Small intestine. The epithelium of the small intestine. Cells of the small intestine What do the cells of the small intestine secrete?

Columnar epitheliocytes- the most numerous cells of the intestinal epithelium, performing the main absorption function of the intestine. These cells make up about 90% of the total number of intestinal epithelial cells. A characteristic feature of their differentiation is the formation of a brush border of densely located microvilli on the apical surface of the cells. The microvilli are about 1 µm long and about 0.1 µm in diameter.

The total number of microvilli per surfaces one cell varies widely - from 500 to 3000. Microvilli are covered on the outside with glycocalyx, which adsorbs enzymes involved in parietal (contact) digestion. Due to microvilli, the active surface of intestinal absorption increases 30-40 times.

Between epitheliocytes in their apical part, contacts such as adhesive bands and tight contacts are well developed. The basal parts of the cells are in contact with the lateral surfaces of neighboring cells through interdigitations and desmosomes, and the base of the cells is attached to the basement membrane by hemidesmosomes. Due to the presence of this system of intercellular contacts, the intestinal epithelium performs an important barrier function, protecting the body from the penetration of microbes and foreign substances.

goblet exocrinocytes- these are essentially unicellular mucous glands located among columnar epithelial cells. They produce carbohydrate-protein complexes - mucins, which perform a protective function and promote the movement of food in the intestines. The number of cells increases towards the distal intestine. The shape of the cells changes in different phases of the secretory cycle from prismatic to goblet. In the cytoplasm of cells, the Golgi complex and the granular endoplasmic reticulum are developed - centers for the synthesis of glycosaminoglycans and proteins.

Paneth cells, or exocrinocytes with acidophilic granules, are constantly located in the crypts (6-8 cells each) of the jejunum and ileum. Their total number is approximately 200 million. In the apical part of these cells, acidophilic secretory granules are determined. Zinc and a well-developed granular endoplasmic reticulum are also detected in the cytoplasm. The cells secrete a secret rich in the enzyme peptidase, lysozyme, etc. It is believed that the secret of the cells neutralizes the hydrochloric acid of the intestinal contents, participates in the breakdown of dipeptides to amino acids, and has antibacterial properties.

endocrinocytes(enterochromaffinocytes, argentaffin cells, Kulchitsky cells) - basal-granular cells located at the bottom of the crypts. They are well impregnated with silver salts and have an affinity for chromium salts. Among endocrine cells, there are several types that secrete various hormones: EC cells produce melatonin, serotonin, and substance P; S-cells - secretin; ECL cells - enteroglucagon; I-cells - cholecystokinin; D-cells - produce somatostatin, VIP - vasoactive intestinal peptides. Endocrinocytes make up about 0.5% of the total number of intestinal epithelial cells.

These cells are updated much more slowly than epitheliocytes. Methods of historadioautography established a very rapid renewal of the cellular composition of the intestinal epithelium. This happens in 4-5 days in the duodenum and somewhat more slowly (in 5-6 days) in the ileum.

lamina propria of the mucous membrane The small intestine is composed of loose fibrous connective tissue containing macrophages, plasma cells, and lymphocytes. There are also both single (solitary) lymph nodules and larger accumulations of lymphoid tissue - aggregates, or group lymph nodules (Peyer's patches). The epithelium covering the latter has a number of structural features. It contains epithelial cells with microfolds on the apical surface (M-cells). They form endocytic vesicles with antigen and exocytosis transfer it to the intercellular space where lymphocytes are located.

Subsequent development and plasma cell formation, their production of immunoglobulins neutralizes the antigens and microorganisms of the intestinal contents. The muscularis mucosa is represented by smooth muscle tissue.

In the submucosa basis of the duodenum are duodenal (Brunner's) glands. These are complex branched tubular mucous glands. The main type of cells in the epithelium of these glands is mucous glandulocytes. The excretory ducts of these glands are lined with border cells. In addition, Paneth cells, goblet exocrinocytes and endocrinocytes are found in the epithelium of the duodenal glands. The secret of these glands is involved in the breakdown of carbohydrates and the neutralization of hydrochloric acid coming from the stomach, the mechanical protection of the epithelium.

Muscular layer of the small intestine consists of inner (circular) and outer (longitudinal) layers of smooth muscle tissue. In the duodenum, the muscular membrane is thin and, due to the vertical location of the intestine, practically does not participate in peristalsis and the promotion of chyme. Outside, the small intestine is covered with a serous membrane.

Up to 2 liters of secretions are produced daily in the small intestine ( intestinal juice) with a pH of 7.5 to 8.0. The sources of the secret are the glands of the submucosa of the duodenum (Brunner's glands) and part of the epithelial cells of the villi and crypts.

· Brunner's glands secrete mucus and bicarbonates. The mucus secreted by the Brunner glands protects the duodenal wall from the action of gastric juice and neutralizes the hydrochloric acid coming from the stomach.

· Epithelial cells of villi and crypts(Fig. 22-8). Their goblet cells secrete mucus, and enterocytes secrete water, electrolytes, and enzymes into the intestinal lumen.

· Enzymes. On the surface of enterocytes in the villi of the small intestine are peptidases(break down peptides into amino acids) disaccharidases sucrase, maltase, isomaltase and lactase (break down disaccharides into monosaccharides) and intestinal lipase(breaks down neutral fats to glycerol and fatty acids).

· Secretion regulation. secretion stimulate mechanical and chemical irritation of the mucous membrane (local reflexes), excitation of the vagus nerve, gastrointestinal hormones (especially cholecystokinin and secretin). Secretion is inhibited by influences from the sympathetic nervous system.

secretory function of the colon. Colon crypts secrete mucus and bicarbonates. The amount of secretion is regulated by mechanical and chemical irritation of the mucous membrane and local reflexes of the enteric nervous system. Excitation of the parasympathetic fibers of the pelvic nerves causes an increase in the secretion of mucus with simultaneous activation of the peristalsis of the colon. Strong emotional factors can stimulate bowel movements with intermittent discharge of mucus without faecal content (“bear disease”).

Digestion of food

Proteins, fats and carbohydrates in the digestive tract are converted into products that can be absorbed (digestion, digestion). Digestion products, vitamins, minerals and water pass through the epithelium of the mucous membrane and enter the lymph and blood (absorption). The basis of digestion is the chemical process of hydrolysis carried out by digestive enzymes.

· Carbohydrates. The food contains disaccharides(sucrose and maltose) and polysaccharides(starches, glycogen), as well as other organic carbohydrate compounds. Cellulose in the digestive tract is not digested, since a person does not have enzymes capable of hydrolyzing it.

à Oral cavity and stomach. a-Amylase breaks down starch into the disaccharide maltose. During the short stay of food in the oral cavity, no more than 5% of all carbohydrates are digested. In the stomach, carbohydrates continue to be digested for an hour before the food is completely mixed with gastric juice. During this period, up to 30% of starches are hydrolyzed to maltose.

à Small intestine. a-Amylase of pancreatic juice completes the breakdown of starches to maltose and other disaccharides. Lactase, sucrase, maltase and a-dextrinase contained in the brush border of enterocytes hydrolyze disaccharides. Maltose is broken down to glucose; lactose - to galactose and glucose; sucrose - to fructose and glucose. The resulting monosaccharides are absorbed into the blood.

· Squirrels

à Stomach. Pepsin, active at pH 2.0 to 3.0, converts 10–20% of proteins to peptones and some polypeptides.

à Small intestine(Fig. 22-8)

Ú Pancreatic enzymes trypsin and chymotrypsin in the intestinal lumen cleave polypeptides into di- and tripeptides, carboxypeptidase cleaves amino acids from the carboxyl end of the polypeptides. Elastase digests elastin. In general, few free amino acids are formed.

Ú On the surface of microvilli of bordered enterocytes in the duodenum and jejunum there is a three-dimensional dense network - glycocalyx, in which numerous peptidases are located. It is here that these enzymes carry out the so-called parietal digestion. Aminopolypeptidases and dipeptidases cleave polypeptides into di- and tripeptides, and di- and tripeptides are converted into amino acids. Then amino acids, dipeptides and tripeptides are easily transported into enterocytes through the microvilli membrane.

Ú In the border enterocytes there are many peptidases specific for the bonds between specific amino acids; within a few minutes, all remaining di- and tripeptides are converted into individual amino acids. Normally, more than 99% of the products of protein digestion are absorbed in the form of individual amino acids. Peptides are very rarely absorbed.

Rice. 22–8 . Villus and crypt of the small intestine. The mucous membrane is covered with a single layer of cylindrical epithelium. Border cells (enterocytes) are involved in parietal digestion and absorption. Pancreatic proteases in the lumen of the small intestine cleave polypeptides coming from the stomach into short peptide fragments and amino acids, followed by their transport into enterocytes. Cleavage of short peptide fragments to amino acids occurs in enterocytes. Enterocytes transfer amino acids to their own layer of the mucous membrane, from where the amino acids enter the blood capillaries. Associated with the glycocalyx of the brush border, disaccharidases break down sugars into monosaccharides (mainly glucose, galactose and fructose), which are absorbed by enterocytes with subsequent release into their own layer and entry into the blood capillaries. The products of digestion (except triglycerides) after absorption through the capillary network in the mucous membrane are sent to the portal vein and then to the liver. Triglycerides in the lumen of the digestive tube are emulsified by bile and broken down by the pancreatic enzyme lipase. The resulting free fatty acids and glycerol are absorbed by enterocytes, in the smooth endoplasmic reticulum of which resynthesis of triglycerides occurs, and in the Golgi complex - the formation of chylomicrons - a complex of triglycerides and proteins. Chylomicrons undergo exocytosis on the lateral surface of the cell, pass through the basement membrane and enter the lymphatic capillaries. As a result of contraction of MMCs located in the connective tissue of the villi, the lymph moves into the lymphatic plexus of the submucosa. In addition to enterocytes, goblet cells that produce mucus are present in the border epithelium. Their number increases from the duodenum to the ileum. In the crypts, especially in the area of ​​their bottom, there are enteroendocrine cells that produce gastrin, cholecystokinin, gastric inhibitory peptide, motilin and other hormones.

· Fats are found in food mainly in the form of neutral fats (triglycerides), as well as phospholipids, cholesterol and cholesterol esters. Neutral fats are part of the food of animal origin, they are much less in plant foods.

à Stomach. Lipases break down less than 10% of triglycerides.

à Small intestine

Ú Digestion of fats in the small intestine begins with the transformation of large fat particles (globules) into the smallest globules - fat emulsification(Fig. 22-9A). This process begins in the stomach under the influence of the mixing of fats with gastric contents. In the duodenum, bile acids and the phospholipid lecithin emulsify fats down to particle sizes of 1 µm, increasing the total surface area of ​​fats by 1000 times.

Ú Pancreatic lipase breaks down triglycerides into free fatty acids and 2-monoglycerides and is able to digest all chyme triglycerides within 1 minute if they are in an emulsified state. The role of intestinal lipase in the digestion of fats is small. The accumulation of monoglycerides and fatty acids at the sites of fat digestion stops the hydrolysis process, but this does not happen because micelles, consisting of several tens of bile acid molecules, remove monoglycerides and fatty acids at the time of their formation (Fig. 22-9A). Cholate micelles transport monoglycerides and fatty acids to enterocyte microvilli, where they are absorbed.

Ú Phospholipids contain fatty acids. Cholesterol esters and phospholipids are cleaved by special pancreatic juice lipases: cholesterol esterase hydrolyzes cholesterol esters, and phospholipase A 2 cleaves phospholipids.

The human small intestine is part of the digestive tract. This department is responsible for the final processing of substrates and absorption (suction).

What is the small intestine?

The human small intestine is a narrow tube about six meters long.

This part of the digestive tract got its name because of the proportional features - the diameter and width of the small intestine is much smaller than those of the large intestine.

The small intestine is divided into the duodenum, jejunum and ileum. The duodenum is the first segment of the small intestine, located between the stomach and the jejunum.

Here the most active processes of digestion take place, it is here that pancreatic and gallbladder enzymes are secreted. The jejunum follows the duodenum, its average length is one and a half meters. Anatomically, the jejunum and ileum are not separated.

The mucosa of the jejunum on the inner surface is covered with microvilli that absorb nutrients, carbohydrates, amino acids, sugar, fatty acids, electrolytes and water. The surface of the jejunum increases due to special fields and folds.

Vitamin B12 and other water-soluble vitamins are absorbed in the ileum. In addition, this area of ​​the small intestine is also involved in the absorption of nutrients. The functions of the small intestine are somewhat different from those of the stomach. In the stomach, food is crushed, ground and primarily decomposed.

In the small intestine, the substrates are decomposed into their constituent parts and absorbed for transport to all parts of the body.

Anatomy of the small intestine

As we noted above, in the digestive tract, the small intestine immediately follows the stomach. The duodenum is the initial section of the small intestine, following the pyloric section of the stomach.

The duodenum begins at the bulb, bypasses the head of the pancreas, and ends in the abdominal cavity with the ligament of Treitz.

The peritoneal cavity is a thin connective tissue surface that covers some of the abdominal organs.

The rest of the small intestine is literally suspended in the abdominal cavity by a mesentery attached to the posterior abdominal wall. This structure allows you to freely move the sections of the small intestine during surgery.

The jejunum occupies the left side of the abdominal cavity, while the ileum is located in the upper right side of the abdominal cavity. The inner surface of the small intestine contains mucous folds called circular circles. Such anatomical formations are more numerous in the initial section of the small intestine and are reduced closer to the distal ileum.

The assimilation of food substrates is carried out with the help of primary cells of the epithelial layer. Cubic cells located throughout the entire area of ​​the mucous membrane secrete mucus that protects the intestinal walls from an aggressive environment.

Enteric endocrine cells secrete hormones into the blood vessels. These hormones are essential for digestion. The squamous cells of the epithelial layer secrete lysozyme, an enzyme that destroys bacteria. The walls of the small intestine are closely connected with the capillary networks of the circulatory and lymphatic systems.

The walls of the small intestine are composed of four layers: mucosa, submucosa, muscularis, and adventitia.

functional significance

The human small intestine is functionally connected with all organs of the gastrointestinal tract, digestion of 90% of food substrates ends here, the remaining 10% are absorbed in the large intestine.

The main function of the small intestine is to absorb nutrients and minerals from food. The digestion process has two main parts.

The first part involves the mechanical processing of food by chewing, grinding, whipping and mixing - all this takes place in the mouth and stomach. The second part of food digestion involves the chemical processing of substrates, which uses enzymes, bile acids, and other substances.

All this is necessary in order to decompose whole products into individual components and absorb them. Chemical digestion occurs in the small intestine - it is here that the most active enzymes and excipients are present.

Ensuring digestion

After rough processing of products in the stomach, it is necessary to decompose the substrates into separate components available for absorption.

1. The breakdown of proteins. Proteins, peptides and amino acids are affected by special enzymes, including trypsin, chymotrypsin and intestinal wall enzymes. These substances break down proteins into small peptides. Protein digestion begins in the stomach and ends in the small intestine.
2. Digestion of fats. This purpose is served by special enzymes (lipases) secreted by the pancreas. Enzymes break down triglycerides into free fatty acids and monoglycerides. An auxiliary function is provided by bile juices secreted by the liver and gallbladder. Bile juices emulsify fats - they separate them into small drops available for the action of enzymes.
3. Digestion of carbohydrates. Carbohydrates are classified into simple sugars, disaccharides and polysaccharides. The body needs the main monosaccharide - glucose. Pancreatic enzymes act on polysaccharides and disaccharides, which promote the decomposition of substances to monosaccharides. Some carbohydrates are not completely absorbed in the small intestine and end up in the large intestine, where they become food for intestinal bacteria.

Absorption of food in the small intestine

Decomposed into small components, nutrients are absorbed by the mucous membrane of the small intestine and move into the blood and lymph of the body.

Absorption is provided by special transport systems of digestive cells - each type of substrate is provided with a separate method of absorption.

The small intestine has a significant internal surface area, which is essential for absorption. Circular circles of the intestine contain a large number of villi that actively absorb food substrates. Modes of transport in the small intestine:

• Fats undergo passive or simple diffusion.
• Fatty acids are absorbed by diffusion.
• Amino acids enter the intestinal wall by active transport.
• Glucose enters through secondary active transport.
• Fructose is absorbed by facilitated diffusion.

For a better understanding of the processes, it is necessary to clarify the terminology. Diffusion is a process of absorption along the concentration gradient of substances, it does not require energy. All other types of transport require the expenditure of cellular energy. We found out that the human small intestine is the main section of food digestion in the digestive tract.

Watch the video about the anatomy of the small intestine:

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Causes and treatment of increased gas formation in adults

Flatulence is called excessive gas formation in the intestines. As a result, digestion is difficult and disrupted, nutrients are poorly absorbed, and the production of enzymes necessary for the body is reduced. Flatulence in adults is eliminated with the help of drugs, folk remedies and diet.

1. Causes of flatulence
2. Diseases that provoke flatulence
3. Flatulence during pregnancy
4. The course of the disease
5. Flatulence treatment
6. Medicines
7. Folk recipes
8. Power correction
9. Conclusion

Causes of flatulence

The most common cause of flatulence is malnutrition. An excess of gases can occur in both men and women. This condition is often provoked by foods that are high in fiber and starch. As soon as they accumulate more than the norm, the rapid development of flatulence begins. The cause is also carbonated drinks and products from which a fermentation reaction occurs (lamb, cabbage, legumes, etc.).

Often, increased flatulence appears due to a violation of the enzyme system. If they are not enough, then a lot of undigested food penetrates into the terminal sections of the gastrointestinal tract. As a result, it begins to rot, fermentation processes are activated with the release of gases. An unhealthy diet leads to a lack of enzymes.

A common cause of flatulence is a violation of the normal microflora of the large intestine. With its stable operation, part of the resulting gases is destroyed by special bacteria, for which this is a source of vital activity. However, when they are overproduced by other microorganisms, the balance in the intestine is disturbed. Gas causes an unpleasant smell of rotten eggs during bowel movements.

The cause of flatulence can also be:

1. Stress, causing muscle spasms and slowing down of the intestines. At the same time, sleep is disturbed. Most often, the disease occurs in women.
2. Surgical operations, after which the activity of the gastrointestinal tract decreases. The progress of the food mass slows down, which provokes the processes of fermentation and decay.
3. Adhesions and tumors. They also interfere with the normal movement of food masses.
4. Milk intolerance causes gas buildup.

Morning flatulence can be caused by a lack of fluid in the body. In this case, the bacteria begin to intensively release gases. Only pure water helps to reduce them. Eating at night also contributes to increased gas formation. The stomach does not have time to rest, and part of the food is undigested. Fermentation appears in the intestines.

In addition to these reasons, there is "senile flatulence of the intestine." Often, gases accumulate during sleep. Their excessive increase appears against the background of age-related changes in the body, due to lengthening of the intestine, atrophy of the muscular wall of the organ, or a decrease in the number of glands that are involved in the release of digestive enzymes. With gastritis, gases often accumulate during sleep.

Diseases that provoke flatulence

Increased gas formation can be caused by a number of diseases:

1. With duodenitis, the duodenum becomes inflamed and the synthesis of digestive enzymes is disrupted. As a result, rotting and fermentation of undigested food begins in the intestines.
2. With cholecystitis during the inflammatory process, the outflow of bile is disturbed. Since it does not enter the duodenum sufficiently, the organ begins to function incorrectly.
3. With gastritis in the gastrointestinal tract, the level of acidity changes and proteins are broken down very slowly. This disrupts the peristalsis of the intestines of the digestive tract.
4. With pancreatitis, the pancreas is deformed and swells. Healthy tissues are replaced by fibrous ones, in which there are almost no living cells. Due to structural changes, the production of digestive enzymes is reduced. There is a deficiency of pancreatic juice, and as a result, the digestion of food is disturbed. Because of this, gas emission is greatly increased.
5. With enteritis, the mucosa of the small intestine is deformed. As a result, the absorption of food and its processing are disturbed.
6. The same thing happens during colitis. The balance of the intestinal microflora is disturbed. These changes lead to increased gas production.
7. In cirrhosis, the liver cannot secrete bile properly. As a result, fats are not fully digested. Increased gas formation usually occurs after fatty foods.
8. During acute intestinal infections, the pathogen most often enters through the mouth with contaminated food or water. After that, harmful microorganisms begin to multiply rapidly and release toxins (toxic substances). They have a negative effect on the muscles of the intestine. Because of this, the removal of gases from the body is disrupted, and they begin to accumulate. There is severe bloating.
9. With obstruction of the gastrointestinal tract, its peristalsis is disturbed due to a mechanical obstacle (helminths, neoplasms, foreign bodies, etc.).
10. With irritable bowel syndrome, the sensitivity of the receptors of its walls changes. This disrupts the motility of the organ, mainly the colon, absorption and secretion. As a result, pronounced flatulence appears.
11. With intestinal atony, the rate of movement of feces and chyme is significantly reduced, which causes the accumulation of gases.
12. With diverticulitis of the intestine, the level of pressure in it is disturbed. Its increase leads to lesions of the muscle layer, defects appear. False diverticulitis is formed and severe flatulence appears.
13. With neurosis, the nervous system is overexcited. As a result, intestinal peristalsis is disturbed.

Flatulence during pregnancy

In women during pregnancy, flatulence occurs for a number of reasons:

• intestinal compression;
• hormonal changes in the body;
• stress;
• violation of the microflora in the intestine;
• malnutrition;
• diseases of the gastrointestinal tract.

Treatment of flatulence during pregnancy is carried out strictly according to the doctor's recommendations. During this period, women cannot take many medicines, and not all folk methods are suitable. A pregnant woman should:

• follow a diet;
• chew food thoroughly;
• exclude carbonated drinks from the diet.

At the same time, a woman needs to be active and wear loose clothing. Flatulence cannot be treated on its own. Medicines should be prescribed only by a doctor. Without his consultation, you can use activated charcoal. It absorbs all toxins and harmful substances. Linex has the same effect.

The course of the disease

The course of the disease is divided into two types:

1. The first is when flatulence manifests itself after an increase in the abdomen due to the accumulation of gases. Their discharge is very difficult due to intestinal spasm. This is accompanied by pain in the abdomen and a feeling of distension.
2. In another variant, gases, on the contrary, intensively exit the intestines. Moreover, this process becomes regular. This phenomenon causes pain in the intestines. But even those around the patient can hear loudly how his stomach rumbles and boils due to the transfusion of the contents.

Flatulence treatment

Medicines

Therapy begins with the elimination of concomitant diseases that provoke strong gas formation.

• Pre- and probiotic preparations are prescribed (Biobacton, Acylact, etc.). Antispasmodics help reduce pain (Papaverine, No-Shpa, etc.).
• To eliminate sudden gas formation, enterosorbents are used (activated carbon, Smecta, Enterosgel and others).
• Drugs are also prescribed that eliminate increased gas formation. Adsobents (activated carbon, Polysorb, etc.) and defoamers (Espumizan, Disflatil, Maalox plus, etc.) are prescribed.
• Flatulence is also treated with enzymatic preparations (Pancreatin, Mezim Forte, etc.).
• When vomiting, Metoclopramide or Cerucal is prescribed.

When flatulence appears for the first time, Espumizan can be used to quickly eliminate symptoms. It belongs to defoaming drugs and collapses gas bubbles immediately in the intestine. As a result, heaviness in the abdomen and pain quickly disappear. Mezim Forte and activated charcoal help to eliminate the same symptoms in a short time.

Folk recipes

Folk remedies for bloating and excessive gas formation:

1. Dill seeds (1 tablespoon) are poured with a glass of boiling water. Infuse until completely cooled. The remedy is filtered and drunk in the morning.
2. Crushed carrot seeds. They need to drink 1 tsp. per day for bloating.
3. A decoction is prepared from dandelion roots. Crushed and dried plant in the amount of 2 tbsp. l. pour 500 ml of boiling water. After the product has cooled, it is filtered. The decoction is divided into 4 parts and gradually drunk during the day.
4. Ginger root is crushed and dried. The powder is consumed in a quarter of a teaspoon per day, after which it is washed down with plain water.
5. An infusion is made from St. John's wort, yarrow and marsh cudweed. All plants are taken in crushed dried form, 3 tbsp. l. The infusion is taken to reduce gas formation.

Increased gas formation can be cured within a day. To do this, parsley root (1 tsp) is infused for 20 minutes in a glass of cold water. Then the mixture is slightly warmed up and drunk every hour in a big gulp until the liquid in the glass runs out.

An infusion of dried thyme and dill seeds helps to quickly get rid of flatulence. They are taken in 1 tsp. and pour 250 ml of boiling water. The product is infused for 10 minutes under a tightly closed lid. From above it is covered with a towel, then filtered. Infusion should be drunk every hour for 30 ml. The last dose should be before dinner.

Power correction

Treatment for flatulence includes diet. It is an auxiliary, but mandatory addition. Flatulence during sleep is often caused by food eaten for dinner.

1. All foods with coarse fiber are removed from the diet.
2. You can not eat legumes, cabbage and other foods that cause fermentation in the intestines.
3. If lactose intolerance is observed, the amount of milk sugar and calories in the diet is reduced.
4. Meat and fish should be lean, steamed or boiled. Bread is eaten dried or stale.
5. Of vegetables, carrots, beets, cucumbers, tomatoes and spinach are allowed.
6. You can eat fat-free yogurt and cottage cheese.
7. Porridges are prepared only from brown rice, buckwheat or oatmeal.
8. It is necessary to abandon fried foods, smoked meats and pickles.
9. Do not drink carbonated and alcoholic drinks.
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Tone The cue intestine is conditionally divided into 3 sections: duodenum, jejunum and ileum. The length of the small intestine is 6 meters, and in persons who consume mainly plant foods, it can reach 12 meters.

The wall of the small intestine is made up of 4 shells: mucous, submucosal, muscular and serous.

The mucous membrane of the small intestine has own relief, which includes intestinal folds, intestinal villi and intestinal crypts.

intestinal folds formed by the mucosa and submucosa and are circular in nature. Circular folds are highest in the duodenum. In the course of the small intestine, the height of the circular folds decreases.

intestinal villi are finger-like outgrowths of the mucous membrane. In the duodenum, the intestinal villi are short and wide, and then along the small intestine they become high and thin. The height of the villi in different parts of the intestine reaches 0.2 - 1.5 mm. Between the villi open 3-4 intestinal crypts.

Intestinal crypts are depressions of the epithelium into its own layer of the mucous membrane, which increase along the course of the small intestine.

The most characteristic formations of the small intestine are intestinal villi and intestinal crypts, which greatly increase the surface.

From the surface, the mucous membrane of the small intestine (including the surface of the villi and crypts) is covered with a single-layer prismatic epithelium. The lifespan of the intestinal epithelium is from 24 to 72 hours. Solid food accelerates the death of cells that produce chalons, which leads to an increase in the proliferative activity of crypt epithelial cells. According to modern ideas, generative zone of the intestinal epithelium is the bottom of the crypts, where 12-14% of all epitheliocytes are in the synthetic period. In the process of vital activity, epitheliocytes gradually move from the depth of the crypt to the top of the villus and, at the same time, perform numerous functions: multiply, absorb substances digested in the intestine, secrete mucus and enzymes into the intestinal lumen. The separation of enzymes in the intestine occurs mainly along with the death of glandular cells. Cells, rising to the top of the villus, are rejected and disintegrate in the intestinal lumen, where they give their enzymes to the digestive chyme.

Among intestinal enterocytes, there are always intraepithelial lymphocytes that penetrate here from their own plate and belong to T-lymphocytes (cytotoxic, T-memory cells and natural killers). The content of intraepithelial lymphocytes increases in various diseases and immune disorders. intestinal epithelium includes several types of cellular elements (enterocytes): bordered, goblet, borderless, tufted, endocrine, M-cells, Paneth cells.

Border cells(columnar) make up the main population of intestinal epithelial cells. These cells are prismatic in shape, on the apical surface there are numerous microvilli that have the ability of slow contraction. The fact is that microvilli contain thin filaments and microtubules. In each microvillus, there is a bundle of actin microfilaments in the center, which are connected on one side to the plasmolemma of the villus apex, and at the base they are connected to a terminal network - horizontally oriented microfilaments. This complex ensures the contraction of microvilli during absorption. There are from 800 to 1800 microvilli on the surface of the border cells of the villi, and only 225 microvilli on the surface of the border cells of the crypts. These microvilli form a striated border. From the surface, the microvilli are covered with a thick layer of glycocalyx. For border cells, the polar arrangement of organelles is characteristic. The nucleus lies in the basal part, above it is the Golgi apparatus. Mitochondria are also localized at the apical pole. They have a well-developed granular and agranular endoplasmic reticulum. Between the cells lie the endplates that close the intercellular space. In the apical part of the cell, there is a well-defined terminal layer, which consists of a network of filaments parallel to the cell surface. The terminal network contains actin and myosin microfilaments and is connected to intercellular contacts on the lateral surfaces of the apical parts of enterocytes. With the participation of microfilaments in the terminal network, intercellular gaps between enterocytes are closed, which prevents the entry of various substances into them during digestion. The presence of microvilli increases the cell surface by 40 times, due to which the total surface of the small intestine increases and reaches 500 m. On the surface of the microvilli are numerous enzymes that provide hydrolytic cleavage of molecules that are not destroyed by the enzymes of gastric and intestinal juice (phosphatase, nucleoside diphosphatase, aminopeptidase, etc.). This mechanism is called membrane or parietal digestion.

Membrane digestion not only a very effective mechanism for the splitting of small molecules, but also the most advanced mechanism that combines the processes of hydrolysis and transport. Enzymes located on the membranes of microvilli have a dual origin: they are partly adsorbed from the chyme, and partly they are synthesized in the granular endoplasmic reticulum of the border cells. During membrane digestion, 80-90% of peptide and glucosidic bonds, 55-60% of triglycerides are cleaved. The presence of microvilli turns the intestinal surface into a kind of porous catalyst. It is believed that microvilli are able to contract and relax, which affects the processes of membrane digestion. The presence of glycocalyx and very small spaces between microvilli (15-20 microns) ensure the sterility of digestion.

After cleavage, the hydrolysis products penetrate the microvilli membrane, which has the ability of active and passive transport.

When fats are absorbed, they are first broken down to low molecular weight compounds, and then fats are resynthesised inside the Golgi apparatus and in the tubules of the granular endoplasmic reticulum. This entire complex is transported to the lateral surface of the cell. By exocytosis, fats are removed into the intercellular space.

Cleavage of polypeptide and polysaccharide chains occurs under the action of hydrolytic enzymes localized in the plasma membrane of microvilli. Amino acids and carbohydrates enter the cell using active transport mechanisms, that is, using energy. Then they are released into the intercellular space.

Thus, the main functions of the border cells, which are located on the villi and crypts, are parietal digestion, which proceeds several times more intensively than intracavitary, and is accompanied by the breakdown of organic compounds to final products and the absorption of hydrolysis products.

goblet cells located singly between the limbic enterocytes. Their content increases in the direction from the duodenum to the large intestine. There are more goblet cell crypts in the epithelium than in the villus epithelium. These are typical mucous cells. They show cyclical changes associated with the accumulation and secretion of mucus. In the mucus accumulation phase, the nuclei of these cells are located at the base of the cells, have an irregular or even triangular shape. Organelles (Golgi apparatus, mitochondria) are located near the nucleus and are well developed. At the same time, the cytoplasm is filled with drops of mucus. After secretion, the cell decreases in size, the nucleus decreases, the cytoplasm is freed from mucus. These cells produce mucus necessary to moisten the surface of the mucous membrane, which, on the one hand, protects the mucous membrane from mechanical damage, and on the other hand, promotes the movement of food particles. In addition, mucus protects against infectious damage and regulates the bacterial flora of the intestine.

M cells are located in the epithelium in the area of ​​localization of lymphoid follicles (both group and single). These cells have a flattened shape, a small number of microvilli. At the apical end of these cells, there are numerous microfolds, so they are called "cells with microfolds". With the help of microfolds, they are able to capture macromolecules from the intestinal lumen and form endocytic vesicles, which are transported to the plasmalemma and released into the intercellular space, and then into the mucosal lamina propria. After that, lymphocytes t. propria, stimulated by the antigen, migrate to the lymph nodes, where they proliferate and enter the bloodstream. After circulating in the peripheral blood, they repopulate the lamina propria, where B-lymphocytes are converted into IgA-secreting plasma cells. Thus, antigens coming from the intestinal cavity attract lymphocytes, which stimulates the immune response in the lymphoid tissue of the intestine. In M-cells, the cytoskeleton is very poorly developed, so they are easily deformed under the influence of interepithelial lymphocytes. These cells do not have lysosomes, so they transport different antigens via vesicles without change. They are devoid of glycocalyx. The pockets formed by the folds contain lymphocytes.

tufted cells on their surface they have long microvilli protruding into the intestinal lumen. The cytoplasm of these cells contains many mitochondria and tubules of the smooth endoplasmic reticulum. Their apical part is very narrow. It is assumed that these cells function as chemoreceptors and possibly carry out selective absorption.

Paneth cells(exocrinocytes with acidophilic granularity) lie at the bottom of the crypts in groups or singly. Their apical part contains dense oxyphilic staining granules. These granules are easily stained bright red with eosin, dissolve in acids, but are resistant to alkalis. These cells contain a large amount of zinc, as well as enzymes (acid phosphatase, dehydrogenases and dipeptidases. Organelles are moderately developed (the Golgi apparatus is best developed). Cells Paneth cells carry out an antibacterial function, which is associated with the production of lysozyme by these cells, which destroys the cell walls of bacteria and protozoa.These cells are capable of active phagocytosis of microorganisms.Due to these properties, Paneth cells regulate the intestinal microflora.In a number of diseases, the number of these cells decreases.In recent years IgA and IgG were found in these cells.In addition, these cells produce dipeptidases that break down dipeptides into amino acids.It is assumed that their secretion neutralizes the hydrochloric acid contained in the chyme.

endocrine cells belong to the diffuse endocrine system. All endocrine cells are characterized

o the presence in the basal part under the nucleus of secretory granules, therefore they are called basal-granular. There are microvilli on the apical surface, which, apparently, contain receptors that respond to a change in pH or to the absence of amino acids in the chyme of the stomach. Endocrine cells are primarily paracrine. They secrete their secret through the basal and basal-lateral surface of cells into the intercellular space, directly affecting neighboring cells, nerve endings, smooth muscle cells, and vessel walls. Part of the hormones of these cells are secreted into the blood.

In the small intestine, the most common endocrine cells are: EC cells (secreting serotonin, motilin and substance P), A cells (producing enteroglucagon), S cells (producing secretin), I cells (producing cholecystokinin), G cells (producing gastrin), D-cells (producing somatostatin), D1-cells (secreting vasoactive intestinal polypeptide). The cells of the diffuse endocrine system are unevenly distributed in the small intestine: the largest number of them is found in the wall of the duodenum. So, in the duodenum, there are 150 endocrine cells per 100 crypts, and only 60 cells in the jejunum and ileum.

Borderless or borderless cells lie in the lower parts of the crypts. They often show mitoses. According to modern concepts, borderless cells are poorly differentiated cells and act as stem cells for the intestinal epithelium.

own mucosal layer built of loose, unformed connective tissue. This layer makes up the bulk of the villi; between the crypts lies in the form of thin layers. The connective tissue here contains many reticular fibers and reticular cells and is very loose. In this layer, in the villi under the epithelium, there is a plexus of blood vessels, and in the center of the villi there is a lymphatic capillary. Substances enter these vessels, which are absorbed in the intestine and transported through the epithelium and connective tissue of t.propria and through the capillary wall. The products of hydrolysis of proteins and carbohydrates are absorbed into the blood capillaries, and fats - into the lymphatic capillaries.

Numerous lymphocytes are located in their own layer of the mucous membrane, which lie either singly or form clusters in the form of single solitary or grouped lymphoid follicles. Large lymphoid accumulations are called Peyer's plaques. Lymphoid follicles can penetrate even into the submucosa. Peyrov's plaques are mainly located in the ileum, less often in other parts of the small intestine. The highest content of Peyer's plaques is found during puberty (about 250), in adults their number stabilizes and sharply decreases in old age (50-100). All lymphocytes lying in t.propria (singly and grouped) form an intestinal-associated lymphoid system containing up to 40% of immune cells (effectors). In addition, at present, the lymphoid tissue of the wall of the small intestine is equated to the bag of Fabricius. Eosinophils, neutrophils, plasma cells and other cellular elements are constantly found in the lamina propria.

Muscular lamina (muscular layer) of the mucous membrane consists of two layers of smooth muscle cells: inner circular and outer longitudinal. From the inner layer, single muscle cells penetrate into the thickness of the villi and contribute to the contraction of the villi and the extrusion of blood and lymph rich in absorbed products from the intestine. Such contractions occur several times per minute.

submucosa It is built from loose, unformed connective tissue containing a large number of elastic fibers. Here is a powerful vascular (venous) plexus and nerve plexus (submucosal or Meisner's). In the duodenum in the submucosa are numerous duodenal (Brunner's) glands. These glands are complex, branched and alveolar-tubular in structure. Their terminal sections are lined with cubic or cylindrical cells with a flattened basally lying nucleus, a developed secretory apparatus, and secretory granules at the apical end. Their excretory ducts open into crypts, or at the base of the villi directly into the intestinal cavity. Mucocytes contain endocrine cells belonging to the diffuse endocrine system: Ec, G, D, S - cells. The cambial cells lie at the mouth of the ducts; therefore, the renewal of gland cells occurs from the ducts towards the terminal sections. The secret of the duodenal glands contains mucus, which has an alkaline reaction and thereby protects the mucous membrane from mechanical and chemical damage. The secret of these glands contains lysozyme, which has a bactericidal effect, urogastron, which stimulates the proliferation of epithelial cells and inhibits the secretion of hydrochloric acid in the stomach, and enzymes (dipeptidases, amylase, enterokinase, which converts trypsinogen into trypsin). In general, the secret of the duodenal glands performs a digestive function, participating in the processes of hydrolysis and absorption.

Muscular membrane It is built of smooth muscle tissue, forming two layers: the inner circular and the outer longitudinal. These layers are separated by a thin layer of loose, unformed connective tissue, where the intermuscular (Auerbach's) nerve plexus lies. Due to the muscular membrane, local and peristaltic contractions of the wall of the small intestine along the length are carried out.

Serous membrane is a visceral sheet of the peritoneum and consists of a thin layer of loose, unformed connective tissue, covered with mesothelium on top. In the serous membrane there is always a large number of elastic fibers.

Features of the structural organization of the small intestine in childhood. The mucous membrane of a newborn child is thinned, and the relief is smoothed (the number of villi and crypts is small). By the period of puberty, the number of villi and folds increases and reaches a maximum value. The crypts are deeper than those of an adult. The mucous membrane from the surface is covered with epithelium, a distinctive feature of which is a high content of cells with acidophilic granularity, which lie not only at the bottom of the crypts, but also on the surface of the villi. The mucous membrane is characterized by abundant vascularization and high permeability, which creates favorable conditions for the absorption of toxins and microorganisms into the blood and the development of intoxication. Lymphoid follicles with reactive centers are formed only towards the end of the neonatal period. The submucosal plexus is immature and contains neuroblasts. In the duodenum, the glands are few, small and unbranched. The muscular layer of the newborn is thinned. The final structural formation of the small intestine occurs only by 4-5 years.