Anatomy of the large and small intestine

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Topographic anatomy of the small and large intestine

Small intestine- a site of the digestive tract between the stomach and the large intestine. It is divided into three divisions - the duodenum, lean and iliac. The beginning and end of the intestine is fixed by the mesentery root to the back wall of the abdominal cavity. The remaining mesentery provides its mobility and position in the form of loops. On three sides they are fringed by the sections of the thick colon; on top - transverse, on the right - ascending, on the left - descending, transforming into sigmoid. Intestinal loops in the abdominal cavity are arranged in several layers, one - superficially, in contact with the large omentum and anterior abdominal wall, others - deeply, adjoining to the back wall. The margin of the small intestine, attached to the mesentery, is called mesenteric, the opposite - free. On the mesenteric margin between the leaves of the mesentery there is a narrow band, not covered by the peritoneum. Stitches when intestinal anastomoses are applied in a region devoid of peritoneum are fragile, which is taken into account by peritonizing this site. The projection on the anterior abdominal wall corresponds to the celiac and hypogastric regions. Twelve-lean-skinny bending, as a rule, is well pronounced. To find flex. duodenojejunalis use Gubarev's reception - a large omentum with a transverse colon is taken up; go on the mesentery to the spine and slide off to the left, grabbing the first, fixed, loop of thin guts. To determine the leading and retracting loops, the Wilms-Gubarev method is used - the intestinal loop is placed along the root of the mesentery, i.e., from top to bottom, from left to right. At the same time, the leading and the upper will be located leading, and to the right and below - the outgoing end of the intestine.

Anomalies in the development of the small intestine - atresia, stenosis, congenital enlargement of the small intestine, bowel movement disorders, etc. Meckel's diverticulum is the protrusion of the small intestine as a result of the pathology of the reverse development of the yolk-intestinal duct. The extraorganic arterial system is represented by the system of the superior mesenteric artery, its branches, arcades and straight vessels. The superior mesenteric artery departs from the abdominal aorta at level I of the lumbar vertebra. In some cases, the superior mesenteric artery may squeeze the duodenum, causing arterio-mesenteric obstruction. From it at the lower edge of the pancreas, the lower anterior and posterior pancreatoduodenal arteries depart. The small intestine branches are divided into jejunal arteries and ileo-intestinal. Each of them divides and supplies blood with a limited area of ​​the intestine - ascending and descending, which anastomose with each other, forming arcs (arcades) of the first order. From them distally depart new branches, which, form second-order arcades, etc.

The last series of arcades, forms a parallel or edge vessel, from which there are direct vessels that supply blood to the gut area. The veins of the small intestine begin to form from straight veins into a system of venous arcades. All veins, merging, form the superior mesenteric vein.

Colon- the end section of the digestive tract. It starts from the ileocecal connection and ends with a rectum with an anal opening. It is divided into three parts - the blind, colon and rectum. The colon is divided into ascending, transverse, descending and sigmoid. The place of transition rising into the transverse is the right colonic bend (hepatic curvature), and the place of transition of the transverse colon to the descending is the left colonic bend (splenic curvature). The ileocecal section is located in the right ileal fossa and is the site of the small intestine transition thick, includes a cecum with a vermiform appendage and an ileocecal connection with a buginium damper. It provides isolation of the small and large intestines.

The cecum is the portion of the large intestine located below the upper edge of the ileum. The appendix, or appendix, is a rudimentary continuation of the blind. At the base of it all three muscle bands of the cecum converge. It is covered with peritoneum on all sides. When the cecum does not have a full peritoneal cover, its posterior wall is tightly fixed to the retroperitoneal tissue and the iliac fascia.

The appendix is ​​covered with peritoneum from all sides, vessels and nerves pass through the mesentery.

The ascending colon is the right lateral region of the abdomen, the continuation of the cecum to the right hypochondrium, where it passes into the right bend - the transition of the ascending colon to the transverse-colon. The ascending colon is mesoperitoneal. The right bend touches the lower surface of the right lobe of the liver, the bottom of the gallbladder, is located intraperitoneally or meso- peritoneally. The transverse colon is located intraperitoneally, begins in the right hypochondrium, passes into actually an epigastric and umbilical area, and then reaches the left hypochondrium, where it passes into the left hypochondrium bend. The left bend of the colon is located intraperitoneally.

The transverse colon is bordered at the top with the liver, gallbladder, large curvature of the stomach and spleen, bottom - with loops of the small intestine, in front - with anterior abdominal wall, behind - with duodenum, pancreas and left kidney, which are separated from her by mesentery and parietal the peritoneum. The descending colon is the left lateral area of ​​the abdomen. Separated from the anterior abdominal wall with loops of the small intestine and a large omentum, behind it are the muscles of the posterior abdominal wall, located mesoperitoneally.

Sigmoid colon - left iliac and pubic region, located intraperitoneally, has considerable mobility. The line of attachment of the mesentery root to the posterior abdominal wall has two sections - the first is directed from left to right, the second - downward. The colon is supplied with blood from two vascular mains - the superior and inferior mesenteric artery. The blood supply of the ileocecal region is provided by the iliac-artery artery.

The structure of the large intestine

Division of large intestine (Fig. 1) several times shorter than the section of the small intestine; for example, in horses it is 35% of the total length of the intestine, in cattle - 20%. The main difference between a large intestine and a thin one is that there are no villi in it. Among the prickly prismatic epithelium, there are many goblet cells. The mucus emitted by them covers the mucous membrane, and also serves to glue undigested particles into stool masses. Colon, or libercany, glands in the large intestine is much larger than in the thin. In the submucosa there are many single lymphoid follicles.

In the large intestine of a horse and a pig, the longitudinal muscular layer forms longitudinal muscle bands - the shadows. The intestinal wall between the shadows gathers into semilunar folds and forms protrusions - pockets. Thanks to the shadows, the division of the large intestine, especially in the horse, reaches a large volume.

The division of the large intestine is divided into the blind, colonic and straight. The cecum isruminantscylindrical, smooth, up to 30-70 cm long. Its initial part without any boundary passes into the colon; blind, rounded, end facing caudally. It lies in the dorsal third of the right half of the abdominal cavity (in the right inguinal and iliac regions and in the lumbar region).

Havepigsthe caecum is conical, thick, short, with three shades and three rows of pockets between them. Located in the lumbar region, the blind end is directed caudally and somewhat to the right.


Fig. 1. Thick intestine:

A- dogs;B- horses;AT- Pigs;D- ruminant;1Ileum;2-cecum;3- dorsaland 4- the ventral knee of the large colon of the horse;5- small horse colon;6- disk of the ruminant intestine;7Cone of pig intestine;8-the beginning of the rectum.

Havehorsesa large intestine in the form of a comma. By capacity twice exceeds the stomach, as if compensating for its small volume. In the cecum of the horse, intractable voluminous plant food is subjected to bacterial fermentation and is prepared for digestion and absorption. On the cecum distinguish: head, body and apex. The head of the stomach-like species; a concave surface of it is called a small curvature, convex is called a large curvature. In the blind intestine there are four shadows, between them four rows of pockets. In the region of small curvature, the ileum is inserted into the cecum in a hub-like manner. This hole with the sphincter is called the hole of the ileum. Next to it lies a hole leading to the large colon, which also closes with the sphincter. The head of the cecum lies in the right ileal, right inguinal areas, in the right hypochondrium and in the umbilical region; body - in the right podvzdohe and in the field of xiphoid cartilage; top - in the region xiphoid cartilage.

When overfeeding or eating poor-quality feed in the caecum, gases can accumulate, which are removed by puncturing the caecum in the right ileal region.

In dogs, the cecum is short, S-shaped, located on the right side of the lumbar region.

The colon is the direct continuation of the cecum.

In ruminants it is long - in cattle 6-9 m. In sheep, -5 m, slightly wider than the small intestine, smooth. It is divided into three sections: an initial gyrus, a spiral labyrinth and an end gyrus. The spiral labyrinth forms in cattle, -2, in sheep and goats, 3 concentric and eccentric spiral turns lying in one plane. Curls of the labyrinth are interconnected by a short mesentery. At the level of the 1st lumbar vertebra, the terminal gyrus begins, which passes into the rectum. In the colon of ruminants, there are no shadows and pockets. It is located on the right surface of the scar, occupying the right half of the abdominal cavity. The rumen intestine is presented as a flat disc: in its center lies the labyrinth of the colon, at the top is duodenum and blind, and on the periphery - the jejunum and ileum.

The colon of the omnivores twists spirally in the form of a cone with concentric, containing two shadows and two rows of pockets, and eccentric curls. The last eccentric curl in the lumbar region forms the terminal gyrus, which passes into the rectum. The base of the cone of the colon lies under the bodies of the lumbar vertebrae, the apex touches the border of the left hypochondrium and the area of ​​the xiphoid cartilage.

The colon of the horse is very voluminous, occupying most of the abdominal cavity. It is divided into two sections: a wide one - a large colon and a narrow one - a small colon.


Fig. 2. A. Topography of the internal organs of the cow (left): 1 - trachea; r - left lung; s is the heart; 4 - grid; 5 - scar; 6 - abomasum; 7 - the spleen (borders are shown dotted line); 8 - diaphragm (part of it is cut off); 9 - loops of jejunum; 10 - rectum; 11 - left horn of the uterus; 12 - left ovary; 13 - the vagina; 14 - urinary bubble; 15 -. urethra.


Fig. 2. B. Topography of the internal organs of the cow (right): 1 - trachea; 2 - right lung; s is the heart; 4 - grid (the boundaries are shown in dotted lines); 5 - book; 6 - diaphragm; 7 - gall bladder; 8 - duodenum; 9 - right and left kidneys; 10 - loops of jejunum; 11 - colonic intestine; 12 - pancreas; 13 - the caecum; 14 - right ovary; 16 - uterus; 16 - bladder; 17 - the vagina; 18 - the straight line intestine.

The large colon forms a horseshoe loop of two interconnected short mesentery knees - ventral and dorsal. The ventral knee has four shadows and four rows of pockets. In the lumbar region, this gut sharply narrows and turns into a small colon.

The small colon with two shadows and two rows of pockets is suspended on a long mesentery. Its loops, together with the loops of the small intestine, lie mainly in the central part of the abdominal cavity, in the plate-shaped depression formed by the blind and large colon.

In dogs, the colon is short, thin, and there are no pockets and pockets in it. This structure of the colon in dogs is explained by the fact that they eat meat, that is, a high-calorie and easily digestible food. The intestine consists of three sections: an ascending transverse and a descending knee.

The rectum is a continuation of the colon, short, lies in the pelvic cavity under the sacral and first caudal vertebrae, ends with an anal anus. In front of the anus, the rectum forms a bottle-shaped extension (omnivores, horse, dog). The mucous membrane of it is collected in numerous, easily smoothed longitudinal folds. On the end of the rectum, the serous membrane is replaced by adventitia.

In the area of ​​the anus there is a special device for the act of defecation - the ejection of stool. The annular layer of muscles forms two sphincters: the inner one - from smooth muscle tissue and the outer one - from the striated muscle. From the pelvis to the side surfaces of the sphincters, the paired anus lift from the longitudinal layer of the muscle tissue is suitable. The lifters of the anus pull it after defecation inside.

2. Large intestine (topography)

Colon# 8212; the final department of the digestive tract.

Begins# 8212; from the ileocecal connection and ends with a rectum with an anal opening. It is divided into three parts # 8212; blind, colon and rectum. The colon is divided into ascending, transverse, descending and sigmoid. The point of transition is ascending to the transverse # 8212; right colonic bend (hepatic curvature), and the place of transition of the transverse collateral into the descending body # 8212; left colonic bend (splenic curvature). The ileocecal section is located in the right ileal fossa and is the site of the small intestine transition thick, includes a cecum with a vermiform appendage and an ileocecal connection with a buginium damper. It provides isolation of the small and large intestines.

Cecum# 8212; the portion of the colon located below the upper edge of the ileum. The appendix, or appendix, is a rudimentary continuation of the blind. At the base of it all three muscle bands of the cecum converge. It is covered with peritoneum on all sides. When the cecum does not have a full peritoneal cover, its posterior wall is tightly fixed to the retroperitoneal tissue and the iliac fascia.

The appendix is ​​covered with peritoneum from all sides, vessels and nerves pass through the mesentery.

Ascending Colon# 8212; right lateral abdomen, continuation of the cecum to the right hypochondrium, where it passes into the right bend # 8212; transition of the ascending colon to the transverse-colon. The ascending colon is mesoperitoneal. The right bend touches the lower surface of the right lobe of the liver, the bottom of the gallbladder, is located intraperitoneally or meso- peritoneally. The transverse colon is located intraperitoneally, begins in the right hypochondrium, passes into actually an epigastric and umbilical area, and then reaches the left hypochondrium, where it passes into the left hypochondrium bend. The left bend of the colon is located intraperitoneally.

The transverse colon is bordered at the top with the liver, gallbladder, large curvature of the stomach and spleen, from below # 8212; with loops of the small intestine, front # 8212; with anterior abdominal wall, posteriorly # 8212; with the duodenum, pancreas and left kidney, which are separated from her by a mesentery and parietal the peritoneum. Descending Colon # 8212; left lateral abdomen. Separated from the anterior abdominal wall with loops of the small intestine and a large omentum, behind it are the muscles of the posterior abdominal wall, located mesoperitoneally.

Sigmoid colon# 8212; the left iliac and pubic region, is located intraperitoneally, has considerable mobility. The line of attachment of the mesentery root to the posterior abdominal wall has two sections # 8212; the first is directed from left to right, the second is # 8212; down. The colon is supplied with blood from two vascular highways # 8212; upper and lower mesenteric arteries. The blood supply of the ileocecal region is provided by the iliac-artery artery.

Sources: http://medichelp.ru/uchebnik/operativnaja-hirurgija/6381-topograficheskaya-anatomiya-tonkogo-i-tolstogo-kishechnika.html, http://www.allvet.ru/knowledge_base/animal_anatomy/stroenie-tolstogo-kishechnika.php, http://www.medkurs.ru/lecture4k/surgery_anatomy/sa32/6680.html



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