Gastric juice: composition, enzymes, acidity. Gastric juice: what it consists of and why it is needed What acid is contained in human gastric juice

The stomach is the most important part of the gastrointestinal tract. One of its main functions is selection. Of course, without this, the process of normal food processing is impossible. Consider the composition, properties and significance of gastric juice for the normal functioning of the body, the conditions associated with the disorder of its production.

Where is juice produced?

Where is gastric juice formed? The place where this fluid is produced is the stomach. It performs the functions of a digestive organ and a food depot.

Its role and importance in the body are enormous. Its functions are:

1. Depository (can place about two liters of liquid or food).
2. Excretory - from 1.5 to 2.5 liters of such a product is excreted per day (sometimes the amount of gastric juice can vary greatly).
3. Motor (under the influence of peristalsis, food is mixed).
4. Absorption (usually alcohol, liquid, salts are absorbed from the stomach).
5. Extretory (some decay products are released with it - such as creatinine, urea and others).
6. The formation of some active substances (for example, a large number of enzymes are produced here, under the influence of which digestion in the stomach is possible).
7. Protective. The role of this function is that the acidic reaction of gastric juice allows bacteria to be destroyed. The body returns poor-quality food by vomiting (this prevents further disorders of food digestion).

What is the gastric compartment

Gastric juice is a substance with a sour taste. The average weight of gastric juice is from 1.002 to 1.007 g/cm3. The color is missing. The acid index is from 0.9 to 1.5. The acidic reaction is given by the content of hydrochloric acid in gastric juice. Other characteristics are:

• water - approximately 99.5% (for this reason, its color is normally absent);
• the presence of dry components of gastric juice - 0.5%;
• mineral components of gastric juice - salts of sulfuric, hydrochloric acids, sodium, calcium and other elements;
• the presence of enzymes that play an important role in digestion, creatinine and other components is detected.

The composition of gastric juice includes such highly active substances, how:

1. Pepsin-A provides hydrolyzing activity of gastric secretion to proteins.
2. Pepsin-C metabolizes hemoglobin.
3. Gelatinase dissolves gelatin, collagen.
4. Chymosin promotes the breakdown of casein.
5. Lipase is produced to digest milk fats.
6. Lysozyme provides bactericidal action. A small amount of this enzyme is formed in the oral cavity.
7. Urease breaks down urea.
8. The Castle factor plays an important role in digestion: it absorbs cyanocobalamin.

Distinguish between total, free and protein-bound hydrochloric acid. Their exact content is shown by the biochemistry of gastric contents.

Sometimes it is possible to change the color of the liquid. If it is yellowish, it means that there are impurities of bile in the stomach. A red or brownish tint indicates that blood has entered the stomach. A putrid smell indicates that intensive processes of decay or fermentation are taking place in this organ.

Important! If, according to the results of the diagnosis, the color of the secret of the stomach changes in the patient, he needs to additionally undergo a diagnostic examination. This condition may indicate the development of dangerous pathologies.

How is the production of gastric juice regulated?

Regulation provides the desired chemical composition of gastric juice, its quantity and daily acidity. There are such periods in digestion:

• interdigestive - when there is no food in the stomach (neutral mucus is secreted);
• digestive (begins after a meal, when the gastric juice is inherent in an acidic reaction).

From the amount of food, its composition depends on what the composition of gastric juice will be at one time or another. All people have one or another characteristic of a secret. There are two phases of regulation of this discharge.

The complex reflex phase includes the following components:

• conditioned reflex (secretion processes are stimulated by visual, olfactory, auditory and other factors);
• unconditioned reflex (the processes of production of acid and enzymes begin from the impact on the receptors of the upper digestive tract).

The reflex arc starts from the receptors, from where the excitation goes to the medulla oblongata. Activity medulla oblongata leads to stimulation of the secretion of gastric juice. Because of this, the so-called appetizing juice will begin to stand out.

Neurohumoral regulation includes nervous and humoral processes. The sympathetic division inhibits digestive activity, while the parasympathetic, on the contrary, activates it. The role of hormones in the formation of this fluid is as follows:

• insulin leads to the excitation of secretion;
• the effect of ACTH is stimulating;
• hormones produced in the gastrointestinal tract additionally regulate the amount of stomach contents.

Why is there mucus in stomach juice?

The composition of the intestinal and gastric juices includes mucus. Its value lies in the fact that it helps to neutralize the aggressive action of the acid. This is the answer to the question why gastric juice does not damage the walls of the organ. Moreover, mucus also protects against the damaging effects of pepsin (and in fact, in its absence, a person develops symptoms of dyspepsia).

The mucus helps coat the food bolus, which improves digestive function. Daily mucus production may vary. The component properties are as follows:

• regulation of the excretory function of glands that produce hydrochloric acid;
• enveloping of the mucosa;
• wrapping food;
• influence on the level of secretion of gastric juice.

Note! An increase in the amount of mucus in the stomach is a symptom of dangerous pathologies. Their treatment involves certain medicines and diet modification. You do not need to self-medicate, as this can harm the body.

How acid is neutralized

It is known that gastric juice consists of bicarbonates. Why is this component included? Gastric juice begins to stand out as soon as the corresponding reflex becomes active in a person. But it doesn't always depend on the ingestion of food. In this case, the acid will begin to damage the organ. To avoid this, bicarbonate ions come to the rescue. The cells that produce it are called superficial.

The formula for such a reaction has been known to us since school. Under the influence of the ion, carbon dioxide and water are formed. What medium is formed in this case? The bicarbonate gives the juice its alkaline properties.

Such properties can prevent a burn of the throat or a burn of the larynx when acidic contents are thrown into the esophagus. This happens with many pathologies of the gastrointestinal tract.

What happens with high acidity

Violation of the secretory function of the stomach occurs quite often as a result of errors in nutrition, stress and other factors. Hypersecretion of gastric juice can be associated with both an increase in acidity and an increase in the amount of discharge itself. What foods cause it? Stimulating the production of gastric juice and its amount of foods and drinks:

• smoked meats;
• marinades;
• pickles;
• seasonings;
• alcohol;
• some fruits;
• fried foods.

The amount of secreted juice in a person increases with:

• stress;
• smoking;
• strong negative or positive emotions.

Symptoms of increased secretion of gastric juice are:

• heartburn;
• pain in the hypochondrium;
• nausea, sometimes vomiting;
• symptoms of dyspepsia (rumbling and transfusion in the abdomen, increased gas formation, diarrhea or constipation).

Secretion can also increase with long-term pathologies of the gastrointestinal tract - such as hyperacid gastritis, ulcers, etc. Timely therapy with antacids, such as Almagel, as well as drugs - inhibitors, can normalize acidity. proton pump(Ranitidine).

What happens with low acidity

Hyposecretion of gastric juice is much less common. Do not assume that this condition is better (based on information obtained from television advertising). On the contrary, hypofunction of the stomach is much more dangerous.

Some people do not know how much acid a person should produce, and believe that the less it is, the better, because then "there will be no heartburn." The mechanism of the stomach is such that for its normal function, its secretion must have an acidic reaction. If little acid is produced, gastric activity drops, and many disease-causing organisms can enter the body.

What does a person feel with low acidity? No need to think that this changes the color of the gastric discharge. It has reduced enzymatic properties, which contributes to the appearance of such symptoms:

• a sharp drop in appetite;
• belching with an unpleasant smell of a spoiled egg;
• bad breath coming from the mouth and not disappearing after brushing your teeth;
• constipation;
• signs of intestinal upset;
• nausea, worse after eating;
• the presence of helminths in the stomach or intestines (they are not neutralized by acid);
• flatulence.

The danger of such a state is as follows:

• due to a decrease in the intensity of digestion processes, a large amount of
• the amount of decay products;
• decreased absorption of absorption leads to anemia, hair loss, etc.;
• the development of autoimmune pathologies and even cancer;
• appearance allergic reactions even for once familiar products;
• due to a decrease in the action of gastric juice on proteins, the patient may develop protein starvation;
• lowering blood pressure.

To treat such a condition, it is necessary to choose a therapy that gives the juice a normal acidity. Sometimes the patient needs to consume hydrochloric acid preparations.

Can stomach acid burn the esophagus

A burn of the esophagus with gastric juice occurs due to its high acidity. Gastric juice, consisting of hydrochloric acid, irritates the mucosa of the esophagus. The severity of the disease is given by a complex of adverse factors - an unbalanced diet, alcohol consumption, etc. As a result of the reflux of acidic contents, ulcers form on the mucosa of the esophagus.

Complications of a burn are quite serious:

• the appearance of erosion on the mucosa;
• perforation of the esophagus;
• hemorrhages;
• blockage of blood vessels.

This condition requires immediate treatment. Taking medications uncontrolled by a doctor complicates the course of the pathology. In some cases, the patient will require medical intervention.

How is acidity measured?

The study of such a parameter is an important component of diagnostic measures. I must say that such laboratory work should be carried out by all clinics and diagnostic centers.

The most common way to find out what the contents in the stomach consists of is pH-metry. Today, the so-called fractional probing with pumping out the contents with a special probe is not used (there is no need to remind that such manipulation is associated with unpleasant symptoms and is now an anachronism). There are modern techniques that allow you to accurately determine the composition of the acid.

If it is not enough, then the biochemical system in the stomach is disturbed. In this case, the patient is referred to other studies to eliminate the risk of cancer. With an ulcer, there may be increased acidity. This is dangerous, because this causes erosion on the mucous membrane.

The composition of the gastric secretion can also vary as a result of lung diseases, hormonal imbalance, diabetes, pathologies of the hematopoietic system. That is why all patients with impaired acid-forming function are additionally referred to such diagnostic examinations, how:

• general and biochemical analyzes blood;
• sugar analysis;
• urine test;
• FEGDS;
• radiography.

Consultation of a neuropathologist, psychiatrist, endocrinologist is indicated.

So, stomach juice has essential in the body. If its acidity changes, it can cause serious illnesses. Timely treatment helps prevent life-threatening complications.

The stomach is a complex bag-shaped organ. The main function is to digest food. Its activity occurs due to the developed muscle tissue and digestive juice, which is produced by the glands of the mucous membrane.

In the article, we will analyze what human gastric juice consists of, its properties and composition.

The main components of gastric juice

The composition of human gastric juice includes numerous components: enzymes, hydrochloric acid, mucus, substances of a protein structure. Each component has its own purpose. The coordinated work of the components of the juice ensures the processing of complex compounds that represent food into simple ones.

A significant role in the process of digestion is given to 5 main substances:

1. Hydrochloric acid is an important component of digestive juice. It is responsible for maintaining normal acidity inside the stomach, promotes the conversion of pepsinogen to pepsin. HCl provides reliable protection against viruses and bacteria. Most pathogenic microorganisms cannot withstand the acidic environment and die.
2. Bicarbonates are involved in the HCl neutralization reaction. Aggressive hydrochloric acid can have a damaging effect on the surface of the gastric mucosa and 12 duodenal ulcer. Bicarbonates protect the mucosa.
3. Pepsinogen is the precursor of pepsin. Under the action of the latter, proteins are broken down. Produced by the chief cells of the mucosa.
4. Mucus provides reliable protection to the inner lining of the stomach from the aggressive components of the juice (pepsin and hydrochloric acid). It is in two states: in the composition of gastric juice and forms a thick layer of gel on the walls of the stomach with a concentration of bicarbonates. They neutralize HCl. Thus, the inner surface of the stomach has mechanical (impermeable to pepsin) and chemical protection (acid neutralization). Mucin is constantly consumed and continuously formed due to the active work of additional cells and glands.
5. Intrinsic Castle Factor is an enzyme that activates vitamin B₁₂. The secret is formed and concentrated in the parietal cells of the fundic glands.

Violation of the secretion of any component of the digestive juice can result in the development chronic diseases Gastrointestinal tract, but first of all the stomach itself will suffer.

The role of gastric juice in digestion

In the process of digestion, the main instance after the oral cavity for food becomes the stomach. The muscular organ, together with enzymes, performs important functions.

The role of gastric juice in digestion will be briefly and clearly described in points:

1. Due to pepsins, large protein molecules are broken and polypeptide chains are formed, consisting of protein compounds. This is the initial stage in the digestion of proteins. At this stage, absorption does not occur, but the protein molecules swell, lose strength, which will later allow them to finally turn into amino acids under the action of the glands of the small intestine, the pancreas.
2. Gastric juice is characterized by a slight lipolytic effect. This means that under its action, the emulsified fats of mother's milk in newborns are broken down. For an adult, this function is not of great importance.
3. Digestive juice has antimicrobial properties. It prevents the further "journey" of bacteria that have entered the stomach with food through the digestive tract.

Where is gastric juice produced

Science has long known how and what gastric juice produces. It is formed as a result of the activity of the entire pool of secretory cells of the mucous membrane of the organ. In an adult, about 2 liters of fluid are produced in 1 day. There are several types of cells that synthesize gastric juice. They differ in localization:

1. Acid-producing cells are located throughout the body and fundus of the stomach. They occupy about 80% of the area of ​​the hollow organ. Accumulations of cellular elements form depressions on the surface of the mucous membrane. They are called gastric pits, which are formed by chief, parietal and mucoid cells. The former secrete pepsinogen. Parietal cells are involved in the production of HCl. Additional or mucoid are responsible for the synthesis of bicarbonates, mucus.
2. A small part of the cellular elements falls on the antrum of the stomach. They specialize in the production of mucus to protect the inner shell from aggressive factors.

Each cell of the stomach performs a specific role. Violation of its anatomy and physiology ends with diseases of the gastrointestinal tract.

Physico-chemical properties of gastric juice

A few facts about gastric juice:

1. Normally, there is a sour smell of gastric contents. It may vary depending on the amount of HCl. With a low level of hydrochloric acid, the presence of fermentation products smells like evaporation of organic acids. For example, milk or vinegar. If the smell of rot emanates from the gastric contents, then the person suffers from oncology.
2. The digestive juice of the stomach is almost colorless. A yellowish tint appears in the presence of low acidity, achylia. Green color indicates a high level of hydrochloric acid,. Red and brown staining indicates the presence of blood.
3. A moderate amount of mucus is normal. Its volume changes with gastritis with low acidity (hypertrophic, atrophic).
4. The volume of the stomach on an empty stomach ranges from 0 to 50 ml.

These characteristics play an important role in the diagnosis of pathology of the gastrointestinal tract. By changing the physico-chemical composition of gastric contents, one can judge the pathology digestive system.

The chemical composition of gastric juice

An inquisitive patient or an 8th grade student is interested in knowing which chemical substances are part of the gastric juice. After all, they trigger the main mechanisms of digestion.

The liquid consists of two main components: water and dry. The dry residue is represented by organic and inorganic compounds.

Inorganic components include:

1. water;
2. chlorides;
3. sulfates;
4. phosphates;
5. bicarbonates;
6. ammonia.

Without the listed components of gastric juice, digestion is impossible.

Table 1. Inorganic composition of gastric juice and the role of components in the process of digestion

What is the biochemical composition of gastric juice and its action

The composition and significance of gastric juice depends on the secretion and activity of biochemical substances. Pepsins play an important role. They are necessary for splitting complex protein structures into simple ones.

Each protein has a universal set of amino acids (AA). The combination of hundreds and thousands of AAs leads to the formation of a huge protein molecule. In order for cells to digest the bulky complex, it must be broken down. Such a task can be performed by special enzymes that are active at a temperature of 37–38 ° C.

There are three types of pepsins:

1. Pepsin A;
2. Pepsin B;
3. Pepsin C.

Them harmonious work promotes the formation of simple substances that are easily digested by the gastrointestinal tract.

The composition of gastric juice includes other enzymes - gastricsin and gastric lipase. Due to the ingestion of the food bolus, the environment in the stomach is alkalized. Important feature gastrixin - digestion of proteins in a less acidic environment, while pepsin becomes less active.

Table 2. Biochemical composition of gastric juice

What enzymes are present in gastric juice

The composition of gastric juice includes enzymes of proteolytic and non-proteolytic nature. The first group of substances specializes in the hydrolysis of proteins. They break bonds between protein structures to form simple peptides. Under the action of non-proteolytic enzymes, fats are broken down.

A number of substances have proteolytic properties: rennin, pepsin, gastrixin, ATP, lactic acid, mucus, gastromucoprotein. The first three enzymes are characterized by a similar primary structure. They come from pepsinogen.

Lipase is a non-proteolytic component. Essential for the breakdown of emulsified milk fats. It is of particular importance for infants.

Table 3. Enzymes that make up gastric juice

Hydrochloric acid is part of the gastric juice. It is formed by the parietal cells of the organ.

According to the anatomy, the gastric mucosa is divided into two regions. One is responsible for the production of HCl, the other for the synthesis of bicarbonates. The latter are necessary to neutralize hydrochloric acid. They prevent its negative impact on the sensitive gastric mucosa.

Interesting to know! In males, the percentage of parietal cells is greater than in women. And the production of hydrochloric acid is higher.

In percentage terms, HCl prevails over other acids several times. A high level of lactic acid may indicate insufficient formation of hydrochloric acid.

The concentration, which is part of the gastric juice, HCl is 160 mmol / l. A highly concentrated solution could completely burn out the mucosa of the organ. Protective substances do not allow the occurrence of an irreversible situation.

HCl is produced in three steps:

1. The smell and taste of food causes the transmission of nerve impulses to the cells of the stomach.
2. When food stretches the walls of the stomach, the hormone gastrin is released. Under its influence, HCl is released by parietal cells.
3. When digested food enters the duodenum, the hormone somatostatin is produced. It blocks the release of hydrochloric acid from the cells.

What is the role of hydrochloric acid in gastric juice

The acid that is part of the gastric juice has the following functions:

1. It promotes the breakdown of protein molecules and swelling.
2. The acid activates pepsinogen, turning it into pepsin.
3. The created acidic environment contributes to the destruction of pathogenic microorganisms and better breakdown of proteins.
4. Under the action of HCl, the activity of the gastrointestinal tract is regulated. Strengthening or inhibition of nervous and humoral influences on the functioning of the gastrointestinal tract depends on the pH level.

The normal level of the main component of gastric juice ensures the proper functioning of the digestive system.

What component of gastric juice has a bactericidal effect

The composition of the gastric juice of a healthy adult is unique, because it provides not only the digestion of food, but also protects against pathogens.

Bactericidal action has 2 substances of gastric juice:

• hydrochloric acid;
• lysozyme.

Lysozyme is a protein with bactericidal properties. It is found in saliva, tears, gastric juice of all known vertebrate organisms. The protein acts on the microbial cell from the outside.

Destruction mechanism pathogenic bacteria consists in violation of the integrity of the peptidoglycan layer of the outer wall of the microorganism. Without the outer shell, the foreign agent dies.

Lysozyme is widely used in medicine for bacterial and viral diseases. The natural component of gastric juice kills harmful microorganisms. Recovery comes faster.

The mucous surface of the stomach has many folds, elongated longitudinally, and elevations (gastric fields), on which there are a large number of pits. In these recesses, gastric juice is secreted. It is produced by the glands of the mucous surface of the organ, looks like a colorless transparent liquid and has a sour taste.

Cells of the glands of the stomach are divided into three groups: main, additional and parietal. Each of them produces different components that are included in the gastric juice. The composition of the main cells is enzymes that help to decompose food substances into simpler, more easily digestible ones. Pepsin, for example, breaks down proteins, and lipase breaks down fats.

Parietal cells are produced without which the necessary acidic environment cannot form in the stomach cavity. Its concentration does not exceed 0.5%. A huge role in digestion also belongs to hydrochloric acid. It is she who helps to soften many substances of the lump of food, makes the enzymes of gastric juice active, and destroys microorganisms. Hydrochloric acid is involved in the formation of digestive hormones. It also stimulates the production of enzymes. Such a concept as "acidity" determines the amount of juice. She is not always the same. Acidity depends on how quickly the juice is released and whether it is neutralized by mucus, which has an alkaline reaction, its level changes with diseases of the digestive system.

Viscosity, which has gastric juice, gives it the mucus produced by additional cells. It makes the hydrochloric acid neutral, thereby reducing the juice. Also, this mucus contributes to the complete digestion of nutrients, protects the mucous membrane from irritation and damage.

In addition to the components listed above, gastric juice contains many inorganic and organic substances, including the Castle factor - a special substance, without which absorption into the body is impossible. small intestine vitamin B 12, necessary for the full maturation of red blood cells in the bone marrow.

Gastric juice, secreted at different times of secretion, has an unequal digestion power. This was established by IP Pavlov. He stated that secretion does not continue continuously: when the process of digestion does not occur, no juice is secreted into the stomach cavity. It is produced only in connection with the reception of food. The secretion of gastric juice can provoke not only food that has entered the stomach or tongue. Even the smell of her, talking about her is the reason for his formation.

Gastric juice can have a different composition and quantity in diseases of the liver, blood, stomach, gallbladder, intestines, etc. Its study is the most important diagnostic method used in modern medicine. It is carried out using gastric tube, which is injected directly into the stomach, sometimes on an empty stomach, sometimes after taking a preparatory breakfast consisting of special irritants. The extracted content is then analyzed. Modern probes have sensors that respond to temperature, pressure and acidity in the organ.

The quality and quantity of it can also change under the influence of experiences, on a nervous basis. Therefore, sometimes it is necessary to conduct repeated analyzes of gastric juice in order to clarify the diagnosis.

It is known that in medical practice it is used as medicinal product with diseases of the stomach, which are accompanied by insufficient secretion of juice or a small amount of hydrochloric acid in it. Use it only as directed by a doctor. The gastric juice prescribed for this purpose can be both natural and artificial.

Gastric juice is a solution containing several digestive enzymes, hydrochloric acid solution and mucus. It is produced by the inner walls of the stomach, penetrated by many glands. The work of their constituent cells is aimed at maintaining a certain level of secretion, creating an acidic environment that facilitates the breakdown of nutrients. It is very important that all the "details" of this mechanism work smoothly.

What is gastric juice?

The secret of the glands located in the gastric mucosa is a clear, colorless, odorless liquid, with flakes of mucus. The value of its acidity characterizes the hydrogen index (pH). Measurements show that the pH in the presence of food is 1.6-2, i.e. the liquid in the stomach is highly acidic. The lack of nutrients leads to alkalization of the contents due to bicarbonates up to pH = 8 (maximum possible indicator). A number of diseases of the stomach is accompanied by an increase in acidity to values ​​of 1-0.9.

The digestive juice secreted by the glands is complex in composition. The most important components - hydrochloric acid, gastric juice enzymes and mucus - are produced by different cells of the inner lining of the organ. In addition to the compounds listed above, the liquid contains the hormone gastrin, other molecules of organic compounds, and minerals. The stomach of an adult produces an average of 2 liters of digestive juice.

What is the role of pepsin and lipase?

Enzymes of gastric juice act as surface-active catalysts for chemical reactions. With the participation of these compounds, complex reactions occur, as a result of which macromolecules of nutrients break down. Pepsin is an enzyme that hydrolyzes proteins into oligopeptides. Another proteolytic enzyme in gastric juice is gastrixin. Proved to exist different forms pepsin, which "adjust" to the structural features of different protein macromolecules.

Albumins and globulins are well digested by gastric juice, connective tissue proteins are less hydrolyzed. The composition of gastric juice is not too saturated with lipases. A small amount of an enzyme that breaks down milk fats is produced by the pyloric glands. Products of lipid hydrolysis, the two main constituents of their macromolecules are glycerol and fatty acids.

hydrochloric acid in the stomach

In the parietal cell elements of the fundic glands, gastric acid is produced - hydrochloric acid (HCl). The concentration of this substance is 160 millimoles per liter.

The role of HCl in digestion:

1. Liquefies the substances that form the food lump, prepares for hydrolysis.
2. Creates an acidic environment in which the enzymes of the gastric juice are more active.
3. Acts as an antiseptic, disinfects gastric juice.
4. Activates hormones and pancreatic enzymes.
5. Maintains the required pH.

Acidity of gastric juice

In solutions of hydrochloric acid, there are not molecules of a substance, but H + and Cl - ions. The acidic properties of any compound are due to the presence of hydrogen protons, while the alkaline properties are due to the presence of hydroxyl groups. Usually, the concentration of H + ions in gastric juice reaches about 0.4-0.5%.

Acidity is a very important characteristic of gastric juice. The rate of its release and properties are different, which was proved 125 years ago in the experiments of the Russian physiologist I.P. Pavlov. The secretion of juice by the stomach occurs in connection with food intake, at the sight of products, their smells, and the mention of dishes.

An unpleasant taste can slow down and completely stop the release of digestive fluid. The acidity of gastric juice rises or falls in certain diseases of the stomach, gallbladder and liver. This indicator is also influenced by human experiences, nervous shocks. A decrease and increase in the secretory activity of the stomach may be accompanied by pain in the upper abdomen.

The role of mucous substances

Mucus is produced by additional superficial cells of the walls of the stomach.
The role of this component of the digestive juice is to neutralize the acidic contents, protect the shell of the digestive organ from the damaging effects of pepsin and hydrogen ions from the composition of hydrochloric acid. The mucous substance makes the gastric juice more viscous, it better envelops the food lump. Other properties of slime:

• contains bicarbonates, giving an alkaline reaction;
• envelops the mucous wall of the stomach;
• has digestive properties;
• regulates acidity.

Neutralization of sour taste and caustic properties of gastric contents

The composition of gastric juice includes bicarbonate anions HCO 3 -. They are secreted as a result of the work of the surface cells of the digestive glands. Neutralization of acidic content occurs according to the equation: H + + HCO 3 - \u003d CO 2 + H 2 O.

Bicarbonates bind hydrogen ions at the surface of the gastric mucosa, as well as at the walls of the duodenum. The concentration of HCO 3 - in the gastric contents is maintained at 45 millimoles per liter.

"Internal factor"

A special role in the metabolism of vitamin B 12 belongs to one of the components of gastric juice - the Castle factor. This enzyme activates cobalamins in the composition of food, which is necessary for absorption by the walls small intestine. The blood is saturated with cyanocobalamin and other forms of vitamin B 12, transports biologically active substances to Bone marrow where red blood cells are formed.

Features of digestion in the stomach

The breakdown of nutrients begins even in the oral cavity, where, under the action of amylase and maltase, polysaccharide molecules, in particular starch, break down into dextrins. Then the food bolus passes through the esophagus and enters the stomach. The digestive juice secreted by its walls contributes to the digestion of about 35-40% of carbohydrates. The action of saliva enzymes, active in an alkaline environment, is terminated due to the acidic reaction of the contents. If this well-established mechanism is violated, conditions and diseases arise, many of which are accompanied by a feeling of heaviness and pain in the stomach, belching, and heartburn.

Digestion is the destruction of macromolecules of carbohydrates, proteins and lipids (hydrolysis). The change in nutrients in the stomach takes about 5 hours. The mechanical processing of food started in the oral cavity, its dilution by gastric juice continues. Proteins undergo denaturation, which facilitates further digestion.

Strengthening the secretory function of the stomach

Increased gastric juice can inactivate some enzymes, because any system, the process goes only under certain conditions. Hypersecretion is accompanied by both increased sap secretion and increased acidity. These phenomena are provoked by spicy seasonings, certain foods, and alcoholic beverages. Prolonged nervous strain, strong emotions also provoke irritable stomach syndrome. Secretion increases in many diseases of the digestive system, in particular in patients with gastritis and peptic ulcer.

Most common symptoms increased content of hydrochloric acid in the stomach - heartburn and vomiting. Normalization of the secretory function occurs when dieting, taking special drugs (Almagel, Ranitidine, Gistak and other drugs). Reduced production of digestive juice is less common, which may be associated with hypovitaminosis, infections, and lesions of the stomach walls.

Gastric juice is a digestive secret of a multicomponent composition, which is produced by various cells of the gastric mucosa.

The composition of gastric juice includes the following chemically active substances: hydrochloric acid, pepsin and pepsinogen, bicarbonates, internal factor Castle, mucus and other chemicals (sulfates and phosphates, chlorides, water and bicarbonates), trace elements (sodium and potassium, magnesium and calcium).

Hydrochloric acid is produced by parietal (parietal) cells of the fundic (main) glands of the stomach. Hydrochloric acid performs a number of basic functions of gastric digestion: it activates the conversion of pepsinogen to pepsin, maintains a certain level of acidity necessary for the implementation of enzymatic processes for the breakdown of nutrients, prepares food proteins for hydrolysis - it contributes to their swelling and cause denaturation, is an obstacle to the introduction of various microbes. In gastric juice, hydrochloric acid has a strictly constant concentration - 0.3-0.5% (160 mmol per liter) and can be contained both in a free state and in a protein-bound state. A decrease or increase in the acidity of gastric juice disrupts the digestion process and can lead to the development of various diseases and the appearance of unpleasant symptoms.

The study of the acidity of gastric juice is carried out by intragastric pH-metry.

The chemical composition of human gastric juice

Digestion of food proteins occurs mainly under the influence of the enzyme pepsin. Each class of proteins is affected by a specific isometric shape of pepsin. Pepsin is formed from pepsinogen at a certain acidity. The enzyme is produced by the chief cells of the main (fundic) glands. Other proteases that are part of the gastric juice and break down food proteins are gelatinase and chymosin. Pepsin and chymosin cause curdling of milk.

Bicarbonates are synthesized by superficial mucoid (additional) cells and serve to protect the surface of the gastric mucosa and duodenum from the aggressive effects of hydrochloric acid. The concentration of HCO3- bicarbonates in gastric juice is 45 mmol per liter.

Castle factor (intrinsic factor) is produced by the parietal cells of the fundic glands and causes the inactive form of vitamin B12 to be converted into an active form that can be absorbed in the gastrointestinal tract.

Mucus is produced by additional surface cells and is the most important factor in protecting the mucosal surface from the aggressive effects of pepsin and hydrochloric acid. Mucus forms a layer of 0.6 mm on the surface of the mucous membrane, which concentrates bicarbonates that neutralize hydrochloric acid.

Water is contained in gastric juice in the amount of 995 g/l.

Physiology of gastric digestive juice

The human stomach produces about 2 liters of gastric juice per day. In the interval between meals, basal secretion occurs, which includes the production of gastric juice in men in the amount of 80-100 ml per hour, hydrochloric acid 2.5-5 mmol per hour, pepsin 20-35 mg per hour. In women, basal secretion is reduced by 25-30%. Gastric juice is colorless and odorless. In case of reflux of intestinal (duodenal) contents into the stomach, it is stained with bile in a yellowish or greenish color. The brown tint of gastric juice acquires due to bleeding from ulcers or erosions, and an unpleasant putrefactive odor - with prolonged intestinal atony and stagnation of intestinal contents. A large number of mucus in the intestines speaks of inflammatory process in the mucous membrane.