Human digestive system. Digestion

In the digestive apparatus, complex physical and chemical transformations of food take place, which are carried out due to the motor, secretory and suction functions of it. In addition, the organs of the digestive system also perform an excretory function, removing the remnants of undigested food and some metabolic products from the body.

Physical processing of food consists in crushing it, stirring it and dissolving the substances it contains. Chemical changes in food occur under the influence of hydrolytic digestive enzymes produced by the secretory cells of the digestive glands. As a result of these processes, complex food substances are broken down into simpler ones, which are absorbed into the blood or lymph and participate in the exchange

substances in the body. In the process of processing food loses its specific specific properties, turning into simple constituent elements that can be used by the body.

For the purpose of uniform and more complete digestion of food

its mixing and movement along the gastrointestinal tract is required. This is provided by the motor function of the digestive tract by contracting the smooth muscles of the walls of the stomach and intestines. Their motor activity is characterized by peristalsis, rhythmic segmentation, pendulum movements, and tonic contraction.

The secretory function of the digestive tract is carried out by the corresponding cells that make up the salivary glands of the oral cavity, the glands of the stomach and intestines, as well as the pancreas and liver. Digestive secretions are electrolyte solutions containing enzymes and other substances. There are three groups of enzymes involved in digestion: 1) proteases that break down proteins;

2) lipases that break down fats; 3) carbohydrases, which break down carbohydrates. All digestive glands produce about 6-8 liters of secretion per day, a significant part of which is reabsorbed in the intestine.

The digestive system plays an important role in maintaining homeostasis due to its excretory function. The digestive glands are able to secrete a significant amount of nitrogenous compounds (urea, uric acid), water, salts, various medicinal and toxic substances into the cavity of the gastrointestinal tract. The composition and amount of digestive juices can be a regulator of the acid-base state and water-salt metabolism in the body. There is a close relationship between the excretory function of the digestive system and the functional state of the kidneys.

The study of the physiology of digestion is primarily the merit of I.P. Pavlov and his students. They developed a new method for studying gastric secretion - a part of the dog's stomach was cut out by surgery while maintaining autonomic innervation. A fistula was implanted into this small ventricle, making it possible to receive pure gastric juice (without food impurities) at any stage of digestion. This made it possible to characterize in detail the functions of the digestive system and reveal the complex mechanisms of their activity. In recognition of I.P. Pavlov's merits in the physiology of digestion, on October 7, 1904, he was awarded the Nobel Prize. Further studies of the processes of digestion in the laboratory of I.P. Pavlov revealed the mechanisms of activity of the salivary and pancreas, liver and intestinal glands. At the same time, it was found that the higher the glands are located in the course of the digestive tract, the more important are the nervous mechanisms in the regulation of their functions. The activity of the glands located in the lower parts of the digestive tract is regulated mainly by the humoral route.

DIGESTION IN VARIOUS DEPARTMENTS OF THE GASTROINAL TRACT

Digestion processes in different parts of the gastrointestinal tract have their own characteristics. These differences relate to the physical and chemical processing of food, motor, secretory, absorption and excretory functions of the digestive system.

DIGESTION IN THE ORAL CAVITY

The processing of the ingested food begins in the oral cavity. Here, it is ground, wetted with saliva, analysis of the taste properties of food, initial hydrolysis of some nutrients and the formation of a food lump. Food in the oral cavity is retained for 15-18 seconds. Being in the oral cavity, food irritates the taste, tactile and temperature receptors of the mucous membrane and papillae of the tongue. Irritation of these receptors causes reflex acts of secretion of the salivary, gastric and pancreas, the release of bile into the duodenum, changes the motor activity of the stomach, and also has an important effect on the implementation of chewing, swallowing and taste assessment of food.

After grinding and grinding with teeth, the food is chemically processed due to the action of hydrolytic enzymes from the young eater. The ducts of three groups of salivary glands open into the oral cavity: mucous, serous and mixed: Numerous glands of the mouth and tongue secrete mucous, mucin-rich saliva, the parotid glands secrete liquid, serous saliva rich in enzymes, and the submandibular and sublingual glands secrete mixed saliva. The protein substance of saliva, mucin, makes the food lump slippery, which makes it easier to swallow food and move it along the esophagus.

Saliva is the first digestive juice that contains hydrolytic enzymes that break down carbohydrates. The salivary enzyme amylase (ptyalin) converts starch into disaccharides, and the enzyme maltase converts disaccharides into monosaccharides. Therefore, when chewing food containing starch for a sufficiently long time, it acquires a sweet taste. Saliva also contains acidic and alkaline phosphatases, a small amount of proteolytic, lipolytic enzymes and nucleases. Saliva has pronounced bactericidal properties due to the presence of the enzyme lysozyme in it, which dissolves the bacterial membrane. The total amount of saliva secreted per day can be 1-1.5 liters.

The food lump formed in the oral cavity moves to the root of the tongue and then enters the pharynx.

Afferent impulses during stimulation of the receptors of the pharynx and the soft palate are transmitted along the fibers of the trigeminal, glossopharyngeal and superior laryngeal nerve to the center of swallowing, located in the medulla oblongata. From here, efferent impulses follow to the muscles of the larynx and pharynx, causing coordinated contractions.

As a result of the successive contraction of these muscles, the food lump enters the esophagus and then moves to the stomach. Liquid food passes the esophagus in 1-2 seconds; solid - in 8-10 s. With the completion of the act of swallowing, gastric digestion begins.

DIGESTION IN THE STOMACH

The digestive functions of the stomach consist in the deposition of food, its mechanical and chemical processing and the gradual evacuation of food contents through the pylorus into the duodenum. Chemical processing of food is carried out by gastric juice, of which a person forms 2.0-2.5 liters per day. Gastric juice is secreted by numerous glands of the body of the stomach, which consist of main, parietal and accessory cells. The main cells secrete digestive enzymes, the lining cells secrete hydrochloric acid and the additional cells secrete mucus.

The main enzymes in gastric juice are proteases and lipases. Proteases include several pepsins, as well as gelatinase and chymosin. Pepsins are secreted as inactive pepsinogens. The transformation of pepsinogens and active pepsin is carried out under the influence of hydrochloric acid. Pepsins break down proteins into polypeptides. Their further breakdown into amino acids occurs in the intestine. Chymosin curdles milk. Gastric lipase only breaks down emulsified fats (milk) into glycerol and fatty acids.

Gastric juice has an acidic reaction (pH during the digestion of food is 1.5-2.5), which is due to the content of 0.4-0.5% hydrochloric acid in it. In healthy people, 40-60 ml of decinormal alkali solution is required to neutralize 100 ml of gastric juice. This indicator is called the total acidity of gastric juice. Taking into account the volume of secretion and concentration of hydrogen ions, the flow rate-hour of free hydrochloric acid is also determined.

Gastric mucus (mucin) is a complex complex of glucoproteins and other proteins in the form of colloidal solutions. Mucin covers the gastric mucosa over the entire surface and protects it from both mechanical damage and self-digestion, since it has a pronounced anti-peptic activity and is able to neutralize hydrochloric acid.

The whole process of gastric secretion is usually divided into three phases: complex reflex (cerebral), neurochemical (gastric) and intestinal (duodenal).

The secretory activity of the stomach depends on the composition and quantity of the incoming food. Meat is a strong irritant to the stomach glands, which are stimulated for many hours. With carbohydrate food, the maximum separation of gastric juice occurs in the complex reflex phase, then the secretion decreases. Fat, concentrated solutions of salts, acids and alkalis have an inhibitory effect on gastric secretion.

Digestion of food in the stomach usually occurs within 6-8 hours. The duration of this process depends on the composition of the food, its volume and consistency, as well as on the amount of secreted gastric juice. Fatty foods linger in the stomach especially for a long time (8-10 hours or more). Fluids pass into the intestines as soon as they enter the stomach.

With the normal functioning of the body, its growth and development, large expenditures of energy are required. This energy is spent on increasing the size of organs and muscles during growth, as well as in the process of human life for movement, maintaining a constant body temperature, etc. The arrival of this energy is provided by the regular intake of food, which contains complex organic substances (proteins, fats, carbohydrates), mineral salts, vitamins and water. All of these substances are also needed to maintain biochemical processes that take place in all organs and tissues. Organic compounds are also used as a building material for the growth of an organism and the reproduction of new cells instead of dying ones.

Essential nutrients in the same form and in the form as they are in food are not perceived by the body. Thus, we can conclude that they need to be subjected to a special treatment - digestion.

Digestion is the process of physical and chemical processing of food, converting it into simpler and more soluble compounds. Such simpler compounds can be absorbed, carried by the blood, and absorbed by the body.

Physical processing is food grinding, grinding, dissolving. Chemical changes consist in complex reactions that occur in various parts of the digestive system, where, under the action of enzymes that are in the secretions of the digestive glands, the breakdown of complex insoluble organic compounds found in food is carried out.

They are converted into soluble and easily absorbed substances by the body.

Enzymes are biological catalysts that are secreted by the body. They differ in a certain specificity. Each enzyme acts only on strictly defined chemical compounds: some break down proteins, others - fats, and still others - carbohydrates.

In the digestive system, as a result of chemical processing, proteins are converted into a set of amino acids, fats are broken down to glycerol and fatty acids, carbohydrates (polysaccharides) to monosaccharides.

In each specific section of the digestive system, specialized food processing operations are carried out. They, in turn, are associated with the presence of specific enzymes in each of the digestive sections.

Enzymes are produced in various digestive organs, among which the pancreas, liver and gallbladder should be distinguished separately.

Digestive system includes the oral cavity with three pairs of large salivary glands (parotid, sublingual and submandibular salivary glands), pharynx, esophagus, stomach, small intestine, which includes the duodenum (the ducts of the liver and pancreas, jejunum and ileum open into it ), and the large intestine, which includes the cecum, colon and rectum. In the colon, the ascending, descending and sigmoid colon can be distinguished.

In addition, the digestive process is affected by such internal organs as the liver, pancreas, gallbladder.

I. Kozlova

"The human digestive system"- article from the section

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9.1. General characteristics of the digestive processes

The human body in the process of life consumes various substances and a significant amount of energy. From the external environment, nutrients, mineral salts, water and a number of vitamins must be supplied, which are necessary to maintain homeostasis, restore the plastic and energy needs of the body. At the same time, a person is not able to assimilate carbohydrates, proteins, fats and some other substances from food without preliminary processing it, which is carried out by the digestive organs.

Digestion is the process of physical and chemical processing of food, as a result of which it becomes possible for the absorption of nutrients from the digestive tract, their entry into the blood or lymph and assimilation by the body. Complex physical and chemical transformations of food take place in the digestive apparatus, which are carried out due to motor, secretory and suction its functions. In addition, the organs of the digestive system perform and excretory function, removing from the body the remnants of undigested food and some metabolic products.

Physical processing of food consists in crushing it, mixing and dissolving the substances it contains. Chemical changes in food occur under the influence of hydrolytic digestive enzymes produced by the secretory cells of the digestive glands. As a result of these processes, complex food substances are split into simpler ones, which are absorbed into the blood or lymph and participate in the body's metabolism. In the process of processing food loses its specific specific properties, turning into simple constituent elements that can be used by the body. Due to the hydrolytic action of enzymes, amino acids and low molecular weight polypeptides are formed from food proteins, glycerol and fatty acids from fats, and monosaccharides from carbohydrates. These digestive products enter the blood and lymph vessels through the mucous membrane of the stomach, small and large intestines. Thanks to this process, the body receives the nutrients necessary for life. Water, mineral salts and some

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the amount of low molecular weight organic compounds can be absorbed into the blood without pretreatment.

In order to evenly and more complete digestion of food, it is required to mix and move it along the gastrointestinal tract. This is ensured motor the function of the digestive tract by contraction of the smooth muscles of the walls of the stomach and intestines. Their motor activity is characterized by peristalsis, rhythmic segmentation, pendulum-like movements and tonic contraction.

Food bolt transfer carried out at the expense peristals, which occurs due to the contraction of the circular muscle fibers and relaxation of the longitudinal. The peristaltic wave allows the food bolus to move only in the distal direction.

Mixing food masses with digestive juices is provided rhythmic segmentation and pendulum movements intestinal wall.

The secretory function of the digestive tract is carried out by the corresponding cells that are part of the salivary glands of the oral cavity; proteases that break down proteins; 2) lipase, splitting fats; 3) carbohydrase, breaking down carbohydrates.

The digestive glands are innervated mainly by the parasympathetic division of the autonomic nervous system and, to a lesser extent, by the sympathetic. In addition, these glands are affected by gastrointestinal hormones. (gastrsh; secrets and choleocystoctt-pancreozymin).

Liquid through the walls of the human gastrointestinal tract moves in two directions. From the cavity of the digestive apparatus, the digested substances are absorbed into the blood and lymph. At the same time, the internal environment of the body releases a number of dissolved substances into the lumen of the digestive organs.

The digestive system plays an important role in maintaining homeostasis due to its excretory functions. The digestive glands are able to secrete into the cavity of the gastrointestinal tract a significant amount of nitrogenous compounds (urea, uric acid), salts, various medicinal and toxic substances. The composition and amount of digestive juices can be a regulator of the acid-base state and water-salt metabolism in the body. There is a close relationship between distinguishing

tial function of the digestive system with the functional state of the kidneys.

9.2. Digestion in various parts of the gastrointestinal tract

Digestion processes in different parts of the gastrointestinal tract have their own characteristics. These are the features of physical and chemical processing of food, motor, secretory, absorption and excretory functions of different parts of the digestive tract.

Digestion in the oral cavity. Food processing begins in the mouth. Here, it is ground, wetted with saliva, initial hydrolysis of some nutrients and the formation of a food lump. Food in the oral cavity is retained for 15-18 seconds. Being in the oral cavity, it irritates the taste, tactile and temperature receptors of the mucous membrane and papillae of the tongue. The irritation of these receptors causes reflex acts of secretion of the salivary, gastric and pancreas, the release of bile into the duodenum, and changes the motor activity of the stomach.

After grinding and grinding with teeth, food is chemically processed due to the action of hydrolytic enzymes in saliva. The ducts of three groups of salivary glands open into the oral cavity: spizy, se-pink and mixed.

Saliva - the first digestive juice that contains hydrolytic enzymes that break down carbohydrates. Saliva enzyme amipase(ptya-lin) converts starch into disaccharides, and the enzyme malataza - disaccharides to monosaccharides. The total amount of saliva secreted per day is 1-1.5 liters.

The activity of the salivary glands is regulated by reflex. Irritation of the receptors of the oral mucosa causes salivation along the mechanism of unconditioned reflexes. In this case, the centripetal nerves are the branches of the trigeminal and glossopharyngeal nerves, along which excitations from the receptors of the oral cavity are transmitted to the centers of salivation located in the medulla oblongata. The effector functions are performed by the parasympathetic and sympathetic nerves. The first of them provide an abundant secretion of liquid saliva, when the second is irritated, thick saliva is released, containing a lot of mucin. Salivation by the mechanism of conditioned reflexes occurs even before food enters the mouth and occurs when

irritation of various receptors (visual, olfactory, auditory), accompanying food intake. In this case, information enters the cerebral cortex, and the impulses coming from there excite the centers of salivation of the medulla oblongata.

Digestion in the stomach. The digestive functions of the stomach consist in the deposition of food, its mechanical and chemical processing and the gradual evacuation of food contents through the pylorus into the duodenum. Chemical processing of food is carried out galldairy juice, which a person produces 2.0-2.5 liters per day. Gastric juice is secreted by the numerous glands of the body of the stomach, which consist of main, lining and additional cells. The main cells secrete digestive enzymes, the lining cells secrete hydrochloric acid, and the accessory cells secrete mucus.

The main enzymes of gastric juice are proteases and whether-groove. Proteases include several pepsins, and gelatinase and hi-mozin. Pepsins are secreted as inactive pepsinogens. The transformation of pepsinogens into active pepsin is carried out under the influence saline acid. Pepsins break down proteins into polypeptides. Their further decay to amino acids occurs in the intestine. Gelatinase promotes the digestion of connective tissue proteins. Chymosin curdles milk. Lipase of gastric juice splits only emulsified fats (milk) into glycerol and fatty acids.

Gastric juice has an acidic reaction (pH during the digestion of food is 1.5-2.5), which is due to the content of 0.4-0.5% hydrochloric acid in it. Gastric acid hydrochloric acid plays an important role in digestion. She calls denaturation and swelling of proteins ^ thereby promoting their subsequent breakdown by pepsins, activates pepsinogens, promotes with the envy milk involved in antibacterial action of gastric juice, activates the hormone gastrin ? formed in the mucous membrane of the pylorus and stimulating gastric secretion, and also, depending on the pH value, enhances or inhibits the activity of the entire digestive tract. Entering the duodenum, hydrochloric acid stimulates the formation of a hormone there secretina, regulating the activity of the stomach, pancreas and liver.

Gastric mucus (muzt) is a complex complex of glucoproteins and other proteins in the form of colloidal solutions. Mucin covers the gastric mucosa over the entire surface and protects it from both mechanical damage and self-digestion, as it possesses

pronounced antipeptic activity and is able to neutralize hydrochloric acid.

The whole process gastric secretion it is customary to divide into three phases: complex reflex (cerebral), neurochemical (gastric) and intestinal (duodenal).

Difficult reflex phase gastric secretion occurs when exposed to conditioned stimuli (type, smell of food) and unconditioned (mechanical and chemical irritation of food receptors of the mucous membrane of the mouth, pharynx and esophagus). The excitement arising in the receptors is transmitted to the food center of the medulla oblongata, from where the impulses along the centrifugal fibers of the vagus nerve go to the glands of the stomach. In response to the irritation of the aforementioned receptors, gastric secretion begins in 5-10 minutes, which lasts 2-3 hours (with imaginary feeding).

Neurochemical phase gastric secretion begins after the entry of food into the stomach and is caused by the action of mechanical and chemical stimuli on its wall. Mechanical stimuli act on the mechanoreceptors of the gastric mucosa and reflexively cause secretion. Natural chemical stimulants of juice secretion in the second phase are salts, extractives of meat and vegetables, protein digestion products, alcohol and, to a lesser extent, water.

A hormone plays a significant role in increasing gastric secretion gastritis, which forms in the wall of the gatekeeper. With the blood, gastrin enters the cells of the gastric glands, increasing their activity. In addition, it stimulates the activity of the pancreas and the secretion of bile.

Intestinal phase gastric secretion is associated with the transition of food from the stomach to the intestines. It develops when chyme irritates the receptors of the small intestine, as well as when nutrients enter the bloodstream and is characterized by a long latency period (1-3 hours) and a long duration of gastric acid secretion with a low content of hydrochloric acid. In this phase, the secretion of the gastric glands is also stimulated by the hormone enterogastrin, secreted by the mucous membrane of the duodenum.

Digestion of food in the stomach usually occurs within 6-8 hours. The duration of this process depends on the composition of the food, its volume and consistency, as well as on the amount of secreted gastric juice. Fatty food lingers in the stomach especially for a long time (8-10 hours).

The evacuation of food from the stomach into the intestines occurs unevenly, in separate portions. This is due to periodic contractions of the muscles of the entire stomach, and especially strong contractions of the sphincter during

goalkeeper. The muscles of the pylorus reflexively contract (the release of food masses stops) when hydrochloric acid acts on the receptors of the duodenal mucosa. After neutralizing the hydrochloric acid, the muscles of the pylorus relax and the sphincter opens.

Digestion in the duodenum. In providing intestinal digestion, the processes occurring in the duodenum are of great importance. Here food masses are exposed to intestinal juice, bile and pancreatic juice. The length of the duodenum is small, so food does not linger here, and the main processes of digestion take place in the lower parts of the intestine.

Intestinal juice is formed by the glands of the mucous membrane of the duodenum, it contains a large amount of mucus and an enzyme peptidezu, splitting proteins. It also contains an enzyme enterokinase, which activates pancreatic juice trypsinogen. The cells of the duodenum produce two hormones - secret and cholecystoctt-pancreozymin, enhancing the secretion of the pancreas.

The acidic contents of the stomach during the transition to the duodenum acquires an alkaline reaction under the influence of bile, intestinal and pancreatic juice. In humans, the pH of the duodenal contents ranges from 4.0 to 8.0. In the breakdown of nutrients, carried out in the duodenum, the role of pancreatic juice is especially great.

The importance of the pancreas in digestion. The bulk of the pancreatic tissue produces digestive juice, which is excreted through the duct into the duodenal cavity. A person secretes 1.5-2.0 liters of pancreatic juice per day, which is a clear liquid with an alkaline reaction (pH = 7.8-8.5). Pancreatic juice is rich in enzymes that break down proteins, fats and carbon-water. Amylase, lactase, nuclease and lipase are secreted by the pancreas in an active state and break down starch, milk sugar, nucleic acids and fats, respectively. Nucleases trypsin and chymotrip-syn are formed by the cells of the gland in an inactive state in the form tripstogene and chymotryshinogen. Trypsinogen in the duodenum under the action of its enzyme enteroctase turns into trypsin. In turn, trypsin converts chymotrypsinogen into active chymotrypsin. Under the influence of trypsin and chymotrypsin, proteins and high molecular weight polypeptides are cleaved to low molecular weight peptides and free amino acids.

The secretion of pancreatic juice begins 2-3 minutes after eating and lasts from 6 to 10 hours, depending on the composition and volume of food.

cabbage soup. It occurs when exposed to conditioned and unconditioned stimuli, as well as under the influence of humoral factors. In the latter case, duodenal hormones play an important role: secretin and cholecystokin-nin-pancreosimin, as well as gastrin, insulin, serotonin, etc.

The role of the liver in digestion. Liver cells continuously secrete bile, which is one of the most important digestive juices. A person produces about 500-1000 ml of bile per day. The process of formation of bile goes on continuously, and its entry into the duodenum is periodic, mainly in connection with food intake. On an empty stomach, bile does not enter the intestines, it goes to the gallbladder, where it concentrates and somewhat changes its composition.

The bile contains bile acids, bile pigments and other organic and inorganic substances. Bile acids are involved in the digestion of food. Bile pigment bilirubgsh is formed from hemoglobin in the process of destruction of red blood cells in the liver. The dark color of bile is due to the presence of this pigment in it. Bile increases the activity of enzymes in pancreatic and intestinal juices, especially lipase. It emulsifies fats and dissolves the products of their hydrolysis, thereby facilitating their absorption.

The formation and secretion of bile from the bladder into the duodenum occurs under the influence of nervous and humoral influences. Nerve influences on the bile excretory apparatus are carried out conditionally and unconditionally reflexively with the participation of numerous reflexogenic zones, and first of all - the receptors of the oral cavity, stomach and duodenum. Activation of the vagus nerve enhances the secretion of bile, the sympathetic nerve inhibits bile formation and stops the evacuation of bile from the bubble. As a humoral stimulator of bile secretion, the hormone cholecystokinin-pancreozymin, which causes contraction of the gallbladder, plays an important role. A similar, albeit weaker, effect is exerted by gastrin and secretin. Glucagon and calcyotonin inhibit the secretion of bile.

The liver, forming bile, performs not only secretory, but also ex-secretory(excretory) function. The main organic excretions of the liver are bile salts, bilirubin, cholesterol, fatty acids and lecithin, as well as calcium, sodium, chlorine, bicarbonates. Getting into the intestines with bile, these substances are excreted from the body.

Along with the formation of bile and participation in digestion, the liver also performs a number of other important functions. The role of the liver is great in exchange forcompanies. The products of digestion of food are carried by the blood to the liver, and here

further processing takes place. In particular, some proteins (fibrinogen, albumin) are synthesized; neutral fats and lipids (cholesterol); urea is synthesized from ammonia. Glycogen is deposited in the liver, fats and lipoids are deposited in small quantities. An exchange is carried out in it. vitamins, especially group A. One of the most important functions of the liver is barrier, consisting in the neutralization of toxic substances and foreign proteins coming from the intestines with blood.

Digestion in the small intestine. Food masses (chyme) from the duodenum move to the small intestine, where they continue to be digested by digestive juices released into the duodenum. At the same time, its own intestinal juice, produced by the Lieberkühn and Brunner glands of the mucous membrane of the small intestine. The intestinal juice contains enterokinase, as well as a full set of enzymes that break down proteins, fats and carbohydrates. These enzymes are involved only in parietal digestion, since they are not secreted into the intestinal cavity. Cavity digestion in the small intestine is carried out by enzymes coming from food chi-mus. Cavity digestion is most effective for the hydrolysis of large molecular substances.

Parietal (membrane) digestion occurs on the surface of the microvilli of the small intestine. It completes the intermediate and final stages of digestion by hydrolysis of intermediate breakdown products. Microvilli are cylindrical outgrowths of intestinal epithelium 1–2 µm in height. Their number is enormous - from 50 to 200 million per 1 mm 2 of the intestinal surface, which increases the inner surface of the small intestine by 300-500 times. The large surface of the microvilli also improves the absorption process. The products of intermediate hydrolysis fall into the zone of the so-called brush border formed by microvilli, where the final stage of hydrolysis and the transition to absorption take place. The main enzymes involved in parietal digestion are amylase, lipase and prbtease. Thanks to this digestion, 80-90% of peptide and glycolysis bonds and 55-60% of triglycerols are broken down.

The motor activity of the small intestine ensures the mixing of the chyme with the digestive secretions and its movement through the intestine due to the contraction of the circular and longitudinal muscles. The contraction of the longitudinal fibers of the smooth muscles of the intestine is accompanied by a shortening of the intestinal area, relaxation is accompanied by its lengthening.

The contraction of the longitudinal and circular muscles is regulated by the vagus and sympathetic nerves. The vagus nerve stimulates intestinal motor function. Inhibitory signals are transmitted along the sympathetic nerve, which reduce muscle tone and inhibit mechanical movements of the intestine. The intestinal motor function is also influenced by humoral factors: serotin, choline and enterokinin stimulate intestinal movements.

Digestion in the large intestine. Digestion of food ends mainly in the small intestine. The glands of the large intestine secrete a small amount of juice, rich in mucus and poor in enzymes. The low enzymatic activity of the juice of the large intestine is due to the small amount of undigested substances in the chyme coming from the small intestine.

An important role in the life of the organism and the functions of the digestive tract is played by the microflora of the large intestine, where billions of various microorganisms live (anaerobic and lactic bacteria, intestinal bacillus, etc.). The normal microflora of the large intestine takes part in the implementation of several functions: protects the body from pathogenic microbes: participates in the synthesis of a number of vitamins (vitamins of group B, vitamin K); inactivates and decomposes enzymes (trypsin, amylase, gelatinase, etc.) from the small intestine, as well as ferments carbohydrates and causes decay of proteins.

The movements of the large intestine are very slow, so about half of the time spent on the digestive process (1-2 days) is spent on the movement of food residues in this part of the intestine.

In the large intestine, water is intensively absorbed, as a result of which feces are formed, consisting of the remnants of undigested food, mucus, bile pigments and bacteria. Emptying of the rectum (defecation) is carried out reflexively. The reflex arc of the defecation act is closed in the lumbosacral spinal cord and provides involuntary emptying of the large intestine. The voluntary act of defecation occurs with the participation of the centers of the medulla oblongata, the hypo-thalamus and the cerebral cortex. Sympathetic nervous influences inhibit rectal motility, parasympathetic - stimulate.

9.3. Absorption of food digestion products

Suction the process of entering the blood and lymph of various substances from the digestive system is called. The intestinal epithelium is the most important barrier between the external environment, the role of which is played by the intestinal cavity, and the internal environment of the body (blood, lymph), where nutrients enter.

Absorption is a complex process and is provided by various mechanisms: filtration, associated with the difference in hydrostatic pressure in media separated by a semipermeable membrane; diff-fusion substances along the concentration gradient; osmosis. The amount of absorbed substances (with the exception of iron and copper) does not depend on the needs of the body, it is proportional to food intake. In addition, the mucous membrane of the digestive system has the ability to selectively absorb some substances and limit the absorption of others.

The ability to absorb is possessed by the epithelium of the mucous membranes of the entire digestive tract. For example, the oral mucosa can absorb essential oils in small amounts, which is the basis for the use of some drugs. To an insignificant extent, the gastric mucosa is also capable of absorption. Water, alcohol, monosaccharides, mineral salts can pass through the gastric mucosa in both directions.

The most intensive absorption process is carried out in the small intestine, especially in the jejunum and ileum, which is determined by their large surface, many times larger than the surface of the human body. The intestinal surface is enlarged by the presence of villi, inside of which there are smooth muscle fibers and a well-developed circulatory and lymphatic network. The intensity of absorption in the small intestine is about 2-3 liters per hour.

Carbohydrates are absorbed into the blood mainly in the form of glucose, although other hexoses (galactose, fructose) can also be absorbed. Absorption occurs mainly in the duodenum and the upper part of the jejunum, but can be partially carried out in the stomach and large intestine.

Protein absorbed in the form of amino acids and in small amounts in the form of polypeptides through the mucous membranes of the duodenum and jejunum. Some amino acids can be absorbed in the stomach and the proximal colon. Absorption of amino acids is carried out both by diffusion and by active transport. After absorption through the portal vein, amino acids enter the liver, where they are deaminated and transaminated.
Fats absorbed in the form of fatty acids and glycerol only in the upper part of the small intestine. Fatty acids are insoluble in water, therefore, absorption and absorption of cholesterol and other lipoids occurs only in the presence of bile. Only emulsified fats can be partially absorbed without prior decomposition to glycerol and fatty acids. Fat-soluble vitamins A, D, E and K also need emulsification in order to be adsorbed. Most of the fat is absorbed into the lymph, then through the thoracic duct, it enters the blood. In the intestine, no more than 150-160 g of fat is absorbed per day.

Water and some electrolytes pass through the membranes of the mucous membrane of the alimentary canal in both directions. Water flows through diffusion. The most intense absorption occurs in the large intestine. Salts of sodium, potassium and calcium dissolved in water are absorbed mainly in the small intestine by the mechanism of active transport, against the concentration gradient.

9.4. Effect of muscle work on digestion

Muscular activity, depending on its intensity and duration, has a different effect on the digestion processes. Regular physical exercise and work of moderate power, increasing metabolism and energy, increase the body's need for nutrients and thereby stimulate the functions of various digestive glands and absorption processes. The development of the abdominal muscles and their moderate activity increase the motor function of the gastrointestinal tract, which is used in the practice of physiotherapy exercises.

However, the positive effect of physical exercises on digestion is not always observed. Work done immediately after a meal slows down the digestion process. At the same time, the complex reflex phase of secretion of the digestive glands is inhibited most of all. In this regard, it is advisable to carry out physical activity no earlier than 1.5-2 hours after eating. At the same time, it is not recommended to work with nato-shchak. Under these conditions, especially with prolonged work, the energy resources of the body are rapidly reduced, which leads to significant changes in body functions and a decrease in working capacity.

With intense muscular activity, as a rule, suppression of the secretory and motor functions of the gastrointestinal tract is observed. This is manifested in the inhibition of salivation, a decrease in secretory,

acid-forming and motor functions of the stomach. At the same time, hard work completely suppresses the complex reflex phase of gastric secretion and much less inhibits the neurochemical and intestinal phases. This also indicates the need to observe a certain break when performing muscle work after eating.

Significant physical activity reduces the secretion of digestive juice of the pancreas and bile; less intestinal juice is released. All this leads to a deterioration in both cavity and par-wall digestion, especially in the proximal parts of the small intestine. The most pronounced suppression of digestion after a meal rich in fats than after a protein-carbohydrate diet.

Suppression of the secretory and motor functions of the gastrointestinal

path with intense muscular work due to inhibition of food
out centers as a result of negative induction from excited motors
body zones of the central nervous system. :

In addition, during physical work, the excitation of the centers of the autonomic nervous system changes with a predominance of the tone of the sympathetic division, which has an inhibitory effect on digestion processes. Depressing effect on these processes and increased secretion of adrenal hormone - adrenaline.

A significant factor influencing the functions of the digestive organs is the redistribution of blood during physical work. Its main mass goes to the working muscles, while other systems, including the digestive organs, do not receive the required amount of blood. In particular, the volumetric blood flow rate of the abdominal organs decreases from 1.2-1.5 l / min at rest to 0.3-0.5 l / min during physical work. All this leads to a decrease in the secretion of digestive juices, a deterioration in the processes of digestion and absorption of nutrients. With many years of intense physical work, such changes can become persistent and serve as the basis for the occurrence of a number of diseases of the gastrointestinal tract.

When playing sports, it should be borne in mind that not only muscle work inhibits digestive processes, but digestion can negatively affect motor activity. Excitation of food centers and the outflow of blood from skeletal muscles to the organs of the gastrointestinal tract reduce the effectiveness of physical work. In addition, a full stomach raises the diaphragm, which adversely affects the functioning of the respiratory and circulatory organs.

The physical and chemical processing of food is a complex process that is carried out by the digestive system, which includes the oral cavity, esophagus, stomach, duodenum, small and large intestine, rectum, and the pancreas and liver with the gallbladder and bile ducts.

The study of the functional state of the digestive system is important mainly for assessing the health of athletes. Dysfunctions of the digestive system are observed in chronic gastritis, peptic ulcer disease, etc. Diseases such as gastric ulcer and duodenal ulcer, chronic cholecystitis are quite common in athletes.

Diagnostics of the functional state of the digestive system is based on the complex application of clinical (history, examination, palpation, percussion, auscultation), laboratory (chemical and microscopic examination of the contents of the stomach, duodenum, gallbladder, intestines) and instrumental (X-ray and endoscopic) research methods. Currently, an increasing number of intravital morphological studies are carried out using biopsy of organs (for example, liver).

In the process of taking anamnesis, athletes find out complaints, state of appetite, clarify the mode and nature of nutrition, calorie content of food taken, etc. During the examination, attention is paid to the condition of the teeth, gums and tongue (normally the tongue is moist, pink, without plaque), color skin, sclera of the eyes and soft palate (in order to detect yellowness), the shape of the abdomen (flatulence causes an increase in the abdomen in the area of ​​the affected intestine). Palpation reveals the presence of pain points in the stomach, liver and gallbladder, intestines; determine the condition (dense or soft) and soreness of the edge of the liver, if it is enlarged, probes even small tumors in the digestive organs. With the help of percussion, it is possible to determine the size of the liver, to reveal an inflammatory effusion caused by peritonitis, as well as a sharp swelling of individual intestinal loops, etc. Auscultation, in the presence of gas and liquid in the stomach, reveals the “splash noise” syndrome; auscultation of the abdomen is an indispensable method for detecting changes in peristalsis (strengthening or absence) of the intestine, etc.

The secretory function of the digestive organs is studied by examining the contents of the stomach, duodenum, gallbladder, etc., extracted with a probe, as well as using radiotelemetric and electrometric research methods. The radio capsules swallowed by the subjects are miniature (1.5 cm in size) radio transmitters. They allow you to receive information directly from the stomach and intestines about the chemical properties of the contents, temperature and pressure in the digestive tract.

A common laboratory method for examining the intestines is the caprological method: a description of the appearance of feces (color, consistency, pathological impurities), microscopy (detection of protozoa, worm eggs, determination of undigested food particles, blood cells) and chemical analysis (determination of pH, soluble protein of enzymes and etc.).

At present, morphological (fluoroscopy, endoscopy) and microscopic (cytological and histological) methods are of great importance in the study of the digestive organs. The advent of modern fibrogastroscopes has significantly expanded the possibilities of endoscopic studies (gastroscopy, sigmoidoscopy).

Dysfunction of the digestive system is one of the most common causes of decreased athletic performance.

Acute gastritis usually develops as a result of food toxicoinfection. The disease is acute and is accompanied by severe pain in the epigastric region, nausea, vomiting, diarrhea. Objectively: the tongue is coated, the abdomen is soft, diffuse soreness in the epigastric region. The general condition worsens due to dehydration and loss of electrolytes with vomit and diarrhea.

Chronic gastritis is the most common disease of the digestive system. In athletes, it often develops as a result of intense training against the background of a violation of a balanced diet: irregular food intake, the use of unusual food, spices, etc. Athletes complain of loss of appetite, sour belching, heartburn, a feeling of bloating, heaviness and pain in the epigastric region, usually worse after eating, occasional vomiting of a sour taste. Treatment is carried out using conventional methods; training and participation in competitions during treatment are prohibited.

Peptic ulcer and duodenal ulcer is a chronic recurrent disease that develops in athletes as a result of disorders of the central nervous system and hyperfunction of the "pituitary - adrenal cortex" system under the influence of great psychoemotional stress associated with competitive activity.

The leading place in gastric ulcer is occupied by epi-gastric pains that arise directly during meals or 20-30 minutes after eating and calm down after 1.5-2 hours; pain depends on the volume and nature of the food. In case of duodenal ulcer, "hungry" and night pains prevail. Dyspeptic symptoms are characterized by heartburn, nausea, vomiting, constipation; appetite is usually preserved. Patients often complain of increased irritability, emotional lability, and rapid fatigue. The main objective sign of an ulcer is pain in the anterior abdominal wall. Sports are contraindicated for peptic ulcer disease.

Often, during the examination, athletes complain of pain in the liver area during physical activity, which is diagnosed as a manifestation of hepatic pain syndrome. Pain in the liver area occurs, as a rule, during the performance of long and intense loads, do not have precursors and are acute. Often they are dull or constantly aching. Irradiation of pain in the back and right scapula is often observed, as well as a combination of pain with a feeling of heaviness in the right hypochondrium. Stopping physical activity or reducing its intensity helps to reduce pain or disappear. However, in some cases, pain can persist for many hours and during the recovery period.

At first, pains appear randomly and not often, later they begin to bother the athlete in almost every training session or competition. Pain can be accompanied by dyspeptic disorders: decreased appetite, feeling of nausea and bitterness in the mouth, heartburn, belching of air, unstable stools, constipation. In some cases, athletes complain of headaches, dizziness, increased irritability, stitching pains in the region of the heart, a feeling of weakness that intensifies during exercise.

Objectively, the majority of athletes show an increase in the size of the liver. In this case, its edge protrudes from under the costal arch by 1-2.5 cm; it is indurated and painful on palpation.

The cause of this syndrome is still not clear enough. Some researchers associate the appearance of pain with overstretching of the hepatic capsule due to overfilling of the liver with blood, others, on the contrary, with a decrease in the blood filling of the liver, with the phenomena of intrahepatic stagnation of blood. There are indications of a connection between the hepatic pain syndrome and the pathology of the digestive system, hemodynamic disturbances against the background of an irrational training regimen, etc. previously viral hepatitis, as well as with the occurrence of hypoxic conditions when performing loads that do not correspond to the functional capabilities of the body.

Prevention of diseases of the liver, gallbladder and biliary tract is mainly associated with adherence to the diet, the main provisions of the training regimen and a healthy lifestyle.

Treatment of athletes with hepatic pain syndrome should be aimed at eliminating diseases of the liver, gallbladder and biliary tract, as well as other concomitant diseases. Athletes should be excluded from training sessions and even more from participation in competitions during the period of treatment.

The prognosis for the growth of sports results in the early stages of the syndrome is favorable. In cases of persistent manifestation, athletes are usually forced to stop playing sports.