home→Gastritis→ What do the cells of the mucous membrane of the small intestine secrete? Resynthesis of simple and complex lipids in the cells of the mucous membrane of the small intestine

What do the cells of the mucous membrane of the small intestine secrete? Resynthesis of simple and complex lipids in the cells of the mucous membrane of the small intestine

Digestive system - III. INTESTINES

The intestine consists of the small and large intestines. It continues the process of digestion of food, which began in the overlying sections of the digestive tube.

The small intestine reaches 5 m in length and consists of three sections: the duodenum (30 cm), the jejunum (2 m) and the ileum (3 m) intestine.

Structure. The wall of the small intestine is formed three shells: mucous, muscular and serous. The mucous membrane is made up of epithelium, lamina propria, muscular lamina and submucosa, which is often described as a self-contained shell. feature relief mucosa of the small intestine is the presence circular folds, villi and crypts, which increase the overall surface area of the small intestine for food digestion and absorption.

Circular folds are protrusions of the mucous membrane (all its layers) into the intestinal cavity.

intestinal villi are protrusions into the lumen of the intestine of the own plate of the mucous membrane, covered with epithelium. In the connective tissue base of the villi located under the basement membrane of the epithelium, there is a dense network blood capillaries, and in the center of the villi - lymphatic capillary. In the stroma of the villi there are single smooth myocytes, providing the movement of the villi, contribute to the process of promoting the products of food digestion absorbed into the blood and lymph. The surface of the villi is covered single layered prismatic border epithelium . It consists of three types of cells: prismatic epithelial cells, goblet cells and endocrine.

Prismatic (columnar, border) epitheliocytes the most numerous, differ in the pronounced polarity of the structure. The apical surface contains microvilli - finger-like protrusions of the cytoplasm with a cytoskeleton, about 1 µm high and 0.1 µm in diameter. Their number in the cell reaches 3 thousand and together they form a striated (brush) border, which increases the absorption surface of the mucous membrane by 30-40 times. On the surface of the microvilli is a glycocalyx, represented by lipoproteins and glycoproteins. The membrane and glycocalyx of microvilli contain a large number of enzymes involved in parietal and membrane digestion, as well as enzymes involved in the function of absorption of the resulting monomers (monosaccharides, amino acids, as well as glycerol and fatty acids).

In the cytoplasm there are developed cytoplasmic reticulum, Golgi complex, mitochondria, lysosomes. In the apical part, adjacent epitheliocytes form intercellular connections coupling type (adhesive belt) And locking type (tight connections) that prevent the penetration of undigested substances and bacteria from the intestinal cavity into the internal environment of the body.

goblet exocrinocytes in the villi are located singly between the border epithelial cells and produce a mucous secretion. They have the shape of a glass, in the leg of which the nucleus and organelles are located, and in the expanded apical part there are secretory granules with mucous contents. The latter, standing out on the surface of the mucosa, moisturize it, which contributes to the movement of chyme along the intestine.

endocrinocytes – hormone-producing cells belonging to the diffuse part of the endocrine system. Like goblet cells, they are scattered singly between bordered epithelial cells. Their apical part reaches the surface of the epithelium and contacts the contents of the intestine, receiving information, and the basal part accumulates hormones in the form of granules that are released into the intercellular environment (acting locally, parocrine) or into the blood (regulating digestion and metabolism in the body).

Intestinal crypts (glands)- these are tubular ingrowths of the epithelium into the lamina propria of the mucosa. Their lumen opens between the bases of neighboring villi. In the small intestine, their number is about 150 million. Among the epithelial cells of the crypts, in addition to the above, as part of the epithelium of the villi ( prismatic, goblet, endocrine) there are undifferentiated epitheliocytes and cells with acidophilic granules (Paneth cells).

Prismatic epitheliocytes, unlike those of the villi, have a lower height, a thinner striated border and a more basophilic cytoplasm. undifferentiated epitheliocytes (cells without a border), represent a population of cells that are the source of regeneration of the epithelium of the crypts and villi. As they proliferate and differentiate, these cells move along the basement membrane from the base of the crypts to the top of the villi, replacing aging and dying prismatic, goblet, and endocrine cells. Complete replacement of epithelial cells of the villi takes 3-5 days.

Cells with acidophilic granules (Paneth cells) located in groups in the bottoms of the crypts. These are prismatic cells, in the apical section of which there are large acidophilic (stained with acidic dyes) granules containing lysozyme (destroys bacterial cell membranes) and dipeptidases (enzymes that break down dipeptides to amino acids). Cell nuclei and cytoplasmic reticulum are displaced to the basal pole.

endocrinocytes: EC cells produce a hormone serotonin, which stimulates the secretory and motor activity of the stomach and intestines.

S cells develop secretin stimulating the secretion of pancreatic juice and bile.

I cells form cholecystokinin/pancreozymin, stimulating the secretion of the pancreas and contraction of the gallbladder.

A-like cells develop enteroglucagon, which increases blood sugar levels and stimulates mucus formation by the integumentary epithelium of the stomach.

D cells form somatostatin, and D1 cells vasointestinal polypeptide (VIP). Somatostatin suppresses the functions of the digestive system, VIP - relaxes smooth muscle, dilates blood vessels, lowers blood pressure.

lamina propria of the mucous membrane The small intestine is formed by loose, irregular connective tissue that forms the stroma of the villi and surrounds the crypts. It contains a large number of reticular and elastic fibers, plexuses of blood and lymphatic capillaries. It also meets lymphoid follicles, the number of which increases in the direction of the ileum. Lymphoid follicles are single and grouped, aggregate (Peyer's patches). The latter are clusters of up to 200 lymphoid follicles. There are about 30 of them and they are located mainly in the ileum. The mucous membrane covering the follicles does not have villi and crypts, and in the epithelium there are special M cells(microfolded). Their basal part forms folds where lymphocytes accumulate, to which M-cells present antigens that they receive as a result of phagocytosis of bacteria from the intestinal lumen. Then the lymphocytes go to the peripheral lymphoid organs, where they are cloned and returned in large numbers back to the intestine, where they turn into effector cells, for example, plasma cells that secrete immunoglobulins (antibodies), which enter the intestinal lumen and perform a protective function.

muscularis lamina The mucous membrane is poorly developed and is represented by two layers of smooth muscle cells.

Submucosa It is formed by loose, unformed connective tissue, in which the plexus of blood and lymphatic vessels and nerve plexuses (submucosal) are located. In the duodenum, there are end sections of glands . In structure, these are complex branched tubular glands. They secrete a mucous, alkaline secret that neutralizes the acid coming from the stomach with food. This is important because the digestive enzymes of the intestine and pancreas are active in an alkaline environment.

Muscular membrane consists of two layers of smooth muscle tissue: inner circular and outdoor longitudinal. However, both layers have a helical orientation. Between layers in an interlayer connective tissue intermuscular vascular and nervous plexus regulating motor activity, intestinal motility.

Serous membrane formed by a layer of loose connective tissue covered with mesothelium.

Up to 2 liters of secretions are produced daily in the small intestine ( intestinal juice) with a pH of 7.5 to 8.0. Sources of secretion - submucosal glands 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's glands protects the wall of the duodenum 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 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”).

Small intestine consists of 3 parts: 1) 12 duodenal (intestinum duodenum), 2) skinny (Intestinum jejunum) and 3) iliac (intestinum lleum). The wall of the small intestine consists of 4 membranes: 1) mucous membrane, including a layer of the epithelium, its own plate and muscular plate; 2) submucosa; 3) muscular membrane, consisting of the inner circular and outer longitudinal layers of smooth myocytes. and 4) sevbnoi. SOURCES OF DEVELOPMENT of the epithelium - intestinal endoderm, loose connective and smooth muscle tissue - mesenchyme, mesothelium of the serous membrane - visceral sheet of splanchnotome.

RELIEF (SURFACE) of the mucous membrane is represented by folds, villi and crypts (simple tubular glands). The folds of the mucous membrane are formed by the mucous membrane and the submucosa, have a circular direction and are called semilunar (plica semilunalls), or circular (plica circularls). VILLI (Villl Intestinalls) are protrusions of the mucous membrane, which include loose connective tissue of the lamina propria, smooth myocytes of the muscular lamina and a single-layer prismatic (intestinal) epithelium covering the villi. The composition of the villi also includes an arteriole branching into capillaries, a venule and a lymphatic capillary. The height of the villi in the duodenum is 0.3-0.5 mm; jejunum and ileum - up to 1.5 mm. The thickness of the villi in the duodenum is greater than that of the jejunum or ileum. There are up to 40 villi per 1 sq. mm in the duodenum, and no more than 30 in the jejunum and ileum.

The epithelium covering the villi is called columnar (eptheli-um colmnarae). It consists of 4 types of cells: 1) columnar epitheliocytes with a striated border (epitheliocytus columnar is cum lim-bus striatus); 2) M-cells (cells with microfolds): 3) goblet exocrinocytes (exocrinocyts caliciformis) and 4) endocrine, or basal-granular cells (endocrinocytus). Striated-rimmed columnar epitheliocytes are so named because they have microvilli on their apical surface. The average height of the microvilli is about 1 µm, the diameter is 0.01 µm, the distance between the microvilli is from 0.01 to 0.02 µm. Between the microvilli contains a highly active alkaline phosphatase, nucleoside diphosphatases, L-glycosidase, O-glycosidase, aminopeptidases. Microvilli contain microtubules and actin filaments. Thanks to these ultrastructures, microvilli carry out movement and absorption. The surface of microvilli is covered with glycocalyx. Digestion in a striated border is called parietal. In the cytoplasm of columnar epitheliocytes, EPS, the Golgi complex, mitochondria are well developed, there are lysosomes and contain multivesicular bodies (a vesicle or vesicle containing smaller vesicles) and microfilaments, which form a cortical layer in the apical part. The nucleus is oval, active, located closer to the basal part. On the lateral surface of columnar epitheliocytes in the apical part of the cells there are intercellular connections: 1) tight insulating contacts (zonula occludens) and 2) adhesive belts (zonula adherens), which close the intercellular gaps. Closer to the basal part of the cells, there are desmosomes and interdigitations between them. The lateral surface of the cell cytolemma contains Na-ATPase and K-ATPase. which are involved in the transport of Na and K through the cytolemma. The functions of columnar epithelial cells with a striated border: 1) produce digestive enzymes involved in parietal digestion, 2) participation in parietal digestion, and 3) absorption of cleavage products. M-CELLS are located in those places of the intestine where there are lymph nodes in the lamina propria of the mucous membrane. These cells belong to a variety of columnar epithelial cells, have a flattened shape. There are few microvilli on the apical surface of these cells, but the cytolemma here forms microfolds. With the help of these microfolds, M-cells capture macromolecules (antigens) from the intestinal lumen, endocytic vesicles are formed here, which then enter the lamina propria of the mucous membrane through the basal and lateral plasmolemma, come into contact with lymphocytes and stimulate them to differentiate. Goblet exocrinodites are mucous cells (mucocytes), have a synthetic apparatus (smooth EPS, Golgi complex, mitochondria), a flattened inactive nucleus is located closer to the basal part. A mucous secretion is synthesized on the smooth EPS, the granules of which accumulate in the apical part of the cell. As a result of the accumulation of secretion granules, the apical part expands and the cell acquires the shape of a glass. After secretion from the apical part, the cell again acquires a prismatic shape.

ENDOCRINE (ENTEROCHROSHRPHILIC) CELLS are represented by 7 varieties. These cells are contained not only on the surface of the villi, but also in the crypts. Crypts are tubular depressions located in the lamina propria. In fact, these are simple tubular glands. Their length does not exceed 0.5 mm. The composition of the crypts includes 5 types of epithelial cells; 1) columnar epitheliocytes (enterocytes), differ from the same cells of the villi by a thinner striated border: 2) goblet ekeocrinocytes are the same as in the villi:

3.) epithelial cells without a striated border are undifferentiated cells, due to which the epithelium of crypts and villi is renewed every 5-6 days; 4) cells with acidophilic granularity (Paneth cells) and 5) endocrine cells. CELLS WITH ACIDOPHILIAN GRAIN are located one by one or in groups in the area of the body and the bottom of the crypts. In these cells, the Golgi complex, granular ER, and mitochondria are well developed. located around the round core. In the apical part of the cells there are acidophilic granules containing a protein-carbohydrate complex. The acidophilia of the granules is explained by the presence of the alkaline protein arginine in them. The cytoplasm of cells with acidophilic granularity (Paneth cells) contains zinc and enzymes: acid phosphate, dehydrogenase and dipephydases, which break down dipeptides to amino acids, in addition, there is lysozyme, which kills bacteria. Functions of Paneth cells; cleavage of dipetidases to amino acids. antibacterial and neutralization of HC1. Crypts and villi of the small intestine represent a single complex due to: 1) anatomical proximity (the crypts open between the villi); 2) crypt cells produce enzymes involved in parietal digestion and 3) crypt and villus cells are renewed every 5-6 days due to undifferentiated crypt cells. ENDOCRINE CELLS of the villi and creep of the small intestine are represented by 1) Ec cells that produce serotonin, motilin and substance P; 2) A-cells that secrete enteroglucagon, which breaks down glycogen into simple sugars; 3) S-cells that produce secretin, which stimulates the secretion of pancreatic juice; 4) 1-cells that secrete cholecystokinin. stimulating liver function, and pancreozymin. activating the function of the pancreas; 5) G-cells. producing gastrin; 0) D-cells secreting somatostatin; 7) D1 cells that produce VIL (vasoactive intestinal peptide). The lamina propria of the mucous membrane is represented by loose connective tissue, which contains many reticular fibers and reticulo-like cells. In addition, in its own plate there are single lymphatic nodules (nodull lymphatlcl solita-rl), the diameter of which reaches 3 mm. and grouped lymph nodules (nodull lyinphatlcl aggregati), whose width is 1 cm and length up to 12 cm. starts to decrease. Functions of lymph nodes: hematopoietic and protective.

The muscular plate of the mucous membrane of the small intestine consists of 2 layers of smooth myocytes: internal circular and external longitudinal. Between these layers there is a layer of loose connective tissue. The submucosal basis consists of loose connective tissue, in which there are all plexuses: nervous, arterial, venous and lymphatic. In the submucosa of the duodenum there are complex branched tubular glands (giandulae submucosae). The terminal sections of these glands are lined mainly with mucocytes with a light cytoplasm, a flattened inactive nucleus. The cytoplasm contains the Golgi complex, smooth ER, and mitochondria; in the apical part, there are granules of mucous secretion. In addition, apical-granular, goblet, undifferentiated, and sometimes parietal cells are found in the terminal sections. The small ducts of the glands of the duodenum are lined with cuboidal epithelium, the larger ducts opening into the intestinal lumen are lined with columnar limbic. The secret of submucosal_zhedez has an alkaline reaction, contains di-peptidases. Meaning of the secret: it breaks down dipeptides to amino acids and alkalizes the acidic contents that came from the stomach into the duodenum. The MUSCLE COATING of the wall of the small intestine consists of 2 layers of smooth myocytes: the inner circular and the outer longitudinal. Between these layers there is a layer of loose connective tissue, in which 2 nerve plexuses are located: 1) the muscular-intestinal nerve plexus and 2) the muscular-intestinal sensitive nerve plexus. Due to the local contraction of the myocytes of the inner layer, the contents of the intestine are mixed, due to the friendly contraction of the inner and outer layers, peristaltic waves arise, which contribute to pushing food in the caudal direction. The serous membrane of the small intestine consists of a connective tissue base covered with mesothelium. The duplication of the serous membrane forms the mesentery of the intestine, which is attached to the dorsal wall of the abdominal cavity. In animals whose body occupies horizontal position , the intestine is suspended on the mesentery. Therefore, the intestines of animals always occupy the correct position, i.e. it does not rotate around the mesentery. In humans, the body is in a vertical position, therefore, conditions are created for the intestine to rotate around the mesentery. With a significant turn of the intestine around the mesentery, partial or complete obstruction occurs, which is accompanied by pain. In addition, the blood supply to the intestinal wall is disrupted and its necrosis occurs. At the first signs of intestinal obstruction, a person needs to give the body a horizontal position so that the intestines are suspended on the mesentery. This is sometimes enough for the intestine to take the correct position and restore its patency without surgical intervention. BLOOD SUPPLY OF THE SMALL INTESTINE is carried out at the expense of those arterial plexuses: 1) submucosal, located in the submucosal base; 2) intermuscular, located in a layer of connective tissue between the outer and inner muscle layers of the muscular membrane and 3) mucous, located in the lamina propria of the mucous membrane. Arterioles depart from these plexuses, branching into cacillaries in all membranes and layers of the intestinal wall. Atrerioles extending from the mucous plexus penetrate into each villus of the intestine and branch into capillaries that flow into the venule of the villus. Venules carry blood to the venous plexus of the mucosa, and from there to the plexus of the submucosa. LYMPH OUTFLOW from the intestine begins with lymphatic capillaries located in the villi of the intestine and in all its layers and membranes. Lymphatic capillaries empty into larger lymphatic vessels. through which lymph enters a well-developed plexus of lymphatic vessels located in the submucosa. The innervation of the SMALL INTESTINE is carried out by two intermuscular plexuses: 1) the muscular-intestinal plexus and 2) the sensitive muscular-intestinal plexus. SENSITIVE MUSCULAR-INTESTINAL nerve plexus is represented by afferent nerve fibers, which are dendrites of neurons coming from 3 sources: a) neurons of the spinal ganglia, b) sensory neurons of the intramural ganglia (Type II Dogel cells) and c) sensory neurons of the vagus nerve node. The musculo-intestinal nerve plexus is represented by various nerve fibers, including axons of neurons of sympathetic ganglions (sympathetic nerve fibers) and ascons of efferent neurons (Type II Dogel cells) embedded in the intramural ganglia. Efferent (sympathetic and parasympathetic) nerve fibers end with motor effectors on smooth muscle tissue and secretory ones on crypts. Thus, there are sympathetic and parasympathetic reflex arcs in the gut, which are already well known. In the gut there are not only three-membered, but also four-membered reflex sympathetic arcs. The first neuron of the four-membered reflex arc is the neuron of the spinal ganglion, the second is the neuron of the lateral intermediate nucleus of the spinal cord, the third neuron is in the sympathetic nerve ganglion, and the fourth is in the intramural ganglion. There are local reflex arcs in the small intestine. They are located in the intramural ganglia and consist of Type II Dogel cells, whose depdrites end in receptors, and whose axons end in synapses on Type I Dogel cells, which are the second neurons of the reflex arc. Their axons terminate in effector nerve endings. FUNCTIONS OF THE SMALL INTESTINE: 1) chemical processing of food; 2) suction; 3) mechanical (motor); 4) endocrine. CHEMICAL PROCESSING OF FOOD is carried out due to 1) intracavitary digestion; 2) parietal digestion and 3) parietal digestion. Intracavitary digestion is carried out due to the enzymes of pancreatic juice entering the duodenum. Intracavitary digestion provides splitting complex proteins to simpler ones. Parietal digestion is carried out on the surface of the villi due to enzymes produced in the crypts. These enzymes break down simple proteins into amino acids. Membrane digestion occurs on the surface of epithelial mucosal overlays due to intracavitary enzymes and enzymes produced in crypts. What are epithelial mucous overlays 7 The epithelium of the villi and crypts of the small intestine is updated every 5-G days. Rejected epithelial cells of crypts and villi are mucous epithelial overlays.

Cleavage of proteins in the small intestine is carried out with the help of trypsin, kinazogen, erypsin. Cleavage of nucleic acids occurs under the influence of nuclease. Cleavage of carbohydrates is carried out with the help of amylase, maltava, saccharase, lactase, glucosidases. Cleavage of lipids occurs due to lipases. The absorption function of the small intestine is carried out through a striated border of columnar epitheliocytes covering the villi. These villi are constantly contracting and relaxing. At the height of digestion, these contractions are repeated 4-6 times per minute. The contractions of the villi are carried out by smooth myocytes located in the stroma of the villus. Myocytes are located radially and obliquely with respect to the longitudinal axis of the villi. The ends of these myocytes are braided with reticular fibers. The peripheral ends of the reticular fibers are woven into the basement membrane of the epithelium of the villi, the central ends into the stroma surrounding the vessels inside the villi. With the contraction of smooth myocytes, there is a decrease in the volume of the stroma located between the vessels and the epithelium of the villi, and a decrease in the volume of the villi themselves. The diameter of the vessels, around which the stroma layer becomes thinner, does not decrease. Changes in the villi during their contraction create conditions for the entry of cleavage products into the blood and lymphatic capillaries of the villi. At the moment when smooth myocytes relax, the volume of the villi increases, intravillous pressure decreases, which favorably affects the absorption of cleavage products into the stroma of the villi. Thus, it seems that the villi are then increasing. then decreasing, they act like an eyedropper; when the rubber cap of the pipette is squeezed, its contents are released, when relaxed, the next portion of the substance is sucked. In 1 minute, about 40 ml of nutrients are absorbed in the intestines. PROTEIN ABSORPTION is carried out through the brush border after their splitting to amino acids. LIPID ABSORPTION IS CARRIED OUT IN 2 WAYS. 1. On the surface of the striated border, with the help of lipase, lipids are broken down to glycerol and fatty acids. Glycerin is absorbed into the cytoplasm of epithelial cells. Fatty acids undergo esterification, i.e. with the help of cholinesterol and cholinesterase, they are converted into fatty acid esters, which are absorbed through the striated border into the cytoplasm of columnar epitheliocytes. In the cytoplasm, esters decompose with the release of fatty acids, which, with the help of kinasogen, combine with glycerol. As a result, lipid droplets with a diameter of up to 1 micron are formed, called chylomicrons. Chylomicrons then enter the stroma of the villi, then into the lymphatic capillaries. The 2nd WAY of lipid absorption is carried out as follows. On the surface of the striated border, lipids are emulsified and combined with protein, resulting in the formation of droplets (chylomicrons) that enter the cytoplasm of cells and intercellular spaces, then into the stroma of the villi and the lymphatic capillary. The MECHANICAL FUNCTION of the small intestine is to stir and push the chyme in a caudal direction. The endocrine function of the small intestine is carried out due to the secretory activity of endocrine cells located in the epithelium of the villi and crypts.

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 section 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 mucous membrane 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.

Substrates are broken down in the small intestine 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 oral cavity 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.

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.
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.
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 colon 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 diets.

Causes of flatulence
Diseases that provoke flatulence
Flatulence during pregnancy
The course of the disease
Flatulence treatment
Medicines
Folk recipes
Power correction
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:

Stress, causing muscle spasms and slowing down of the intestines. At the same time, sleep is disturbed. Most often, the disease occurs in women.
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.
Adhesions and tumors. They also interfere with the normal movement of food masses.
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:

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.
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.
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.
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.
With enteritis, the mucosa of the small intestine is deformed. As a result, the absorption of food and its processing are disturbed.
The same thing happens during colitis. The balance of the intestinal microflora is disturbed. These changes lead to increased gas formation.
In cirrhosis, the liver cannot secrete bile properly. As a result, fats are not fully digested. Increased gas formation usually occurs after fatty foods.
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.
With obstruction of the gastrointestinal tract, its peristalsis is disturbed due to a mechanical obstacle (helminths, neoplasms, foreign bodies, etc.).
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.
With intestinal atony, the rate of movement of feces and chyme is significantly reduced, which causes the accumulation of gases.
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.
With neurosis nervous system 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 should not take many medicines, and folk methods not all will fit. 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. Medications should only be prescribed 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:

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 fullness.
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:

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.
Crushed carrot seeds. They need to drink 1 tsp. per day for bloating.
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.
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.
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. For this, parsley root (1 tsp) is infused for 20 minutes in a glass 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.

All foods with coarse fiber are removed from the diet.
You can not eat legumes, cabbage and other foods that cause fermentation in the intestines.
If lactose intolerance is observed, the amount of milk sugar and calories in the diet is reduced.
Meat and fish should be lean, steamed or boiled. Bread is eaten dried or stale.
Of vegetables, carrots, beets, cucumbers, tomatoes and spinach are allowed.
You can eat fat-free yogurt and cottage cheese.
Porridges are prepared only from brown rice, buckwheat or oatmeal.
It is necessary to abandon fried foods, smoked meats and pickles.
Do not drink carbonated and alcoholic drinks.

In the mucous membrane of the small intestine there are glandular cells located on the villi, which produce digestive secrets that are secreted into the intestine. These are Brunner's glands of the duodenum, Lieberkün's crypts of the jejunum, and goblet cells.

Endocrine cells produce hormones that enter the intercellular space, and from there are transported to the lymph and blood. Cells secreting protein secretion with acidophilic granules in the cytoplasm (Paneth cells) are also localized here. The volume of intestinal juice (normally up to 2.5 liters) may increase with local exposure to certain food or toxic substances on the intestinal mucosa. Progressive dystrophy and atrophy of the mucous membrane of the small intestine are accompanied by a decrease in the secretion of intestinal juice.

Glandular cells form and accumulate a secret and, at a certain stage of their activity, are rejected into the intestinal lumen, where, disintegrating, they release this secret into the surrounding fluid. Juice can be divided into liquid and solid parts, the ratio between which varies depending on the strength and nature of the irritation of the intestinal cells. The liquid part of the juice contains about 20 g/l of dry matter, which consists partly of the content of desquamated cells coming from the blood of organic (mucus, proteins, urea, etc.) and inorganic substances - about 10 g/l (such as bicarbonates, chlorides, phosphates). The dense part of the intestinal juice looks like mucous lumps and consists of undestroyed desquamated epithelial cells, their fragments and mucus (goblet cell secretion).

In healthy people, periodic secretion is characterized by relative qualitative and quantitative stability, which contributes to maintaining the homeostasis of the enteric environment, which is primarily chyme.

According to some calculations, in an adult with digestive juices, up to 140 g of protein per day enters food, another 25 g of protein substrates is formed as a result of desquamation of the intestinal epithelium. It is not difficult to imagine the significance of protein losses that can occur with prolonged and severe diarrhea, with any form of indigestion, pathological conditions associated with enteral insufficiency - increased intestinal secretion and impaired reabsorption (reabsorption).

The mucus produced by the goblet cells of the small intestine is an important component of secretory activity. The number of goblet cells in the villi is greater than in the crypts (up to approximately 70%) and increases in the distal small intestine. Apparently, this reflects the importance of the non-digestive functions of mucus. It has been established that the cellular epithelium of the small intestine is covered with a continuous heterogeneous layer up to 50 times the height of the enterocyte. This epithelial layer of mucous overlays contains a significant amount of adsorbed pancreatic and a small amount of intestinal enzymes that implement the digestive function of mucus. The mucous secretion is rich in acidic and neutral mucopolysaccharides, but poor in proteins. This provides the cytoprotective consistency of the mucous gel, mechanical, chemical protection of the mucous membrane, prevention of penetration into the deep tissue structures of large molecular compounds and antigenic aggressors.