Sections of the digestive tube. Digestive organ complex

In the human body The digestive complex of organs plays an exceptional role, since it ensures the maintenance of trophism and vital activity of all cells and tissues. The organs of the digestive complex carry out mechanical processing and chemical breakdown of food components into simpler compounds that can be absorbed into the blood and lymph and absorbed by all cells of the body to maintain their vital functions and perform special functions.

Organs of the digestive complex are derivatives of embryonic digestive tube, in which three divisions are distinguished. Organs develop from the anterior (head) section oral cavity, pharynx and esophagus; from the middle (trunk) - stomach, small intestine, large intestine, liver and gallbladder, pancreas; from the posterior - the caudal part of the rectum. Each of the listed organs is characterized by specific structural and functional features determined by the embryonic rudiments of tissues and organs.

Development and general plan of the structure of the digestive tube

Main organs of the digestive complex are formed during the development of the embryonic intestinal tube, which initially ends blindly at the head and tail ends and is connected to the yolk sac through the yolk stalk. Later, the embryo develops oral and anal bays. The bottom of these bays, in contact with the wall of the primary intestine, forms the oral and cloacal membranes. At the 3-4th week of embryogenesis, the oral membrane breaks through.

At the beginning of the 3-4th month there is rupture of the cloacal membrane. The intestinal tube becomes open at both ends. Five pairs of gill pouches appear in the cranial part of the foregut. The ectoderm of the oral and anal bays serves as the starting material for the development of stratified squamous epithelium of the vestibule of the oral cavity and the caudal part of the rectum. The intestinal endoderm is the source of the formation of the epithelium of the mucous membrane and glands of the gastroenteric section of the digestive tube.

Connective tissue and smooth muscle tissue elements of the digestive organs are formed from mesenchyme, and the single-layer squamous epithelium of the serous membrane is formed from the visceral layer of the splanchnotome. Striated muscle, present in the composition individual organs digestive tube, develops from mitomes. Elements nervous system are derivatives of the neural tube and ganglion plate.

Wall of the digestive tube throughout it has a general structure plan. It is formed by the following membranes: mucosa with submucosa, muscular and external (serous or adventitial). The mucous membrane consists of epithelium, the lamina propria and the muscular lamina. The latter is not present in all organs. This membrane is called the mucous membrane due to the fact that its epithelial surface is constantly moistened with mucus secreted by mucous cells and multicellular mucous glands. The submucosa is represented by loose fibrous connective tissue.

It contains blood and lymphatic vessels, nerve plexuses and accumulations of lymphoid tissue. The muscular layer is formed, as a rule, by two layers of smooth muscle tissue (inner - circular and outer - longitudinal). The intermuscular connective tissue contains blood and lymphatic vessels. This is also where nerve plexus. The outer membrane is either serous or adventitial. The serous membrane consists of mesothelium and a connective tissue base. The adventitia is formed only by loose connective tissue.

Derivatives of the anterior part of the digestive tube

Oral organs(lips, cheeks, gums, teeth, tongue, salivary glands, hard palate, soft palate, tonsils) perform the following main functions: mechanical processing of food; chemical treatment food (wetting with saliva, digestion of carbohydrates by amylase and maltose of saliva); tasting food using the organ of taste; swallowing and pushing food into the esophagus. In addition, some organs of the oral cavity (for example, tonsils) perform protective function, preventing the penetration of microbes into the body, participate in the formation of the body’s immune response.

Educational video on the development of the gastrointestinal tract (embryogenesis)

digestive tube

Lecture outline:

1. General characteristics and functions of the digestive system.

2. General plan of the structure of the digestive tube.

3. Oral cavity. Structural and functional organization.

4. Pharynx.

5. Esophagus.

6. Stomach.

7. Small intestine

8. Colon.

The digestive system unites a number of organs, which together ensure the body’s absorption from the external environment of substances necessary to fulfill its plastic and energy needs. It includes the digestive tube and the glands located outside it, the secretion of which helps digest food particles: three pairs of large salivary glands, the liver and the pancreas.

The digestive tube has anterior, middle and posterior sections. The anterior section includes the oral cavity, pharynx and esophagus. The secretions of the major and minor salivary glands are released into the oral cavity. The main function of the anterior part of the digestive tube is the mechanical and initial chemical processing of food. The middle section of the digestive tube includes the stomach, small intestine, and part of the large intestine (towards its caudal part). The excretory ducts of the liver and pancreas flow into the small intestine (its section called the duodenum). The main functions of the middle section of the digestive tube are chemical processing (digestion) of food, absorption of substances and the formation of feces from undigested food debris. The posterior section of the digestive tube, the caudal part of the rectum, ensures the removal of undigested food particles outside the body.

Language ( lingua) - muscular n than organ that, in addition to participating in the mechanical processing of food and swallowing, also provides articulation (sound production) and tasting. There are lower, lateral and upper surfaces of the tongue, which have a number of structural features.

The lower surface of the tongue is covered with a multilayer flat non-keratinizing epithelium. It has a well-developed lamina propria and submucosa, the presence of which determines the displacement of the mucous membrane relative to the muscular base of the tongue. On the lower surface of the tongue, on both sides of its frenulum, the excretory ducts of the sublingual and submandibular salivary glands flow into the oral cavity. Due to the rich vascularization the lower surface of the tongue and the high penetration of its epithelium for a variety of chemical compounds, medications (validol, nitroglycerin) are placed under the tongue to ensure their rapid absorption and entry into the blood. The upper and lateral surfaces of the tongue are covered with a mucous membrane, motionlessly fused with the muscular base of the tongue. The epithelium and the lamina propria of the mucous membrane form here protrusions with a characteristic structure, which are called the papillae of the tongue. There are filamentous, conical, leaf-shaped, mushroom-shaped and e frontal papillae.

Composed of the epithelium of the lateral surfaces of the leaf-shaped, mushroom-shaped and groove O prominent papillae contain taste buds - the so-called taste budsbulbs, therefore, the role of these types of tongue papillae is associated primarily with tasting. The body of the tongue is formed by bundles of striated muscle fibers, which are located in three mutually perpendicular planes. The dense connective tissue median septum divides the tongue muscle into right and left halves. Between muscle base tongue and the lamina propria of the mucous membrane of its back, a dense plexus of collagen and elastic fibers forms the so-called reticular layer, which plays the role of the aponeurosis of the tongue. In the connective tissue of the root of the tongue there is a cluster of lymphocytes that form the lingual tonsil. Lymphocytes form a spherical cluster.

Localized between bundles of striated muscle fibers of the tongue a large number of small salivary glands that produce protein, mucous or protein-mucus secretion. Glands that produce protein secretions are located mainly near the leaf-shaped and grooved papillae. These are complex alveolar branched glands. Mucous glands are located in the root area and on the lateral surfaces of the tongue. These are complex alveolar-tubular branched glands, the secretion of which is rich in mucins. The excretory ducts of the mucous glands of the root of the tongue open into the crypts of the lingual tonsil. Mixed protein-mucosal glands are localized mainly in the anterior parts of the tongue; their excretory ducts open on the lower surface of the tongue along the folds of its mucous membrane.

Sky ( palatum) is the partition between the nasal and oral cavities. There are hard and soft e Bo, the latter in its rear part turns into a tongue. At the heart of solid e ba there are bone plates fused in the midline. On the side of the oral cavity, the hard palate is covered with a mucous membrane, covered with a multilayer flat non-keratinizing epithelium into which tall connective tissue papillae of the lamina propria grow. Topographically, in the composition of solid e ba there are four zones: fatty, glandular, marginal and zone n e long seam. The area of ​​adipose tissue covers the anterior part of the hard tissue. e ba. In this area, under the mucous membrane, there is fatty tissue, which is an analogue of the submucosa of other parts of the oral cavity. The glandular zone occupies the posterior part of the hard tissue. e ba. In this area between the mucous membrane and the periosteum of the bone plates, groups of small salivary glands are localized, which produce a mucous-protein secretion.

The marginal zone in the form of an arc covers the solid surface. e Bo and is the place of transition of its mucous membrane into the gums of the upper jaw. In the marginal zone, the mucous membrane of the hard tissue e batightly fused with the periosteum of the base of the alveolar processes. Along the midline of the hard e ba passes zone n e long seam. In this area, as in the marginal zone, the mucous membrane is tightly fused with the periosteum of the bone plates. Epithelium in the suture area of ​​the hard n e ba forms characteristic thickenings, especially well developed in childhood: then they look like concentric layers of epithelial cells and are called epithelial bodies n e ba. The tight fusion of the mucous membrane with the periosteum in the suture area and the marginal zone determines its real estate.

Soft nyo bo and tongue is a continuation of the back of the hard n e ba, however, if based on solid n e ba bone plates lie, then soft n e Bo and uvula have a mucous membrane. In the mucous membrane of the soft tissue e ba and uvula distinguish two surfaces - oral and nasal, as well as a transition zone. In fetuses and newborns, the boundary between these surfaces lies on the line of bending of the mucous membrane from the nasal to the oral surface. In adults, this border shifts towards the nasal surface so that the entire uvula is covered with epithelium characteristic of the oral cavity. The oral surface of the mucous membrane of the soft tissue e ba and tongue are covered with multi-layer flat non-keratinizing epithelium. The lamina propria forms high papillae; the muscular lamina mucosa is absent. In soft n e The uvula and uvula have a well-developed submucosa, which contains salivary glands that produce mucous secretion. Nasal mucosal surface e The ba is covered with a single-layer multirow ciliated epithelium, which is characteristic of the upper respiratory tract. On its surface, ducts of small glands open that produce mucus. In the transition zone, the epithelium turns from multilayered squamous into multirowed prismatic, and the latter becomes single-layered multirow ciliated.

The palatine tonsils are located between the palatoglossus and velopharyngeal arches. The structure of the tonsil is based on the folds of the mucous membrane. In the depths of the folds of epithelium growing into the lamina propria of the mucous membrane, 10-20 slits are formed - crypts. When crypts branch, secondary crypts are formed. Around the crypts there are spherical accumulations of lymphocytes - lymph nodes with light (reactive) centers. The nodules are formed predominantly by B-lymphocytes and plasmacytes. The loose connective tissue of the lamina propria of the mucous membrane merges with the submucosa, where the final secretory sections of the mucous glands of the pharynx are located. The muscular coat is formed by cross-striated muscle tissue and forms two layers - the outer circular and the inner longitudinal. The adventitia is formed by loose fibrous connective tissue.

The pharynx (throat, pharynx) is a cone-shaped canal 12...14 cm long that connects the oral cavity with the esophagus. The pharynx is where the digestive and respiratory tract. The wall of the pharynx is made up of four membranes - mucous, submucosal, muscular and adventitial Noah. There are three sections of the pharynx - nasal, oral and laryngeal.

The mucous membrane of the nasal section is covered with a single-layer multirow ciliated epithelium (respiratory type). In the area where the cardiac glands are localized, diverticula, ulcers and tumors of the esophagus often occur. The muscular plate of the mucous membrane is formed by longitudinally oriented bundles of smooth myocytes, between whichareplexus of elastic fibers. The submucosa of the esophagus is formed by loose connective tissue, in which the final secretory sections of the own glands of the esophagus are located. In structure, these are complex branched alveolar-tubular glands with a mucous type of secretion. Proper glands are concentrated mainly on the ventral surface of the upper third of the esophagus. Multilayer flat non-keratinizing the epithelium of the tonsil crypts is dense infiltrated numerous lymphocytes and neutrophilic granulocytes, as a result of which it received the name reticular epithelium. In the crypt space you can see exfoliated epithelial cells, lymphocytes that migrated here from the follicles, as well as foreign particles. Inflammation palatine tonsils is called tonsillitis.

The esophagus is a section of the digestive tube about 30 cm long that connects the pharynx with the stomach cavity. The esophagus is located between the sixth cervical and eleventh thoracic vertebrae. The wall of the esophagus is formed by four membranes: mucous, submucosal, muscular and external ( adventitial noisy or serous). The esophageal mucosa has three layers; epithelium, lamina propria and muscularis lamina. Esophageal stratified squamous epithelium non-keratinizing; In old age, keratinization is possible. During the transition to the stomach, the stratified squamous epithelium of the esophagus is replaced by a single-layer prismatic one. lamina propriashellThe esophagus is formed by loose connective tissue, the ingrowth of which into the epithelium forms papillae.

As part of the lamina propria of the mucous membrane at the level signet-shaped cartilage of the larynx and in the area of ​​​​the transition of the esophagus to the stomach the final sections of the cardiac glands lie. These are simple tubular or tubulo-alveolar branched glands that produce primarily mucus. In addition to mucocytes, they include a significant number of endocrine cells, as well as single parietal cells, about the cake produce H + - ions. The ducts of the cardiac glands are formed by single-layer cylindrical epithelium, which directly transforms into multilayered epithelium. The muscular layer of the upper third of the esophagus is formed by transversely striated muscle tissue. In the middle third of the organ, smooth myocytes join the cross-striated muscle fibers. The muscular lining of the lower third of the esophagus is formed by smooth muscle tissue. There are internal circular and external longitudinal layers muscularis propria esophagus, although individual muscle bundles may have an oblique longitudinal direction. Thickening of the inner layer of the muscular lining of the esophagus at the level signet-shaped The cartilage of the larynx forms the upper sphincter of the esophagus, and when the latter passes into the stomach - lower sphincter. The outer lining of the esophagus above the diaphragm is formed by loose connective tissue (tunica adventitia). Under the diaphragm, the adventitial membrane becomes serous: the loose connective tissue here is covered with a single layer of mesothelial cells.

Stomach ( gaster, ventriculus) - a sac-like expansion of the digestive tube with a volume of 1.7...2.5 liters, into which food crushed and moistened in the oral cavity enters through the esophagus. The wall of the stomach is formed by four membranes - mucous, submucosal, muscular serous. A feature of the relief of the gastric mucosa is the presence of folds, fields and pits. The mucous membrane is constructed of three layers - the epithelium, the lamina propria and the muscularis lamina. The gastric mucosa produces an internal antianemic factor necessary for the absorption of vitamin B12, which enters the stomach with nutrients. The plasmalemma of the apical surface of epithelial cells forms microvilli. In the apical part of the cell, granules of mucous secretion accumulate, which, when secreted, cover the surface of the mucous membrane and protect it from the digestive action gastric juice. Consequently, the gastric mucosa can be considered as a continuous glandular field. Near the bottom of the gastric pits, which are ingrowths of the surface epithelium into the lamina propria of the mucous membrane, there are poorly differentiated, actively proliferating cells. As they differentiate and age, they move toward the surface of the mucous membrane, followed by exfoliation into the lumen of the stomach.

The lamina propria of the gastric mucosa is built from loose connective tissue in which the gastric glands lie. There are three types of glands: intrinsic, cardiac and pyloric. The proper glands of the stomach are simple tubular, unbranched or weakly branched, located in the area of ​​the fundus and body of the stomach. The final secretory section is formed by the bottom and body of the own gland, the excretory duct is formed by the isthmus and neck. The secretion of several of the stomach's own glands flows into the gastric pit. Each gland is built from five types of cells: main exocrinocytes, parietal exocrinocytes, cervical and accessory mucocytes, and endocrinocytes.

The secretory products of the main cells - pepsinogen and chymosin - are localized in the apical part of the cells in the form of zymogenic granules (the so-called Langley granules). The latter have oxyphilic properties and refract light well. In the apical (closer to the lumen of the gland) part of the cells, granules of protein secretion accumulate. The plasmalemma of the apical surface of the main exocrinocytes forms microvilli. The basal part of the cell contains a round nucleus and well-defined elements of the Golgi complex. Chymosin breaks down milk proteins and is produced primarily in childhood.

Parietal exocrinocytes of the gastric glands secrete H-ions, resulting in an acidic environment in the stomach. Parietal cells are located alone in the area of ​​the bottom and body of the own glands, between basolateral parts of the main exocrinocytes. These are large cells of irregular round shape with one or two nuclei and oxyphilic cytoplasm. The latter contains a significant number of mitochondria and is penetrated by a branched system of intracellular tubules, through which secretory products enter the intercellular tubules, and from there into the lumen of the gland.Cervical mukocytes form the excretory ducts of their own glands. These are cubic or prismatic cells, in the basal part of which the nuclei are localized, and secretory mucus granules accumulate in the apical part. Among cervical mucocytes there are poorly differentiated cells that are the source of physiological regeneration of gastric glandulocytes and cells of the gastric pits. Accessory mucocytes, scattered singly in the glands, resemble cervical mucocytes in structure and function.

Endocrinocyteslocalized alone between the main cells, mainly in the area of ​​the bottom and body of the glands. They belong to dissociated endocrine system gastrointestinal tract, or APUD systems. The cardiac and pyloric glands are located in the same areas of the stomach. In structure, these are simple tubular, highly branched glands. IN pyloric glands There are no chief and parietal cells; in the cardiac glands they are present in small quantities. The cardiac and pyloric glands also contain a significant number of endocrine cells. In the lamina propria of the mucous membrane between gastric glands There are accumulations of lymphocytes in the form of diffuse infiltrates or single lymphatic follicles. The number of the latter increases in the pyloric part of the stomach.

Small intestine (intestinum tenue) - part of the digestive tube located in the lower part abdominal cavity between the stomach and the cecum. The length of the small intestine is 4...5 m, the diameter in the proximal section is 5 cm, in the distal direction the intestine thins in diameter to 3 cm. It has three sections: the duodenum, the hungry intestine and the longitudinal intestine. The duodenum has the shape of a horseshoe, approximately 30 cm long. Completing the characteristics of the gastric mucosa, it should be noted that in its pyloric part the gastric pits deepen significantly.

The submucosal base of the stomach is formed by loose connective tissue in which the submucosal nerve plexuses are located - external (Shabadasha) and internal (Meissner). The muscular lining of the stomach is formed by three layers of smooth myocytes: outer longitudinal, middle circular and inner oblique longitudinal.

The wall of the small intestine is formed by four membranes: mucous, submucosal, muscular and serous. The mucous membrane consists of three layers - the epithelium, the lamina propria and the muscularis lamina. The epithelium of the mucous membrane of the small intestine is single-layer cylindrical. The lamina propria is formed by loose connective tissue, the muscular lamina is formed by smooth myocytes. A feature of the relief of the mucous membrane of the small intestine is the presence of circular folds, villi and crypts.

The villus is a finger-shaped protrusion of the mucous membrane with a height of 0.5.., 1.5 mm directed into the lumen of the small intestine. The villus is based on the connective tissue of the lamina propria, in which single smooth myocytes occur. The surface of the villi is covered with columnar epithelium, which contains three types epithelial cells: columnar epithelial cells, goblet cells and intestinal endocrinocytes. Columnar epithelial cells of the villi make up the bulk of the epithelial layer of the villi. It's high cylindrical cells measuring 8x25 microns. On the apical surface they contain microvilli (the latter should not be confused with the villi of the small intestine), which under a light microscope have a characteristic appearance of a striated frame. The height of microvilli is about 1 µm, diameter - 0.1 µm. Thanks to the presence of both villi and microvilli, the absorption surface of the mucous membrane of the small intestine increases a hundred times. Columnar epithelial cells have an oval nucleus, well-developed ergastoplasm, and a lysosomal apparatus. The apical part of the cells contains tonofilaments, with the participation of which obturator plates and tight junctions are formed, permeable to substances from the lumen of the small intestine.

Columnar epithelial cells of the villi are the main functional element of the processes of digestion and absorption in small intestine. The microvilli of these cells adsorb enzymes and the nutrients they break down on their surface. The products of the breakdown of proteins and carbohydrates - amino acids and monosaccharides - are transported from the apical to the basal part of the cells, from where they enter the capillaries of the connective tissue base of the villi through the basement membrane. A similar absorption path is also characteristic of water dissolved in it. mineral salts and vitamins. Fats are digested either by phagocytosis of droplets emulsified fat (chylomicrons), columnar epithelial cells, or by absorption of glycerol and fatty acids (the latter are formed from neutral fats under the action of lipases) with the subsequent resynthesis of neutral fat in the cytoplasm of the cells. Goblet cells are single-celled glands that produce mucous secretions. The shape of the cells is characterized by their name: in the expanded apical part they accumulate secretory products, in the lower part of the cell, narrowed like the stem of a glass, the nucleus, endoplasmic reticulum, and Golgi complex are located. Single goblet cells are scattered on the surface of the villi surrounded by columnar epithelial cells with a border. The secretion of goblet cells moisturizes the surface of the mucous membrane, thereby promoting the movement of food particles to the colon.

Endocrinocytes, as well as goblet cells scattered alone among columnar epithelial cells with a border. Among the endocrinocytes of the small intestine, EC-, A-, S-, I-, G-, D-, D1-cells are distinguished. The products of their synthetic activity are a number of biologically active substances that exert a local regulatory effect on secretion, absorption and intestinal motility. Hormones that are produced by endocrinocytes of the small intestine enter the hemocapillaries of the connective tissue base of the villi and are transported with the blood to their target cells: columnar epithelial cells with a border, goblet cells, smooth myocytes of the vascular wall of the mucous and muscular membranes of the intestine.

Crypts are tubular ingrowths of epithelium into the lamina propria of the intestinal mucosa. The entrance to the crypt opens between the bases of adjacent villi. The depth of the crypts is 0.3..0.5 mm, the diameter is about 0.07 mm. There are over 150 million crypts in the small intestine, which, like villi, significantly increase the functionally active area of ​​the small intestine. Among the crypt epithelial cells, in addition to the cells previously characterized as part of the villi (columnar cells with a border, goblet cells and endocrinocytes), there are also columnar cells without a border and exocrinocytes with acidophilic granules (Paneth cells). The peculiarity of columnar epithelial cells with a border as part of the crypts is their slightly lower height compared to similar cellular elements of the villi, as well as pronounced basophilia of the cytoplasm. The goblet cells of the villi and crypts do not differ significantly. The number of endocrinocytes in the crypts is higher than on the villi; the functional activity of the endocrinocytes of the villi and crypts is the same.

The secretory products of Paneth cells are dipeptidases - enzymes that break down dipeptides into amino acids. It is also believed that cells with acidophilic granules produce enzymes that neutralize the acidic components of gastric juice that enter the small intestine along with food particles. Columnar epithelial cells without borderrepresent a population of poorly differentiated cells that are the source of physiological regeneration of the epithelium of the crypts and villi of the small intestine. The structure of these cells resembles columnar cells with a border, but there are no microvilli on their apical surface.

The lamina propria of the mucous membrane of the small intestine is formed by loose connective tissue, which contains a lot of elastic and reticular fibers, hemo- and lymphocapillaries. Clusters of lymphocytes form here single and grouped lymphatic follicles, the number of which increases in the direction from the duodenum to the hungry intestine. The largest accumulations of lymphatic follicles pass through the muscular plate of the mucous membrane into the submucosa of the intestine. In places where grouped lymphatic follicles are localized, villi of the mucous membrane are usually absent. The maximum number of lymphatic accumulations in the wall of the small intestine is found in children; with age, their number decreases. In addition to lymphocytes, the connective tissue of the lamina propria of the mucous membrane contains eosinophilic granulocytes and plasmacytes. The muscular plate of the mucous membrane is formed by two layers of smooth myocytes - the inner circular and outer longitudinal.

The submucosa of the wall of the small intestine is formed by loose connective tissue, which contains a significant number of blood and lymphatic vessels and nerve plexuses. IN duodenum The terminal secretory sections of the duodenal (Bruner's) glands lie in the submucosa. In structure, these are complex branched tubular glands with a mucous-protein secretion, which resemble the pyloric glands of the stomach. The terminal secretory sections of the duodenal glands are built from mucocytes, Paneth cells and endocrinocytes (S-cells). The excretory ducts of the Brunerian glands open near the base of the crypts or between adjacent villi. The excretory ducts of the glands are built from mucocytes of cubic or prismatic shape, which are replaced near the surface of the mucous membrane by columnar cells with a border. There are especially many lymphatic follicles in the wall of the appendix, which, due to its high saturation with lymphoid elements, is sometimes also called the tonsil of the abdominal cavity. The epithelium of the mucous membrane of the appendix is ​​single-layer prismatic. The muscular layer of the small intestine is formed by two layers of smooth myocytes: internal oblique-circular and external oblique-longitudinal. Between both layers of muscle tissue lie layers of connective tissue rich in neurovascular plexuses.

Large intestine ( intestinum erassum) - part of the digestive tube that ensures the formation and excretion of feces. Excretory substances (metabolic products), salts of heavy metals, and the like accumulate in the lumen of the colon. The bacterial flora of the colon produces vitamins B and K, and also ensures the digestion of fiber. The mucous membrane of the colon is formed by a single-layer columnar epithelium, a connective tissue lamina propria, and a muscular lamina constructed of smooth muscle tissue. A feature of the relief of the colon mucosa is the presence of a large number of crypts and the absence of villi. The vast majority of cells in the epithelial layer of the colon mucosa are goblet cells; there are significantly fewer columnar epithelial cells with a striated border and endocrinocytes. Goblet cells produce a large amount of mucus, which envelops the surface of the mucous membrane, and, mixing with undigested food particles, promotes the passage of feces in the caudal direction. Near the base of the crypts are located undifferentiated cells, as a result of proliferation of which physiological regeneration of the epithelium occurs. Sometimes Pannett cells can be found in crypts. The named cell populations do not differ significantly from similar cellular elements of the small intestine.

In the loose connective tissue of the lamina propria of the mucous membrane there are significant accumulations of lymphocytes. It contains a large number of Pannett cells and intestinal endocrinocytes. The latter synthesize the bulk of endogenous serotonin and melatonin in the body. This fact, as well as the high content of lymphoid elements, obviously explains the important place that the vermiform appendix occupies in the immune defense system of the human body.

The muscular plate of the colon mucosa is formed by two layers of smooth myocytes: internal circular and external oblique. The muscular plate of the mucous membrane in different parts of the large intestine has unequal development: in the vermiform in the process, for example, it is poorly developed. The submucosa of the colon is formed by loose connective tissue, in which there is an accumulation of fat cells, as well as a significant number of lymphatic follicles. The neurovascular plexuses are located in the submucosa.

The muscular layer of the colon is formed by two layers of smooth myocytes: the internal circular and the external longitudinal, between which lie layers of loose connective tissue. In the colon, the outer layer of smooth myocytes is not continuous, but forms three longitudinal ribbons. The contraction of individual segments of the internal circular layer of smooth myocytes of the muscularis mucosa ensures the formation of transverse folds of the colon wall. The outer lining of the vast majority of the colon is serous; in the caudal part of the rectum, the serous membrane passes into the adventitia. The rectum has a number of structural features that should be considered in more detail. It distinguishes between the upper (pelvic) and lower (anal) parts, which are separated from one another by transverse folds. The submucosa and the inner circular layer of the muscularis are involved in the formation of the latter. The mucous membrane of the upper part of the rectum is covered with a single-layer cubic epithelium, which forms numerous deep crypts. The mucous membrane of the anal part of the rectum is made up of three zones of different structure: columnar, intermediate and cutaneous. The columnar zone is covered with multilayer cubic, the intermediate zone is covered with multilayer flat non-keratinizing, skin - multilayered squamous keratinizing epithelium. The lamina propria of the columnar zone forms 10-12 longitudinal folds and contains many blood lacunae, the blood from which will flow into hemorrhoidal veins. Single lymph nodes, the terminal sections of the rudimentary anal glands, are located here. The latter pass into the submucosa. The lamina propria of the intermediate zone is rich in elastic fibers, lymphocytes and tissue basophils; The terminal sections of the sebaceous glands are located here. In the connective tissue lamina propria of the mucous membrane of the skin zone, hair follicles, terminal sections of apocrine sweat glands, sebaceous glands. The muscular plate of the rectal mucosa is formed by the inner circular and outer longitudinal layers of smooth myocytes.

The submucosa of the rectum is formed by loose connective tissue in which the nerve and vascular plexuses are located. Among the latter, we should highlight the plexus of hemorrhoidal veins, with the loss of wall tone of which hemorrhoidal bleeding can occur. In the submucosa of the rectum there are a large number of baroreceptors (Vater-Pacini bodies), the irritation of which plays a significant role in the mechanisms of defecation. In the submucosa of the columnar zone, as in the lamina propria of its mucous membrane, the terminal sections of the rudimentary anal glands are located. These are six to eight branched tubular epithelial formations, which from the surface of the mucous membrane reach the inner circular layer of the muscular layer. When the anal glands become inflamed, they can cause rectal orifices.

The muscular layer of the rectum is formed by internal circular and external longitudinal layers of smooth myocytes, between which lie layers of connective tissue. The muscularis propria forms two sphincters, which play a significant role in the act of defecation. The internal sphincter of the rectum is formed by thickening of the smooth myocytes of the inner layer of the muscular layer, the external sphincter is formed by bundles of fibers of striated skeletal muscle tissue. The upper part of the rectum is covered with a serous membrane, the anal part with an adventitial membrane.

The wall of the digestive canal along its length has three layers: the inner one is the mucous membrane, the middle one is the muscular layer and the outer one is serosa.

The mucous membrane performs the function of digestion and absorption and consists of a layer of its own, the lamina propria and the muscularis laminae. The proper layer, or epithelium, is supported by loose connective tissue, which includes glands, blood vessels, nerves and lymphoid formations. The oral cavity, pharynx, and esophagus are covered with stratified squamous epithelium. The stomach and intestines have a single-layer cylindrical epithelium. The lamina propria of the mucous membrane, on which the epithelium lies, is formed by loose fibrous unformed connective tissue. It contains glands, accumulations of lymphoid tissue, nerve elements, blood and lymphatic vessels. The muscularis mucosa consists of smooth muscle tissue. Under the muscular plate there is a layer of connective tissue - the submucosal layer, which connects the mucous membrane with the muscular layer lying outward.

Among the epithelial cells of the mucous membrane are goblet-shaped, single-celled glands that secrete mucus. This is a viscous secretion that wets the entire surface of the digestive canal, which protects the mucous membrane from the harmful effects of solid food particles and chemicals and facilitates their movement. The mucous membrane of the stomach and small intestine contains numerous glands, the secretion of which contains enzymes involved in the process of digesting food. According to their structure, these glands are divided into tubular (simple tube), alveolar (vesicle) and mixed (alveolar-tubular). The walls of the tube and vesicle consist of glandular epithelium; they secrete a secretion that flows through the opening of the gland onto the surface of the mucous membrane. In addition, glands can be simple or complex. Simple glands are a single tube or vesicle, while complex glands consist of a system of branched tubes or vesicles that empty into the excretory duct. The complex gland is divided into lobules, separated from each other by layers of connective tissue. In addition to the small glands located in the mucous membrane digestive tract, there are large glands: salivary, liver and pancreas. The last two lie outside the digestive canal, but communicate with it through their ducts.

The muscular lining of most of the alimentary canal consists of smooth muscle with an inner layer of circular muscle fibers and an outer layer of longitudinal muscle fibers. In the wall of the pharynx and the upper part of the esophagus, in the thickness of the tongue and soft palate there is striated muscle tissue. When the muscle membrane contracts, food moves through the digestive canal.

The serous membrane covers the digestive organs located in the abdominal cavity and is called the peritoneum. It is shiny, whitish in color, moistened with serous fluid and consists of connective tissue, which is lined with single-layer epithelium. The pharynx and esophagus are covered on the outside not by the peritoneum, but by a layer of connective tissue called adventitia.

The digestive system consists of the mouth, pharynx, esophagus, stomach, small and large intestines, as well as two digestive glands - the liver and pancreas

Using lectures (presentations and text of lectures are posted on the department’s website), textbooks, additional literature and other sources, students must prepare the following theoretical questions:

1. General characteristics of the digestive system.

2. Oral cavity. Lips, cheeks, gums, hard and soft palate, their structure and functions.

3. Tongue, tissue composition and structural features of the mucous membrane of the lower, lateral and upper surface of the tongue.

4. Papillae of the tongue, their morphofunctional characteristics.

5. Structure and function of the taste bud.

6. Sources of development, structure and tissue composition of the tooth.

7. Histological structure, chemical composition enamel, dentin, cement.

8. Pulp and periodontium of the tooth, their structure and function.

9. Development of teeth. Milk and permanent teeth.

10. Features of nutrition and innervation of the tooth.

11. Age-related changes and dental regeneration.

12. General plan of the structure of the digestive tube. Histological structure of the pharyngeal wall.

13. Morphology of the mucous and submucous membrane of the esophagus.

14. Glands of the esophagus, their localization, microscopic structure and function.

15. Features of the structure of the muscular membrane in various parts of the esophagus.

16. Lympho-epithelial pharyngeal ring of Pirogov, its significance.

17. Morphology and function of the palatine tonsils.

18. General plan of the structure of the stomach, its sections and membranes.

19. Features of the fine structure of the gastric mucosa.

20. Stomach glands: their types, localization and general structural plan.

21. Own glands of the stomach, structure and cellular composition, significance.

22. Pyloric and cardiac glands of the stomach, cellular composition, functional significance.

23. Morphofunctional characteristics of the muscular and serous membranes of the stomach.

24. Development of membranes and tissue composition of the wall of the small intestine.

25. Features of the structure of the mucous membrane. Morphology and significance of the crypt-villus system.

26. Morphofunctional characteristics of cells of single-layer cylindrical bordered epithelium of villi and crypts of the mucous membrane.

27. Fine and ultramicroscopic structure of columnar epithelial cells with a border and their participation in parietal digestion.

28. Submucosa of the small intestine. The fine structure of the duodenal glands and their functional significance.

29. Localization and functional significance of aggregated lymphatic follicles (Peyer's patches) in the wall of the small intestine.

30. The structure of the muscular and serous membranes of the small intestine in its various parts.

31. Histophysiology of absorption in the small intestine.

32. Sources of embryonic development of the middle and posterior sections of the digestive tube.

33. Anatomical sections and structure of the membranes of the colon wall.

34. Features of the relief of the mucous membrane.

35. Vermiform appendix, its structure and significance.

36. Sections of the rectum, their functional features.

37. Histophysiology of the colon.

General characteristics of the digestive system. The digestive system unites a number of organs, which together ensure the body’s absorption from the external environment of substances necessary to fulfill its plastic and energy needs. It includes the digestive tube and the glands located outside it, the secretion of which helps digest food particles: three pairs of large salivary glands, the liver and the pancreas.

The digestive tube has anterior, middle and posterior sections. The secretions of the major and minor salivary glands are released into the oral cavity. The main function of the anterior part of the digestive tube is the mechanical and initial chemical processing of food. The middle section of the digestive tube includes the stomach, small intestine, and part of the large intestine (towards its caudal part). The excretory ducts of the liver and pancreas flow into the small intestine (its section called the duodenum). The main functions of the middle section of the digestive tube are chemical processing (digestion) of food, absorption of substances and the formation of feces from undigested food debris. The posterior section of the digestive tube, the caudal part of the rectum, ensures the removal of undigested food particles outside the body.

The wall of the digestive tube is formed by four membranes: mucous, submucosal, muscular and outer. The mucous membrane includes the epithelial lamina, the lamina propria, formed by loose connective tissue, and the muscular lamina, built from smooth muscle tissue. The epithelial plate of the mucous membrane has a number of features in the anterior, middle and posterior sections of the digestive tube. The mucous membrane in the oral cavity, pharynx and esophagus is covered with stratified squamous non-keratinizing or partially keratinizing epithelium. In the middle section of the digestive tube, starting from the stomach, the epithelium becomes single-layered cylindrical. In the esophagus, the mucous membrane forms deep longitudinal folds that facilitate the passage of food from the mouth to the stomach. Features of the relief of the gastric mucosa are the presence of folds, fields and pits. In the small intestine, the mucous membrane, in addition to folds, forms specific outgrowths - villi and tubular depressions - crypts. The presence of villi and crypts provides an increase in the area of ​​contact of the mucous membrane with food debris that is subject to chemical treatment. This facilitates the digestion process, as well as the absorption of chemical compounds - products of the enzymatic breakdown of food. In the colon, villi disappear, crypts and folds facilitate the formation and movement of feces. The posterior section of the digestive tube, like the anterior one, is lined with multilayered squamous non-keratinizing epithelium.

The muscular plate of the mucous membrane is formed by one to three layers of smooth myocytes. In some parts of the digestive tube, in particular in the oral cavity, the muscular plate of the mucous membrane is absent.

In the esophagus and duodenum, the terminal secretory sections of the exocrine glands are located in the submucosa. In the submucosa of the esophagus, stomach and intestines there are submucosal nerve plexuses - external (Shabadasha) and internal (Meisner), which innervate the mucous membrane and glands, isolated and concentrated lymphatic follicles, blood and lymphatic vessels.

The muscular membrane of the anterior section of the digestive tube towards the middle third of the esophagus is formed by striated muscle tissue; in the lower sections of the esophagus it is gradually replaced by smooth muscle tissue. The muscular lining of the middle section of the digestive tube is formed by smooth muscle tissue. In the caudal part of the rectum, smooth muscle tissue is supplemented by striated muscle tissue, which reaches its maximum development as part of the external sphincter of the caudal part of the rectum. Between the individual layers of the muscular lining of the esophagus, stomach and intestines, the intermuscular nerve plexus (Auerbach) is located, which provides innervation to the muscular lining of these organs.

The outer shell of the digestive tube in its anterior (above the diaphragm) and posterior sections is represented by loose connective tissue, the so-called adventitial membrane). The esophagus under the diaphragm, as well as the entire middle section of the digestive tube, is covered with a serous membrane, which is formed by loose connective tissue with single-layer epithelium (mesothelium) on the surface. Under the serous membrane of the stomach and intestines there is a subserosal autonomic nerve plexus that innervates the visceral layer of the peritoneum.

Lip (labium) is a formation covering the entrance to the oral cavity. Which is based on striated muscle tissue. The lip consists of three parts: mucous, intermediate and cutaneous. The outer skin of the lip is covered with thin skin: the epithelium here is multilayered squamous and keratinized; the connective tissue base of the skin contains hair follicles and the terminal secretory sections of the sebaceous and sweat glands.

The stratified squamous epithelium of the oral cavity, the caudal part of the rectum, and the epithelium of the salivary glands develop from the ectoderm of the oral and anal bays of the embryo. From the intestinal endoderm, a single-layer epithelium of the stomach, small and most of the large intestine, glandular parenchyma of the liver and pancreas is formed. The source of development of connective tissue of the lamina propria of the mucous membrane, submucosa and outer shell of the digestive tube is mesenchyme. The mesothelium of the serous membrane develops from the visceral layer of the splanchnotome.

The oral cavity (cavitas oris) is the part of the anterior section of the digestive tube in which mechanical processing, tasting and primary chemical processing of food are carried out. The organs of the mouth play an important role in the act of articulation (sound production). Partial disinfection of nutrients from pathogenic microorganisms is also carried out here.

The vestibule of the oral cavity is limited in front by the lips and cheeks, and in the back it is limited by the gums and teeth. The oral cavity itself is limited in front by the gums and teeth, and in the back it passes into the pharynx. The tongue is located in the oral cavity, and the excretory ducts of the major and minor salivary glands flow here. At the border of the oral cavity with the nasopharynx there are clusters of lymphoid elements - tonsils, which form the Pirogov-Waldeyer lymphoepithelial pharyngeal ring.

The front door of the mouth and the oral cavity are covered with multilayered squamous non-keratinizing epithelium, which on the back of the tongue (as part of its filiform papillae), as well as on the gums and hard palate, may be subject to keratinization. The loose connective tissue of the lamina propria of the mucous membrane in the oral cavity is penetrated by a dense network of hemocapillaries, contains many lymphocytes, and also forms the so-called papillae (ingrowth of connective tissue into the epithelium). The muscular plate of the mucous membrane in the oral cavity is absent.

The mucous membrane on the lips, cheeks, lower surface of the tongue, as part of the soft palate and uvula lies on a well-defined connective tissue submucosal base, which ensures the displacement of the mucous membrane relative to tissues located deeper. In the gums, upper and lateral surfaces of the tongue, and hard palate, there is no submucosa; the mucous membrane here is fused either directly with the periosteum (gums, hard palate) or from the perimysium of striated muscles (tongue). This structural feature predetermines the non-displacement of the mucous membrane of the named structural components of the oral cavity to the tissues that lie deeper. There are two zones: outer smooth and inner villous. The keratinizing epithelium of the outer zone is graceful, transparent, hair, sweat glands here they disappear, only the sebaceous glands are preserved. Inner zone The intermediate surface of the lip of newborns is covered with epithelial protrusions called villi. With age, these villi gradually become smaller and become invisible. There are no sebaceous glands in the inner part of the transitional surface of the lip; in the multilayered non-keratinizing epithelium, high papillae grow in from the side of the connective tissue, which lies deeper. The presence of hemocapillaries in their composition, which shine through a thin layer of epithelium, causes the red color of the lips.

The mucous part of the lip is covered with stratified non-keratinizing epithelium. The lamina propria of the mucous membrane directly passes into the submucosa. The terminal secretory sections of the minor labial salivary glands are localized in the submucosa. In structure, these are complex alveolar-tubular glands that produce mucous-protein secretion. The ducts of the glands are formed by multilayered squamous non-keratinizing epithelium; they open on the mucous surface of the lip.

The cheek (bucca) is a skin-muscular formation that limits the vestibule of the oral cavity on the sides. The surface is covered with thin skin; the base of the cheek, like the lips, is made up of striated muscle tissue. On the mucous surface of the cheek, three zones are distinguished: maxillary, mandibular and intermediate. The latter is a section of the mucous membrane about 10 mm wide that stretches from the corner of the mouth to the processes of the lower jaw.

The structure of the mucous membrane of the maxillary and mandibular zones of the cheek is identical and resembles the structure of the mucous surface of the lip: stratified squamous non-keratinizing epithelium lies on the connective tissue of the lamina propria, which directly passes into the submucosa. In the latter, as well as between the bundles of striated muscles of the cheek, a large number of small salivary glands with a mucous-protein type of secretion are localized.

In the intermediate zone of the cheek in embryonic and early childhood, the mucous membrane forms numerous villi - the same as in the transitional part of the lip. There are no salivary glands in the intermediate part of the cheek, but there are a small number of reducible sebaceous glands. The intermediate zone of the cheek and the transitional part of the lip is the area of ​​contact between the skin and the epithelium of the oral cavity, which arises in embryogenesis as a result of the growth of embryonic anlages during the formation of the oral opening. On the surface of the mucous membrane of the cheek - at the level of the second upper molars - the excretory ducts of the parotid salivary glands open.

Gums (gingivae) are bony outgrowths of the upper and lower jaws covered with mucous membrane. There are free and attached parts of the gums. The attached part corresponds to the area of ​​the gums fused with the periosteum of the alveolar processes and the surface of the neck of the tooth. The free part is adjacent to the surface of the tooth, separated from the latter by a gum pocket. That part of the gums that is located in the spaces between adjacent teeth is called the interdental gingival papilla.

There is no submucosa in the gums and therefore their mucous membrane is motionlessly fused with the periosteum of the alveolar processes. It is covered with stratified squamous non-keratinizing epithelium, which may partially be subject to keratinization. Gingival epithelial cells are characterized by a high glycogen content. The surface layer of the lamina propria of the mucous membrane forms high narrow papillae that grow into the epithelium. The deep layer of the lamina propria directly passes into the periosteum of the alveolar processes.

Near the neck of the tooth, the gum epithelium is tightly fused with the surface of the tooth, limiting the gap-like space, which is called the gum pocket. The depth of the gum pocket is 1...1.5 mm. Its bottom is the place of attachment of the epithelium to the cuticle of the enamel of the tooth neck, and its walls are the surface of the tooth neck and the free edge of the gums. When salts are deposited in the gum pocket and bacterial toxins act, detachment of the epithelium from the tooth surface can occur (destruction of the epithelial attachment). In this case, a gate is formed for the penetration of microorganisms into the space of the dental socket, which predetermines the development of inflammation of the periodontal tissues (periodontal disease).

The tongue (lingua) is a muscular organ that, in addition to participating in the mechanical processing of food and swallowing, also provides articulation (sound production) and tasting. There are lower, lateral and upper surfaces of the tongue, which have a number of structural features.

Introduction

The digestive system includes digestive tube(gastrointestinal tract, or gastrointestinal tract) and related large glands: salivary glands, liver and pancreas.

A huge number of small digestive glands are part of the wall of the digestive tube.

During the digestion process, mechanical and chemical processing of food and subsequent absorption of the products of its breakdown occur.

The digestive system is conventionally divided into three main sections: anterior, middle and posterior. includes the organs of the oral cavity, pharynx and esophagus. Here, mainly mechanical processing of food occurs. Middle section consists of the stomach, small and large intestines, as well as the liver and pancreas. In this department, primarily the chemical processing of food, the absorption of the products of its breakdown and the formation of feces are carried out.

Posterior is represented by the caudal part of the rectum and provides the function of evacuation of undigested food debris from the digestive canal. In addition to the digestive function itself, this system also performs excretory, immune, and endocrine functions. The excretory function is to excrete through the wall of the digestive tract harmful substances

, which is especially important in case of dysfunction.

The immune function is to capture, process and transport antigens from food, with subsequent development.

The endocrine function is to produce large number

various hormones with local and systemic effects. Development

The epithelial lining of the digestive tube and glands develop from endoderm and ectoderm. From endoderm a single-layer prismatic mucous membrane of the stomach, small and most of the large intestine, as well as the glandular parenchyma of the liver and pancreas are formed. From ectoderm

In the oral and anal bays of the embryo, a multilayered squamous epithelium of the oral cavity, salivary glands and caudal rectum is formed.

Mesenchyme

• is a source of development of connective tissue and blood vessels, as well as smooth muscles of the digestive organs. From mesoderm),
• – visceral layer of the splanchnotome – a single-layer squamous epithelium (mesothelium) of the outer serous membrane (visceral layer of the peritoneum) develops. General plan of the structure of the digestive tube),
• The digestive tube in any of its sections consists of four membranes: internal - mucous membrane ( tunica mucosa
• submucosa ( tela submucosa muscle membrane ( tunica muscularis).

) And

outer membrane, which is represented by either the serous membrane (

It received its name due to the fact that its surface is constantly moistened by mucus secreted by the glands.

• This shell usually consists of three plates:
• epithelial plate (epithelium), lamina propria ( tunica mucosa
• lamina propria mucosae muscular plate of the mucosa ().

lamina muscularis mucosae

The epithelium in the anterior and posterior sections of the digestive tube is multilayered flat, and in its middle section it is single-layered prismatic. In relation to the epithelium, the digestive glands are located either endoepithelial (for example, goblet cells in the intestine), or exoepithelial

: in the lamina propria of the mucous membrane (esophagus, stomach) and in the submucosa (esophagus, duodenum) or outside the digestive canal (liver, pancreas).

The lamina propria of the mucous membrane lies under the epithelium, separated from it by the basement membrane and is represented by loose fibrous membrane.

Here there are blood and lymphatic vessels, nerve elements, and accumulations of lymphoid tissue. In some sections (e.g. esophagus, stomach) simple glands may be located here. The muscular plate of the mucous membrane is located at the border with the submucosa and consists of 1-3 layers formed by smooth muscle cells.

In some areas (tongue, gums) there are no smooth muscle cells.

Relief of the mucosa The membranes throughout the entire digestive canal are heterogeneous. Its surface can be smooth (lips, cheeks), form depressions (dimples in the stomach, crypts in the intestines), folds (in all departments), villi (in the small intestine).

The relief of the mucosa depends on the muscular plate of the mucosa, as well as on the severity of the submucosa.

As a rule, it consists of two layers - an outer longitudinal and an inner circular one. In the anterior and posterior sections of the digestive canal it is predominantly striated, and in the middle (larger) section it is smooth. The muscle layers are separated by connective tissue, which contains blood and lymphatic vessels and the intermuscular nerve plexus of Auerbach ( plexus nervorum intermuscularis s. myenteric

).

Contractions of the muscle membrane help mix and move food through the digestion process. 4. Outer shell Most of the digestive tube is covered serosa– visceral layer of the peritoneum.

The peritoneum consists of a connective tissue base (i.e., the adventitial membrane itself), in which blood vessels and nerve elements are located, and is covered with single-layer squamous epithelium - mesothelium.

Damage to the mesothelium leads to the formation of adhesions – i.e. fusion of the underlying connective tissue of neighboring organs and disruption of their mobility. In the esophagus and part of the rectum, the serous membrane is absent.

In such places, the digestive tube is covered on the outside

adventitia consisting only of loose connective tissue. Vascularization

. The wall of the digestive tube along its entire length is abundantly supplied with blood and lymphatic vessels. The arteries form the most powerful plexuses in the submucosa, which are closely connected with the arterial plexuses lying in the lamina propria of the mucosa. In the small intestine, arterial plexuses also form in the muscular layer. Networks of blood capillaries are located under the epithelium of the mucous membrane, around the glands, crypts, gastric pits, inside the villi, papillae of the tongue and in the muscle layers. Veins also form plexuses of the submucosa and mucosa.. Efferent innervation is provided by ganglia of the autonomic nervous system, located either outside the digestive tube (extramural sympathetic ganglia) or within it (intramural parasympathetic ganglia). The extramural ganglia include the superior cervical, stellate and other nodes of the sympathetic chain, innervating the esophagus, the ganglia of the solar (celiac) and pelvic plexuses, innervating the stomach and intestines. Intramural are the ganglia of the intermuscular (Auerbachian), submucosal (Meissnerian) and subserous or adventitial plexuses. Axons of efferent neurons of the sympathetic and parasympathetic plexuses innervate muscles and glands.

Afferent innervation is carried out by the endings of sensory dendrites nerve cells, located in the intramural ganglia, and the endings of the dendrites of the sensory cells of the spinal ganglia. Sensitive nerve endings are located in muscles, epithelium, and fibrous connective tissue. Afferent endings in the wall of the digestive canal can be polyvalent, i.e. simultaneously innervate various tissues - epithelial, muscle, connective, as well as blood vessels.

In the epithelium of the mucous membrane and glands of all parts of the digestive system, but especially in its middle section, there are single cells - apudocytes. They secrete biologically active substances (neurotransmitters and hormones) have both a local effect, regulating the function of glands and vascular smooth muscles, and overall impact

on the body.

In the digestive organs, their combination is sometimes called the gastroenteropancreatic system (GEP system).

• There are more than 10 types of main cells in this system of the gastrointestinal tract. (Some terms from practical medicine: gastroenterology gastroenterology, ; gastro-Greek gaster gasteros or gastros stomach + Greek entera intestines, intestines +
• logos [teaching) - a section of internal medicine that studies the etiology, pathogenesis and clinical forms of predominantly non-infectious diseases of the gastrointestinal tract, developing methods for their diagnosis, treatment and prevention; commissure(s)