properties of food. In the following hours, the intensity and duration of the secretion of gastric juice is determined by the chemical properties of food (food components, products of its digestion, hormones). It was also found that most of the juice is released after eating meat, less - bread and milk. The duration of juice secretion is different: for meat, juice is released within 7 hours, for bread - 10 hours, for milk - 6 hours.

The highest acidity of gastric juice is observed after eating meat and the lowest after eating bread.

Regulation of gastric secretion.

The entire period of gastric secretion is divided into three phases:

Difficult reflex phase is carried out on the basis of conditioned and unconditioned reflexes. The juice that begins to be released when the olfactory, visual, auditory receptors are irritated, Pavlov called fiery, appetizing. This juice is secreted in small quantities, but it is rich in enzymes and therefore has a large digestive capacity. From the moment food enters the oral cavity, unconditioned reflex department gastric juice. From the receptors in the oral cavity, nerve impulses enter the food center of the medulla oblongata through the fibers of the trigeminal, facial, glossopharyngeal nerves. Excitation from the food center through the efferent fibers reaches the glands of the stomach and increases their secretory activity. The first phase of gastric secretion lasts 30-40 minutes and is essential for digestion.

Gastric phase of secretion occurs when food comes into contact with the mucous membrane of the stomach itself. Under the influence of food irritation mechanoreceptors In the stomach, the resulting excitement reaches the alimentary center of the medulla oblongata along the sensory fibers of the vagus nerve, and from it, along the secretory nerves, nerve impulses are sent to the stomach glands.

Among chemical substances that can have a direct effect on the secretion of the glands of the gastric mucosa include extractives, alcohols, food breakdown products (albumoses and peptones). A strong effect on gastric secretion has histamine , which is contained in food substances and gastric mucosa, as well as acetylcholine released when food substances come into contact with the mucous membrane of the pylorus canal. In the mucous membrane of the pylorus of the stomach, a hormone is formed gastrin , which, being absorbed into the blood, also stimulates the secretion of gastric juice.

Intestinal phase of gastric secretion begins from the moment food enters the intestines. Food gruel irritates mechano-, osmo-, chemoreceptors of the intestinal mucosa and reflexively changes the intensity of gastric secretion. The secretion of the glands of the stomach is inhibited by the products of the breakdown of fat, hormones: gastrogastron and enterogastorone, produced by the mucous membrane of the stomach and upper part of the small intestine.

Motor function of the stomach.

Three kinds motor phenomena in the stomach: peristaltic, systolic and tonic. The motor function of the stomach is provided by the work of smooth muscles. This function assists in mixing, crushing and propelling stomach contents into the duodenum.

Peristaltic movements carried out by contraction of the circular muscles of the stomach. The wave of contraction begins in the cardiac region and spreads to the pyloric sphincter. Peristaltic waves occur in a person with a frequency 3 times in 1 min.

Systolic contractions associated with muscle contraction of the antrum of the pyloric stomach. These movements provide the transition of a significant part of the contents of the stomach into the duodenum.

Tonic contractions - non-peristaltic stomach movements due to changes in muscle tone. They help move the contents of the stomach.

With an empty stomach, there are periodic contractions ( hungry motor skills), which are replaced by a state (period) of rest. This type of contraction of the stomach muscles is associated with hunger. In humans, the duration of periods of work of the stomach is 20-50 minutes, periods of rest last 45-90 minutes or more. The periodic contractions of the stomach stop with the start of eating and digestion. In addition to these types of contractions in the stomach, there are antiperistalsis, which is observed with the act of vomiting.

Regulation of the motor function of the stomach. It is carried out due to neurohumoral mechanisms. The vagus nerves excite the motor activity of the stomach, the sympathetic nerves, in most cases, inhibit. The motility of the stomach is influenced by humoral factors. Insulin, gastrin, histamine, potassium ions excite the contraction of the smooth muscles of the stomach, inhibit - enterogastron, cholecystokinin-pancreosimin, adrenaline, norepinephrine.

Digestion in the small intestine.

Intestinal juice.

Has a very economical local secretion mechanism. It is separated only at the site of food irritation in the intestinal mucosa. Neither the sight, nor the smell of food, nor the irritation of the food in the oral cavity affects the separation of intestinal juice. 2.5 liters of intestinal juice are separated per day. Intestinal juice is an opaque, colorless liquid with a fishy odor and an alkaline reaction.

There are 22 enzymes in intestinal juice, 6 main ones:

1. Sucharase - breaks down sucrose into glucose and fructose

2. Alkaline phosphatase - plays a major role in the exchange of phosphorus, cleaves phosphates from various compounds

3. Amylase - breaks down carbohydrates to maltose

4. Lipase - breaks down animal fats to glycerol and fatty acids

5. Peptidase - breaks down polypeptides (scraps of protein molecules) to amino acids

6. Enterokinase - activates the trypsinogen of pancreatic juice

Cavity and parietal (membrane) digestion.

In intestinal juice, a liquid and a dense part are distinguished. The dense part is mucous lumps, consisting of desquamated cells of the intestinal epithelium. These cells are destroyed and enzymes that carry out cavity digestion are released from them.

Some of the intestinal enzymes are firmly fixed on the alkaline border of the epithelium. Here, on the border of the extracellular and intracellular environment, the final hydrolysis of nutrients takes place. This parietal digestion was discovered by Ugolev in 1958.

Small intestine movements.

There are two types of movement:

Pendulum - in a short section of the intestine, alternately longitudinal and annular muscles contract. Food moves forward and backward, mixes well and is saturated with intestinal juice.

Peristaltic (worm-like) - observed only if there is food in the intestine. Moves chyme towards the large intestine

In an adult, about 2-2.5 liters of gastric juice is formed and secreted during the day. Gastric juice is acidic (pH 1.5-1.8). It contains water - 99% and dry residue - 1%. The dry residue is represented by organic and inorganic substances. The main inorganic component of gastric juice is hydrochloric acid, which is free and bound to proteins. Hydrochloric acid has a number of functions:

• 1) promotes denaturation and swelling of proteins in the stomach, which facilitates their subsequent breakdown by pepsins;
• 2) activates pepsinogens and converts them into pepsins;
• 3) creates an acidic environment necessary for the action of enzymes in gastric juice;
• 4) provides antibacterial action of gastric juice;
• 5) promotes normal evacuation of food from the stomach;
• 6) stimulates pancreatic secretion.

In addition, the gastric juice contains the following inorganic substances: chlorides, bicarbonates, sulfates, phosphates, sodium, potassium, calcium, magnesium, etc. The composition of organic substances includes proteolytic enzymes, the main role among which is played by pepsins. Pepsins are excreted in an inactive form as pepsinogens. Under the influence of hydrochloric acid, they are activated. The optimum protease activity is at a pH of 1.5-2.0. They break down proteins to albumosis and peptones. Gastrixin hydrolyzes proteins at a pH of 3.2-3.5. Rennin (chymosin) causes milk curdling in the presence of calcium ions, as it converts the soluble protein caseinogen into an insoluble form - casein.

There are also non-proteolytic enzymes in gastric juice. Gastric lipase is not very active and only breaks down emulsified fats. Hydrolysis of carbohydrates continues in the stomach under the influence of salivary enzymes. This becomes possible because the food lump that has entered the stomach is gradually saturated with acidic gastric juice, and at this time, the action of saliva enzymes continues in the inner layers of the food lump in an alkaline environment. The composition of organic substances includes lysozyme, which provides the bactericidal properties of gastric juice. Gastric mucus, containing mucin, protects the gastric mucosa from mechanical and chemical irritation and from self-digestion. The stomach produces gastromucoprotein, or Castle's intrinsic factor. Only in the presence of an internal factor is the formation of a complex with vitamin B12, which is involved in erythropoiesis, possible. The gastric juice also contains amino acids, urea, uric acid. The glands of the stomach, outside the digestion process, secrete only mucus and pyloric juice. The separation of gastric juice begins at the sight, smell of food, and its entry into the oral cavity. The duration of the secretory process, the amount, digesting capacity of gastric juice, its acidity are in strict dependence on the nature of the food, which is provided by nervous and humoral influences. The proof of the existence of such a dependence is the classical experiments carried out in the laboratory of I.P. Pavlova on dogs with an isolated small ventricle. The animals received bread as a carbohydrate food, lean meat containing mostly protein, and milk containing proteins, fats and carbohydrates. The largest amount of gastric juice was produced when eating meat, medium - bread, small - milk (due to the contained fats). The duration of juice secretion was also different: for bread - for 10 hours, for meat - 8 hours, for milk - 6 hours. The digestive power of the juice decreased in the following order: meat, bread, milk; acidity - meat, milk, bread. It was also found that gastric juice with high acidity better breaks down proteins of animal origin, and with low acidity - plant proteins.

Secretory function of the stomach carried out by the gastric glands that produce gastric juice. They consist of three types of cells: the main ones involved in the production of enzymes; lining (parietal), involved in the production of hydrochloric (hydrochloric) acid, and additional, secreting mucoid secretion (mucus). It also includes an internal castle factor (gastromukoprotein), which is involved in the regulation of hematopoiesis. On an empty stomach, mucus is also secreted by the cylindrical epithelium, which covers the gastric mucosa. The glands of the cardiac stomach secrete mainly mucus. There are no parietal cells in the glands of the pyloric section. Therefore, hydrochloric acid is absent in the secretion of the glands of this department and its pH is 7.8-8.4. The main role in gastric digestion is played by the glands of the fundus, which includes three secretory zones: the bottom, lesser curvature and the body of the stomach (Fig. 11.11). These glands have all three types of cells and secrete most of the gastric juice.

Gastric juice composition... At rest ( fasting) from the human stomach, you can extract about 50 ml of gastric contents of a neutral or slightly acidic reaction (pH 6.0). It is a mixture of saliva and gastric juice.

The total amount of gastric juice, which is separated in a person during the usual diet, is 2.0-2.5 liters per day. It is a colorless, transparent, slightly opalescent liquid with a specific gravity of 1.002-1.007. There may be flakes of mucus in the juice.

Gastric juice has an acidic reaction (pH 0.8-1.5) due to the high content of hydrochloric (hydrochloric) acid in it (0.3-0.5%). The water content in the juice is 99.0-99.5%, and that of dense substances is 1.0-0.5%. Solid residue is represented by organic and inorganic substances: chlorides (5-6 g / l), sulfates (10 mg / l), phosphates (10-60 mg / l), bicarbonates (0-1.2 g / l) sodium, potassium , calcium and magnesium, ammonium (20-80 mg / l). A significant part of minerals is absorbed into the bloodstream in the stomach and intestines and is involved in maintaining the constancy of the internal environment.

The main inorganic component of gastric juice - hydrochloric acid. The organic portion of the solid residue consists of enzymes and mucoids (see below). A small amount of nitrogen-containing substances of a non-protein nature (urea, uric acid, lactic acid, etc.) are present in the residue, which must be removed from the body.

Gastric juice - a complex chemical designed for the digestion of food. It is produced by cells gastric mucosa and is an odorless, sour, transparent substance. Color changes to green and yellow indicate impurities in the content duodenum or bile, a brown or red tint may be the result of blood impurities, a putrid odor indicates problems with the transport of stomach contents to the intestines.

The rate of secretion of gastric juice, its neutralization with mucus, as well as the state of health of the organs of the digestive system determine the acidity of gastric juice. Normally, the secretion of gastric juice into the cavity is almost not secreted, this should only happen when food enters. Although it is even normal to release juice when smelling food, seeing it, and sometimes when talking and thinking about it. An unpleasant sight or smell of food can significantly or completely stop juice production.

The main components of gastric juice are:

• Hydrochloric acid , which is one of the most important substances that make up the gastric juice. Its functions are to maintain the necessary acid balance in the stomach, promotes the formation of a special substance that protects the body from the penetration of pathogens from the gastrointestinal tract - pepsin , prepares food for hydrolysis, activates, provides swelling of food proteins.

• Bicarbonates protect the duodenum and gastric mucosa by neutralizing hydrochloric acid in these areas. Superficial accessory cells produce this substance, its concentration is 45 mmol / L in gastric juice.

• Slime - one of the main protectors of the gastric mucosa. It creates a layer of gel about half a millimeter thick that concentrates bicarbonates, thereby protecting the required areas from the damaging effects of pepsin and hydrochloric acid. The mucus is also produced by extra superficial cells. Only a small content of mucus in the gastric juice is normal, its high concentration indicates inflammatory processes on the gastric mucosa.

• Pepsin is the main enzymeresponsible for the breakdown of proteins. Its different isoforms interact with different proteins. They are formed from pepsinogens produced by endocrine system of the body .

Other components of gastric juice include water, ammonia, phosphates, sulfates, chlorides, bicarbonates of calcium, potassium, magnesium, sodium and other substances.

The human stomach normally produces about 2 liters of this substance per day. Not stimulated by food, at rest in men, the secretion is:

• Gastric juice - about 90 ml / hour
• Hydrochloric acid - 3-4 mmol / hour
• Pepsin - about 22-30 mg / hour

The secretion of these substances in a woman's body is 20-30% less.

Analysis

Analysis of gastric juice is an important diagnostic method, which is carried out using special probes. The analysis is carried out on an empty stomach or using special stimulants. A probe is used to extract gastric juice or stomach contents.

Natural gastric juice or its artificial substitutes can be used to treat certain stomach diseases, which are accompanied by insufficient secretion.