The absolute length of the intestine in cats that eat meat reaches 2.1 m. For comparison: in herbivores, such as sheep or goats, this parameter is 22–43 m. The ratio of the length of the animal’s body to the length of the intestine is 1: 3. There are thin and large intestine.

Small intestine

The length of the small intestine in cats is 1.7 m. It begins at the level of the pylorus of the stomach and is divided into 3 main parts: duodenum (the first and shortest part small intestine, into which the bile ducts and pancreatic ducts exit), the jejunum and ileum. The pancreas lies in the right hypochondrium and secretes several liters of pancreatic secretion into the duodenum per day, containing enzymes that break down proteins, carbohydrates, fats, as well as the hormone insulin, which regulates blood sugar levels. The liver with the gallbladder in cats is located in the right and left hypochondrium; blood flowing through the portal vein from the stomach, spleen and intestines passes through it and is filtered. The liver produces bile, which converts fats before they can be absorbed into blood vessels intestinal wall. The bile duct is slightly curved. Its opening and the opening of the pancreas are located at a distance of 5–8 cm from the pyloric sphincter of the stomach.

The intestinal mucosa is better suited for digestion and absorption of food. Epithelial cells lining inner surface small intestine are called enterocytes. The mucous membrane is collected in folds called villi. Each villi is well supplied with blood vessels and has a dead-end lymphatic vessel (lacteal). Absorbed substances are transported through these vessels. nutrients from the small intestine to the liver and other parts of the body. The duodenum has a relatively porous structure and is capable of secreting a large volume of fluid into the lumen. The degree of permeability decreases accordingly in the jejunum, ileum and large intestine, where only fluid resorption takes place. This way, fluid is retained in the body, which saves it from dehydration.

The bulk of proteins is digested in the small intestine to amino acids under the action of pancreatic enzymes. They are absorbed into enterocytes through specific transporters and transported to the liver through the portal vein. Carbohydrates (cats get most of their carbohydrates in the form of starches) are broken down in the small intestine into glucose and other monosaccharides by pancreatic enzymes. In enterocytes, glucose is rapidly released into the bloodstream and transported to the liver through the portal vein. Dietary fats mainly consist of triglycerides, which can be easily broken down and absorbed when exposed to salts bile acids to glycerol and fatty acids, and cholesterol and phospholipid can be digested by cats, but not as efficiently. This occurs under the influence of bile secreted by the liver and stored in the gallbladder. Since the cell membrane of enterocytes consists of lipids, the absorption process occurs passively and is often accompanied by the absorption of vitamins dissolved in fats. Inside enterocytes fatty acids converted into triglyceride and attached to lipoproteins, forming chylomicrons, which are excreted into the milk duct for transport to main system blood circulation and, accordingly, to the liver and other tissues.

Thus, any disruption of the small intestine (eg infection) can cause diarrhea and anorexia (loss or lack of appetite) due to the virus attacking the enterocytes of the villous apex. Well-digestible foods are necessary to reduce the cost of enzymes and increase the absorption area, which simultaneously achieves good level nutrient consumption. Eating small amounts of food does not exceed the digestive and absorption capabilities of the intestines and reduces the risk of diarrhea.

Large intestine

This section of the intestine is represented by the cecum, colon and rectum. The cecum is a short, blunt tube 2–4 cm long located under the 2nd–4th lumbar vertebrae. It communicates widely with the colon, which lacks a vermiform appendix - the appendix. The colon is a short intestine that is shaped like a horseshoe. It is located in the lumbar region, where it forms an arc. The rectum, which has a powerful muscular structure, lies at the level of the 4th–5th sacral vertebra. On the mucous membrane of the large intestines there are crypts - depressions where the intestinal glands are located, but there are few cells that secrete enzymes. The columnar epithelium of the mucous membrane contains many goblet cells that secrete mucus. Feces are formed in the large intestine.

In the large intestine, the final hydrolysis of nutrients occurs with the assistance of enzymes of the intestinal tract and enzymes of microorganisms. The most active activity of the intestinal microflora is observed in the colon: absorption of water and electrolytes, which is necessary for the formation feces and preventing dehydration; fermentation of food residues by abundant bacterial flora. From leftover food rich in nitrogen, bacteria produce large amounts of ammonia, which is absorbed and travels through the portal vein to the liver, where it is processed into urea, which is excreted by the kidneys. Due to strong peristaltic contractions, the remaining contents of the large intestine enter the rectum through the descending colon, where feces accumulate. The release of feces into environment occurs through the anal canal (anus). The anus has two sphincters: deep, consisting of smooth muscle fibers, and external, made of striated muscles.

Structure

Small intestine is a narrowed section of the intestinal tube.

Slim department intestines is very long, representing the main part of the intestine and ranges from 2.1 to 7.3 meters in dogs. Suspended on a long mesentery, the small intestine forms loops that fill most of the abdominal cavity.

Small intestine leaves the end of the stomach and divides into three various departments: duodenum, jejunum and ileum. The duodenum accounts for 10% of the total length of the small intestine, while the remaining 90% of the length of the small intestine consists of the jejunum and ileum.

Blood supply

The wall of the thin section is richly vascularized.

Arterial blood It enters through the branches of the abdominal aorta - the cranial mesenteric artery, and to the duodenum also through the hepatic artery.

Venous drainage occurs in the cranial mesenteric vein, which is one of the roots of the portal vein of the liver.

Lymphatic drainage from the intestinal wall comes from the lymphatic sinuses of the villi and intraorgan vessels through the mesenteric (intestinal) lymph nodes into the intestinal trunk, which flows into the lumbar cistern, then into the thoracic lymphatic duct and cranial vena cava.

Innervation

The nervous supply of the thin section is represented by branches vagus nerve and postganglionic fibers of the solar plexus from the semilunar ganglion, which form two plexuses in the intestinal wall: intermuscular(Auerbach's) between the layers of the muscle membrane and submucosal(Meissner) in the submucosal layer.

Control of intestinal activity by the nervous system is carried out both through local reflexes and through vagal reflexes involving the submucosal nerve plexus and intermuscular nerve plexus.

Intestinal function is regulated by the parasympathetic nervous system, the center of which is its medulla oblongata, from where the vagus nerve (10th pair of cranial nerves, respiratory-intestinal nerve) extends to the small intestine. Sympathetic vascular innervation regulates trophic processes in the small intestine.

The processes of local control and coordination of motility and secretion of the intestine and associated glands are of a more complex nature; nerves, paracrine and endocrine chemicals take part in them.

Topography

Intestinal lining

The functional features of the small intestine leave an imprint on its anatomical structure. Highlight mucous membrane And submucosal layer, muscular (external longitudinal and internal transverse muscles) And serous intestinal lining.

Mucous membrane

Mucous membrane forms numerous devices that significantly increase the suction surface.

These devices include circular folds, or Kirkring folds, in the formation of which not only the mucous membrane, but also the submucosal layer, and lint, which give the mucous membrane a velvety appearance. The folds cover 1/3 or 1/2 of the circumference of the intestine. The villi are covered with a special bordered epithelium, which carries out parietal digestion and absorption. The villi, contracting and relaxing, perform rhythmic movements with a frequency of 6 times per minute, due to which they act as a kind of pumps during suction.

In the center of the villus there is a lymphatic sinus, which receives fat processing products. Each villus from the submucosal plexus contains 1-2 arterioles, which break up into capillaries. Arterioles anastomose with each other and during absorption all capillaries function, while during a pause there are short anastomoses. Villi are thread-like outgrowths of the mucous membrane, formed by loose connective tissue rich in smooth myocytes, reticulin fibers and immunocompetent cellular elements, and covered with epithelium.

The length of the villi is 0.95-1.0 mm, their length and density decreases in the caudal direction, that is, in the ileum the size and number of villi are much smaller than in the duodenum and jejunum.

Histological structure

The mucous membrane of the thin section and villi is covered with a single-layer columnar epithelium, which contains three types of cells: columnar epithelial cells with a striated border, goblet exocrinocytes(secrete mucus) and gastrointestinal endocrinocytes.

The mucous membrane of the thin section is replete with numerous parietal glands - the common intestinal, or Lieberkühn's glands (Lieberkühn's crypts), which open into the lumen between the villi. The number of glands averages about 150 million (in the duodenum and jejunum there are 10 thousand glands per square centimeter of surface, and 8 thousand in the ileum).

The crypts are lined with five types of cells: epithelial cells with a striated border, goblet glandulocytes, gastrointestinal endocrinocytes, small borderless cells of the crypt bottom (stem cells of the intestinal epithelium) and enterocytes with acidophilic granules (Paneth cells). The latter secrete an enzyme involved in the breakdown of peptides and lysozyme.

Lymphoid formations

For duodenum characteristic tubular-alveolar duodenal, or Bruner's glands, which open into crypts. These glands are a continuation of the pyloric glands of the stomach and are located only on the first 1.5-2 cm of the duodenum.

The final segment of the thin section ( ileum) is rich in lymphoid elements, which lie in the mucous membrane at different depths on the side opposite to the attachment of the mesentery, and are represented by both single (solitary) follicles and their clusters in the form of Peyer's patches.

Plaques begin already in the final part of the duodenum.

The total number of plaques is from 11 to 25, they are round or oval in shape, length from 7 to 85 mm, and width from 4 to 15 mm.
The lymphoid apparatus takes part in the digestive processes.

As a result of the constant migration of lymphocytes into the intestinal lumen and their destruction, interleukins are released, which have a selective effect on the intestinal microflora, regulating its composition and distribution between the thin and thick sections. In young organisms, the lymphoid apparatus is well developed, and the plaques are large.

With age, a gradual reduction of lymphoid elements occurs, which is expressed in a decrease in the number and size of lymphatic structures.

Muscularis

Muscularis represented by two layers of smooth muscle tissue: longitudinal And circular, and the circular layer is better developed than the longitudinal one.

The muscularis propria provides peristaltic movements, pendulum movements, and rhythmic segmentation that propel and mix the intestinal contents.

Serosa

Serosa- visceral peritoneum - forms the mesentery, on which the entire thin section is suspended. At the same time, the mesentery of the jejunum and ileum is better expressed, and therefore they are combined under the name mesenteric colon.

Functions

Digestion of food is completed in the small intestine under the action of enzymes produced by the wall ( liver And pancreas) and wall ( Lieberkühn and Brunner) glands, absorption of digested products into the blood and lymph, and biological disinfection of incoming substances.

The latter occurs due to the presence of numerous lymphoid elements enclosed in the wall of the intestinal tube.

Great also endocrine function thin section, which consists in the production of some biologically active substances by intestinal endocrinocytes (secretin, serotonin, motilin, gastrin, pancreozymin-cholecystokinin, etc.).

It is customary to distinguish three sections of the thin section:

• initial segment, or duodenum,
• middle segment, or jejunum,
• and the final segment, or ileum.

Duodenum

Structure

The duodenum is the initial section of the thin section, which is connected to the pancreas and the common bile duct and has the form of a loop facing caudally and located under the lumbar spine.

The length of the intestine is on average 30 cm or 7.5% of the length of the thin section. This section of the thin section is characterized by the presence of duodenal (Bruner's) glands and a short mesentery, as a result of which the intestine does not form loops, but forms four pronounced convolutions.

Topography

The cranial part of the intestine forms S-shaped, or sigmoid gyrus, which is located in the pylorus region, receives the ducts of the liver and pancreas and rises dorsally along the visceral surface of the liver.

Under the right kidney, the intestine makes a caudal turn - this cranial gyrus of the duodenum, and goes to descending part, which is located in the right iliac.

This part passes to the right of the root of the mesentery and under the 5-6 lumbar vertebrae passes to the left side transverse part, dividing the mesentery into two roots in this place, and forms caudal gyrus of the duodenum.

The intestine is then directed cranial to the left of the mesenteric root as ascending part. Before reaching the liver, it forms duodejejunal gyrus and passes into the jejunum. Thus, a narrow loop is formed under the spine anterior root mesentery containing the right lobe of the pancreas.

Jejunum

Structure

The jejunum is the longest part of the small section and is about 3 meters, or 75% of the length of the small section.

The intestine got its name due to the fact that it has a half-dormant appearance, that is, it does not contain voluminous contents. The diameter exceeds the ileum located behind it and is secreted a large number vessels passing through a well-developed mesentery.

Due to its considerable length, developed folds, numerous villi and crypts, the jejunum has the largest absorption surface, which is 4-5 times greater than the surface of the intestinal canal itself.

Topography

The intestine forms 6-8 skeins, which are located in the region of the xiphoid cartilage, the umbilical region, the ventral part of both ilia and groins.

Ileum

Structure

The ileum is the final part of the thin section, reaching a length of about 70 cm, or 17.5% of the length of the thin section. Externally, the intestine is no different from the jejunum. This section is characterized by the presence of a large number of lymphoid elements in the wall. The final section of the intestine has thicker walls and the highest concentration of Peyer's patches. This section runs straight under the 1st-2nd lumbar vertebrae from left to right and in the area of ​​the right ilium flows into the cecum, connecting with it by a ligament. At the confluence ileum in the blind, the narrowed and thickened part of the ileum forms ileo-cecal valve, or ileal papilla, which has the appearance of a relief ring-shaped damper.

Topography

This section of the small intestine received its name due to its topographic proximity to the iliac bones, to which it is adjacent.

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there are bundles of smooth muscle cells. The mesh has the thickest muscular layer.

In the book, unlike other chambers of the proventriculus, the muscular lamina of the mucous membrane is well developed, which, in the form of a continuous layer, separates the lamina propria from the submucosa and extends into the leaflets.

IN large leaves extend into the submucosa and even the inner layer of the muscular layer.

IN As a result, the leaves can shorten and lengthen.

The abomasum is the stomach itself with an intestinal-type mucous membrane. The structure of its wall is similar to the structure of the wall of a single-chamber intestinal-type stomach. In the abomasum, zones of cardiac, fundic and pyloric glands are also distinguished. The zone of the cardiac glands looks like a narrow strip at the cranial edge of the abomasum. The pyloric glands lie in the pyloric part of the abomasum.

The most common glands are fundic. The difference from the stomach of a pig and a horse is that the gastric pits in the abomasum are narrow. Only one gland opens into each fossa. The fundic glands have a long neck and a relatively short body. The pyloric glands are longer than those of other farm animals.

MIDDLE INTESTINE OR SMALL INTESTINE

The midgut (small intestine) is long (over 40 m in large intestines and about 30 m in small intestines) cattle and horses, over 20 m in pigs) and consists of the duodenum, jejunum, ileum (Fig. 106) and wall glands associated with the duodenum: liver and pancreas. The diameter of the small intestine is relatively small. The most active processes of digestion and absorption of food occur in the small intestine.

Duodenum- intestinum duodenum (Fig. 107)

for cattle 90-120 cm long, for small cattle - about 50 cm. Width 5-7 cm for large cattle and 2-3 cm for small cattle. Suspended on a short mesentery, and in places lies extraperitoneally. As a result, it does not change its position in the abdominal cavity.

It is located mainly in the right hypochondrium and only slightly extends into the lumbar region. Starting from the abomasum, it goes forward to the liver. Near the gate of the liver in the right hypochondrium it makes an S-shaped bend, rises caudodorsally, reaches the right kidney, from here it goes back to the ilium, after which it turns left and forward and passes into the jejunum without sharp boundaries. Approximately in the middle, the bile duct flows into the duodenum, and a little further from it - the pancreatic duct.

Vrakin V.F., Sidorova M.V.	MORPHOLOGY OF FARM ANIMALS

Rice. 106. Intestines of large horns, cattle (A), pigs (B) and horses

1 - pylorus of the stomach; 2 - duodenum; 3 - jejunum; 4

Ileum; 5 - cecum and its 6 - apex; 7 - body; 8 - head (base); 9 -tenii; 10- pockets; 11- colon and its 12 - initial, 13 - centripetal, 14 - centrifugal and 15 - final loops; 16 - left ventral and dorsal positions; 17 - diaphragmatic positions; 18- right ventral and dorsal positions; 19- small colon; 20 - rectum.

The intestine is innervated by the branches of the vagus nerve and the celiac plexus. It receives blood from the branches of the celiac artery.

U pig intestine long 40-80 cm, lies in the right hypochondrium and lumbar region. Heading back, it does not reach the ilium, makes a turn near the right kidney and returns to the liver, where it passes into the jejunum. The bile duct opens at the beginning of the duodenum, and the pancreas - closer to the middle.

U The horse's intestine is about 1 m long and lies in the right hypochondrium and lumbar region. Its initial section is somewhat expanded. Behind the right kidney, the intestine turns to the left, where it passes into the jejunum.

Vrakin V.F., Sidorova M.V.	MORPHOLOGY OF FARM ANIMALS

The hepatic and pancreatic ducts flow side by side at a distance of 10-12 cm from the pylorus.

Fig. 107. Section of the mucous membrane of the duodenum:

A - villus; B-crypt; I - epithelium; 1 - bordered; 2 - goblet; 3 - endocrine and 4 - borderless cells; 5

Paneth cell; II - lamina propria of the mucous membrane; 6 - blood capillary: 7 - lymphatic capillary; 8 - smooth muscle cells; III - muscular plate of the mucous membrane.

The jejunum - intestinum jejunum - is the longest and narrowest intestine. In cattle its length is 37-39 m, in sheep it is about 25 m. It hangs on the mesentery, forming many loops and curls. Located in the form of a garland around the labyrinth of the colon, mainly in right half abdominal cavity: in the hypochondrium, iliac and inguinal regions. Without sharp boundaries it passes into the ileum. Innervated by the branches of the mesenteric plexus, vascularized by the cranial mesenteric artery.

U pig intestine long 15-20 m hangs on a long mesentery, is easily removable, occupies all free spaces in the abdominal cavity between the liver and colon. It is better to examine it in the hypochondrium. In addition, its loops extend into the xiphoid process, umbilical, iliac and inguinal regions.

U horse gut length 20-30 m, 6-7 cm wide. Hangs on a long mesentery (up to 50 cm), located in a cup-shaped depression formed by the large colon and cecum. It is better to examine the hypochondrium and left iliac region.

The ileum - intestinum ilium - is short, lies in the right ileal region. In farm animals, its length is

Vrakin V.F., Sidorova M.V.	MORPHOLOGY OF FARM ANIMALS

It is about 50 cm long. It is suspended on a short mesentery. Starts from the last turn of the jejunum and ends at the confluence with the large intestine at the border of the cecum and colon. In the horse it flows into the head of the cecum. Innervated by the branches of the mesenteric plexus, vascularized by the branches of the cranial mesenteric artery.

Histological structure of the small intestine. Small intestines

la - tube-shaped organs. Their wall is formed by the mucous membrane, submucosa, muscular and serous membranes.

The mucous membrane consists of three layers: epithelium, lamina propria and lamina muscularis. The epithelium lining the intestinal lumen is single-layer cylindrical. It contains several types of cells. The most common are bordered - suction and goblet, producing mucus.

lamina propria of the mucous membrane formed by loose fiber

low connective and reticular tissues with a large number of different cells. It contains both fibroblastic cells (fibroblasts, histiocytes) and blood cells (lymphocytes and other leukocytes). It branches out into a large number of blood and lymphatic vessels that form networks and nerve fibers, and also contains intestinal glands (crypts). The lamina propria contains many lymphocytes and lymphatic follicles. Single or solid lymphatic follicles of microscopic size. Clusters of lymphatic follicles - lymphatic (Peyer's) patches - convex macroscopic formations ranging in length from several centimeters to several meters.

Muscular plate of the mucous membrane consists of smooth muscle

woven fabric, the bundles of which form 2 layers: annular and longitudinal. The relief of the mucous membrane is not smooth. It gathers into folds in the re-

The result of contraction of the muscular plate and muscular membrane, which straighten as food passes. Non-expanding folds and numerous protrusions - villi - are formed, many times increasing the surface of the mucous membrane, which is very important for intensifying the processes of digestion and absorption.

Villus is a protrusion of the mucous membrane formed by all its layers. In cattle it is leaf-shaped, in other farm animals it is finger-shaped. On an area of ​​1 mm2 there are 25-40 villi with a height of 0.4-0.5 mm.

Each villi is covered with epithelium, which includes border, goblet and endocrine cells.

The main type of cells is bordered (enterocytes with a striated border) - cylindrical in shape, tightly attached to each other by closing (tight) contacts, which isolates the internal environment of the body from the intestinal cavity. The elongated nucleus is shifted to the basal pole. At the apical pole there are several hundred microvilli, which, together with the supra-membrane complex of the cell (glycocalyx), form

Vrakin V.F., Sidorova M.V.	MORPHOLOGY OF FARM ANIMALS

cut a striated (brush) border. It increases the suction surface of the cell by almost 30 times. In addition, a large number of enzymes involved in the breakdown and transport of absorbed substances (phosphatases, aminopeptidases, glucosidases, etc.) were found in it, due to which these processes most actively occur on the microvilli of the striated border. This type of digestion is called parietal digestion, in contrast to cavity digestion, which occurs in the intestinal lumen. In bordered enterocytes, a submembrane complex of microfilaments and microfibrils is well expressed. It apparently promotes the transport of absorbed substances deep into the cell. In the deeper parts of the cytoplasm, a granular cytoplasmic reticulum and many lysosomes are well developed. Mitochondria are localized mainly in the basal part of the cell.

Goblet cells have typical structure(see glandular epithelium). They produce mucus, which moisturizes the inner surface of the intestines and thereby promotes the movement of food masses. The number of goblet cells increases from the duodenum to the ileum.

Endocrine (argentaffin) cells unevenly distributed.

They are found throughout the epithelial layer of the mucous membrane. They come in several types: secreting serotonin, enterogastrin, cholecystokinin and others biologically active substances regulating the activity of the digestive system.

The villous epithelium is separated from the underlying stroma by a basement membrane. The villous stroma is formed by loose connective and reticular tissue. Under the epithelium there is a vascular network, into the capillaries of which substances from the bordered enterocytes enter. In the stroma along the villus there are bundles of smooth muscle cells, and in its middle there is a lymphatic capillary - sinus (in sheep there are several of them). When muscle cells contract, the villus changes its shape, as a result of which the food mass is mixed and new portions of it come into contact with the striated border, and blood and lymph are also pushed through the capillaries, carrying the nutrients that have entered them outside the villus.

Intestinal crypts (intestinal glands) are depressions in the epithelium of the mucus

zestous membrane in the form of simple tubular, sometimes branched glands. Several crypts may be located around one villus. The total number of them in the small intestine exceeds 100 million. The epithelial layer of the mucous membrane is the same for villi and crypts. The same types of cells are found in the crypts as in the villi. In the upper parts of the crypts, bordered cells predominate and goblet cells are found. Deeper are the borderless undifferentiated cells, among which mitoses are frequent. These cells are cambial for the cells of the villi and crypts, since the life cycle of the intestinal epithelium does not exceed 2-3 days. At the bottom of the crypts lie

endocrine (argentaffin), apical granular, cells with acidophilic granularity (Paneth), etc.

Vrakin V.F., Sidorova M.V.	MORPHOLOGY OF FARM ANIMALS

The submucosa is formed by loose fibrous connective tissue, in which, along with collagen, there are also reticular fibers that form a three-dimensional network. There are many vessels in the submucosa, and the submucosal nerve plexus is developed. In the submucosa of the initial section of the small intestine lie the glands of the duodenum - duodenal (submucosal) glands.

Duodenal (submucosal) glands in cattle and horses are developed over a length of 4-5 m, in sheep - 60-70 cm, in pigs - 3-5 m, that is, they are located in the walls of the duodenum and at the beginning of the jejunum. These are complex tubular (in ruminants - alveolar-tubular) glands that produce mucous (in ruminants - mixed) secretion. In ruminants, the glands are located in separate packages; in pigs, they form a continuous layer of densely lying terminal sections. The terminal sections can be light or dark, from high and low cells, depending on the phase of secretion. The gland ducts open onto the surface of the mucosa either independently or into the bottom of the crypts.

The muscular layer of smooth muscle tissue forms circular and longitudinal layers, separated by a connective tissue layer with the intermuscular nerve plexus.

The serous membrane consists of loose connective tissue and mesothelium, passes into the mesentery and intestinal ligaments.

Liver - hepar (Fig. 108) is the largest wall gland of the body, especially in embryonic period, when it is a hematopoietic organ and occupies most of the abdominal cavity. The functions of the liver are varied.

Rice. 108. Diagram of the liver lobes from the visceral surface:

A - cattle; B - horses; B - pigs; 1 - left lobe; 2 - left lateral and 3 - left medial lobes; 4 - esophagus; 5 - caudal vena cava; 6 - caudate lobe with caudate process; 7- portal vein; 4 - hepatic artery; 9 - hepatic duct; 10 - bile duct; 11- gallbladder; 12-square share; 13 - round ligament.

Vrakin V.F., Sidorova M.V.	MORPHOLOGY OF FARM ANIMALS

How digestive gland, it produces bile, which emulsifies fats, saponifies fatty acids, and enhances the action of pancreatic enzymes. The liver performs a barrier function, neutralizing exogenous and endogenous toxins that enter the blood from the gastrointestinal tract, including toxic products of protein metabolism, converting them into urea. The liver deposits carbohydrates, vitamins A, E, D, K, blood (up to 20%), synthesizes the most important blood plasma proteins (fibrinogen, globulins, albumins, prothrombin), phosphoproteins, vitamin B12. In total, the liver performs over 500 functions in the body.

The liver of cattle is massive, brown-red in color, weakly divided into lobes (right and left). It has a convex diaphragmatic surface adjacent to the diaphragm, and concave - visceral surface, facing the insides. The stomach, intestines and right kidney form depressions on it. Almost in the center of the visceral surface there is a depression - the hilum of the liver. In the area of ​​the portal, the liver enters the hepatic artery, portal vein, nerves, and exits hepatic duct And lymphatic vessels. This is where the lymph nodes are located. Ventral to the hilum lies the gallbladder. Moves away from him cystic duct, when it merges with the hepatic duct, the bile duct is formed, which flows into the duodenum.

The mediodorsal edge of the liver is blunt, the rest are sharp. On the blunt edge there are depressions of the esophagus and caudal vena cava, which grows into the liver tissue. The hepatic veins open into it. On the sharp ventral edge there is a shallow notch that separates the left lobe. In many animals, a deserted umbilical vein in the form of round ligament of the liver, which goes to the navel. Between the left and right lobes, the caudate lobe is distinguished, located above the gate, with a large caudate process, hanging down at the right end of the liver, and the quadrate lobe - the area of ​​the liver below the gate, between the round ligament and the gallbladder.

The liver is innervated by branches of the vagus nerve and solar plexus. Vascularized by the hepatic artery, which arises from the celiac artery. It is located in the right hypochondrium, reaching the 2-3rd lumbar vertebra on the right, and the sternum on the left. The liver is attached to the diaphragm, kidney, and duodenum by ligaments. It is connected to the stomach by the lesser omentum.

The pig's liver is relatively larger (up to 2.5%) than that of cattle, yellowish color. The right and left lobes are separated from each other by a deep notch. Each of them, in turn, is divided into lateral and medial lobe. The caudal vena cava grows into the liver tissue. The gate of the liver is shifted to the dorsal edge. Square lobe of triangular shape. The caudate lobe is small, the caudate process is not clearly defined. The kidney does not touch the liver. The liver is located in the right and left hypochondrium almost equally. The ventral edge enters the region of the xiphoid process.

Vrakin V.F., Sidorova M.V.	MORPHOLOGY OF FARM ANIMALS

In a horse, the left lobe is divided into left lateral And left medial lobe. The caudate process is relatively small. The quadrate lobe is delimited on the left by the round ligament, on the right by the notch. The horse, like other equids (as well as camels, deer, many rodents, etc.), lacks a gallbladder. Bile enters the duodenum through hepatic duct.

Histological structure of the liver (Fig. 109). The liver is a compact organ. It consists of connective tissue stroma and parenchyma formed by epithelium of endodermal origin. The liver has an extremely developed vascular bed, since almost all liver functions are performed in close contact with the blood. The thin connective tissue capsule of the liver is covered with a serous membrane on top. In the gate area connective tissue capsule penetrates into the organ and branches, dividing it into lobules. Among farm animals, the lobulation of the liver is clearly visible in the pig; in other animals it can be traced due to the peculiar regular arrangement of the interlobular vessels: the interlobular artery, vein and bile duct lie side by side, forming a triad. Triads are located at the border between the lobules. Intralobular connective tissue is absent. In lobules at special treatment only the finest network of reticular fibers is noticeable.

The liver lobules are polygonal in shape, in cross-section they look like 5-6 triangles with a diameter of 0.7-2 mm. They are educated liver plates, consisting of liver cells - hepatocytes. The hepatic plates are separated by wide blood capillaries - sinusoids, formed as a result of the fusion of arterial and venous capillaries. In the center of the lobule is the central vein of the lobule, into which blood flows from the sinusoidal capillaries. The liver plates consist of two rows of cells and have a radial direction. Along their length from the periphery of the lobule to its center, the liver plates anastomose with each other, forming a network, but at the same time, each hepatocyte necessarily contacts the sinusoidal capillary with at least one side.

Inside the liver plates there are bile capillaries. They do not have their own walls; they are grooves formed by the plasmalemma of neighboring hepatocytes. Connecting with each other, the grooves form the thinnest tubes, visible only through an electron microscope. The areas of the plasma membrane of hepatocytes that form the walls of the bile capillary are delimited by the adhesion zone and the dense zone, which excludes contact of bile with blood. The bile capillaries blindly begin in the center of the lobule. Bile flows through them to the periphery of the lobule, where it enters interlobular gall excretory duct, lined with cubic epithelium. The interlobular excretory ducts unite and form hepatic duct.

Vrakin V.F., Sidorova M.V.	MORPHOLOGY OF FARM ANIMALS

Rice. 109. Scheme of the histological structure of the liver:

A - liver lobule; B - location biliary tract and blood vessels in the lobule; B - hepatocyte; 1- hepatic plate; 2 - sinusoid; 3 - central vein; 4 - interlobular connective tissue; 5 - artery; 6 - vein and 7 - interlobular bile duct; 8 - bile capillary; 9 - microvilli; 10 - circumsinusoidal space (Disse); 11-mitochondria; 12

Granular cytoplasmic reticulum; 13 - Golgi complex; 14_lysosomes; 15 - agranular cytoplasmic reticulum; 16 - capillary endothelium; 17 - stellate cell.

The close contact that exists between the liver parenchyma and its vascular bed is expressed in the peculiarities of their structure. Between hepatocytes and capillary endothelium there is no basement membrane and there is a

Vrakin V.F., Sidorova M.V.	MORPHOLOGY OF FARM ANIMALS

circlesine space(Disse), filled with tissue fluid. Here the exchange of substances between blood and hepatocytes occurs. Numerous hepatocyte microvilli are directed into it, reaching the endothelium.

In addition to the usual endothelium, the composition of the endothelium of sinusoidal capillaries

al cells include processes stellate reticuloendotheliocytes

(Kupffer cells)- modified blood macrophages that are part of the capillary wall. They are liver macrophages. They are primarily contacted by microbes, toxins, and foreign substances that enter the blood. By phagocytizing them, they then transfer the products of their processing to hepatocytes (through the space of Disse) for further disposal or use in metabolic processes. When activated, stellate cells increase in size, are isolated from the endothelial layer, and their processes penetrate deeply into the lumen of the capillary and the space of Disse.

Hepatocytes are polygonal cells with a large round nucleus lying in the center. There are also binucleate cells. In cattle and horses their number is small (8%), in pigs it reaches 40%. With age, the number of binuclear and polyploid hepatocytes increases to 80%.

IN All organelles of general importance are developed in the cytoplasm. Mitochondria are especially numerous, the number of which reaches 2500, free and bound ribosomes, and cisterns of the cytoplasmic reticulum. Various inclusions accumulate in hepatocytes: glycogen, fat, vitamins, etc. There is a certain cycle of functional activity and direction: during the day, bile secretion predominates, at night - glycogen synthesis; glycogen is deposited first in the center of the lobule and then at the periphery, and fat - vice versa.

IN In hepatocytes, there are 2 functional poles: bile, facing the bile capillary, and vascular, in contact with the sinusoidal blood capillary. There are microvilli at both poles.

Blood circulation in the liver. The portal vein, which carries blood from the digestive organs and spleen, and the hepatic artery enter and branch in parallel with the liver. Between the lobes their branches form interlobular veins and arteries. Together with the interlobular bile ducts they form triads. From interlobular vessels to at different levels retreat circumlobular arteries veins branching into capillaries. The capillaries enter the lobules and merge with each other, forming wide sinusoidal capillaries, carrying mixed blood. Blood moves slowly from the periphery of the lobule to its center. At the same time, its composition changes, and the liver performs its many functions. In the center the blood flows into central vein of the lobule. Thus, in the liver, the capillaries are between two veins. This phenomenon is called the miraculous liver network. From the central vein of the lobule, blood flows into sublobular vein. The latter unite and through a number of vessels flow into hepatic veins, opening into the caudal vena cava. The liver vessels have sphincters that regulate blood flow in it. Blood flow from the veins of the intestines, stomach, pancreas and

Vrakin V.F., Sidorova M.V.	MORPHOLOGY OF FARM ANIMALS

the spleen through the liver to the caudal vena cava is called the portal blood

imagination.

Pancreas- pancreas (Fig. 110) - refers to glands with double secretion - external and internal.

As an exocrine gland, it produces pancreatic (pancreatic) juice containing trypsin, chemotrypsin, carboxypeptidase, ribonuclease, lipase and other enzymes that break down proteins, fats and carbohydrates of feed. As an endocrine gland, it produces hormones (insulin, glucagon, lipocaine) that regulate carbohydrate metabolism and are involved in the regulation of protein and fat metabolism. The exocrine part of the gland makes up 97% of its mass and therefore determines its size and shape.

U cattle iron yellow-brown in color, has a tuberous surface and consists of a body (middle part), left and right lobes. It is located in the right hypochondrium and in the right part of the lumbar region. Body

And the right lobe lies along the duodenum. The left lobe extends to the left and is adjacent to the scar. The excretory duct opens at the end of the duodenum. The caudal vena cava passes between the lobes. The gland is innervated by the vagus and sympathetic nerves. It receives blood from the branches of the celiac artery.

U in a pig, the right lobe stretches along the duodenum to the right kidney, the left lobe is adjacent to the spleen and left kidney, so that the gland lies in both hypochondriums and extends into the lumbar region. The excretory duct opens into the duodenum at a distance 15-25 cm from the pylorus.

The horse's iron is grayish-pink in color. Lies in both hypochondriums. The body is located in the S-shaped bend of the duodenum. The right lobe is weakly separated from the body, the left lobe lies on the lesser curvature of the stomach. The main excretory duct opens into the duodenum along with the hepatic duct. Sometimes there is an accessory excretory duct that opens separately.

Histological structure. The pancreas is a compact organ, a complex walled alveolar gland. The top is covered with a serous membrane. The connective tissue stroma forms a thin capsule, from which interlobular layers of connective tissue extend. Intralobular layers of loose connective tissue are poorly developed. The stroma contains blood vessels and nerves, there are small autonomic ganglia (clusters of nerve cells) and nerve endings.

Exocrine parenchyma is formed by epithelium of endodermal origin and consists of terminal sections and excretory ducts.

MORPHOLOGY OF FARM ANIMALS

A - appearance; B - histological structure of the gland lobule area; 1

- duodenum; 2 - right lobe of the pancreas; 3

Body; 4 - left lobe; 5 - portal vein; 6 - cranial mesenteric artery; 7- alveolus; 8 - acinar cell; 9 - zymogenic and 10 - basophilic zones; 11-insertion duct; 12 - centroacinous cell; 13

- intralobular and 14- interlobular connective tissue; 15 - intralobular and 16 - interlobular excretory ducts; 17 - islet; 18 – B – cell; 19-A-cell; 20 capillary.

The acinar cell has a clearly defined apicobasal differentiation. Its basal, more expanded part is filled with a mass of flat sacs of a granular cytoplasmic reticulum, perceives basic dyes, for which it is called the basophilic, or homogeneous, zone. The round nucleus is shifted to the basal part of the cell. Above it is the Golgi complex. At the apical pole of the cell, large round granules of secretion accumulate - zymogen, which includes various enzymes in an inactive form. The granules are stained with acidic dyes, for which this part of the cell is called the oxyphilic, or zymogenic, zone. The secretion is secreted through the apical pole in a merocrine manner and enters the excretory duct system.

The excretory duct of the smallest diameter is called intercalary, since it is pressed to different depths into the alveoli. As a result, the cells of its wall appear to be inserted into the center of the acinus and are therefore called centroacinous. In sections, their elongated light nuclei can be seen lying inside the alveoli. The diameter of the intercalary ducts is smaller than the alveoli. Their wall is formed by flattened cells with light cytoplasm, poor in organelles. The intercalary ducts unite first into small ones intralobular excretory ducts, then into larger intralobular ducts and, finally, into interlobular excretory ducts. The latest images

there is a common excretory duct of the pancreas, going to twelve

duodenum. As the diameter of the duct increases, the height of its epithelium increases, and the surrounding layers of connective tissue thicken and become denser.

Endocrine parenchyma makes up about 3% of the mass of the pancreas, represented by pancreatic islets (Langerhans). They have an irregularly rounded, ellipsoidal or process-shaped shape and are well supplied with blood. Several capillaries can usually be seen in the islet. Islets consist of several types of cells that produce different hormones. They differ from each other only with special processing. Islet cells smaller than acinar ones and lighter. All of them contain small mitochondria, a well-developed Golgi complex and secretory granules characteristic of each cell type.

The most numerous are up to 70-75% B- or β-cells. These cells are stained basophilically with special dyes. Their grain size is soluble in alcohol and insoluble in water. The insulin they produce can

Igor Nikolaev

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In the intestines of animals, the final breakdown of feed and absorption of nutrients and microelements into the body occurs. The food bolus is affected by enzymes that are produced by internal and external glands. Internal glands are located on the walls of the intestine itself.

External glands include the pancreas and liver. The intestine of cattle consists of a thin and thick section. They, in turn, are divided into separate sections, which perform digestive system a certain function. The total length of a cow's intestines is 63 m. What are the structural features of the cattle intestines? How does the food bolus break down in it?

Small intestine

The small intestine consists of 3 sections: duodenum, jejunum and ileum. The length of the duodenum in humans is 12 fingers. In a cow it is 120 cm. It connects the intestines with the rennet of the stomach. The duodenum passes from the right hypochondrium to the liver, rises to the spine, makes an S-shaped zigzag and returns to the liver.

The inside of the intestine is covered by a mucous membrane. It forms many folds. There are depressions between them. Folds and depressions consist of columnar epithelial cells.

It contains many small villi. Between the villi, at the base, there are crypts. These are tubular recesses. Folds and depressions of the mucous membrane, villi and crypts increase the absorption surface. The suction surface area is several times larger than the cow's body area.

Four types of glands act on the food bolus in the duodenum:

1. in crypts;
2. in the mucous membrane;
3. pancreas;
4. liver.

The pancreas is the supplier of pancreatic secretion. Every day the animal secretes several liters of enzymes. They break down proteins, fats and carbohydrates. The gland secretes insulin and glucagon, which regulate the amount of sugar in the blood.

The weight of the gland is 5-6 kg, which is 1.1% of the total weight of the animal. It occupies the place from the 12th rib to the 4th lumbar spine. At the level of the 4th vertebra, the gland has an additional duct. It is connected to the outlet of the gallbladder.

The liver produces bile and purifies the blood. The blood vessels of the intestines, spleen, and stomach approach it. The outflow of blood occurs through the portal vein. The weight of the liver is 1.4% of the weight of the animal. The organ is located in the right hypochondrium at the level of the 8th and last rib. Gallbladder connected to the duodenum by the hepatic duct. The bubble hangs from the sharp edge of the liver.

Digestive system of a cow

It is necessary to monitor the quality of feed. Putrefactive bacteria and mold can cause liver disease. The most common is hepatitis. Cows should not be given potato sprouts or lupine.

Hepatitis occurs when poisoned by poisonous plants. The duration of the illness is 4 weeks. If after this period recovery has not occurred, the animal is discarded. The body is disposed of.

The longest section of the small intestine is the jejunum. Its length is 35 m. It forms many loops and is attached to the mesentery. It is a continuation of the duodenum. It contains a small amount of digestive debris.

The continuation of the jejunum is the ileum. Its length is 1 m. It ends in a thickening and passes into the large intestine. There are plaques on the surface of the mucous membrane of the jejunum and ileum. Leukocytes concentrate on them and lymphoid tissues. This is a kind of protective mechanism against infectious agents.

Large intestine

The diameter of the large intestine is significantly larger than the diameter of the small intestine. There are no villi on the inner mucous membrane. The mucous membrane forms folds. Glands are located in the recesses, crypts, but they secrete few enzymes. The epithelium consists of goblet cells that secrete mucus. Feces are formed in the large intestine. Sections of the large intestine:

• caecum; has a cylindrical shape; intestinal length 70 cm; in cows, this section is located in the upper right part of the abdominal cavity; the final part is located in the lumbar region, where it connects to the colon;
• colon; located above the jejunum; has a large diameter; the mucous membrane forms tenias and pockets;
• straight; V this department the intestines accumulate feces; located in the area of ​​4-5 vertebrae of the sacral region.

Fiber is broken down in the large intestine: 20%. Microbes and enzymes promote the fermentation of carbohydrates. Putrefactive bacteria break down protein residues. As a result, phenols, indole, and skatole are formed. The substances are very toxic.

The accumulation of feces in the large intestine will negatively affect the overall health of the animal. Toxins penetrate into the blood, causing intoxication of the entire body. Feces from the rectum exit through the anus.

The animal's body temperature is measured through the anus. The rectum is freed from feces manually. The thermometer is placed in the tube. The tube is tied to the tail. This way it won't fall out into the intestines. The measurement lasts 10 minutes.

Bowel twisting

The intestines have a complex location in the abdominal cavity. Numerous loops and bends of its walls are held in place by long mesenteries. They are connected along the entire length with others internal organs, with the diaphragm, with the walls of the abdominal cavity.

Sometimes pathologies are observed in the location of the cow's intestines. It may form knots or twist around the mesentery. The lumen in the intestinal tubes decreases. The process of breaking down fats, carbohydrates, proteins and fiber is disrupted. Fecal masses are poorly formed. Peristalsis is disrupted. Feces cannot pass through the anus.

Causes of the disease:

1. sharp turns when moving, sudden stops, active jumps;
2. coups while the animal is lying on the ground;
3. increased gas formation in certain parts of the intestine;
4. presence of stones;
5. intestinal adhesions;
6. tumors;
7. non-compliance with feeding regimen; plentiful one-time portion of feed;
8. gastrointestinal diseases.

Animals experience pain. Intoxication of the body, constipation, and dehydration occur. Cows refuse food and produce milk poorly. Productivity drops sharply.

• The animal tries to lie down with its legs retracted, rolls on the ground or takes a sitting dog position.
• The body temperature rises to 40 C, the sclera of the eyes turn red.
• When listening, sounds characteristic of digestion are not detected.
• As tympany develops, the abdomen enlarges.
• Feces do not pass.
• The functioning of the stomach is disrupted. It accumulates bile and a large amount of lactic acid. The food begins to rot.
• Pulse and breathing are rapid.

Housekeepers will not be able to determine intestinal torsion themselves. Urgent veterinary assistance is required. He performs a rectal examination. Thickening of the rectum is noted, nodules are palpated, and the intestine and mesentery are incorrectly positioned. Cattle can withstand this condition for up to 2 days. Horses die within a day.

Treatment is aimed at relieving symptoms. The stomach is washed, gases are removed by puncture, injections are made with painkillers, antispasmodics. The main treatment is laparotomy, but surgical intervention rarely come running.

To prevent intestinal torsion, it is necessary to follow all rules for feeding and keeping animals. Feed is supplied 3 times a day at the same time. Serving a large portion of food at once is unacceptable.

Cows should not be allowed to move too actively during the heat period, when they are especially emotional. Stud bulls and fattening young animals are given exercise, but it is not recommended to provoke active movements after feeding.

Large intestine: structure, species features, topography.

Colon.

Large intestine -intestinumcrassum. Consists of the cecum, colon and rectum. Functions: Absorption of nutrients and water ends there, and feces are formed. In herbivores and omnivores, the contents of the colon are retained for a long time, which is necessary for the breakdown of fiber by numerous bacteria and ciliates. In addition, the products of fiber hydrolysis, vitamins K and B, synthesized by microflora, are absorbed here, hormones are produced, characterized by systemic and local effects, and immune protection is provided.

The length of the large intestine in a domestic bull ranges from 6.4 to 11 m; for small cattle (sheep and goats) - from 4 to 7 m; in a domestic pig the average is 4.5 m; for a horse – ranges from 6 to 9 m; in a dog the average is 0.6 m; and in a rabbit it exceeds 2 m.

The wall of all parts of the colon has a similar histological structure. It contains the following layers: mucous membrane, consisting of epithelium, lamina propria and muscularis, submucosa, muscular and serous membranes. Features of the colon– absence of villi of the mucous membrane, weak development of microvilli on epithelial cells, a large number of goblet exocrinocytes.

Mucous membrane The colon is lined with a single-layer prismatic epitheoium, which invaginates into the connective tissue of the lamina propria, forming crypts with wide openings and a lumen. In the integumentary epithelium and crypts there are distinguished: prismatic cells, goblet cells, endocrine and undifferentiated cambial elements. The native layer of the mucous membrane is significantly thickened. In its loose connective tissue in large quantities there are granulocytes, mast and lymphoid cells, as well as blood capillaries and nerve fibers. There are also single and grouped lymph nodes here. The number of crypts changes with age. For example, in a one-day-old calf it is 15 million, and in a ten-year-old cow it increases to 150 million. The muscular plate in the mucous membrane of the large intestine is more pronounced than in the small intestine and is represented by circular and longitudinal layers of smooth muscle. In the connective tissue of the submucosa, elastic fibers and adipose tissue are found in large quantities.

Muscularis The colon is formed by circular and longitudinal layers of smooth muscle. Its longitudinal layer forms cords -teniae, since its length is significantly less than the length of the intestine. Between the cords there is no longitudinal layer of myocytes, but a circular one forms pockets –haustra. In the connective tissue between the muscle layers there are elements of the intermuscular nerve plexus.

Serosa has no pronounced structural features.

Caecum.

Caecum -cecum domestic bull, 30-70 cm long, smooth-walled, cylindrical in shape, large in diameter. It lies in the upper quarter of the right half of the abdominal cavity. The cecum begins from the ileum and colon at the level of the middle of the lumbar region; it is slightly curved and the apex is directed backwards. It distinguishes body -corpusceci And top -apexceci. At the junction of the cecum with the colon, the ileum flows and forms ileocecocolic foramen –ostiumileocecocolicum which is closed sphincter of the ileum -m. sphincterilei. Caecocolic foramen –ostiumcecocolicum has no sphincter.

Peculiarities: In the domestic pig, the cecum is relatively short, but of large diameter. She carries three ribbons - tenii –teniae, three rows pockets –haustra and extends from the middle of the lower back to its end. The body of the intestine lies next to the posterior end of the left kidney, and the apex descends ventrally, backward and to the right.

The horse's cecum is large - 130 cm and has the shape of a giant comma. It distinguishes base –basisceci, body -corpusceci And top -apexceci. The head has a convex greater curvature -curvaturececimajor and concave small curvature -curvaturececiminor. There are two openings on the lesser curvature: the first is the entrance of the ileum into the cecum, and the second is the exit of the colon from the cecum. The entrance and exit openings have sphincters. The base of the cecum is located in the right hypochondrium, right iliac region and in the right half of the lumbar region. Body of the cecum right side goes down and forward in umbilical region; the apex of the cecum is located in the region of the xiphoid cartilage. The cecum has four longitudinal ribbons-tenia - dorsal, ventral, medial and lateral. The lateral and ventral ribbons are absent at the apex; a ligament extends from the dorsal ribbon to the ileum. The remaining tapes are free. The intestinal wall forms four rows of pockets in the spaces between the bands. The cecum is in contact with the lumbar muscles, right kidney, liver, pancreas, duodenum, right and ventral parts abdominal wall, with loops of the jejunum and small colon. The body and apex of the cecum are surrounded by the large colon.

In the dog, the cecum forms two or three bends, suspended on a short mesentery between the second and fourth lumbar vertebrae.

Colon.

Colon –intestinumcolon represents middle section colon. In the animals studied, it is divided into three sections : ascending colon –colonascendens, transverse colon –colontransversum And descending colon -colondescends. The greatest development with pronounced species features the ascending part of the intestine acquires: in the domestic bull it is located in the form of a spirally twisted disk; in a horse it looks like a double horseshoe, and in a domestic pig it is twisted into a cone. Only in a dog does it have a primitive linear movement.

In the domestic bull, the ascending colon reaches a length of 6-9 m and is divided into three segments: the initial loop, the spiral labyrinth and the terminal loop.

Initial loop -ansaproximaliscoli it is a direct continuation of the cecum; the boundary between them is the inlet of the ileum into the cecum. From it the initial loop goes forward; under the right kidney it turns sharply back and goes over its initial section towards the pelvis, where it passes to the left side, making another turn near the cecum. The intestine then moves forward and, at the level of the third lumbar vertebra, enters the spiral labyrinth.

Spiral labyrinth –ansaspiraliscoli is located on the right wall of the scar and in one plane forms convolutions of two orders - centripetal and centrifugal. Centripetal gyri -gyricentripetales the colon, forming 1.5-2.0 turns, go clockwise in the labyrinth. In the center of the disc the intestine makes central bend -flexuracentralis, after which it generates the corresponding number centrifugal revolutions –gyricentrifugals, going counterclockwise. This way it reaches the starting loop and moves into the ending loop.

End loop -ansadistaliscoli smaller diameter than the initial one. It is directed cranially and becomes short transverse colon -colontransversum. Then it goes towards the pelvis in the form descending colon -colondescends, imperceptibly passing into the rectum.

Peculiarities: in the domestic pig, the ascending colon forms a labyrinth in the form of a cone, which with a wide base faces dorsally into the region of the xiphoid cartilage. A centripetal spiral is directed from the wide base of the cone to the center of its apex. It forms the periphery of the cone. The initial loop of intestine is large in diameter and has two teni bands and two rows of pockets. From the center it turns into a centrifugal spiral, following back to the base of the cone and enclosed inside it. The diameter of this part of the loop is smaller. It has no ribbons or pockets. The terminal loop is adjacent to the duodenum, reaches the stomach and the left lobe of the pancreas, turns to the left and passes into the transverse colon.

In a horse, the colon is divided into large - ascending, transverse and small - descending.

Large colon -coloncrassum starts from the cecum, goes forward along the right side of the abdominal cavity and forms ventral right position –colonventraldextrum. Near the diaphragm, the large colon turns from right to left and forms sternal bend -flexurasternalis. Then it is directed along the left side of the abdominal cavity back to the entrance to the pelvic cavity and forms ventral left position –colonventralsinistrum. At the entrance to the pelvic cavity, the large colon turns upward and backward, forming pelvic bend -flexurapelvina. From the bend, the colon follows the path it has already taken. Located above the ventral position, it forms dorsal left position –colondorsalesinistrum, which connects to the left ventral position intercolic mesentery -mesocolon. At the diaphragm, the dorsal portion of the large colon forms diaphragmatic bend -flexuradiaphragmatica and goes into dorsal right position –colondorsaledextrum. The last indicated section of the intestine has the largest diameter and forms ampulla of the colon -ampullacolli. In the caudal direction, its diameter sharply decreases, while the large colon passes into the transverse colon. This section of the intestine is relatively short and quickly passes into small colon -colontenue.

The large colon has four bands and four rows of pouches. There are no ribbons or pockets on her pelvic curve, and the diameter of the intestine here is minimal. In the left dorsal position, the diameter of the intestine gradually increases, three bands and three rows of pouches appear.

The initial part of the large colon is connected to the cecum by the cecum-colic ligament and is attached to the anterior root of the mesentery. The terminal dilated part of the colon is connected by ligaments to the head of the cecum, pancreas, liver, diaphragm and duodenum.

Small colon -colontenue is a continuation of the transverse colon. It has a small diameter, the same throughout the entire intestine, two ribbons and two rows of pockets. The intestine hangs on a long mesentery and forms loops lying in the left iliac region near the entrance to the pelvis. The small colon imperceptibly passes into the rectum.

In the dog, the colon consists of three parts: the right ascending part, running medially from the duodenum forward to the stomach; a short transverse and left descending part, heading back under the left kidney and forming a gentle gyrus in the lumbar region.

Rectum.

Rectum -rectum passes in the pelvic cavity under the spine. In front of the anus, the longitudinal layer of the muscular membrane on the right and left sides forms muscle of the rectum and tail -m. rectococcygeus, which goes up and back to the first caudal vertebrae. The mucous membrane of the rectum and anus is collected in longitudinal folds; it is devoid of villi, but has intestinal glands and many goblet cells, the secretion of which makes the mucous membrane slippery.

Peculiarities: in a domestic pig, the rectum ends with the anus; it is usually surrounded by adipose tissue; there is an ampulla of the rectum. Peyer's patch is quite developed - up to 7 cm. Lymphatic nodules are numerous.

In a horse, the rectum forms an ampulla-shaped expansion. The serous membrane is present only in its anterior part, and at the level of the fourth (fifth) sacral vertebra and caudally, the outside of the intestine is already covered with connective tissue. The muscles of the rectum and tail are well developed.

In a dog, the rectum forms an ampulla-shaped expansion. On the side of the anus there are small glandular sacs called paraanal sinuses. They lie between the levator anus and its external sphincter. The secretion of the paraanal glands gives dogs a specific smell.

Anal canal.

Anal canal (anus) –canalisanalis (anus) is the end of the rectum, adapted for temporary retention and ejection of feces. The anus protrudes somewhat outward under the tail in the form of an elevation with a central opening. On the surface it is covered with hairless skin containing sebaceous and sweat glands.

The skin of the anus is folded onto its inner surface, forming skin area of ​​the anus -zonecutaneaani. Numerous small holes open here anal glands -gll. circumanales. In this area, a circular layer of smooth muscle forms internal anal sphincter -m. sphincteraniinternus. It is separated from the mucous membrane by a well-developed submucosal layer, and from the external sphincter by a fascial layer. External anal sphincter -m. sphincteraniexternus covers the perimeter of the internal sphincter and is a transversely striated muscle that closes the anal canal. The average thickness of the external sphincter is about 1.5 cm, and the thickness ranges from 0.5 to 1.5 mm.

In the cranial direction, the skin zone of the anus passes into intermediate zone -zoneintermediaani, lined with stratified squamous epithelium and devoid of glands. It is separated from the skin area anal-cutaneous line -lineaanocutanea, and from the mucous membrane of the rectum, lined with marginal epithelium, anorectal line -lineaanorectalis.

In the intermediate zone it stands out in the form of a belt columnar zone –zonecolumnarisani with longitudinal folds separated by sinuses.

Muscle of the rectum and tail -m. rectococcygeus goes from the ventral and lateral walls of the rectum and anus to the first caudal vertebrae. Action: pulls the anus back when excreting feces.

Elevator anus –m. levatorani starts from the ischial spine and pelvic ligament and ends in the wall of the anus. Action: pulls the anus forward after excretion of feces.

Suspensory ligament of the anus -lig. suspensoriumani one end is attached to the second caudal vertebra, the other ends in a loop around the anus. Action: Supports the anus.

Peculiarities: In a domestic pig, the anus is constructed essentially in the same way as in a domestic bull.

In a horse, the skin of the anus is rich in sebaceous and sweat glands; the cutaneous-anal and anorectal lines are clearly expressed; submucosal loose connective tissue, suspensory ligament, internal and external sphincters are well developed.