Small intestine (Intestinum Tenue) - Department digestive tractlocated between the stomach and the colon. The small intestine with thick forms the intestines is the longest part of the digestive system. As part of the small intestine, a duodenum, skinny, ileum is distinguished. In the small intestine, chimus (food cashem), treated with saliva and gastric juice, is exposed to intestinal and pancreas, as well as bile. In the lumen of the small intestine, with stirring of Himus, its final digestion and suction of products of its splitting occur. Food residues are moving into a colon. Endocrine function of the small intestine is important. Endocrinocytes of its coating epithelium and glands produce biologically active substances (secretin, serotonin, motilin, etc.).

The small intestine begins at the border level of the bodies of the thoracic and I lumbar vertebrae, ends in the right iliac hole, is located in the region of the ward (the average area of \u200b\u200bthe abdomen), reaching the entrance to a small pelvis. The length of the small intestine in an adult is 5-6 m. Men have an intestine longer than in women, while in a living person a small intestine is shorter than that of a corpse that has no muscle tone. Length duodenal gut is 25-30 cm; About 2/3 of the length of the small intestine (2-2.5 m) occupies a skinny and approximately 2.5-3.5 m - the ileum. The diameter of the small intestine is 3-5 cm, it decreases towards the colon. The duodenum does not have a mesense in contrast to the skinny and iliac guts, which are called the mesenteric part of the small intestine.

Skinny intestine (Jejunum) and the iliac (Ileum) make up the mesenteric part of the small intestine. Most of them is located in the umbilical area, forming 14-16 loops. Part of the loops descends into a small pelvis. The hinges of the hectic intestine mainly lie in the left top, and the iliac - in the right bottom abdominal cavity. The strict anatomical boundary between the skinny and the ileum is absent. Kepened from intestinal loops is a large gland, rear - parietal peritone, lining the right and left mesenteric sinuses. Skinny and iliac guts with mesenter are connected to the back of the abdominal cavity. The root of the mesentery ends in the right iliac yam.

The walls of the small intestine are formed by the following layers: mucous membrane with a submucosal base, muscular and outer shells.

The mucous membrane (Tunica Mucosa) of the small intestine has circular (kerkring) folds (Placae Circularis). Their total number reaches 600-700. The folds are formed with the participation of the submembrance base of the intestine, their dimensions decrease towards the colon. The average height of folds is 8 mm. The presence of folds increases the surface area of \u200b\u200bthe mucous membrane by more than 3 times. In addition to circular folds, longitudinal folds are characteristic of the duodenal. They are in the upper and downstairs of the duodenum. The most pronounced longitudinal fold is located on the medial wall of the descending part. In her lower department There is an elevation of the mucous membrane - large papilla duodenal gut(Papilla Duodeni Major), or nipple fare.Here the shared opening opens the overall bull duct and the pancreatic duct. Up from this papilla on the longitudinal fold is available small duodenal nipples(Papilla Duodeni Minor), where the supplement of the pancreas opens.

The mucous membrane of the small intestine has numerous grown - intestinal villi (Villi Intestinales), there are about 4-5 million on the square of 1 mm 2 mucous membranes of the duodenum and the skinny intestine. The average length of the villi is 0.7 mm. The dimensions of the villi decrease towards the ileum. Allocate sheet-, tongue, finger-shaped veins. The first two types are always oriented across the axis of the intestinal tube. The longest patches (about 1 mm) have predominantly leaf shape. At the beginning of the church, VILLINs usually have a tong form. Distal form Village becomes a finger, their length is reduced to 0.5 mm. The distance between the Villages is 1-3 microns. Pork is formed by a loose connective tissue covered with epithelium. In the thickness of the Village, many smooth mioitates, reticular fibers, lymphocytes, plasma cells, eosinophils. In the center of Village is a lymphatic capillary (Milky Sinus), around which blood vessels are located (capillaries).

From the surface of intestinal patches are covered with single-layer high cylindrical epitheliumlocated on the basal membrane. The main mass of epithelocytes (about 90%) is columnar epitheliocytes with a barn brush cut. Kaimka is formed by microvills of apical plasma membrane. On the surface of the microorus sheet is a glycocalix, represented by lipoproteins and glycosaminoglycans. The main function of the column epitheliocytes is absorption. The composition of the coating epithelium includes many glass-shaped cells - single-cell glands secreting mucus. On average, 0.5% of the cell epithelium cells falls on endocrine cells. In the thickness of the epithelium there are also lymphocytes penetrating from the stroma of the villi through the basal membrane.

In the lumens between the vaults on the surface of the epithelium of the entire small intestine, intestinal glands are opened (Glandulae Intestinales), or crypts. In the twelfth gauge there are also mucous duodenal (brunner) gland complex tubular shapes located mainly in the submucosal basis, where they form slices with dimensions of 0.5-1 mm. Intestinal (Liborkyunovs) The small intestine gland has a simple tubular shape, they occupy a place in their own plate of the mucous membrane. The length of the tubular glands is 0.25-0.5 mm, the diameter is 0.07 mm. On an area of \u200b\u200b1 mm 2 mucous membranes of the small intestine, there are 80-100 intestinal glands, their walls are formed by one layer of epithelocytes. In total, in the small intestine there are more than 150 million glands (Crypt). Among epithelial cells The glands are distinguished by columnar epithelocytes with a barreled cut, glassoid cells, intestinal endocrinocytes, adaptable cylindrical (stem) cells and patenet cells. Stem cells are a source of intestinal epithelium regeneration. Endocrinocytes produce serotonin, cholecystokinin, secretine, etc. Patenet cells secrete Erepsin.

For its own plate mucosa, the small intestine is characterized by a large number of reticular fibers that form a thick network. In its own plate, lymphocytes, plasma cells, eosinophils, a large number of single lymphoid nodules are always present (in children - 3-5 thousand).

In the mesenteric part of the small intestine, especially in iliac, there are 40-80 lymphoid, or peer, plaques (Noduli Lymfoidei aggregati), which are accumulated by single lymphoid nodules that are organs of the immune system. Plaques are located preferably in the anti-raccane edge of the intestine, have an oval shape.

Muscular mucosa plate (Lamina Muscularis Mucosae) has a thickness of up to 40 microns. It differs in the inner circular and outer longitudinal layers. From the muscular plate into the crowd of its own plate of the mucous membrane and in the sublimatural basis, separate smooth myocytes are deployed.

The sublifted base (Tela submucosa) of the fine intestine is formed by a loose fiber junction. It is thicker there are branches of blood and lymphatic vessels and nerves, various cell elements. 6 submucosity of the duodenum are the secretory departments of duodenal (brunper) glands.

Muscular shell (Tunica Muscularis) The small intestine consists of two layers. The inner layer (circular) thickness of the outer (longitudinal) layer. The direction of the beams of myocytes is not strictly circular or longitudinal, but has a spiral move. In the outer layer of the coil spirals are more stretched compared to the inner layer. Nervous plexus and vessels are located between the muscle layers in the loose connective tissue.

The delicious intestine includes three departments: a duodenum, skinny and iliac.

In the small intestine, all kinds of nutrients are chemical treatment - proteins, fats and carbohydrates.

In the digestion of proteins, the enzymes of pancreatic juice (tripsin, chymotrypsin, collagenase, elastase, carboxylase) and intestinal juice (aminopptidase, leucinopeptidase, alanineptidase, tripeptidases, dipeptidases, enterocinate) are involved.

Enterokinase is produced by the cells of the intestinal mucosa in inactive form (kinasegen), ensures the transformation of the inactive tripsinogen enzyme into the active tRIPSIN. Peptidases provide further consistent hydrolysis of peptides, which began in the stomach, to free amino acids, which are absorbed by the intestinal epithelocytes and enroll into the blood.

In the digestion of carbohydrates, pancreatic enzymes and intestinal juice are also involved: β- amylase, amylo-1,6-glucosidase, oligo-1,6-glucosidase, malalhaz (α-glucosidase), lactase, which split polysaccharides and disaccharides to simple sugars (monosaccharides) - glucose, fructose, galactose, absorbed by epitheliocytes of intestines and entering blood.

Pancreatic lipases, splitting triglycerides, and intestinal lipase, providing hydrolytic splitting of monoglycerides. Products splitting fat in the intestines are fatty acids, glycerin, monoglycerides, which come to the blood and mostly in the lymphatic capillaries.

In the small intestine process occurs suction Split products of proteins, fats and carbohydrates in blood and lymphatic vessels. In addition, the intestine performs a mechanical function: pushes the chimus in the caudal direction. This function is carried out due to peristaltic abbreviations of the muscle shell of the intestine. The endocrine function performed by special secretory cells is to develop biologically active substances - serotonin, histamine, motilin, secretine, enteroglucastagon, cholecystokinin, pancreativity, gastrine and gastroin inhibitor.

Development. The small intestine begins to develop on the 5th week of embryogenesis. Pork epithelium, crypt and duodenal glands of the small intestine are formed from intestinal entoderma. In the first phases of the differentiation of the epithelium, single-row cubic, then it becomes a two-row prismatic, and, finally, a single-layer prismatic epithelium is formed on the 7-8th week. For the 8-10th week of development, VILROWN and Crypts arise. Circular folds are formed during the 20-24th week. By this time, duodenal glands appear. The cells of the intestinal epithelium in a 4-week embryo are not differentiated and characterized by high proliferative activity. Differentiation of epithelocytes begins on the 6-12th week of development. There are columnar (carbonated) epithelocytes for which the intensive development of microwaves that increase the resorption surface is characterized. Glycocalix begins to form by the end of the embryonic - the beginning of the fruit period. At this time, ultrastructural signs of resorption are observed in epithelocytes - a large number of vesicles, lysosomes, multi-mezzular and Mescal Taurus. Box and shaped exocrinocytes are differentiated at the 5th week of development, endocrinocytes - at the 6th week. At this time, transitional cells with undifferentiated granules prevail among endocrinocytes, EU cells, G-cells and S cells are detected. EU cells are dominated in the fetal period, most of which are not reported to the crypt lumen ("closed" type); In a later flicer period, the "open" cell type appears. Exocrinocytes with acididophilic granules are unoccupied in the embryos and fruit of man. The own plate of the mucous membrane and the submucoscent base of the small intestine are formed from the mesenchym on the 7-8th week of embryogenesis. Smooth muscular fabric in the wall of the small intestine develops from the mesenchyma undesown in various sections intestinal wall: At the 7-8th week, the inner circular layer of the muscular shell appears, then on the 8-9th week - the outer longitudinal layer, and, finally, the muscle plate of the mucous membrane occurs on the 24-28th week of development of the fetus. The serous sheath of the small intestine is laid at the 5th week of embryogenesis from the mesenchym (its connecting part) and visceral sheet of mesoderm (her mesothelium).

Structure. The wall of the small intestine is constructed from the mucous membrane, the submissible base, muscular and serous shells.

The inner surface of the small intestine has a characteristic relief due to the presence of a number of formations - circular folds, vile and crypt (Liborku's intestinal glands). These structures increase the total surface of the small intestine, which contributes to the performance of its basic functions of digestion. Intestinal patches and crypts are the main structural-functional units of the mucous membrane of the small intestine.

Circular folds (picae Circulares.) Educated mucous membrane and submucosal base.

Intestinal villi. (villi Intestinales.) They are protruding the flip-or-shaped mucous membrane, freely walking into the slope of the small intestine.

The shape of the villi in the newborn and in the early postal period of the finance period, and adults are flattened - sheet. The flap of the formated form has two surfaces - cranial and caudal and two edges (ridges).

The number of Village in the small intestine is very large. Most of all in the duodenum and a flowable intestine (22-40 Village per 1 mm2), are somewhat less - in the ileum (18-31 Villas per 1 mm2). In the Villina wide and short (the height of them is 0.2-0.5 mm), in the skinny and iliac intestine they are somewhat thinner, but above (up to 0.5-1.5 mm). The structural elements of all layers of the mucous membrane participate in the formation of each villus.

Intestinal crypts (Libekyun glands) ( cryptae Seu Glandulae Intestinales) Present the recesses of the epithelium in the form of numerous tubes lying in their own plate of the mucous membrane. Their mouths are opened in the clearance between Villas. On 1 mm2 of the surface of the intestine accounts for up to 100 crypt, and in total in the small intestine more than 150 million crypt. Each crypt has a length of about 0.25-0.5 mm, the diameter is up to 0.07 mm. The total area of \u200b\u200bKrypt in the small intestine is about 14 m2.

Mucous membrane small intestine consists of single-layer Prismatic Carbon Epithelium (epithelium Simplex Columnarum Limbatum), own layer of mucous membrane ( lamina Propria Mucosae.) and muscle layer of the mucous membrane ( lamina Muscularis Mucosae.).

The epithelial shape of the small intestine contains four main cell populations:

• stop epithelocytes ( epithelioCyti Columnares.),
• box and shaped exocrinocytes ( exocrinocyti Calciformes.),
• patenet cells, or apocrinocytes with acidophilic granules ( exocrinocyti Cum Granulis Acidophilis),
• endocrinocytes ( endocrinocyti.), or K-cell (Kulchitsky cells),
• as well as m-cells (with microscopes), which are modifications of columnar epithelocytes.

The source of development of these populations is stem cells located at the bottom of Kripte, of which commed precursor cells are first formed, which are divided by mitosis and differentiate into a specific appearance of epithelocytes. Previous cells are also in crypta, and in the differentiation process moves in the direction of the vertex of the villus, where differentiated cells are located incapable of division. They finish the life cycle here and are listed. The entire cycle of update of epithelocytes in a person is 5 ... 6 days.

Thus, the epithelium crypt and the villi represents a unified system in which several can be distinguished cell compartmentslocated at various stages of differentiation, and each compartment is about 7 ... 10 cell layers. All intestinal crypt cells are one clone, i.e. are descendants of one stem cell. The first compartment is represented by 1 ... 5 rows of cells in the basal part of the crypt - combined precursor cells of all four types of cells - columnar, glassoid, panetive and endocrine. Panketovsky cells differentiated from stem cells and precursor cells are not moved, but remain at the bottom of the crypt. The remaining cells after 3-4 divisions of precursor cells in crypts (a transit population that makes up the 5-15-e-rows of cells) is moved to the navinku, where they make a transit-undeted population and a population of differentiated cells. Physiological regeneration (Update) Epithelium in the Krypt-Persink complex is provided by the mitotic division of precursor cells. The reparative regeneration is based on a similar mechanism, and the epithelial defect is eliminated by the reproduction of cells.

In addition to epithelocytes, lymphocytes located in the epithelial reservoir can be located in the intercellular spaces and then migrating in l. Propria. And hence in lymphocapillary. Lymphocytes are stimulated by antigens entering the intestines, and play an important role in the immunological protection of the intestine.

The structure of intestinal villi

From the surface of each intestinal pork is lined with a single-layer prismatic epithelium. The epithelium distinguishes the three main types of cells: columnar epithelocytes (and their variety - M-cells), glass-shaped exocrinocytes, endocrinocytes.

Star epithelocytes Vile ( epithelioCyti Columnares Villi.), or enterocytes, constitute the bulk of the epithelial reservoir covering the Vorsinka. These are prismatic cells characterized by a pronounced polarity of the structure, reflecting their functional specialization - ensuring resorption and transport of substances coming from food.

On the apicial cell surface is available standing Kaimka (limbus Striatus.), formed by many microvones. The number of microwaves per 1 μm2 of the cell surface is from 60 to 90. The height of each microville in humans is about 0.9-1.25 μm, the diameter is 0.08-0.11 μm, the gaps between microvills are 0.01-0.02 μm. Thanks to a huge number of microwaves, the absorption surface of the intestine increases at 30 ... 40 times. In microwaves there are thin filaments and microtubules. In each microvinka, there is a central part where the bunch of actin microfilaments is vertically located, which are connected on one side with the plasmolem of the tip of the villi, and at the base of the villus are connected to the terminal network - horizontally oriented microfulats in the apical part of the enterocyt cytoplasm. This complex provides a reduction in microvascular during the suction process. On the surface of the microorusok is a glycocalix represented by lipoproteins and glycoproteins.

In the plasmolem and glycicalce MicroSorsok of a barreled Kaimki detected high content Enzymes involved in the splitting and transport of suction substances: phosphatases, nucleosideidididide phosphatases, L-, D-glycosidases, aminoptidases, etc. The phosphatase content in the epithelium of the small intestine exceeds their level in the liver almost 700 times, and 3/4 of their quantity is in the car . It has been established that the splitting of food substances and absorption them are most intensively in the area of \u200b\u200bthe running kaim. These processes were called prieuchena and membrane digestion In contrast, the intestinal tube, and intracellular, which is intertwined.

In the apical part of the cell there is a well-pronounced terminal layer, which consists of a network of filaments located parallel to the cell surface. The terminal network contains actin and mosic microfilaments and is connected to the intercellular contacts on the side surfaces of the apical parts of enterocytes.

In the apicial parts of enterocytes there are connecting complexes consisting of two types of dense insulating contacts ( zonula Occludens.) and adhesive belts, or tapes ( zonula adherens.) connecting neighboring cells and closing the message between the intestinal lumen and intercellular spaces.

With the participation of the microfilaments of the terminal network ensures the closure of intercellular slots between enterocytes, which prevents the flow of various substances in the process of digestion. Under the terminal network in the apical part of the enterocyte there are tubes and tanks with a smooth endoplasmic network involved in the suction processes of fats, as well as mitochondria, ensuring the energy of the processes of suction and transport of metabolites.

In the basal part of the bond epithelocyte are the core of the oval shape, the synthetic apparatus - ribosomes and the granular endoplasmic network. The Golges apparatus is located above the core, while its tanks lie vertically with respect to the surface of enterocyte. The lysosomes and secretory vesicles forming in the area of \u200b\u200bthe Golgji apparatus are moved to the apical part of the cell and are localized directly under the terminal network and along the lateral plasmolemma.

It is characteristic of the presence between the basal parts of the enterocytes of wide intercellular spaces, limited by their lateral plasmolemmas. On lateral plasmamams there are folds and processes that are connected to the iszhats of neighboring cells. With the active suction of fluid, the folds are placed and the volume of the intercellular space increases. In the basal parts of enterocytes there are subtle lateral basal processes in contact with similar processes of neighboring cells and lying on the baseal membrane. Basal processes are connected by simple contacts and ensure the closure of the intercellular space between enterocytes. The presence of intercellular spaces of this type is characteristic of the epithelials involved in fluid transport; In this case, the epithelium functions as a selective barrier.

In the lateral plasmolem of enterocyte, enzymes of the transport of ions (Na +, K + -Aftaz) are localized, which play an important role in the transfer of metabolites from apical plasmolem to lateral and in the intercellular space, and then through the basal membrane in l. Propria. and capillaries.

Enterocytes also perform a secretory function, producing metabolites and enzymes necessary for terminal digestion (entry and membrane). The synthesis of secretory products occurs in the granular endoplasmic network, and the formation of secretory granules - in the Golgi apparatus, from where secretory vesicles containing glycoproteins are transported to the cell surface and are localized in apical cytoplasm under the terminal network and along the lateral plasmolemma.

M-cells (cells with microscopes) are a type of enterocytes, they are located on the surface of group lymphatic follicles (peer plaques) and single lymphatic follicles. They have a complicated form, a small number of microvones and obtained their name due to the presence of microslosts on their apical surface. With the help of microslosts, they are able to capture macromolecules from the intestinal lumen and form endocytosis vesicles transported to basolateral plasmolsters and further into the intercellular space. Thus, an antigen estate can come from the cavity, which attract lymphocytes, which stimulates in the lymphoid tissue of the intestine.

Box-shaped exocrinocytes (exocrinocyti Caliciformes.) There are one in the vile among the columnar cells. Their number increases in the direction of the duodenum to the iliac. In its structure, these are typical mucous cells. They are observed cyclic changesassociated with accumulation and subsequent secretion of mucus. In the accumulation phase, the core of these cells is pressed to their base, the cells of the mucus are visible in the cytoplasm of cells above the core. The Golgi and Mitochondria apparatus are located near the kernel. The formation of the secret takes place in the area of \u200b\u200bthe Golgi apparatus. In the stage of accumulation of mucus in the cell, a large number of highly modified mitochondria is found. They are large, bright, with short cristes. After the secretion of the secretion, the bundle cell becomes narrow, the kernel decreases, the cytoplasm is exempt from the pellets of the secret. The mucus secreted by glass-like exocrinocytes serves to moisturize the surface of the intestinal mucosa and it helps to promote food particles, and also participates in the processes of the on-sleep digestion. Under the epithelium of the villi is the basal membrane, followed by a loose fiber junction tissue of its own plate mucosa. It takes the blood and lymphatic vessels and nerves oriented along Village. There are always separate smooth muscle cells in the stroma, derivatives of the muscle layer of the mucous membrane. Bundles of smooth myocytes are wrapped with a network of reticular fibers that bind them with a stroma villus and a basal membrane. The reduction of myocytes contributes to the pushing of the aggravated food hydrolysis products into the blood and the lummy of the bowl of the intestine. Other bundles of smooth muscle cells penetrating into the submembratus base form circular layers around vessels passing there. Reducing these muscular groups regulates blood supply.

The structure of intestinal crypta

Epithelial lining of intestinal crypt contain stem cells, precursor cells of columnar epithelocytes, glassoid exocrinocytes, endocrinocytes and patenet cells (exocrinocytes with acidophilic granules) at all stages of development.

Stop epithelocytes constitute the bulk of the crypt epithelium. Compared to similar cells, the villies are lower, have a more subtle run out of the cut and the basophilic cytoplasm. In the epithelialocytes of the lower half crypt often visible figures of mitosis. These elements serve as a source of regeneration for both epithelial cells of porcelines and crypt cells. Wine-shaped exocrinocytes are constantly in the crypts, their structure is similar to those described in the Village. Exocrinocytes with acididophilic granules ( exocrinocyti Cum Granulis Acidophilis, S PANETH), or Patenet cells are located in groups or one by the bottom of the crypt. In their apical parts, dense strongly refractive lights of granules are visible. These granules are sharply acididophone, stained with eosin in bright red, dissolve in acids, but stable to alkalis. Cytochemically, the granules found a protein-polysaccharide complex, enzymes (dipeptidases), lizozyme. In the cytoplasm of the basal part there is significant basophilia. A little mitochondria is located around a large rounded kernel, the Golgji apparatus is located above the core. Acidophilia granules are due to the presence of a rich arginine protein. In the PAnet cells, a large amount of zinc was revealed, as well as enzymes - acid phosphatases, dehydrogenase and dipeptidases. The presence of a number of enzymes in these cells indicates the participation of their secret in the processes of digestion - the splitting of dipeptides to amino acids. An equally important is the antibacterial function of the secret, associated with the production of lysozyme, which destroys the cell walls of bacteria and the simplest. Thus, PAnet cells play an important role in the regulation of the bacterial flora of the small intestine.

Endocrinocyte In Kripte, much more than in Villas.

The most numerous are EU cellssecreting serotonin, Motilin and substance P. A-cells, producing enterogllucagon, small. S-cellsproducing secretin, distributed in different intestinal deposits irregularly. In addition, the intestines found I-cellssecreting cholecystokinin and pancreatimine - biologically active substances that have a stimulating effect on the function of the pancreas and liver. Detected also found G-cellsproducing gastrin, D- and D1 cells producing active peptides (somatostatin and vasoactive intestinal peptide - VIP).

For its own plate mucous membrane, the content of a large number of reticular fibers is characterized. They form a thick network throughout their own record and, applying to the epithelium, are involved in the formation of the basal membrane. The process cells similar to the structure with reticular cells are closely connected with reticular fibers. In its own plate there are constantly eosinophils, lymphocytes, as well as plasma cells. It has vascular and nervous plexuses.

The muscular plate of the mucous membrane consists of two layers: internal circular and external (more loose) - longitudinal. Thickness of both layers of about 40 microns. They also have ore-running bundles of muscle cells. From the inner circular muscular layer, individual muscle cells are deployed into the own plate of the mucous membrane.

Sublifier base Often it contains slices. It contains vessels and sublimated nervous plexus.

Muscular shell The small intestine consists of two layers: internal - circular (more powerful) and outdoor - longitudinal. The direction of the stroke of the muscle cells in both layers is not strictly circular and longitudinal, but spiral. In the outer layer of curls of the spirals are more stretched compared to the inner layer. Between the muscle layers there is a layer of loose fibrous connective tissue, in which the nodes of the muscular-intestinal nerve plexus and vessels are located.

The function of the muscular shell is stirring and pushing the chimus along the intestine. In the small intestine distinguish between two species. Local abbreviations are due mainly by the abbreviations of the inner layer of the muscular shell. They are committed rhythm - 12-13 times per minute. Other reductions - peristaltic - are caused by the effect of muscle elements of both layers and distributed sequentially along the entire length of the intestine. Peristaltic cuts are stopped after the destruction of the muscular-intestinal nerve plexus. The increase in the peristaltics of the small intestine occurs when the sympathetic (?) Nerves are excited, weakening - when the wandering nerve is excited.

In the mucous membrane of the small intestine there are ferrous cells located on vile, which produce digestive secrets that are distinguished by the intestine. This is the Brunner of the duodenal gland, the crippes of the cushion, glass-shaped cells.

Endocrine cells produced hormones that enter the intercellular space, and where they are transported in lymph and blood. Here the cellular cells with acidophilic granules in the cytoplasm (PAnet cells) are localized here. The volume of intestinal juice (normally up to 2.5 liters) may increase with the local exposure of some food or toxic substances on the intestinal mucosa. The progressive dystrophy and atrophy of the mucous membrane of the small intestine is accompanied by a decrease in the secretion of intestinal juice.

The glandular cells form and accumulate the secret and at a certain stage of their activities are rejected into the intestinal lumen, where, decaying, give this secret into the surrounding fluid. Juice can be divided into liquid and dense parts, the ratio between which changes depending on the strength and nature of the irritation of intestinal cells. The liquid part of the juice contains about 20 g / l of dry matter, consisting partially from the contents of desquamidated cells coming from the blood of organic (mucus, proteins, urea, etc.) and inorganic substances - approximately 10 g / l (such as bicarbonates, chlorides, phosphates). The dense part of the intestinal juice has the form of mucous lumps and consists of non-destructive deskvamated epithelial cells, fragments and mucus (secrets of glassoid cells).

In healthy people, periodic secretion is characterized by relative qualitative and quantitative stability, which contributes to maintaining the homeostasis of the enteral medium, which is primarily a chimus.

According to some calculations, an adult with digestive juices enters up to 140 g of protein per day, another 25 g of protein substrates is formed as a result of the desquamation of intestinal epithelium. It is not difficult to present the significance of protein losses that can occur with a long and heavy diarrhea, with any forms of digestive disorders, pathological conditions associated with enteral insufficiency - enhanced sublock secretion and impaired reverse absorption (reabsorption).

The mucus synthesized by glass-shaped cells of the small intestine is an important component of secretory activity. The number of glazing cells in the composition of the villi is greater than in the crypta (approximately 70%), and increases in the distal sections of the small intestine. Apparently, this reflects the importance of non-oxide mucus functions. It has been established that the cellular epithelium of the small intestine is coated with a solid heterogeneous layer with a thickness of up to 50-fold height of enterocyte. In this overpithelial layer of mucous overlays, there is a significant amount of adsorbed pancreatic and minor number of intestinal enzymes that implement the digestive function of the mucus. The mucous secret is rich in acidic and neutral mucopolysaccharides, but poor proteins. This provides the cytoprotective consistency of the mucous gel, mechanical, chemical protection of the mucous membrane, preventing the penetration into the deep structure of the tissue of large-molecular compounds and antigenic aggressors.

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Stomach

The muscular wall of the stomach consists of three layers of smooth muscles: the outer longitudinal, medium circular, internal oblique. There are nervous plexuses between muscle layers. Outside the stomach, almost from all sides is covered with a serous shell. The cavity of the stomach is lined with a mucous membrane covered with single-layer cylindrical epithelium. Due to the presence of a muscular plate and a submucosal base, the mucous membrane forms numerous stomach folds. On the surface of the mucous membrane there are gastric foxes, at the bottom of which are opening numerous gastric glands.

The glands, depending on their location, are divided into the foundal (the most numerous, located in the body and the day of the stomach, secrete pepsinogen, hydrochloric acid, mucus and bicarbonate); Cardial (produces mucous secret) and pyloric (secrete mucus and intestinal hormone hormone) (Fig. 2).

Gastric glands are secreted per day 2-3 liters of gastric juice containing water, hydrochloric acid, pepsinogen, bicarbonate, mucus, electrolytes, lipase and internal caste factor - an enzyme that translates the inactive shape of vitamin B 12 coming from food to active, digested . In addition, the intestinal hormone hormone is secreted in the pyloric gastric pharmaceutical department.

The mucus covers the entire inner surface of the stomach, forming a layer with a thickness of about 0.6 mm, which envelops the mucous membrane and protects it from mechanical and chemical damage.

The main cells of the gastric glands secrete pepsinogen, which under the action of HCl turns into an active proteolytic pepsin enzyme. The latter manifests its specific activity only in an acidic medium (the optimal RN range is 1.8-3.5). In an alkaline medium (pH 7.0), pepsin is irreversibly denatured. There are several pepsin isoforms, each of which affects its protein class. The shell cells have a unique ability to secrete into the lumen of the stomach strongly concentrated hydrochloric acid in the form of H + and CL ions.

Fig. 2. Structure of the secretory function of the stomach.

Regulation of gastric secretion occurs as follows. The increase in the secretion of hydrochloric acid occurs under the action of nervous incentives, histamine, hormone gastroy, the allocation of which, in turn, is stimulated by food falling into the stomach, its mechanical stretching. The oppression of the secretion of hydrochloric acid occurs under the action of a high concentration of hydrogen ions H +, which inhibit the selection of gastrine. Also in the shepherd cells produced internal factor.

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Departments of the small intestine

Functions of the small intestine: mixing of chimus with pancreatic secrets, liver and intestinal juice, prevailing food, absorption of digested material (proteins, fats, carbohydrates, minerals, vitamins), further promotion of digested material on the gastrointestinal tract, secretion of hormones, immunological protection.

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Features of the structure of the mucous membrane

fine intestine

The intestinal mucous membrane consists of circular folds of Kerkringa, Village and Crypt. The functional unit of the mucous membrane is a vile with its internal content and a crypt that shares the adjacent vehicles (inside the veins are blood and lymphatic capillaries). Pork epithelium cells are called enterocytes, enterocytes are involved in digestion and suction of substances.

In the depths of the crypt, cylindrical cells are formed, they are proliferated and they ripen very quickly (within 24-36 hours), migrating to the top of the villus, felt by the solid cells. The absorption of various components of food occurs at the top of the villus, and the secretion in the crypts.

Epithelial cells of the small intestine: enterocytes (are responsible for suction of food), mucocytes (produce mucus) endocrine cells produce substances that stimulate the activity of the liver, pancreas and enterocytes.

The enzymes of the small intestine include: enterocinate (activator of all pancreas enzymes); enzymes acting on carbohydrates (amylase, maltaz, lactase, sugar); Enzymes acting on polypeptides (nucleotidase, Erepsin). Enzymes acting on fats (lipases), the intestines receives from the pancreas.
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Bile as one of the digestive components

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Colon

In the mucous membrane of the thick bowel, there are no veils, although microvils are available on the surface of the epithelial cells. The large intestine, especially in the region of Apandix, contains a large amount of lymphoid tissue and plasma cells, providing immune protection of the body.

Neuroimmunoandocrine interrelation of all gastrointestinal cells are particularly clearly traced when describing the diffuse endocrine system, which is represented by non-separate glands, but by individual cells.

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Diffuse Endocrine System: Acupudices of the gastrointestinal tract

Currently, the concept of diffuse endocrine system is synonymous with the concept of APUD system. Many authors reconcally use the last term, and the cells of this system call "apidocytes". Apud is an abbreviation composed of the initial letters of words denoting the most important properties of these cells - Amine Precursor Uptake and DecarBoxylation - absorption of amine precursors and their decarboxylation. Under the amines, it means a group of neuroamin - catecholamines (for example, adrenaline, norepinephrine) and indolaminines (for example, serotonin, dopamine).

There is a close metabolic, functional, structural connection between monoaminergic and peptidegic mechanisms of APUD endocrine cells. They combine the products of oligopeptide hormones with the formation of neuroamine. The ratio of the formation of regulatory oligopeptides and neuroamines in different neuroendocrine cells may be different. Oligopeptide hormones produced by neuroendocrine cells have a local (Paracroan) action on organs of organs in which they are localized, and distant (endocrine) - on the general functions of the body up to the highest nervous activity. APUD-series endocrine cells detect close and direct dependence on nerve pulses entering them in sympathetic and parasympathetic innervation, but do not react to trop hormones of the front lobe of the pituitary gland. The arud system includes about 40 types of cells, which are actually in fact in all organs. Almost half of the apoocyte is located in the gastrointestinal tract. And if you consider cells that are in the liver, pancreas, salivary glands, the language, then most of the apoocytes belong to digestive system. In this regard, it is possible to consider the gastrointestinal tract and a particularly 12-point intestine, in which many apidocytes, as an endocrine organ, and this endocrine system is called the enterine system, the cells, its components, are enterinocytes. Their varieties denoted by English letters are as follows:

1. EC cells (cage of the Kulchik, enterochromaffin cell) are found in all departments of the digestive tract, but are mainly located in the pyloric glands of the stomach and the crypts of the small intestine. They produce serotonin, melatonin, Mothilin. In enterochromaphhin cells, about 90% of the total serotonin-synthesized in the human body is formed.

2. D-cells are localized mainly in a 12-risen intestine and a cisch. We produce somatostatin, which reduces the level of somatotropic hormone.

3. D1 cells are located preferably in the 12thistanchine. A vasoactive intestinal peptide (VIP) is produced, which expands the vessels, slows down the secretion of the gastric juice.

4. ECL cells are detected in the foundal part of the stomach. Contain histamine and catecholamine.

5. R-cells are located in the pyloric part of the stomach, in a 12-tupest intestine, in the tekchka. Synthesize bombiness, stimulating the secretion of hydrochloric acid, pancreatic juice.

6. N-cells are located in the stomach, the ileum. The neurotenzine is synthesized, which stimulates the secretion of hydrochloric acid and other glands.

7. G-cells are localized, mainly in the pylorical part of the stomach. Gastrin is synthesized, stimulating the secretion of gastric juice, as well as enkephalin-morpho-like peptide.

8. K-cells are mainly in the 12thistanchine. Synthesize gastringging hormone (hypoda), which slows down the secretion of hydrochloric acid.

9. S-cells are also localized, mainly in the 12-risen intestine. Secretin hormone is producing, stimulating the secretion of the pancreas.

10. I-cells are located in a 12-risen intestine. The hormone is synthesized by a cholecystokinin-panopozlinin, stimulating the secretion of the pancreas. Eg cells are localized in the small intestine, produce enteroglukgon.

Small intestine

The delicious intestine provides the final digestion of food, absorbing all nutrients, as well as mechanical food advancement towards the thick bowel and some evacuator function. In the small intestine distinguish several departments. The plan for the structure of these departments is the same, but there are some differences. The relief of the mucous membrane forms circular folds, intestinal patches and intestinal crypts. Folds are formed by the mucous membrane and the submucosal base. Vilki is a finger-shaped rose of own plates covered on top of the epithelium. Crypts are the recesses of the epithelium into its own plate of the mucous membrane. Pieces, lining the slim intestine - single-layer prismatic. In this epithelium distinguish:

• Stroll enterocytes
• Box and shaped cells
• M cells
• Patenet cells (with acidophobic grain)
• Endocrine cells
• Undifferentiated cells

1. EC cells produce serotonin
2. ECL cells produce histamine
3. P cells produce bambasin
4. And cells synthesize enterogllucag
5. To cells, work pancreatic

1. Internal circular layer
2. Outdoor longitudinal layer