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Blood supply and innervation of the small intestine. Small intestine, functions, sections, location, structural features, wall structure

It is the longest section of the digestive tract. It is located between the stomach and large intestine. In the small intestine, food gruel (chyme), processed with saliva and gastric juice, is exposed to intestinal juice, bile, and pancreatic juice; here the digestion products are absorbed into the blood and lymphatic vessels (capillaries). The small intestine is located in the womb (middle abdomen) downward from the stomach and transverse colon, reaching the entrance to the pelvic cavity. The length of the small intestine in a living person ranges from 2.2 to 4.4 m; in men the intestine is longer than in women. In a corpse, due to the disappearance of the tone of the muscular membrane, the length of the small intestine is 5-6 m. The small intestine has the shape of a tube, the diameter of which at its beginning is on average 47 mm, and at the end - 27 mm. The upper border of the small intestine is the pylorus of the stomach, and the lower border is the ileocecal valve at the point where it flows into the cecum.

The small intestine has the following sections:

  • duodenum;
  • Jejunum;
  • Ileum;

The jejunum and ileum, unlike the duodenum, have a well-defined mesentery and are considered the mesenteric part of the small intestine.

  • Duodenum represents the initial section of the small intestine, located on the posterior wall of the abdominal cavity. The length of the duodenum in a living person is 17-21 cm, and in a corpse it is 25-30 cm. The intestine begins from the pylorus and then goes around the head of the pancreas in a horseshoe shape. It has four parts: upper, descending, horizontal and ascending.
  • Upper part starts from the pylorus of the stomach to the right of the 12th thoracic or 1st lumbar vertebra, goes to the right, slightly backward and upward and forms the upper flexure of the duodenum, passing into the descending part. The length of this part of the duodenum is 4-5 cm. Behind the upper part there is the portal vein, the common bile duct, and its upper surface is in contact with the quadrate lobe of the liver.
  • Descending part starts from the superior flexure of the duodenum at the level of the 1st lumbar vertebra and descends along the right edge of the spine downwards, where at the level of the 3rd lumbar vertebra it turns sharply to the left, resulting in the formation of the inferior flexure of the duodenum. The length of the descending part is 8-10 cm. The right kidney is located posterior to the descending part, and the common bile duct runs to the left and somewhat posteriorly. Anteriorly, the duodenum is crossed by the root of the mesentery of the transverse meningeal colon and adjacent to the liver.
  • Horizontal part starts from the lower bend of the duodenum, goes horizontally to the left at the level of the body of the 3rd lumbar vertebra, crosses the inferior vena cava lying in front of the spine, then turns upward and continues into the ascending part.
  • Rising part ends with a sharp bend down, forward and to the left at the left edge of the body of the 2nd lumbar vertebra - this is the duodenum-jejunum bend or the place of transition of the duodenum into the jejunum. The bend is fixed to the diaphragm with the help of the muscle that suspends the duodenum. Behind the ascending part is the abdominal part of the aorta, and at the junction of the horizontal part into the ascending part, the superior mesenteric artery and vein pass over the duodenum, entering the root of the mesentery of the small intestine. Between the descending part and the head of the pancreas there is a groove in which the end of the common bile duct is located. Connecting with the pancreatic duct, it opens into the lumen of the duodenum at its major papilla.

The duodenum does not have a mesentery and is located retroperitoneally. The peritoneum is adjacent to the intestine in front, except for those places where it is crossed by the root of the transverse meningeal colon and the root of the mesentery of the small intestine. The initial section of the duodenum - its ampulla (bulb) is covered with peritoneum on all sides. On the inner surface of the wall of the duodenum, circular folds are visible, characteristic of the entire small intestine, as well as longitudinal folds that are present in the initial part of the intestine, in its ampulla. In addition, the longitudinal fold of the duodenum is located on the medial wall of the descending part. In the lower part of the fold there is a large duodenal papilla where the common bile duct and pancreatic duct open with a common opening. Above the major papilla is the minor duodenal papilla, on which is located the opening of the accessory duct of the pancreas. Duodenal jelly opens into the lumen of the duodenum. They are located in the submucosa of the intestinal wall.

Vessels and nerves of the duodenum. The superior anterior and posterior pancreaticoduodenal arteries (ie gastroduodenal artery) and the inferior pancreaticoduodenal artery (ie superior mesenteric artery) approach the duodenum, which anastomose with each other and give duodenal branches to the intestinal wall. The veins of the same name drain into the portal vein and its tributaries. The lymphatic vessels of the intestine are directed to the pancreaticoduodenal, mesenteric (upper) celiac and lumbar lymph nodes. The innervation of the duodenum is carried out by direct branches of the vagus nerves and from the gastric, renal and superior mesenteric plexuses.

X-ray anatomy of the duodenum

The initial section of the duodenum is identified, called the “bulb,” which is visible in the form of a triangular shadow, with the base of the triangle facing the pylorus of the stomach and separated from it by a constriction (contraction of the pyloric sphincter). The apex of the “bulb” corresponds to the level of the first circular fold of the duodenal mucosa. The shape of the duodenum varies individually. Thus, a horseshoe shape, when all its parts are well defined, occurs in 60% of cases. In 25% of cases, the duodenum has the shape of a ring and in 15% of cases - the shape of a loop located vertically, resembling the letter “U”. Transitional forms of the duodenum are also possible. The mesenteric part of the small intestine, into which the duodenum continues, is located below the transverse colon and its mesentery and forms 14-16 loops, covered in front by the greater omentum. Only 1/3 of all loops are on the surface and accessible to view, and 2/3 lie deep in the abdominal cavity and to examine them it is necessary to straighten the intestine. About 2/5 of the mesenteric part of the small intestine belongs to the jejunum and 3/5 to the ileum. There is no clearly defined boundary between these parts of the small intestine.

The jejunum is located immediately after the duodenum, its loops lie in the left upper part of the abdominal cavity.

The ileum, being a continuation of the jejunum, occupies the right lower part of the abdominal cavity and flows into the cecum in the region of the right iliac fossa. The jejunum and ileum are covered on all sides by peritoneum (lie intraperitoneally), which forms the outer serous membrane of its wall, located on a thin subserous base. Due to the fact that the peritoneum approaches the intestine on one side, the jejunum and ileum have a smooth free edge covered with peritoneum and the opposite mesenteric edge, where the peritoneum covering the intestine passes into its mesentery. Between the two layers of the mesentery, arteries and nerves approach the intestine, veins and lymphatic vessels exit. Here on the intestine there is a narrow strip not covered by peritoneum. The muscular layer underlying the subserous base contains an outer longitudinal layer and an inner circular layer, which is better developed than the longitudinal one. At the junction of the ileum and the cecum there is a thickening of the circular muscle layer. Next to the muscular layer, the submucosal base is quite thick. It consists of loose fibrous connective tissue, which contains blood and lymphatic vessels and nerves.

The internal mucous membrane is pink at the level of the duodenum and jejunum and grayish-pink at the level of the ileum, which is explained by the different intensity of blood supply to these sections. The mucous membrane of the small intestine wall forms circular folds, the total number of which reaches 650. The length of each fold is 1/2-2/3 of the circumference of the intestine, the height of the folds is about 8 mm. The folds are formed by the mucous membrane with the participation of the submucosa. The height of the folds decreases in the direction from the jejunum to the ileum. The surface of the mucous membrane is velvety due to the presence of outgrowths - intestinal villi 0.2-1.2 mm long. The presence of numerous (4-5 million) villi, as well as folds, increases the absorption surface of the mucous membrane of the small intestine, which is covered with a single-layer prismatic epithelium and has a well-developed network of blood and lymphatic vessels. The basis of the villi is the connective tissue of the lamina propria of the mucous membrane with a small number of smooth muscle cells. The villus contains a centrally located lymphatic capillary - the lacteal sinus. Each villus includes an arteriole, which divides into capillaries, and venules emerge from it. Arterioles, venules and capillaries in the villi are located around the central lacteal sinus, closer to the epithelium. Among the epithelial cells covering the mucous membrane of the small intestine, goblet cells that secrete mucus (unicellular glands) are found in large numbers. Along the entire surface of the mucous membrane, between the villi, numerous tubular-shaped intestinal glands open, secreting intestinal juice. They are located deep in the mucous membrane. Numerous single lymphoid nodules are localized in the mucous membrane of the small intestine, the total number of which in young people reaches an average of 5000. In the mucous membrane of the ileum there are large accumulations of lymphoid tissue - lymphoid plaques (Peyer's patches) - group lymphoid nodules, the number of which ranges from 20 to 60. They are located on the side of the intestine opposite to its mesenteric edge, and protrude above the surface of the mucous membrane. Lymphoid plaques are oval, their length is 0.2-10 cm, width - 0.2-1.0 cm or more.

Vessels and nerves of the jejunum and ileum

15-20 small intestinal arteries (branches of the superior mesenteric artery) approach the intestine. Venous blood flows through the veins of the same name into the portal vein. Lymphatic vessels flow into the mesenteric (upper) lymph nodes, from the terminal ileum into the ileocolic nodes. The wall of the small intestine is innervated by branches of the vagus nerves and the superior mesenteric plexus (sympathetic nerves).

X-ray anatomy of the jejunum and ileum

X-ray examination allows you to see the position and relief of the mucous membrane of the small intestine. The loops of the jejunum are located on the left and in the middle of the abdominal cavity, vertically and horizontally, the loops of the ileum are located in the lower right part of the abdomen (some of its loops descend into the pelvis), vertically and in an oblique direction. The small intestine on radiographs is visible in the form of a narrow ribbon 1-2 cm wide, and with reduced wall tone - 2.5-4.0 cm. The contours of the intestine are uneven due to circular folds protruding into the intestinal lumen, the height of which on radiographs is 2-3 mm in the jejunum and 1-2 mm in the ileum. With a small amount of X-ray contrast mass in the intestinal lumen (“weak” filling), the folds are clearly visible, and with “tight” filling (a lot of mass has been introduced into the intestinal lumen), the size, position, shape and contours of the intestine are determined.

Small intestine: sections, innervation, blood supply, lymphatic drainage.

Intestinum tenue, small intestine, begins at the pylorus and, having formed a whole series of loop-shaped bends along the way, ends at the beginning of the large intestine. In a living person, the length of the small intestine does not exceed 2.7 m and is extremely variable. In the small intestine, mechanical (promotion) and further chemical processing of food takes place under alkaline reaction conditions, as well as the absorption of nutrients.

The small intestine is divided into three sections: 1) duodenum, duodenum, - the section closest to the stomach, 25 - 30 cm long; 2) jejunum, jejunum, which accounts for 2/5 of the small intestine minus duodenum, and 3) ileum, ileum, the remaining 3/5

Innervation, blood supply, lymphatic drainage: Arteries of the small intestine, aa. intestinales jejunales et ileales, come from a. mesenterica superior. Duodenum feeds from aa. pancreaticoduodenales superiores (from a. gastroduodenalis) and from aa. panereaticoduodenales inferiores (from a. mesenterica superior). Venous blood flows through the veins of the same name into v. portae.

Lymphatic vessels carry lymph in the nodi lymphatici coeliaci et mesenterici (see section on the lymphatic system).

Innervation from the autonomic nervous system. There are three nerve plexuses in the intestinal wall: the subserous plexus, plexus subserosus, the musculoenteric plexus, plexus myentericus, and the submucosal plexus, plexus submucosus. The feeling of pain is transmitted through the sympathetic pathways; peristalsis and secretion decrease. N. vagus enhances peristalsis and secretion.

35. Small intestine: topography and structural features of the wall of different sections. Duodenum, duodenum, bends around the head of the pancreas in a horseshoe shape. There are four main parts in it: 1) pars superior is directed at the level of the first lumbar vertebra to the right and back and, forming a downward bend, flexura duodeni superior, passes into 2) pars descendens, which descends, located to the right of the spinal column, to the third lumbar vertebra ; here the second turn occurs, flexura duodeni inferior, with the intestine directed to the left and forming 3) pars horizontdlis (inferior), running transversely in front of v. cava inferior and aorta, and 4) pars ascendens, rising to the level of the I-II lumbar vertebra on the left and in front. Topography of the duodenum. On its way, the duodenum fuses with the head of the pancreas along the inner side of its bend; in addition, pars superior is in contact with the quadrate lobe of the liver, pars descendens is in contact with the right kidney, pars horizontalis passes between a. and v. mesentericae seperiores in front and aorta and v. cava inferior - behind. Duodenum does not have a mesentery and is only partially covered by peritoneum, mainly in front. The relationship to the peritoneum of the area closest to the pylorus (for about 2.5 cm) is the same as the outlet part of the stomach. The anterior surface of the pars descendens remains uncovered by the peritoneum in its middle section, where the pars aescendens is intersected anteriorly by the root of the mesentery of the transverse colon; The pars horizontalis is covered with peritoneum in front, with the exception of a small area where the duodenum is crossed by the root of the mesentery of the small intestine, which contains the vasa mesenterica superiores. However, duodenum can be classified as extraperitoneal organs. When the pars ascendens duodeni passes into the jejunum on the left side of the I or, more often, II lumbar vertebra, a sharp bend of the intestinal tube, flexura duodenojejunalis, is obtained, with the initial part of the jejunum directed downward, forward and to the left. Flexura duodenojejunalis, due to its fixation on the left side of the II lumbar vertebra, serves as an identification point during surgery to locate the beginning of the jejunum.

It is a syndrome that occurs in various diseases of the gastrointestinal tract and is manifested by disturbances of peristalsis and evacuation function with morphological changes in the affected part of the intestine.

Small intestine- a tube placed between the pyloric sphincter and the cecum, its length is about 4/5 of the entire length of the gastrointestinal tract. The total length of the small intestine is proportional to a person's height (approximately 160% of body length). The small intestine is divided into 3 parts: duodenum, empty intestine and ileum.

Empty gut- proximal (oral) portion of the small intestine, making up approximately 40% of the total length. This section of the small intestine has the largest diameter, a thicker wall, and more pronounced circular folds of the mucosa. The mesentery of the small intestine contains less fatty tissue than the mesentery of the ileum.

Ileum, which accounts for 60% of the total length, in the distal section contains pronounced accumulations of lymphoid tissue located in the submucosa.

The empty intestine and ileum are located intraperitoneally and have a long mesentery that fixes them to the posterior wall of the abdomen.

Blood supply. Arterial blood enters the small intestine from the superior mesenteric artery, the branches of which form the following arteries:

1. Inferior pancreaticoduodenal artery.

2. Small intestinal arteries, which form numerous, several tiers, arcuate anastomoses (arcades).

3. Ileocolic artery - one of its branches supplies blood to the terminal part of the ileum.

Venous drainage occurs into the portal vein system. The superior mesenteric vein carries blood from the small intestine to it.

Lymphatic drainage. The lymphatic vessels of the small intestine are called mammary vessels because of their characteristic milky white color after eating. Lymph from the small intestine, passing through numerous lymph nodes at the root of the mesentery, enters the common mesenteric trunk. The latter, after connecting with the abdominal lymphatic trunk, flows into the left lumbar lymphatic trunk.

Innervation. Parasympathetic (vagus nerves) and sympathetic nerve fibers take part in the innervation of the small intestine. They are part of the nerve plexuses:

1. Abdominal aortic plexus.

2. Solar plexus.

3. Superior mesenteric plexuses. Parasympathetic innervation accelerates contractile movements of the intestinal wall, and sympathetic innervation weakens them.

The structure of the wall of the small intestine. The mucous membrane lines the intestinal villi, which increases its absorption area by approximately 500 m2. The mucous membrane is collected in circular kerkring folds, which give it a characteristic appearance. The submucous membrane is very well expressed; in fact, it provides the ability for intestinal anastomoses. The loose fibrous connective tissue of the submucosa contains Meissner's nerve plexus, blood and lymphatic vessels. The muscular layer consists of 2 layers: external longitudinal and internal circular. Between them is the intermuscular nerve plexus of Auerbach, from the outside the intestinal wall is covered with a serous membrane, or peritoneum. The empty intestine and ileum are covered with peritoneum on all sides throughout.

The root of the mesentery of the small intestine is attached to the posterior wall of the abdominal cavity along a line running from top to bottom from the left side of the body of the second lumbar vertebra to the right iliosacral joint.

Physiology. Food, water, and fluids secreted by the stomach, liver and pancreas (about 10 liters per day) enter the small intestine. The main functions of the small intestine: secretory, hydrolysis of food ingredients, endocrine, motor, absorption and excretory.

There are two types of contractile movements of the intestinal wall - pendulum-like and peristaltic. As a result of pendulum-like movements, chyme moves with digestive juices, and peristaltic movements move the food mass along the intestine in the distal direction.

Intestinal obstruction occurs in 9% of all patients with acute surgical pathology of the abdominal organs. The disease occurs at any age, but mainly between 25-50 years. Men get sick more often (66.4%) than women (33.6%). Mortality is about 17% and after acute pancreatitis is one of the largest among acute surgical pathologies of the abdominal organs.

The process of further digestion of parts of food and subsequent absorption of digestion products into the blood occurs in the small intestine (intestinum tenue). This is the longest section of the digestive tract, the length of which is 4–6 m. The small intestine begins from the pylorus of the stomach and ends with the ileocecal (ileocecal) opening at the point where the small intestine flows into the large intestine. It consists of an amesenteric part, represented by the duodenum, and a mesenteric part, which includes the jejunum and ileum. The mesenteric part almost completely occupies the lower part of the peritoneum Duodenum(duodenum)) is located behind the pyloric (pyloric) part of the stomach and arcuately covers the head of the pancreas. Its length is 25–27 cm. It starts from the pylorus of the stomach at the level of the body of the XII thoracic vertebra or the I lumbar vertebra and ends at the level of the II–III lumbar vertebrae. In the duodenum, there is an upper part, which is the initial section, a descending part, horizontal, or lower part. , passing into the ascending part. The upper part is adjacent to the quadrate lobe of the liver, and the lower part is adjacent to the head of the pancreas. The descending part runs along the right edge of the bodies of the I–III lumbar vertebrae. Adjacent to it behind is the right kidney and the inferior vena cava, and in front is the root of the mesentery of the transverse colon and its right bend. On the major papilla of the duodenum, the pancreatic duct and the common bile duct open into the descending part through a common orifice. When the upper part passes into the descending part, the superior flexure of the duodenum is formed. The lower part is located almost horizontally, which explains its name. Anteriorly, it crosses the inferior vena cava. When the descending part passes into the lower part, the lower bend of the duodenum is formed. The ascending part is directed upward along the oblique, passing in front of the abdominal aorta, and passes into the jejunum, forming a sharp bend of the duodenum. The wall of the duodenum consists of three layers. The outer serous membrane (peritoneum) covers it only in front. The middle muscular layer has a thickness of about 0.5 mm and is formed by two layers of smooth muscle: the outer - longitudinal and the inner - circular (circular). The mucous membrane is lined with single-layer prismatic epithelium with a striated border. It forms circular folds, the surface of which is covered with finger-like projections - intestinal villi. Their number is up to 40 villi per 1 mm2, which gives the duodenum a velvety appearance. The duodenum contains uniquely complex tubular-alveolar duodenal (Brunner's) glands, which lie in the submucosa of the upper part of the organ, and tubular intestinal crypts (Lieberkühn's glands), located in the lower part in the depths of the mucous membrane. Digestive processes occurring in duodenum, are largely carried out due to the products of the liver and pancreas.

Mesenteric part of the small intestine is located in the lower part of the abdominal cavity, its length is 4–6 m, and its diameter is 2–4 cm. The proximal part of the small intestine is called the jejunum, makes up approximately 2/5 and without visible boundaries passes into the ileum which is in the right iliac fossa on level IV of the lumbar vertebra opens into the initial part of the large intestine, called the cecum. This part of the small intestine is held by the mesentery, which is a wide fold of peritoneum, consisting of two sheets. One edge of the mesentery is attached to the posterior wall of the peritoneum, and the other covers the small intestine, keeping it suspended. The walls of the jejunum and ileum have the same structure as the duodenum. The outer layer is formed by the serous membrane, and the mucous membrane is lined with single-layer prismatic epithelium with a striated border. It forms approximately 700–900 transverse circular folds covered with intestinal villi in the amount of 4–5 million, which are thinner and shorter than the villi of the duodenum. In the thickness of the mucous membrane there are lymphatic follicles, which are accumulations of lymphatic tissue. The submucosa contains blood vessels and nerves.

Small intestine. Opened with a longitudinal incision. 1 - folds of the small intestine (circular); 2 - mucous membrane and submucosa; 3 - muscular layer; 4 - serous membrane (peritoneum); 5 - longitudinal layer of the muscle membrane; 6 - small intestinal artery; 7 - mesentery of the small intestine.
Villi of the small intestine Some of the villi were opened by a longitudinal incision. 1 - epithelial cover of the mucous membrane; 2 - goblet cells (unicellular glands); 3 - network of blood capillaries of the villi; 4 - central lymphatic sinus (capillary) of the villi; 5 - villus artery; 6 - villus vein; 7 - network of blood and lymphatic vessels of the mucous membrane; 8 - lymphoid nodule.
Mucosa of the small intestine 1 - mucous membrane of the small intestine; 2 - submucosa; 3 - muscular layer; 4 - lymphatic follicles; 5 - mesentery; 6 - transverse circular folds

In the duodenum, the breakdown of fats, proteins, and carbohydrates is completed under the influence of three digestive juices - intestinal, pancreatic and bile. The composition of intestinal juice is a colorless, cloudy liquid with a specific fishy odor; has a slightly alkaline reaction. 2-3 liters of intestinal juice are secreted per day. It has liquid and dense parts. The liquid part consists of water, minerals and organic substances (most of them are proteins, as well as mucus and metabolic products - amino acids, urea, etc.) The dense part is formed by mucous lumps consisting of rejected epithelial cells, which, when destroyed, secrete enzymes:

enterokinase – activates pancreatic pepsinogen;

peptidases - break down polypeptides into amino acids;

alkaline phosphatase – digests phospholipids (breaks off phosphates);

lipase – breaks down fats into glycerol and fatty acids;

Carbohydrases: amylase, lactase, sucrase, maltase - break down carbohydrates into monosaccharides.

Mechanical irritation of the small intestine stimulates the release of the liquid part of the juice, and the products of food digestion stimulate the release of enzymes.

Vessels and nerves of the duodenum. The superior anterior and posterior pancreaticoduodenal arteries (ie gastroduodenal artery) and the inferior pancreaticoduodenal artery (ie superior mesenteric artery) approach the duodenum, which anastomose with each other and give duodenal branches to the intestinal wall. The veins of the same name drain into the portal vein and its tributaries. The lymphatic vessels of the intestine are directed to the pancreaticoduodenal, mesenteric (upper) celiac and lumbar lymph nodes. The innervation of the duodenum is carried out by direct branches of the vagus nerves and from the gastric, renal and superior mesenteric plexuses. 15-20 small intestinal arteries (branches of the superior mesenteric artery) approach the intestine. Venous blood flows through the veins of the same name into the portal vein. Lymphatic vessels flow into the mesenteric (upper) lymph nodes, from the terminal ileum into the ileocolic nodes. The wall of the small intestine is innervated by branches of the vagus nerves and the superior mesenteric plexus (sympathetic nerves).

General characteristics of tumors. Properties of tumors (atypia, tumor progression, recurrence, metastasis). Structure, types of tumor growth (expansive, invasive, endophytic, exophytic)..

A tumor or neoplasm is a pathological process that occurs in all living organisms. In humans, there are more than 200 types of tumors that form in any tissue and in any organ. Malignization is the transition of tissue to tumor. Currently, in Russia, the most common cancer among men is lung cancer, followed by stomach and skin cancer. In women - breast cancer, then stomach and skin cancer. Treatment consists primarily of surgery, as well as radiation and chemotherapy.

A tumor is a pathological process characterized by uncontrolled proliferation of cells, while the growth and differentiation of cells is disrupted due to changes in their genetic apparatus. Properties of the tumor: autonomous and uncontrolled growth, atypia, anaplasia or new properties not inherent in a normal cell and cataplasia.

The structure of the tumor in shape: the shape of a node, a mushroom cap, saucer-shaped, in the form of papillae, in the form of cauliflower, etc. Surface: smooth, tuberous, papillary. Localization: deep within the organ, on the surface, in the form of a polyp, diffusely penetrating. On a section it can be in the form of a homogeneous white-gray tissue, gray-pink (fish meat), fibrous structure (in the testicles). The size of the tumor depends on the speed and duration of its growth, origin and location. According to the degree of differentiation and growth, the tumor can be:

1) expansive, i.e. it grows out of itself, pushing aside tissue. The parenchymal elements surrounding the tumor tissue atrophy, and the tumor is surrounded by a capsule. Growth is slower and more often benign in nature. Malignantly occurs in the thyroid gland and kidneys;

2) oppositional growth due to neoplastic transformation of normal cells into tumor cells;

3) infiltrating growth. In this case, the tumor grows into the surrounding tissues and destroys them. Growth occurs in the direction of least resistance (along intertissue gaps, along nerve fibers, blood and lymphatic vessels).

Based on the ratio of tumor growth to the lumen of a hollow organ, they are distinguished: endophytic (infiltrating growth deep into the organ wall) and exophytic growth (into the organ cavity).

Microscopic structure. Parenchyma is formed by cells that characterize this type of tumor. The stroma is formed both by the connective tissue of the organ and by the cells of the tumor itself. Tumor parenchyma cells induce fibroblast activity and can produce stromal intercellular substance. They produce a specific protein substance – angeogenin, under the influence of which capillaries are formed in the tumor stroma.

Homologous tumors - their structure corresponds to the structure of the organ in which they develop (these are mature differentiated tumors). Heterologous tumors: their cellular structure differs from the organ in which they develop (poorly or undifferentiated tumors). Benign tumors are homologous, slowly growing, highly differentiated, do not metastasize and do not affect the organization. Malignant tumors consist of poorly or undifferentiated cells, lose their similarity with tissue, have cellular atypia, grow quickly and metastasize.

Metastases can be hematogenous, lymphogenous, implantation and mixed. In benign tumors, the tissue identity is easy to determine (unlike malignant ones). It is very important to determine the histogenesis of the tumor, since there are different approaches to treatment. Establishing the histogenesis of a tumor is based on the function that this tumor cell performs, i.e., it is assumed to determine the substances produced by this cell. It must produce the same substances as normal tissue (for example, a normal fibroblast and one altered by the process of malignancy produce the same substance - collagen).

Cell function can also be determined using additional staining reactions or monoclonal antisera. The histogenesis of the tumor is sometimes difficult to establish due to severe anaplasia of the cell, which is unable to perform a certain function. If the histogenesis of a malignant tumor cannot be determined, then such a tumor is called blastoma: large cell, spindle cell, polymorphic cell. Blastomas are a combined group of tumors, since various malignant tumors can transform into blastoma.

Nonepithelial or mesenchymal tumors develop from connective, adipose, muscle tissue, blood and lymphatic vessels, synovial tissue and bone.

Tumor development through qualitatively distinguishable successive stages:

a) pretumor - hyperplasia and pretumor dysplasia;

b) non-invasive tumor (“cancer in situ”): tumor growth in itself without destruction of the basement membrane and without the formation of stroma and blood vessels; the duration of the course can reach 10 years or more;

c) invasive tumor growth;

d) metastasis.

Some malignant tumors can also go through the stage of a benign tumor (for example, colon and stomach cancer can develop from an adenoma).

TO before tumor processes currently include dysplasia, which is characterized by the development of changes not only in parenchymal, but also in stromal elements. Epithelial dysplasia is the best studied.

Epithelial dysplasia characterized by impaired proliferation and differentiation of the epithelium with the development of cellular atypia (various size and shape of cells, an increase in the size of nuclei and their hyperchromia, an increase in the number of mitoses and their atypia) and a violation of histoarchitectonics (loss of polarity of the epithelium, its histo- and organ specificity, thickening of the basement membrane, violation of the ratio of its various components, etc.).

At the stage of dysplasia, changes in the functioning of oncoproteins, growth factors, integrin receptors and adhesion molecules are recorded using immunohistochemistry and molecular biology; genetic re-

construction sites can be significantly ahead of morphological ones and serve as early methods for diagnosing precancerous conditions.

There are 3 degrees of epithelial dysplasia: mild, moderate and severe. Dysplasia is a reversible process, however, with severe dysplasia, there is a significant increase in the risk of a malignant tumor.

Severe dysplasia is difficult to distinguish from carcinoma in situ.

In most cases, the dysplastic process occurs against the background of previous cellular hyperplasia due to chronic inflammation and impaired regeneration, which can be accompanied by the appearance of multicentric foci of hyperplasia, dysplasia and tumor - the tumor field. IV. Basic properties of the tumor.

1. Autonomous growth (independent of the regulatory mechanisms of the body).

2. Atypism - deviation from the norm.

A. Morphological:

1) tissue atypia:

Violation of the ratio of parenchyma and stroma; changes in the size and shape of tissue structures;

2) Cellular atypia:

Polymorphism (various shapes and sizes) of cells and nuclei;

Increased nuclear-cytoplasmic ratio;

An increase in the amount of DNA, often aneuploidy (odd number of chromosomes);

Hyperchromia (more intense staining) of the nuclei;

0 appearance of large nucleoli;

Increased number of mitoses, irregular mitoses.

b. Biochemical:

Changes in metabolism;

Deviations from normal metabolism detected using histochemical methods are called histochemical atypia.

V. Antigenic. Five types of antigens can be detected in tumor cells:

1) antigens of tumors associated with viruses;

Tumors. General provisions 183

2) antigens of tumors associated with carcinogens;

3) transplantation-type isoantigens - tumor-specific antigens;

4) oncofetal, or embryonic, antigens:

Carcinoembryonic antigen (more often detected in colorectal carcinomas),

Alpha-fetoprotein (determined in hepatocellular carcinoma and germ cell tumors);

5) heteroorgan antigens. Immunohistochemical detection of various antigens

used in practice to verify tumors.

G. Functional reduction or disappearance of a function characteristic of mature tissue.

3. Tumor progression (clonal evolution).

Most tumors develop from a single cell, i.e. are initially monoclonal.

As the tumor grows, it becomes heterogeneous: subclones of cells appear that have new properties, in particular the ability to invade and metastasize.

As a rule, selection of newly emerging clones leads to greater malignancy of the tumor.

4. Invasion and metastasis.

A. Invasion.

It is characterized by infiltrating tumor growth (the ability to spread into surrounding tissues, including blood vessels).

Is carried out due to:

a) loss of contact inhibition (continued growth upon contact with other cells);

6) reducing the expression of adhesion molecules, as a result of which tumor cells can grow separately from each other without forming complexes;

c) changes (increase, decrease, distortion of function) of receptors for the components of the extracellular matrix. In particular, an increase in the expression of receptors for laminin (a component of basement membranes) at a certain stage promotes the penetration of tumor cells into basement membranes;

d) release of cellular proteases (collagenase, elastase, etc.) that destroy the extracellular matrix.

The spread of tumor cells from the primary tumor to other organs with the formation of secondary tumor nodes - metastases.

This is done in various ways:

1) lymphogenous;

2) hematogenous;

3) implantation (usually along the serous membranes when the tumor grows into the serous cavities);

4) perineurally (into the central nervous system along the flow of cerebrospinal fluid).

A multi-stage process (metastatic cascade), the stages of which (for the main forms of metastasis) are presented:

a) growth and vascularization of the primary tumor (tumors less than 0.1-0.2 cm do not have their own vessels), the appearance of a tumor subclone capable of metastasis;

b) invasion into the lumen of the vessel (intravasation);

c) circulation and survival of the tumor embolus in the bloodstream (lymph flow);

d) attachment to the vessel wall in a new place and release into the tissue (extravasation); carried out using receptor mechanisms;

e) overcoming tissue protective mechanisms and the formation of a secondary tumor.

5. Secondary changes in tumors.

Foci of necrosis and apoptosis (associated with the action of immune defense factors, cytokines, in particular TNF, ischemia in poorly vascularized tumors), etc.;

Hemorrhages (associated with imperfect angiogenesis in tumors and invasive growth);

Slime;

Small intestine, intestinum tenue , is the longest section of the digestive tract. It is located between the stomach and large intestine (Fig. 208). In the small intestine, food gruel (chyme), processed with saliva and gastric juice, is exposed to intestinal juice, bile, and pancreatic juice; here the digestion products are absorbed into the blood and lymphatic vessels (capillaries). The small intestine is located in the womb (middle abdomen), downward from the stomach and transverse colon, reaching the entrance to the pelvic cavity.

The length of the small intestine in a living person ranges from 2.2 to 4.4 m; Men have a longer intestine than women. In a corpse, due to the disappearance of the tone of the muscular membrane, the length of the small intestine is 5-6 m. The small intestine has the shape of a tube, the diameter of which at its beginning is on average 47 mm, and at the end - 27 mm. The upper border of the small intestine is the pylorus of the stomach, and the lower border is the ileocecal valve at the place where it flows into the cecum.

The small intestine has the following sections: duodenum, jejunum and ileum. The jejunum and ileum, unlike the duodenum, have a well-defined mesentery and are considered the mesenteric part of the small intestine.

Duodenum, duodenum, is the initial section of the small intestine, located on the posterior wall of the abdominal cavity. The length of the duodenum in a living person is 17-21 cm, and in a corpse - 25-30 cm. The intestine begins from the pylorus and then goes around the head of the pancreas in a horseshoe shape. It has four parts: upper, descending, horizontal and ascending.

upper part,pars superior, starts from the pylorus of the stomach to the right of the XII thoracic or I lumbar vertebra, goes to the right, slightly backward and upward and forms the superior flexure of the duodenum, flexura duode- ni superior, moving into the descending part. The length of this part of the duodenum is 4-5 cm.

Behind the upper part are the portal vein, the common bile duct, and its upper surface is in contact with the quadrate lobe of the liver.

Descending partpars descendens, starts from the superior flexure of the duodenum at the level of the 1st lumbar vertebra and descends along the right edge of the spine downwards, where at the level of the 3rd lumbar vertebra it turns sharply to the left, resulting in the formation of the inferior flexure of the duodenum, flexura duodeni inferior. The length of the descending part is 8-10 cm. The right kidney is located posterior to the descending part, and the common bile duct runs to the left and somewhat posteriorly. Anteriorly, the duodenum is crossed by the root of the mesentery of the transverse colon and adjacent to the liver.

horizontal part,pars horizontalis, starts from the lower flexure of the duodenum, goes horizontally to the left at the level of the body III lumbar vertebra, crosses the inferior vena cava lying in front of the spine, then turns upward and continues V the ascending part.

The ascending partpars ascendens, ends with a sharp bend downward, forward and to the left at the left edge of the body of the II lumbar vertebra - this is a twelve and firsno-skinny bend, flexura duodenojejunalis, or duodenal junction V skinny. The bend is fixed to the diaphragm using muscle that suspenses the duodenumT.suspensorius duodeni. Behind the ascending part is the abdominal part of the aorta, and at the junction of the horizontal part into the ascending part, the superior mesenteric artery and vein pass over the duodenum, entering the root of the mesentery of the small intestine. Between the descending part and the head of the pancreas there is a groove in which the end of the common bile duct is located. Connecting with the pancreatic duct, it opens into the lumen of the duodenum at its major papilla.

The duodenum does not have a mesentery and is located retroperitoneally. The peritoneum is adjacent to the intestine in front, except for those places where it is crossed by the root of the transverse colon (pars descendens) and root of the mesentery of the small intestine (pars hori- sontalis). The initial section of the duodenum is its ampoule (“bulb”),ampulla, covered with peritoneum on all sides.

On the inner surface of the duodenal wall are visible circular folds,plicae circuldres, characteristic of the entire small intestine, as well as longitudinal folds that are present in the initial part of the intestine, in its ampulla. Besides this, longitudinal fold of the duodenum,plica longitudinalis duodeni, located on the medial wall of the descending part. At the bottom of the fold there is major duodenal papilla,papilla duodeni major, where the common bile duct ■ and the pancreatic duct open through a common opening. Located superior to the major papilla minor duodenal papilla,papilla duodeni minor, on which the opening of the accessory pancreatic duct is located. Open into the lumen of the duodenum duodenal glands, glandulae duodendles. They are located in the submucosa of the intestinal wall.

Vessels and nerves of the duodenum. The superior anterior and posterior pancreatoduodenal arteries (from the gastroduodenal artery) and the inferior pancreatoduodenal artery (from the superior mesenteric artery) approach the duodenum, which anastomose with each other and give duodenal branches to the intestinal wall. The veins of the same name drain into the portal vein and its tributaries. The lymphatic vessels of the intestine are directed to the pancreaticoduodenal, mesenteric (upper), celiac and lumbar lymph nodes. Innervation of the duodenum is carried out by direct branches of the vagus nerves and from the gastric, renal and superior mesenteric plexuses.

X-ray anatomy of the duodenum. The initial part of the duodenum is distinguished called "onion"bulbus duodeni, which is visible in the form of a triangular shadow, with the base of the triangle facing the pylorus of the stomach and separated from it by a narrow constriction (contraction of the pyloric sphincter). The apex of the “bulb” corresponds to the level of the first circular fold of the duodenal mucosa. The shape of the duodenum varies individually. Thus, a horseshoe shape, when all its parts are well defined, occurs in 60% of cases. In 25% of cases, the duodenum has the shape of a ring and in 15% of cases, the shape of a loop located vertically, resembling the letter “U”. Transitional forms of the duodenum are also possible.

The mesenteric part of the small intestine, into which the duodenum continues, is located below the transverse colon and its mesentery and forms 14-16 loops, covered in front by the greater omentum. Only 1/3 of all loops are on the surface and visible, and 2/3 lie deep in the abdominal cavity and to examine them it is necessary to straighten the intestine. About 2/3 of the mesenteric part of the small intestine belongs to the jejunum and 3 D to the ileum. Clear There is no clear boundary between these parts of the small intestine.

Jejunum, jejunum, located directly after the duodenum, its loops lie in the left upper part of the abdominal cavity.

Ileum, ileum, being a continuation of the jejunum, it occupies the lower right part of the abdominal cavity and flows into the cecum in the area of ​​the right iliac fossa.

The jejunum and ileum are covered on all sides by peritoneum (lie intraperitoneally), which forms the outer serous membrane,tunica serosa, its walls, located on a thin subserous base,tela subserosa. Due to the fact that the peritoneum approaches the intestine on one side, a smooth free edge covered with peritoneum and the opposite mesenteric edge are distinguished from the jejunum and ileum, where the peritoneum covering the intestine passes into its mesentery. Between the two layers of the mesentery, arteries and nerves approach the intestine, veins and lymphatic vessels exit. Here on the intestine there is a narrow strip not covered by peritoneum.

Lying under the subserous base muscle membrane,tuni­ ca muscularis, contains an outer longitudinal layer, stratum longitudindle, and the inner circular layer, stra­ tum circuldre, which is better developed than the longitudinal one. At the point where the ileum enters the cecum there is a thickening of the circular muscle layer.

Next to the muscle layer submucosa,tela submucdsa, quite thick. It consists of loose fibrous connective tissue, which contains blood and lymphatic vessels and nerves.

Internal mucous membrane,tunica mucosa, has a pink color at the level of the duodenum, jejunum and grayish-pink at the level of the ileum, which is explained by the different intensity of blood supply to these sections. The mucous membrane of the wall of the small intestine forms circular folds and, plicae circulares, the total number of which reaches 650 (Fig. 209). The length of each fold is "/2 - 2/3 of the circumference of the intestine, the height of the folds is about 8 mm. The folds are formed by the mucous membrane with the participation of the submucosa. The height of the folds decreases in the direction from the jejunum to the ileum. The surface of the mucous membrane is velvety due to the presence of outgrowths - intestinal villi,villi intestindles, 0.2-1.2 mm long (Fig. 210). The presence of numerous (4-5 million) villi, as well as folds, increases the absorption surface of the mucous membrane of the small intestine, which is covered with single-layer prismatic epithelium and has a well-developed network of blood and lymphatic vessels. The basis of the villi is the connective tissue of the lamina propria of the mucous membrane with a small number of smooth muscle cells. The villus contains a centrally located lymphatic capillary - the lacteal sinus (Fig. 211). Each villus includes an arteriole, which divides into capillaries, and venules emerge from it. Arterioles, venules and capillaries in the villi are located around the central lacteal sinus, closer to the epithelium.

Among the epithelial cells covering the mucous membrane of the small intestine, goblet cells that secrete mucus (unicellular glands) are found in large numbers. Numerous tubular shapes open across the entire surface of the mucous membrane between the villi. intestinal glands,gldndulae intestinales, secreting intestinal juice. They are located deep in the mucous membrane.

In the mucous membrane of the small intestine there are many localized: single lymphoid nodules,noduli lymphatici soli- tarii, the total number of which in young people reaches an average of 5000. In the mucous membrane of the ileum there are large accumulations of lymphoid tissue - lymphoid plaques (Peyer's patches) - group lymphoid nodules,noduli lymphatici aggregati, the number of which ranges from 20 to 60 (Fig. 212). They are located on the side of the intestine opposite to its mesenteric edge, and protrude above the surface of the mucous membrane. Lymphoid plaques are oval, their length is 0.2-10 cm, width - 0.2-1.0 cm or more.

Vessels and nerves of the jejunum and ileum. 15-20 small intestinal arteries (branches of the superior mesenteric artery) approach the intestine. Venous blood flows through the veins of the same name into the portal vein. Lymphatic vessels flow into the mesenteric (upper) lymph nodes, from the terminal ileum into the ileocolic nodes. The wall of the small intestine is innervated by branches of the vagus nerves and the superior mesenteric plexus (sympathetic nerves).

X-ray anatomy of the jejunum and ileum. X-ray examination allows you to see the position and relief of the mucous membrane of the small intestine. The loops of the jejunum are located on the left and in the middle of the abdominal cavity, vertically and horizontally, the loops of the ileum are located in the lower right part of the abdomen (some of its loops descend into the pelvis), vertically and in an oblique direction. The small intestine on radiographs is visible in the form of a narrow ribbon 1-2 cm wide, and with reduced wall tone - 2.5-4.0 cm. The contours of the intestine are uneven due to circular folds protruding into the intestinal lumen, the height of which on radiographs is 2-3 mm in the jejunum and 1-2 mm in the ileum. With a small amount of radiopaque mass in the intestinal lumen (“weak” filling), the folds are clearly visible, and with “tight” filling (a lot of mass has been introduced into the intestinal lumen), the size, position, shape and contours of the intestine are determined.