The liver is a vital exocrine gland in humans. Its main functions include neutralizing toxins and removing them from the body. In case of liver damage, this function is not performed and harmful substances enter the blood. With the bloodstream they flow through all organs and tissues, which can lead to serious consequences.

Since there are no nerve endings in the liver, a person may not even suspect that there is any disease in the body for a long time. In this case, the patient goes to the doctor too late, and then treatment no longer makes sense. Therefore, it is necessary to carefully monitor your lifestyle and undergo regular preventive examinations.

Anatomy of the liver

According to the classification, the liver is divided into independent segments. Each is connected to a vascular inflow, outflow and bile duct. In the liver, the portal vein, hepatic artery and bile duct are divided into branches, which in each segment are collected into veins.

The organ consists of afferent and efferent blood vessels. The main afferent vein functioning in the liver is the portal vein. The drainage veins include the hepatic veins. Sometimes there are cases when these vessels independently flow into the right atrium. Basically, the veins of the liver flow into the inferior vena cava.

The permanent venous vessels of the liver include:

• right vein;
• middle vein;
• left vein;
• vein of the caudate lobe.

Portal

The portal vein of the liver is a large vascular trunk that collects blood that passes through the stomach, spleen and intestines. After collection, it delivers this blood to the lobes of the liver and transfers the already purified blood back into the general channel.

Normally, the length of the portal vein is 6-8 cm, and its diameter is 1.5 cm.

This blood vessel originates behind the head of the pancreas. Three veins merge there: the inferior mesenteric vein, the superior mesenteric vein and the splenic vein. They form the roots of the portal vein.

In the liver, the portal vein divides into branches that diverge throughout all hepatic segments. They accompany the branches of the hepatic artery.

The blood carried by the portal vein saturates the organ with oxygen and delivers vitamins and minerals to it. This vessel plays an important role in digestion and detoxifies the blood. If the functioning of the portal vein is disrupted, serious pathologies arise.

Diameter of hepatic veins

The largest of the liver vessels is the right vein, the diameter of which is 1.5-2.5 cm. Its flow into the inferior cava occurs in the area of ​​​​its anterior wall near the hole in the diaphragm.

Normally, the hepatic vein, formed by the left branch of the portal vein, enters at the same level as the right one, only on the left side. Its diameter is 0.5-1 cm.

The diameter of the vein of the caudate lobe in a healthy person is 0.3-0.4 cm. Its mouth is located slightly below the place where the left vein flows into the inferior vena cava.

As you can see, the sizes of the hepatic veins differ from each other.

The right and left ones, passing through the liver, collect blood from the right and left hepatic lobes, respectively. The middle and vein of the caudate lobe are from the lobes of the same name.

Hemodynamics in the portal vein

According to an anatomy course, arteries pass through many organs of the human body. Their function is to saturate the organs with the substances they need. Arteries bring blood to the organs, and veins remove it. They transport processed blood to the right side of the heart. This is how the systemic and pulmonary circulation works. The hepatic veins play a role in it.

The gate system functions specifically. The reason for this is its complex structure. From the main trunk of the portal vein, many branches branch off into venules and other bloodstreams. That is why the portal system, in fact, constitutes another additional circle of blood circulation. It purifies blood plasma from harmful substances such as breakdown products and toxic components.

The portal vein system is formed as a result of the union of large vein trunks near the liver. From the intestine, blood is carried by the superior mesenteric and inferior mesenteric veins. The splenic vessel emerges from the organ of the same name and receives blood from the pancreas and stomach. It is these large veins, merging, that become the basis of the crow vein system.

Near the entrance to the liver, the trunk of the vessel, dividing into branches (left and right), diverges between the lobes of the liver. In turn, the hepatic veins are divided into venules. A network of small veins covers all lobes of the organ inside and out. Once contact between blood and soft tissue cells occurs, these veins will carry blood into the central vessels that emerge from the middle of each lobe. After this, the central venous vessels unite into larger ones, from which the hepatic veins are formed.

liver blockage?

Hepatic vein thrombosis is a liver pathology. It is caused by a violation of internal circulation and the formation of blood clots that block the outflow of blood from the organ. Official medicine also calls it Budd-Chiari syndrome.

Thrombosis of the hepatic veins is characterized by partial or complete narrowing of the lumens of blood vessels, resulting from the impact of a blood clot. Most often it occurs in those places where the mouth of the liver vessels is located and they flow into the vena cava.

If there are any obstructions in the liver to the outflow of blood, the pressure in the blood vessels increases and the hepatic veins dilate. Although the blood vessels are very elastic, too much pressure can cause them to rupture, resulting in internal bleeding and possibly death.

The question of the origin of hepatic vein thrombosis is still not closed. Experts on this issue are divided into two camps. Some consider hepatic vein thrombosis to be an independent disease, while others argue that it is a secondary pathological process caused as a result of complications of the underlying disease.

The first case includes thrombosis, which occurred for the first time, that is, we are talking about Budd-Chiari disease. The second case includes Budd-Chiari syndrome, which manifested itself due to a complication of the primary disease, which is considered the main one.

Due to the difficulty in separating measures for diagnosing these processes, the medical community usually calls liver circulatory disorders not a disease, but a syndrome.

Causes of hepatic vein thrombosis

Blood clots in the liver occur due to:

1. Protein S or C deficiency.
2. Antiphospholipid syndrome.
3. Changes in the body associated with pregnancy.
4. Long-term use of oral contraceptives.
5. Inflammatory processes occurring in the intestines.
6. Connective tissue diseases.
7. Various peritoneal injuries.
8. The presence of infections - amoebiasis, hydatid cysts, syphilis, tuberculosis, etc.
9. Tumor invasions of the liver veins - carcinoma or renal cell carcinoma.
10. Hematological diseases - polycythemia, paroxysmal nocturnal hemoglobinuria.
11. Hereditary predisposition and congenitality of hepatic vein defects.

The development of Budd-Chiari syndrome usually lasts from several weeks to months. Against this background, cirrhosis and portal hypertension often develop.

Symptoms

If unilateral hepatic obstruction has developed, no special symptoms are observed. directly depends on the stage of development of the disease, the location where the blood clot formed, and the complications that arise.

Often, Budd-Chiari syndrome is characterized by a chronic form, which is not accompanied by symptoms for a long time. Sometimes signs of hepatic thrombosis can be detected by palpation. The disease itself is diagnosed solely as a result of instrumental research.

Chronic blockage is characterized by symptoms such as:

• Mild pain in the right hypochondrium.
• Feeling of nausea, sometimes accompanied by vomiting.
• Change in skin color - yellowing appears.
• The sclera of the eyes turn yellow.

The presence of jaundice is not necessary. In some patients it may be absent.

Symptoms of acute blockage are more obvious. These include:

• Sudden onset of vomiting, in which blood gradually begins to appear as a result of a rupture in the esophagus.
• Severe pain that is epigastric in nature.
• A progressive accumulation of free fluids in the peritoneal cavity, which occurs due to venous stagnation.
• Sharp pain throughout the abdomen.
• Diarrhea.

In addition to these symptoms, the disease is accompanied by an enlargement of the spleen and liver. Acute and subacute forms of the disease are characterized by liver failure. There is also a fulminant form of thrombosis. It is extremely rare and dangerous because all the symptoms develop very quickly, leading to irreparable consequences.

Diagnosis of blockage of hepatic vessels

Budd-Chiari syndrome is characterized by a clear clinical picture. This greatly facilitates the diagnosis. If the patient has an enlarged liver and spleen, there are signs of fluid in the peritoneal cavity, and laboratory tests indicate elevated blood clotting rates, first of all, the doctor begins to suspect the development of thrombosis. However, he is obliged to carefully study the patient's medical history.

Significant reasons to suspect thrombosis in a patient include the following signs:

In addition to the fact that the doctor studies the medical history and conducts a physical examination, the patient needs to donate blood for a general and biochemical analysis, as well as for coagulation. You also need to take a liver test.

To accurately make a diagnosis, the following examination methods are used:

• ultrasound examination;
• X-ray of the portal vein;
• contrast study of blood vessels;
• computed tomography (CT);
• magnetic resonance imaging (MRI).

All these studies make it possible to assess the degree of enlargement of the liver and spleen, the severity of vascular damage, and detect the location of the blood clot.

Complications

If a patient contacts a doctor late or changes resulting from thrombosis are diagnosed late, the risk of complications increases. These include:

• liver failure;
• portal hypertension;
• hepatocellular carcinoma;
• ascites;
• encephalopathy;
• bleeding from the dilated hepatic vein;
• porosystemic collateralization;
• mesenteric thrombosis;
• peritonitis, which is bacterial in nature;
• liver fibrosis.

Treatment

In medical practice, two methods of treating Budd-Chiari syndrome are used. One of them is medicinal, and the second is through surgery. The disadvantage of medications is that it is impossible to recover completely with their help. They give only short-term effect. Even if the patient promptly consults a doctor and is treated with medications, without the intervention of a surgeon, almost 90% of patients die within a short period of time.

The main goal of therapy is to eliminate the underlying causes of the disease and, as a result, restore blood circulation in the area affected by thrombosis.

Drug therapy

In order to remove excess fluid from the body, doctors prescribe medications with a diuretic effect. To prevent further development of thrombosis, the patient is prescribed anticoagulants. Corticosteroids are used to relieve abdominal pain.

In order to improve blood characteristics and accelerate the resorption of formed blood clots, fibrinolytics and antiplatelet agents are used. In parallel, maintenance therapy is carried out aimed at improving metabolism in liver cells.

Surgical therapy

Conservative treatment methods for a diagnosis associated with thrombosis cannot provide the necessary result - restoration of normal circulation in the affected area. In this case, only radical methods will help.

1. Establish anastomoses (artificial synthetic connections between vessels that allow blood circulation to be restored).
2. Place a prosthesis or mechanically dilate a vein.
3. Place a shunt to reduce blood pressure in the portal vein.
4. Liver transplant.

In the case of a fulminant course of the disease, practically nothing can be done. All changes happen very quickly, and doctors simply do not have time to take the necessary measures.

Prevention

All measures to prevent the development of Budd-Chiari syndrome are reduced to the fact that you need to regularly visit medical institutions in order to undergo the necessary diagnostic procedures as a preventive measure. This will help to promptly detect and begin treatment of hepatic vein thrombosis.

There are no special preventive measures for thrombosis. There are only measures to prevent relapse of the disease. These include taking blood thinning anticoagulants and undergoing examinations every 6 months after surgery.

Structure of the liver, size of the liver, segments of the liver. Vascular system of the liver. Arterial blood supply. Portal vein. Biliary system. Ultrastructure of the liver.

Anatomy of the liver

Liver- one of the largest organs of the human body, playing an important role in digestion and metabolism. It is difficult to name another organ with as wide a variety of functions as the liver.

The relative size and weight of the liver are subject to significant fluctuations depending on age. The weight of the liver of an adult is 1300 - 1800. The liver of newborns and children in the first month of life occupies 1/2 or 1/3 of the abdominal cavity, averaging 1/18 of the body weight, and in adults it is only 1/36 of the body weight. However, already in three-year-old children, the liver has the same relationship with the abdominal organs as in adults, although its edge protrudes more from under the costal arch due to the child’s short chest.

The liver is covered by peritoneum on all sides, with the exception of the gate and part of the posterior surface. The parenchyma of the organ is covered with a thin, durable fibrous membrane (Glisson's capsule), which enters the parenchyma of the organ and branches in it.

Skeletotopy of the liver

The liver is located directly below the diaphragm in the upper right abdominal cavity, a small part of the organ in an adult extends to the left of the midline. The organ has stable landmarks in relation to the skeleton, which are used to determine its boundaries (Fig. 1). The upper border of the liver on the right with maximum exhalation is located at the level of the 4th intercostal space along the right nipple line, the upper point of the left lobe reaches the 5th intercostal space along the left parasternal line. The upper edge of the liver has a slightly oblique direction, running along a line from the fourth right rib to the cartilage of the fifth left rib. The anterior inferior edge of the liver on the right along the axillary line is at the level of the 10th intercostal space, its projection coincides with the edge of the costal arch along the right nipple line. Here the anterior edge departs from the costal arch and stretches obliquely to the left and upward; along the midline it is projected in the middle of the distance between the navel and the base of the xiphoid process. Next, the anterior edge of the liver crosses the left costal arch and at the level of the VI costal cartilage along the left parasternal line passes into the upper edge.

Determination of the projection of the anterior edge of the liver very important when performing percutaneous needle biopsy of the liver. The anterior projection of the liver has the appearance of an almost right-angled triangle, mostly covered by the chest wall, only in the epigastric region the lower edge of the liver extends beyond the costal arches and is covered by the anterior abdominal wall. The posterior projection of the liver occupies a relatively narrow strip. The upper edge of the liver is projected at the level of the lower edge of the IX thoracic vertebra, and the lower border runs along the middle of the XI thoracic vertebra.

The location of the liver changes depending on the position of the body. In a vertical position, the liver lowers slightly, and in a horizontal position it rises. The displacement of the liver during breathing is used during its palpation: in most cases, it is possible to determine its lower edge during the deep inspiration phase.

Rice. 1

It is important to remember the variations in the position of the liver in relation to the sagittal plane of the body; distinguish between the right-sided and left-sided position of the liver. In the right-sided position, the liver lies almost vertically and has a highly developed right lobe and a reduced left one. In some cases, the entire organ does not cross the midline, being located in the right half of the abdominal cavity. In a left-sided position, the organ lies in a horizontal plane and has a well-developed left lobe, sometimes even extending beyond the spleen. These variations in the position of the liver must be taken into account when assessing the results of scanning and echolocation of the organ.

Segmental division of the liver

According to external signs, the liver is divided into right and left lobes of unequal size. On the upper convex surface, the border between the lobes is the place of attachment of the falciform ligament; on the lower surface, the border is the left and right longitudinal grooves. In addition, the quadrate and caudal lobes are distinguished, which were previously classified as the right lobe. The quadrate lobe is located between the anterior sections of two longitudinal grooves. The caudal lobe of the liver is located between the posterior sections of the longitudinal grooves. The gallbladder is located in the anterior part of the recess on the lower surface of the right lobe of the liver. In the deep transverse groove on the lower surface of the right lobe there is the gate of the liver. Through the gate, the hepatic artery and portal vein with their accompanying nerves enter the liver, and the common hepatic bile duct and lymphatic vessels exit.

The basis of modern anatomical and functional division is the doctrine of the segmental structure of the liver. Lobes, sectors, segments are usually called areas of the liver of various sizes that have separate blood and lymph circulation, innervation and outflow of bile. The portal vein, hepatic artery, bile ducts and hepatic veins branch in the liver. The course of the branches of the portal vein, hepatic artery and bile duct within the organ is relatively identical. These vessels and bile ducts are usually called the Glissonian, or portal, system, in contrast to the hepatic veins, which are called the caval system. Segmental division of the liver is carried out along the portal and caval systems. Division of the liver according to the portal system is more often used in surgical practice, as it has more anatomical justifications.

The intrahepatic architecture of the portal vein underlies most segmental division patterns (Fig. 2). The classification of S. Couinaud (1957) has become widespread, according to which the liver is divided into 2 lobes - right and left, 5 sectors and 8 most constantly occurring segments. The segments, grouped along radii around the gate of the liver, are included in larger independent sections of the organ, called sectors. Thus, segments III and IV form the left paramedian sector. The left lateral sector (monosegmental includes only segment II, and the right paramedian sector includes segments V and VIII, the right lateral sector includes segments VI and VII; segment I is the dorsal sector (monosegmental). Each lobe, sector or segment of the liver has in most cases, the so-called Glissonian pedicle, accessible to surgical treatment, in which, closely adjacent to each other, are located the branches of the portal vein, hepatic artery and hepatic duct, covered with a connective tissue membrane.

Blood vessels

Blood enters the liver from the portal vein and hepatic artery; 2/3 of the blood volume enters through the portal vein and only 1/3 through the hepatic artery. However, the importance of the hepatic artery for the functioning of the liver is great, since arterial blood is rich in oxygen.

Arterial blood supply to the liver carried out from the common hepatic artery (a. hepatica communis), which is a branch of the truncus coeliacus. Its length is 3 - 4 cm, diameter 0.5 - 0.8 cm. The hepatic artery directly above the pylorus, not reaching 1-2 cm from the common bile duct, is divided into a. gastroduodenalis and a. hepatica propria. The proper hepatic artery (a. hepatica propria) passes upward in the hepatoduodenal ligament, while it is located to the left and somewhat deeper than the common bile duct and in front of the portal vein. Its length ranges from 0.5 to 3 cm, diameter from 0.3 to 0.6 cm. The proper hepatic artery in its initial section gives off a branch - the right gastric artery and, before entering the gate of the liver or directly at the gate, is divided into the right and left branch. In some cases, a branch arises from the hepatic artery - the quadrate lobe of the liver. Typically, the left hepatic artery supplies the left, quadrate, and caudal lobes of the liver.

Right hepatic artery supplies mainly the right lobe of the liver and gives an artery to the gallbladder.

Arterial anastomoses of the liver are divided into two systems: extraorgan and intraorgan. The extraorgan system is formed mainly by branches extending from a. hepatica communis, aa. gastroduodenalis and hepatica dextra. The intraorgan collateral system is formed through anastomoses between the branches of the liver's own artery.

Venous system of the liver represented by afferent and efferent veins. The main afferent vein is the portal vein. The outflow of blood from the liver occurs through the hepatic veins, which flow into the inferior vena cava.

Portal vein(vena portae) is most often formed from two large trunks: the splenic vein (v. lienalis) and the superior mesenteric vein (v. mesenterica superior).

Rice. 2. Scheme of segmental division of the liver: A - diaphragmatic surface; B - visceral surface; B - segmental branches of the portal vein (projection on the visceral surface). I - VIII - liver segments, 1 - right lobe; 2 - left lobe.

The largest tributaries are the gastric veins (v. gastrica sinistra, v. gastrica dextra, v. prepylorica) and the inferior mesenteric vein (v. mesenterica inferior) (Fig. 3). The portal vein most often begins at the level of the second lumbar vertebra behind the head of the pancreas. In some cases, it is located partially or completely within the parenchyma of the gland, has a length of 6 to 8 cm, a diameter of up to 1.2 cm, and has no valves. At the level of the portal of the liver v. portae is divided into the right branch, which supplies the right lobe of the liver, and the left branch, which supplies the left, caudal and quadrate lobes.

Portal vein connected by numerous anastomoses with the vena cava (portocaval anastomosis). These are anastomoses with the veins of the esophagus and the veins of the stomach, rectum, periumbilical veins and veins of the anterior abdominal wall, as well as anastomoses between the roots of the veins of the portal system (superior and inferior mesenteric, splenic, etc.) and the veins of the retroperitoneal space (renal, adrenal, testicular veins or ovary, etc.). Anastomoses play an important role in the development of collateral circulation in case of outflow disorders in the portal vein system.

Portocaval anastomoses are especially well expressed in the rectal area, where the v. rectalis superior, flowing into v. mesenterica inferior, and vv. rectalis media et inferior, related to the inferior vena cava system. On the anterior abdominal wall there is a pronounced connection between the portal and caval systems through vv. paraumbilicales. In the area of ​​the esophagus through connections v. gastrica sinistra and v.v. oesophagea an anastomosis of the portal vein with v. is created. azygos, i.e., the system of the superior vena cava (Fig. 4).

Hepatic veins(v.v.hepaticae) are the efferent vascular system of the liver. In most cases there are three veins; right, middle and left, but their number can greatly increase, reaching 25. The hepatic veins drain into the inferior vena cava below where it passes through the opening in the tendinous part of the diaphragm into the chest cavity.

Rice. 3. Portal vein and its large branches (according to L. Schiff). P - portal vein; C - gastric vein; IM - inferior mesenteric vein; S - splenic vein; SM - superior mesenteric vein.

In most cases, the inferior vena cava passes through the posterior part of the liver and is surrounded by parenchyma on all sides.

Portal hemodynamics characterized by a gradual drop from high pressure in the mesenteric arteries to the lowest level in the hepatic veins. It is important that the blood passes through two capillary systems: the capillaries of the abdominal organs and the sinusoidal bed of the liver. Both capillary networks are connected to each other by the portal vein.

Blood of the mesenteric arteries under a pressure of 120 mm Hg. Art. enters the network of capillaries of the intestines, stomach, and pancreas. The pressure in the capillaries of this network is 15 - 10 mm Hg. Art. From this network, blood enters the venules and veins that form the portal vein, where normally the pressure does not exceed 10 - 5 mm Hg. Art. From the portal vein, blood is directed into the interlobular capillaries, from there it enters the hepatic venous system and passes into the inferior vena cava. The pressure in the hepatic veins ranges from 5 mm Hg. Art. to zero.

Thus, the pressure drop in the portal bed is 120 mmHg. Art. Blood flow may increase or decrease with changes in pressure gradient. G. S. Magnitsky (1976) emphasizes that portal blood flow depends not only on the pressure gradient, but also on the hydromechanical resistance of the portal vessels, the value of which is determined by the total resistance of the first and second capillary systems. A change in resistance at the level of at least one capillary system leads to a change in the total resistance and an increase or decrease in portal blood flow. It is important to emphasize that the pressure drop in the first capillary network is 110 mmHg. Art., and in the second - only 10 mm Hg. Art. Consequently, the main role in changing portal blood flow is played by the capillary system of the abdominal organs, which is a powerful physiological tap. Significant fluctuations in hydromechanical resistance occur as a result of changes in the lumen of blood vessels under the influence of nervous and humoral regulation. Through the portal bed in humans, blood flows at an average speed of 1.5 l/min, which corresponds to 1/3 of the IOC.

Liver histotopography

Liver It is a mass of liver cells penetrated by blood sinusoids. According to modern concepts, hepatocytes form anastomosing plates from one row of cells that are in close contact with the branched blood labyrinth of the sinusoids (Fig. 5). Since 1883, the main morphophysiological unit of the liver has been considered a “classical” hexagonal lobule; its center is the hepatic vein - the initial link of the venous system that collects blood flowing from the liver. The parenchyma of the lobules is formed by radially located hepatic beams; these are plate-like formations one cell thick. The lobules are separated from each other by layers of connective tissue called portal fields associated with the fibrous capsule of the liver.

Rice. 4. Portocaval anastomoses (according to B V Petrovsky): 1 - portocaval anastomoses in the rectal area 2 - anastomoses in the esophagus. 3 - anastomoses in the stomach, IVC - inferior vena cava. PV - portal vein

The interlobular connective tissue of a normal liver is poorly developed. The portal fields contain branches of the portal vein, hepatic artery, bile and lymphatic canaliculi. Penetrating through the terminal plate of hepatocytes, which separates the parenchyma of the lobules from the portal field, the portal vein and hepatic artery give their blood to the sinusoids. The sinusoids drain into the central vein of the lobule. The diameter of the sinusoids ranges from 4 to 25 microns, depending on the functional state of the liver. At the point where the venule flows into the sinusoid and the sinusoid into the hepatic vein, there are external and internal smooth muscle sphincters that regulate blood flow into the lobule. The hepatic arteries, like the corresponding veins, break up into capillaries. They enter the liver lobule and, at its periphery, merge with capillaries originating from the portal veins. Due to this, blood coming from the portal vein and the hepatic artery mixes in the intralobular capillary network (Fig. 6).

Rice. 5. Reconstruction of a liver fragment according to N. Elias

There is another point of view, according to which the secretory lobule or an acinar unit similar to it is taken as a morphophysiological unit. The liver parenchyma is functionally divided into small areas with a portal field in the center, limited by the central veins of two adjacent hepatic lobules, 3-4 such fragments of parenchyma form a complex acinus or portal lobule with a vascular bundle of the portal tract in the center and hepatic veins lying in three corners on the periphery .

Intralobular sinusoids, representing the microvasculature of the circulatory system of the liver, are in direct contact with each hepatocyte. The unique structure of the walls of the hepatic sinusoids contributes to the maximum exchange between the bloodstream and the hepatic parenchyma. The wall of the liver sinusoids does not have the basement membrane characteristic of the capillaries of other organs and is built from a single row of endothelial cells. Between the endothelial cells and the surface of the liver cells there is a free perisinusoidal space - the space of Disse. It has been established that the surface of endothelial cells is covered with a substance of mucopolysaccharide nature, which also fills the cellular pores of Kupffer cells, intercellular gaps and spaces of the DNA. This substance carries out intermediary exchange between blood and liver cells. The functionally active surface of liver cells increases significantly due to numerous tiny outgrowths of the cytoplasm - microvilli.

Rice. 6. 1 - portal vein; 2 - hepatic artery; 3 - sinusoids; 4 - internal sphincter; 5 - central vein; 6 - external sphincter; 7 - arteriole.

Endothelial cells, depending on their functional state, are divided into endothelial cells themselves, which perform a support function, active endothelial cells (Kupffer cells), which have a phagocytic function, and fibroplastic cells, which participate in the formation of connective tissue. Histochemical examination in the cytoplasm of Kupffer cells reveals an increased content of RNA, PAS-positive granules, and high activity of acid phosphatase.

The connective tissue of the portal fields, along with the portal triad, including branches of the portal vein, hepatic artery and interlobular bile ducts, contains single lymphocytes, histiocytes, plasma cells and fibroblasts. The connective tissue of the portal tracts is represented by collagen fibers, clearly visible when stained with picrofuchsin or the three-color Mallory method.

Biliary system

Its initial link is the intercellular bile canaliculi (capillaries), formed by the biliary poles of two or more adjacent hepatocytes (Fig. 7). Bile canaliculi do not have their own wall; they are formed by the cytoplasmic membranes of hepatocytes. Histological examination does not reveal bile canaliculi, but is clearly visible in the reaction to alkaline phosphatase. Intercellular bile canaliculi, merging with each other at the periphery of the hepatic lobule, form larger perilobular bile ducts (terminal ductules, cholangioles). Cholangioles are formed by cuboidal epithelial cells. During electron microscopic examination, microvilli are visible on the surface of the epithelial cells of the cholangioles. Passing through the terminal plate of hepatocytes, in the periportal zone the cholangioles flow into the interlobular bile ducts (ducts, cholangae). The walls of these ducts are formed by connective tissue; in larger ducts there is also a layer of smooth muscle fibers.

Rice. 7. Intrahepatic bile ducts (according to N. Popper, F. Schaffner). 1 - liver cell; 2 - Kupffer cell; 3 - sinusoid; 4 - intercellular bile canaliculus; 5 - perilobular bile duct; b - interlobular bile duct; 7 - vein; 8 - lymphatic vessel.

Rice. 8. Extrahepatic bile ducts. 1 - gallbladder; 2- - ductus cysticus; 3 - ductus hepaticus; 4 - ductus choledochus; 5 - ductus pancreaticus; 6 - sphincter Oddi.

On the lower surface of the liver, in the region of the transverse groove, the left and right bile ducts join to form the common hepatic duct. The latter, merging with the cystic duct, flows into the common bile duct 8–12 cm long. The common bile duct opens into the lumen of the duodenum in the area of ​​the major duodenal papilla. The distal end of the common bile duct is dilated, in its wall there is a layer of smooth muscle - the sphincter (Fig. 8),

Ultrastructure of hepatocyte

Upon electron microscopic examination, the hepatocyte has an irregular hexagonal shape with unclearly defined angles.

There is a sinusoidal pole facing the blood sinusoid and a biliary pole facing the bile canaliculus (Fig. 9). The cytoplasmic membrane of the hepatocyte consists of outer and inner layers, between them there is an osmiophobic layer 2.5 - 3.0 nm wide. The membrane has pores that provide communication between the endoplasmic reticulum and the extracellular environment. Numerous membrane outgrowths - microvilli - are especially clearly expressed at the sinusoidal pole of the hepatocyte; they increase the functionally active area of ​​the hepatocyte. Numerous metabolites are captured by the villi of the sinusoidal pole, and secretion is carried out at the biliary pole of the hepatocyte. These processes are regulated by enzyme systems, in particular alkaline phosphatase and ATPase. Hyaloplasm, the main substance of the cytoplasm of hepatocytes, is weakly osmiophilic, with vaguely defined small granules, vesicles and fibrils. Soluble components of the cytoplasmic matrix include a significant amount of protein, a small amount of RNA and lipids, enzymes of glycolysis, transamination, etc. The hyaloplasm contains cytoplasmic organelles and inclusions. Core. Round and light, it is located in the central part of the hepatocyte, has a clearly visible nuclear envelope, a few small clumps of chromatin and from 1 to 4 round oxyphilic nucleoli. In rare cases, hepatocytes contain two nuclei.

The nuclear envelope in hepatocytes is closely connected with the endoplasmic reticulum: direct transitions of the outer membrane of the nuclear envelope into the membranes of the endoplasmic reticulum and communication of the slit-like space between the membranes of the nuclear envelope with the tubules of the granular endoplasmic reticulum are observed. DNA and histones in the form of a deoxyribonucleoprotein complex, acidic proteins, rRNA, and mRNA are localized in the chromatin of the nucleus. Numerous enzymes involved in the synthesis of RNA, DNA and protein are found in the hepatocyte nucleus.

The endoplasmic reticulum of the hepatocyte is represented by a system of tubules and cisterns formed by parallel membranes. The endoplasmic reticulum consists of two parts: granular (granular) and smooth. Under physiological conditions, the granular part is much more developed than the smooth part; it is located mainly around the nucleus and mitochondria; on its outer membrane there are numerous osmiophilic granules with a diameter of 12 - 15 nm - ribosomes. The membranes of the smooth endoplasmic reticulum are located near the biliary pole of the hepatocyte, where the synthesis of glyco- and lipoproteins, glycogen, and cholesterol occurs. Both parts of the endoplasmic reticulum are closely interconnected, representing a system of continuous tubes. The physiological role of the endoplasmic reticulum is the neutralization of medicinal and toxic substances, conjugation of bilirubin, metabolism of steroids, biosynthesis of proteins secreted by the cell into the tissue fluid, and direct participation in carbohydrate metabolism.

Rice. 9. Scheme of the ultrastructure of a hepatocyte (I), Kupffer cell (II), bile-epithelial cell (III) (according to A.F. Blyuger). 1 - core; 2 - nucleolus; 3 - nuclear membrane; 4 - rough endoplasmic reticulum; 5 - smooth endoplasmic reticulum; 6 - mitochondria; 7 - Golgi complex; 8 - lysosomes; 9 - polyribosomes; 10 - ribosomes; II - microtubule; 12 - desmosome; 13 - vacuole; 14 - space of Disse; 15 - bile canaliculus; 16 - peroxisome; 17 - pinocytotic vesicles; 18 - sinusoids", 19 - lipids; 20 - basement membrane: 21 - microvilli; 22 - glycogen; 23 - interlobular bile duct; 24 - centriole.

Golgi apparatus, or lamellar complex, consists of double membranes forming flattened sacs and small vesicles. It is usually located in close proximity to the smooth endoplasmic reticulum at the biliary pole of the hepatocyte. The functional purpose of the Golgi apparatus is determined by its important role in secretory processes. Depending on the phase of bile secretion, the components of the Golgi apparatus change. Its participation in the formation of lysosomes and glycogen is assumed.

In the cytoplasm of hepatocytes, in close topographic contact with the tubular system described above, there are granular formations: mitochondria, lysosomes, microbodies.

Mitochondria have very variable shape and location in the cell depending on its location in the lobule or the characteristics of the functional state. Typically, mitochondria are round, oval or elongated, surrounded by a three-layer membrane. The inner layer of membranes forms membrane partitions - cristae, on which granular particles are located. Oxidative phosphorylation occurs in granular particles. The mitochondrial matrix has a fine-grained structure, containing RNA granules, thin strands of DNA and single lipid inclusions. The most important enzyme systems are localized in mitochondria; the central place among them is occupied by the enzymes of the Krebs cycle, deamination and transamination enzymes.

Lysosomes They have a round or ellipsoidal shape, surrounded by a single-layer lipoprotein membrane. Lysosomes are usually localized at the biliary pole of the hepatocyte, and therefore they are called peribiliary bodies. The greatest number of lysosomes are contained in the peripheral zones of the hepatic lobule. Lysosomes are considered as an apparatus for intracellular digestion and are divided into primary, which have not yet used their lytic enzymes, and secondary, in which contact between hydrolases and the substrate has already occurred. Secondary lysosomes are divided into digestive vacuoles, which carry out the lysis of exogenous substances that enter the cell through pinocytosis and phagocytosis, autophagy vacuoles, which carry out the lysis of endogenous material, and residual bodies, or segrosomes, containing compact material in which the breakdown of the substrate is completed. The function of lysosomes can be defined as “intracellular digestion”; they participate in protective reactions, the formation of bile, and ensure intracellular homeostasis. In addition to organelles, the cytoplasm of hepatocytes contains various inclusions: glycogen, lipids, pigments, lipofuscins.

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The general outflow of blood into the vena cava is carried out through the hepatic veins. % of all blood passes through the hepatic artery itself, the rest through the portal vein. Consequently, venous blood from the digestive tract, pancreas and spleen returns to the heart only after passing additionally through the liver. This feature of the blood circulation of the liver, called portal circulation, is associated with digestion and the performance of a barrier function.

Blood in the portal circulatory system passes through two networks of capillaries. The first network is located in the walls of the digestive organs, pancreas, and spleen; it provides the absorption, excretory and motor functions of these organs. The second network of capillaries is located directly in the liver parenchyma. It ensures its metabolic and excretory functions, preventing intoxication of the body by products formed in the digestive tract.

Research by N.V. Eck showed that if blood from the portal vein is directed directly into the vena cava, i.e. bypassing the liver, the body will be poisoned with a fatal outcome.

A feature of microcirculation in the liver is the close connection between the branches of the portal vein and the hepatic artery proper with the formation of sinusoidal capillaries in the liver lobules, to the membranes of which hepatocytes are directly adjacent. The large contact surface of blood with hepatocytes and slow blood flow in sinusoidal capillaries create optimal conditions for metabolic and synthetic processes.

In the portal circulatory system, arterial blood is under pressure mm Hg. Art. enters the first network of capillaries (for example, the intestinal wall), where it decreases to 100 mHg. Art. After passing through the second network of capillaries, already in the hepatic veins it is 0-5 mm Hg. Art. This pressure difference ensures the forward movement of blood.

Regulation of portal hemodynamics is carried out through a system of periodically contracting input and output sphincters of sinusoidal capillaries. This system adapts the blood flow to the activity of the abdominal organs, and also ensures the deposition of blood.

Rice. 8.31. Mammalian fetal circulation:

1 - aortic arch, 2 - botal duct, 3 - left pulmonary artery, 4 - pulmonary trunk, 5 - branches from the iliac arteries, passing into the umbilical ones, 6 - placental vein, carrying arterial blood, 7 - umbilical arteries from the fetal iliac artery, 8 - placenta, 9 - caudal vena cava, 10 - tract of Arans, 11 - liver, 12 - right atrium, 13 - foramen ovale in the atria, 14 - cranial vena cava

How is the blood supply to the liver structures?

The liver plays one of the main roles in metabolism. The ability to perform its functions, in particular neutralization, directly depends on how blood flows through it.

The peculiarity of the blood supply to the liver, unlike other internal organs, is that in addition to arterial blood saturated with oxygen, it also receives venous blood rich in valuable substances.

The structural unit of the liver is a lobe, which has the shape of a faceted prism, in which hepatocytes are located in rows. Each lobule is approached by a vascular triad of interlobular vein, artery and bile duct, which are also accompanied by lymphatic vessels. The blood supply to the lobules is divided into 3 channels:

1. Influx to the lobules.
2. Circulation inside the lobules.
3. Outflow from the hepatic lobules.

Blood sources

Arterial (about 30%) comes from the abdominal aorta via the hepatic artery. It is necessary for the normal functioning of the liver and to perform complex functions.

At the porta hepatis, the artery divides into two branches: the one going to the left supplies the left lobe, and the one going to the right supplies the right lobe.

From the right one, which is larger, a branch goes to the gall bladder. Sometimes a branch extends from the hepatic artery to the quadrate lobe.

Venous (about 70%) enters through the portal vein, which is collected from the small intestine, colon, rectum, stomach, pancreas, and spleen. This explains the biological role of the liver for humans: hazardous substances, poisons, medications, and processed products come from the intestines for neutralization and decontamination.

What is the blood supply algorithm?

Both sources of venous and arterial blood enter the organ through the gates of the liver, then they branch greatly, dividing into:

All these vessels have a thin muscle layer.

Penetrating into the lobule, the interlobular artery and vein merge into a single capillary network running along the hepatocytes to the central part of the lobule. In the center of the lobule, the capillaries gather into the central vein (it is devoid of a muscle layer). The central vein then flows into the interlobular, segmental, and lobar collecting vessels, forming 3–4 hepatic veins at the outlet at the hilum. They already have a good muscle layer, flow into the inferior vena cava, and it, in turn, enters the right atrium.

In general, the blood supply in the hepatic lobule can be displayed as follows:

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B→ K → Cv A→, where B and A are the interlobular artery and vein, K is the capillary, Cv is the central vein of the lobule.

Anastomoses

The portal vein has numerous connections (anastomoses) with other organs. This is necessary for extreme necessity: if there are disturbances in the liver, and due to high pressure resistance, blood cannot flow there, through anastomoses it goes into the venous bed of these organs and thus does not stagnate, but enters the heart, although it never purified.

The portal vein has anastomoses with:

• Stomach.
• The anterior wall of the abdomen and the veins located near the navel.
• Esophagus.
• Veins of the rectum.
• Inferior vena cava.

Therefore, if a clear venous pattern in the form of a jellyfish appears on the abdomen, dilated veins are found during examination of the esophagus and rectum, we can safely say that the anastomoses are working in an enhanced mode, and in the portal vein the increased pressure prevents the passage of blood.

Blood pressure increases with cirrhosis and other diseases; this condition is called portal hypertension.

Regulation of blood supply

The liver normally contains about half a liter of blood. Its advancement is carried out due to the pressure difference: it comes from the arteries under a pressure of at least 110 mm. rt. st, which in the capillary network is reduced to 10 mm. rt. Art., in the portal veins it is within 5, and in the collecting venules it can even be 0.

Normal functioning of the organ requires constant maintenance of blood volume. To do this, the body has 3 types of regulation, which work thanks to the valve system of veins.

Myogenic regulation

Muscular regulation is most important because it is automatic. When muscles contract, they narrow the lumen of the vessel, and when they relax, they expand.

The structure of the walls of blood vessels

Thus, they regulate the constancy of blood supply under the influence of various factors: physical activity, during rest, pressure fluctuations, and diseases.

Humoral regulation

Carried out with the help of hormones:

Adrenalin. Produced during stress, it enters the blood and acts on the alpha-adrenergic receptors of the portal vein, causing its narrowing.

In small arterial vessels of the parenchyma, it acts on beta-adrenergic receptors and dilates intrahepatic vessels.

Norepinephrine and angiotensin. They affect both the venous and arterial systems equally, leading to a narrowing of all vessels, resulting in a decrease in the amount of blood supplied to the liver.

Acetylcholine. Dilates arterial vessels, which means improves blood supply to the liver. But it narrows the venules, i.e. prevents blood from flowing out of the organ. As a result, the blood is deposited in the liver.

Other hormones, such as thyroxine, glucocorticoids, insulin and glucagon, increase metabolic processes, which increases blood flow. Metabolites produced in tissues (histamine, prostaglandin, carbon dioxide) reduce portal inflow, but increase arterial blood flow.

Nervous regulation

It is slightly expressed, therefore it plays a minor role in the regulation of blood circulation.

• Sympathetic innervation. Carried out by branches from the celiac plexus. Causes vasoconstriction, which reduces blood flow.
• Parasympathetic. Comes from the vagus nerve (X pair). Has no effect.

1. An important indicator of impaired hepatic circulation is congested veins of the anastomoses.
2. Liver recovery occurs extremely slowly, and poor circulation only aggravates the situation.
3. The altered hormonal background of a person with diabetes mellitus, diseases of the thyroid gland and adrenal glands can make changes in the portal circulation.

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Liver circulation

The liver has a unique blood circulation, since most of its parenchymal cells are supplied with mixed venous (portal) and arterial blood. At rest, oxygen consumption by the liver is almost 20% of the oxygen consumption of the entire body; oxygen is supplied by the hepatic artery, which delivers 25-30% of the blood entering the liver and 40-50% of the oxygen consumed by the liver.

In the branch of the hepatic artery, blood is delivered at a pressure close to the pressure in the aorta (in the portal vein it does not exceed mmHg). When two blood streams connect

Rice. 18. Scheme of the structure of the hepatic lobule (according to C.G. Child): 1 - branch of the portal vein; 2 - branch of the hepatic artery; 3 - sinusoid; 4- central vein; 5 - liver tower (beam); 6 - interlobular bile duct; 7 - interlobular lymphatic vessel

in sinusoids their pressure is equalized (8-9 mm Hg). The section of the portal bed in which the most significant decrease in pressure occurs is localized near the sinusoids.

In critical conditions, hemodynamic disturbances of the liver are of significant importance: resistance to blood flow in the portal section of the hepatic bed increases, the flow of portal blood to the hepatocyte decreases, and the liver switches to a predominantly arterial blood supply. The blood flow through the sinusoids slows down, and conglomeration of blood cells occurs in the capillaries and sinusoids. Due to the development of capillary spasm and shutdown of a significant part

Fig. 19. Scheme of the structure of the intrahepatic bile ducts (according to N. Rorre, F. Schaffner): 1 - branch of the portal vein; 2 - sinusoids; 3 - stellate reticuloendotheliocyte; 4 - hepatocyte; 5 - intercellular bile canaliculus; 6 - interlobular bile duct; 7 - interlobular bile duct; 8 - lymphatic vessel

sinusoids, blood circulation in the liver begins to occur through a system of shunts, oxygen tension in the liver tissue decreases, which leads to hypoxia of the organ. According to E.I. Galperin (1988), changes in microcirculation with blockade of portal blood flow are an autonomous reaction of the liver that occurs in response to an adverse effect. In the light of modern concepts, it is believed that it is disorders of the hepatic microcirculation and disorders of transcapillary metabolism that play a leading role in the pathogenesis of acute liver failure.

Features of portal circulation and blood supply to the liver

V.V. Bratus, T.V. Talaeva “Circulatory system: principles of organization and regulation of functional activity”

Venous (stagnant, passive) hyperemia is a pathological change in blood circulation caused by difficulty in the outflow of venous blood while maintaining its delivery to the tissues through the corresponding arteries. Venous congestion can be general and local, acute and chronic.

The myocardium of the atria and ventricles, separated by fibrous rings, is synchronized in its work by the conduction system of the heart, which is common to all its departments (Fig. 1.30).

The main source of blood supply to the heart is the coronary arteries (Fig. 1.22). The left and right coronary arteries branch from the initial part of the ascending aorta in the left and right sinuses. The location of each coronary artery varies both in height and circumference of the aorta. The mouth of the left vein.

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Blood circulation of the liver.

We admire the amazing creations of man. And we take for granted the vital activity of the body, the harmonious relationship between its structure and functions. Almost none of us are surprised, for example, by the constant, uninterrupted and accurate functioning of the liver that does not stop even for a minute throughout our lives. Ancient doctors worshiped the functions of organs that were mysterious to them and treated them as a “miracle.” Hippocrates considered the liver to be the “engine of nutrition”, Galen - the central hematopoietic and circulatory organ.

Even the reformer of medieval medicine Vesalius, the founder of scientific anatomy, wrote that “. the liver is perhaps the most important of the digestive organs and the workshop of thick blood, which is the fuel of the soul, requiring food and drink and that which is necessary to the nature of the body.”

Harvey and Malpighi said a new and, finally, scientific word about blood circulation in the body. And the research of biologists and physicians of the 19th-20th centuries brought a lot of new valuable data. And although even today it cannot be said that the functions of the liver are fully understood, we can rightfully say: not many vital processes in the body occur without the active participation of the liver. So, we will talk about the structure and functions, and most importantly, about the amazing and very unique blood circulation of the liver.

The structure of the liver.

The main functional unit of the liver is the hepatic lobule. There are about a million of them, and each lobule is built from approximately 350 thousand liver cells, arranged in radii, like spokes in a wheel. In the center of the lobule, like the axis of a wheel, runs a blood vessel - the central vein - this is the structure of the hepatic lobule in brief.

Liver cells, unlike cells of other organs, are short prisms with eight surfaces. The smallest blood vessels of the liver pass through tubes located at the corners of the cells. The tubes running in the middle of the liver cells are bile capillaries, through which the bile produced in the cells flows.

So, blood and bile. They flow in the liver towards each other; the first - from the periphery of the hepatic lobules to their center; the second - on the contrary - from the center of the hepatic lobules to the periphery. The opposite directions in the flow of bile and blood are explained by the complex functions of the liver - the largest digestive gland that produces bile, and the organ that receives and processes blood. What are the functions of the liver?

First of all, the liver is an active participant in carbohydrate metabolism. There is no human organ richer in glycogen, the so-called animal sugar, than the liver. It is a glycogen “depot”. The main source of glycogen is carbohydrates, absorbed into the blood from the intestines and transported through the portal vein system to the liver.

The liver is a blood filter.

The role of the liver in metabolism is no less important. Foreign substances formed during the transformation of proteins are poisons for the body. Passing through the circulatory system of the liver, they linger in its cells for some time and are neutralized. Thus, the liver, a faithful guardian of the body, saves it from severe poisoning.

The liver neutralizes not only foreign proteins, but also many potent poisons. For example, a poison such as morphine, passing through the liver cells, does not exhibit a toxic effect even in such quantities that would be fatal to the body if it were introduced into the blood that had already left the liver. The same can be said about pathogens. If the blood saturated with them undergoes the “quarantine service” of the liver cells, much fewer dangerous enemies spread in the body.

The participation of the liver in protein metabolism is not limited to the retention of foreign proteins. As blood flows through the liver, amino acids are partially accumulated here and from them “reserve protein” is synthesized, which is easily used by the body when little protein comes from food. Thus, after blood loss, the normal content of some blood plasma proteins is quickly restored. If the functions of the liver are impaired, say, as a result of severe poisoning, then the restoration of the normal protein composition of the blood is extremely slow.

Finally, during the period of intrauterine development, the child’s liver has a hematopoietic function, producing red blood cells - erythrocytes.

So, the hematopoietic function, participation in carbohydrate and protein metabolism, the most important role in protecting the body from harmful substances - all these and other various functions of the liver are carried out by liver cells. And their need for nutrients and oxygen is provided by the complex, very unique blood circulation of the organ - the portal vein system and the hepatic artery.

The liver is located in the upper abdominal cavity under the diaphragm. On its lower surface three clear grooves are visible: two longitudinal ones are connected by one transverse one in the shape of the letter “n”. The transverse groove is the so-called portal of the liver, where the hepatic artery and nerves enter, from where the lymphatic vessels and the excretory duct exit, directing bile to the duodenum. The portal vein also enters the portal of the liver.

The veins extending from the digestive organs gradually enlarge and form the superior and inferior mesenteric veins. They, in turn, merge with the splenic vein and pass into a large portal vein 3-4 centimeters long. The portal vein collects blood not only from the digestive organs. One of its roots is the splenic vein, which contains a certain amount of newly formed white blood cells - leukocytes produced in the spleen.

The blood passing through the spleen, thanks to the protective activity of this organ, is freed from “waste” red cells and pathogenic microbes, foreign particles, etc. that have entered the bloodstream. Thus, the spleen helps the liver, to some extent cleansing and neutralizing its portions of the blood.

Having entered the gate of the liver, the portal vein divides into two or three branches located between the lobes of the liver. These branches, as a result of repeated and sequential division, give rise to a large number of interlobular veins. The interlobular veins, located along the periphery of the hepatic lobule, and the central vein, lying in its center, are connected by capillaries, forming the so-called miraculous venous network. It differs from all other capillary networks, intended mainly for nutrition and tissue respiration, in that both before and after branching into capillaries, the composition of the blood in the network remains venous. In ordinary capillary networks, as is known, arterial blood passes into venous blood.

This feature is determined by the exclusive role of the liver itself. Blood rich in nutrients is eagerly awaited by every cell and every tissue in the body. The blood receives nutrients in the walls of the gastrointestinal tract. And before it gets to the heart, which sends the blood on a further journey through the blood vessels, it will certainly go through a cleansing stage in the liver.

Liver cells are directly adjacent to the very thin wall of the blood capillary. Thanks to this, they quickly absorb nutrients from the blood and retain harmful metabolic products, process them, and just as quickly, as needed, can release into the blood what was previously accumulated in them. All these processes are regulated and controlled by the nervous system.

To carry out complex functions and normal life, the liver naturally needs arterial blood rich in oxygen. Oxygen is brought to the liver by the hepatic artery. It gives rise to interlobular arteries, which then break up into a network of blood capillaries through which arterial blood flows. But these arterial capillaries immediately flow into the capillary network of the hepatic lobule, and in it, as we have already said, venous blood flows.

Here, in the capillary network of the liver lobule, mixing of arterial and venous blood occurs. This is another feature of the blood circulation of the liver: the liver tissue receives oxygen not only from the arterial capillaries, but also from the capillaries through which mixed venous and arterial blood flows. This additional enrichment of liver cells with oxygen is very important for the body.

So, thanks to the existence of the portal circulation, our blood flows through the following two capillary networks in succession: the gastrointestinal tract and the spleen, and then the liver. In the liver, all substances that enter the blood through the portal system are processed and accumulated, and then, as needed, they are again released into the blood or, together with bile, return to the intestines.

Some liver diseases disrupt its “quarantine” functions and impede blood flow. In such cases, the so-called anastomoses become of great importance - vessels connecting the portal vein or its roots with adjacent veins that flow directly into the inferior and superior vena cava, and, consequently, into the heart.

In a healthy person, anastomoses either do not participate in the blood circulation at all, or participate very little. When the liver becomes a “stumbling block” in the path of blood flow, the anastomoses begin to work.

For example, such a connection between the branches of the portal and vena cava is located on the anterior abdominal wall in the navel area. When blood flow through the portal vein is obstructed, blood rushes into the superior and inferior vena cava, bypassing the portal vein. At the same time, the anastomoses significantly expand and twist, taking on a bizarre shape. Ancient doctors called this system of anastomoses the “head of Medusa,” by analogy with the head of one of the three winged sisters (female monsters) described in Greek mythology - Medusa - Gorgons with snakes instead of hair on their heads.

Participation in the blood circulation of anastomoses is a kind of “vacation” for the liver, during which it gets the opportunity to restore its functions that are extremely necessary for the body.

The structure and functions of the liver and its circulatory system, which are irreplaceable in the body, are surprisingly expedient. But their possibilities are not unlimited. And a person should not for a moment, has no right to forget that the liver - his faithful friend and protector - also needs protection from the abuse of carbohydrates, fats, proteins, alcohol and nicotine. Take care of your liver!

Features of blood supply to the liver

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The enrichment of liver tissue occurs through two vessels: the artery and portal vein, which are branched in the left and right lobes of the organ. Both vessels enter the gland through the “gate” located at the bottom of the right lobe. The blood supply to the liver is distributed in the following percentage: 75% of the blood passes through the portal vein, and 25% through the artery. The anatomy of the liver involves the passage of 1.5 liters of valuable fluid every 60 seconds. at pressure in the portal vessel - domm Hg. Art., in the artery - up to 120 mm Hg. Art.

Features of the liver circulatory system

The liver plays a major role in metabolic processes occurring in the body. The quality of an organ’s functions depends on its blood supply. The liver tissues are enriched with blood from the artery, which is saturated with oxygen and nutrients. Valuable fluid enters the parenchyma from the celiac trunk. Venous blood, saturated with carbon dioxide and coming from the spleen and intestines, leaves the liver through the portal vessel.

The anatomy of the liver includes two structural units called lobules, which are similar to a faceted prism (the edges are created by rows of hepatocytes). Each lobule has a developed vascular network, consisting of an interlobular vein, artery, bile duct, and lymphatic vessels. The structure of each lobule suggests the presence of 3 blood streams:

• for the flow of blood serum to the lobules;
• for microcirculation inside the structural unit;
• to drain blood from the liver.

25-30% of the blood volume circulates through the arterial network under pressure up to 120 mmHg. Art., in the portal vessel - 70-75% (10-12 mm Hg). In sinusoids, the pressure does not exceed 3-5 mm Hg. Art., in the veins - 2-3 mm Hg. Art. If pressure increases, excess blood is released into the anastomoses between the vessels. After processing, arterial blood is directed into the capillary network, and then sequentially enters the hepatic vein system and accumulates in the lower hollow vessel.

The blood circulation rate in the liver is 100 ml/min, but with pathological dilatation of blood vessels due to their atony, this value can increase to 5000 ml/min. (about 3 times).

The interdependence of arteries and veins in the liver determines the stability of blood flow. When blood flow in the portal vein increases (for example, against the background of functional hyperemia of the gastrointestinal tract during digestion), the rate of movement of red liquid through the artery decreases. And, conversely, when the blood circulation rate in the vein decreases, perfusion in the artery increases.

The histology of the liver circulatory system suggests the presence of the following structural units:

• main vessels: hepatic artery (with oxygenated blood) and portal vein (with blood from unpaired peritoneal organs);
• an extensive network of vessels that flow into each other through lobar, segmental, interlobular, perilobular, capillary structures with a connection at the end into an intralobular sinusoidal capillary;
• efferent vessel - collecting vein, which contains mixed blood from the sinusoidal capillary and directs it to the sublobular vein;
• vena cava, designed to collect purified venous blood.

If for some reason blood cannot move at normal speed through the portal vein or artery, it is redirected to the anastomoses. A special feature of the structure of these structural elements is the ability to communicate with the blood supply system of the liver with other organs. True, in this case, the regulation of blood flow and redistribution of the red liquid is carried out without purifying it, so it, without lingering in the liver, immediately enters the heart.

The portal vein has anastomoses with the following organs:

• stomach;
• the anterior wall of the peritoneum through the periumbilical veins;
• esophagus;
• rectal section;
• the lower part of the liver itself through the vena cava.

Consequently, if a distinct venous pattern appears on the abdomen, resembling the head of a jellyfish, varicose veins of the esophagus and rectum are detected, it should be stated that the anastomoses are working in an enhanced mode, and in the portal vein there is a strong excess of pressure that prevents the passage of blood.

Regulation of blood supply to the liver

The normal amount of blood in the liver is considered to be 1.5 liters. Blood circulation is carried out due to the difference in pressure in the arterial and venous group of vessels. To ensure stable blood supply to the organ and its proper functioning, there is a special system for regulating blood flow. To do this, there are 3 types of regulation of blood supply, working through a special valve system of veins.

Myogenic

This regulatory system is responsible for muscular contraction of the vascular walls. Due to muscle tone, the lumen of blood vessels, when they contract, narrows, and when they relax, they expand. With the help of this process, the pressure and speed of blood flow increases or decreases, that is, the stability of the blood supply is regulated under the influence of:

Excessive physical activity and pressure fluctuations negatively affect the tone of liver tissue.

• exogenous factors such as physical activity, rest;
• endogenous factors, for example, during pressure fluctuations, the development of various diseases.

Features of myogenic regulation:

• ensuring a high degree of autoregulation of hepatic blood flow;
• maintaining constant pressure in the sinusoids.

Humoral

Regulation of this type occurs through hormones, such as:

Hormonal imbalances can negatively impact liver function and integrity.

• Adrenalin. It is produced during stress and affects the α-adrenergic receptors of the portal vessel, causing relaxation of the smooth muscles of the intrahepatic vascular walls and a decrease in pressure in the blood flow system.
• Norepinephrine and angiotensin. They have the same effect on the venous and arterial systems, causing a narrowing of the lumen of their vessels, which leads to a decrease in the amount of blood entering the organ. The process is started by increasing vascular resistance in both channels (venous and arterial).
• Acetylcholine. The hormone helps to expand the lumen of arterial vessels, which means it improves blood supply to the organ. But at the same time, a narrowing of the venules occurs, therefore, the outflow of blood from the liver is disrupted, which provokes the deposition of blood into the hepatic parenchyma and a jump in portal pressure.
• Metabolic products and tissue hormones. Substances dilate arterioles and narrow portal venules. There is a decrease in venous circulation against the background of an increase in the flow rate of arterial blood with an increase in its total volume.
• Other hormones - thyroxine, glucocorticoids, insulin, glucagon. The substances cause an increase in metabolic processes, while blood flow increases against the background of a decrease in portal inflow and an increase in arterial blood supply. There is a theory that adrenaline and tissue metabolites influence these hormones.

Nervous

The influence of this form of regulation is secondary. There are two types of regulation:

1. Sympathetic innervation, in which the process is controlled by the branches of the celiac plexus. The system leads to a narrowing of the lumen of blood vessels and a decrease in the amount of incoming blood.
2. Parasympathetic innervation, in which nerve impulses come from the vagus nerve. But these signals have no effect on the blood supply to the organ.

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The blood supply to the liver directly affects the quality of the functions performed by the organ. The process is carried out using a system of arteries and veins connecting the liver with other organs. Blood enters through two vessels and is distributed throughout the organ through branches of the left and right lobes.

Impaired tissue circulation deprives the liver of important nutrients and oxygen. The body's main filter does not perform the detoxification function well. As a result, the entire body suffers and overall health is impaired.

Venous blood, containing a mass of toxic substances, moves towards the liver from the intestines. It enters the liver directly through the portal vein. Next, there is a division into small interlobular veins.

Arterial blood enters the liver through the hepatic artery, which also branches into smaller interlobular arteries. Interlobular vessels of both types push blood into the sinusoids. There is mixed blood flow. It then drains into the central vein, and from there into the hepatic and inferior vena cava.

Liver circulation diagram

The liver, as a parenchymal organ, that is, an organ that does not have cavities, in its anatomy consists of structural units - lobules. Each lobule is formed by hepatocytes - specific cells. The prismatic lobules unite to form the right and left lobes of the liver. Blood supply is carried out directly by the system of arteries, veins, and connecting vessels.

The peculiarity of the blood supply to the liver is that the organ receives not only arterial blood, like all other internal organs, but mostly venous blood. The arteries supply nutrients and oxygen. And the veins carry blood for subsequent detoxification.

At an average blood flow rate of 100 ml per second, the blood supply is considered normal. As blood pressure changes, the speed changes. The smooth operation of arteries and veins helps regulate blood supply. In diseases of the biliary system, there is often a high blood flow rate in the portal vein and low blood flow in the arteries.

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The hepatic mass fills the right dome of the diaphragm and extends to the left of the body midline below the heart (Fig. 1 A). The most typical shape of the anterior surface of the liver, namely its decreasing volume to the left of the falciform ligament, is very convenient for laparoscopic access to extrahepatic biliary structures. The apex of the lateral segment of the left lobe of the liver may have the form of a fibrous continuation, which is an embryonic remnant (Fig. 1 B). Less common is enlargement of the right lobe of the liver downwards, which may cause additional difficulties (Fig. 1 B). The edge of the liver is directed from above to the left and below to the right, leaving part of the anterior wall of the stomach and pylorus open on the left and the proximal part of the transverse colon on the right. The tip of an unchanged gallbladder may protrude between the colon and the lower edge of the liver.

When studying the anatomy of the liver in three projections, one must always correlate it with the anatomy of neighboring organs. The relationship between the liver and the diaphragm is determined by the commonality of their embryonic origin - the transverse septum (Fig. 2 A). The areas of the liver not covered by peritoneum are the result of the transition of the parietal peritoneum from the lower surface of the diaphragm to the liver. This feature of the distribution of the peritoneum forms a diamond-shaped crown above the liver, called the coronary ligament.

The border of attachment of the “ligaments” is located on the upper surface of the liver far above and posteriorly, forming a deep suprahepatic pocket on the right. In the center of this area is the confluence of the inferior vena cava with the main hepatic veins. Anteriorly, the coronary ligament passes into the falciform ligament, the head portion of the ventral mesentery. Along the edges, left and right, the anterior and posterior surfaces of the coronary ligament come together at an acute angle and form triangular ligaments.

When the surgeon transects the left triangular ligament to mobilize the lateral segment of the left lobe of the liver, he must be aware of the proximity of the hepatic veins and the inferior vena cava. Access to these vessels, if damaged, will be extremely difficult due to their deep localization. Small veins running from the posterior surface of the liver directly to the inferior vena cava reflect the peculiarity of the evolutionary development of the vena cava from the dorsal part of the venous plexus of the liver. Note the location of the inferior left phrenic vein, which passes along the anterior semicircle of the esophageal opening of the diaphragm. This is a very common anatomy variant.

The organs of the upper floor of the abdominal cavity, when viewed on a CT scan slice, are located in the shape of a kidney or bean (Figure 2 B). The spine and large vessels fill the cavity, and the organs themselves are located posteriorly and to the sides, in the diaphragmatic recesses. The most posterior position is occupied by the kidneys.

In a sagittal section (Fig. 3), the abdominal cavity has a wedge shape due to the slope of the lumbar spine and adjacent lumbar muscles. The hepatorenal volvulus (Morrison's pouch) is the outermost space of the abdominal cavity. To the right and behind, the lower surface of the liver goes around the kidney with perinephric fiber, and in front of it is the hepatic angle of the colon.

A sagittal section of the right upper quadrant of the abdominal cavity (Fig. 4) shows that the inferior vena cava is located in the center of the abdominal cavity, and immediately in front of it is the hepatoduodenal ligament with the portal vein. On a frontal cholangiogram, the common bile duct usually runs along the right edge of the lumbar vertebrae. To view small details without overlapping images of underlying structures, the patient should be turned slightly to the right (Fig. 5).

If the liver is elevated, the hepatogastric omentum becomes visible, another derivative of the ventral mesentery, which extends from the lesser curvature of the stomach to the groove of the venous ligament and the porta hepatis (Fig. 6). The free edge of the omentum surrounds the bile ducts and forms the hepatoduodenal ligament. The place of contact between the anterior surface of the fundus of the stomach and the lower surface of the lateral segment of the left lobe of the liver is also visible. The initial section of the duodenum, previously closed by the edge of the liver, is visible, and the relative position of the intestine and the lower surface of the quadrate lobe, as well as the gallbladder, is visible. And finally, on the right, the relative position of the hepatic angle of the colon, the right lobe of the liver and the gallbladder is open.

When the stomach and duodenum are retracted, the root of the mesentery of the transverse colon and the boundaries of the omental bursa behind the lesser omentum become visible (Fig. 7). In the upper part of the bursa, the caudate lobe of the liver is visible, which is usually of considerable size. The fold of peritoneum between the liver and pancreas has the appearance of a ridge formed by the hepatic artery, passing through the retroperitoneal space of the omental bursa and turning into the hepatoduodenal ligament.

When the posterior layer of the parietal peritoneum is separated, the anatomical structures of the porta hepatis and their relationship with the pancreas are exposed (Fig. 8). The trunk of the celiac artery is usually divided into three branches, giving rise to the left gastric artery, hepatic and splenic arteries.

And let’s complete the review of the organs of the upper abdominal cavity with a rear view (Fig. 9). The right lobe of the liver extends posteriorly over the superior pole of the right kidney, so that the right adrenal gland is enclosed between the kidney, liver, and inferior vena cava. The inferior vena cava, for a greater or lesser extent, is located in the fossa separating the right and left lobes of the liver. To the left of the vena cava lies the caudate lobe of the liver.

The gastrohepatic omentum extends from the lesser curvature of the stomach to the hilum of the spleen and the groove of the venous ligament. The esophagus is located immediately to the left of the quadrate lobe, between the lower thoracic aorta posteriorly (behind the crura of the diaphragm) and the lateral segment of the left lobe of the liver anteriorly. The cone-shaped edge of the left lobe protrudes above the cardia of the stomach, reaching the anterior border of the spleen. The fourth section of the duodenum goes obliquely upward between the body of the pancreas in front (removed) and the aorta (removed) behind.

On the lower surface of the liver there is a deep central transverse groove formed by its gate (Fig. 10). The common bile duct, hepatic artery and portal vein - the main anatomical structures of the portal - are adjacent to the right side of the groove, and their branches go to the left side, located for a considerable distance outside the hepatic tissue. The plane drawn along the gall bladder bed and the inferior vena cava mainly separates the left and right lobes of the liver (the caudate lobe extends on both sides).

Near the end of the portal groove on the left side, the round ligament of the liver (a remnant of the umbilical vein) passes through a small depression. The extrahepatic portion of the round ligament below the umbilical notch lies along the free edge of the falciform ligament. From the left end of the portal, a groove of the venous ligament stretches obliquely posteriorly, which runs from the left branch of the portal vein to the inferior vena cava near the diaphragm. The hepatogastric omentum extends from the same groove, continuing to the porta hepatis and surrounding the main portal structures in the form of the hepatoduodenal ligament.

Between the omentum and the inferior vena cava is the caudate lobe of the liver. The caudate and right lobes are connected by a narrow isthmus - the caudate process, lying between the gate and the vena cava. It is the roof of the omental opening connecting the omental bursa and the abdominal cavity. The anterior edge of this opening is the hepatoduodenal ligament, and the posterior edge is the vena cava. The inferior inversion of the parietal peritoneum onto the liver crosses the inferior vena cava immediately inferior to the liver and partially follows the depression of the right adrenal gland on the inferior surface of the right lobe.

It is important for the laparoscopist surgeon to know the segmental structure of the liver (shown in the oblique caudal plane, Fig. 11). Knowledge of the normal anatomy of the bile ducts (which occurs in 70% of cases) is necessary to recognize possible anomalies, identify ductal branches that are not visualized on cholangiograms (due to damage or obstruction), and be more careful about the anatomical structures adjacent to the gallbladder bed. Each biliary segment contains the bile duct, a branch of the portal vein and a branch of the hepatic artery. The hepatic veins run between the segments.

The right and left lobes of the liver are separated by a plane passing through the gall bladder bed and the fossa of the inferior vena cava, and each lobe is divided into two segments. The median hepatic vein is located at the junction of both lobes. The right lobe is divided by an oblique transverse plane, running correspondingly to the right hepatic vein, into anterior and posterior segments. The left hepatic vein divides the left lobe into medial and lateral segments. Each of these large segments consists of an upper and lower part.

The caudate lobe, located behind the upper part of the medial segment, is in contact to varying degrees with both lobes. The terminal sections of the hepatic artery and portal vein are anastomosed with the initial sections of the hepatic vein at the level of the hepatic lobules. Portal vessels and ducts enter each segment from the side of the centrally located gate. The gallbladder bed is formed by the inferior surfaces of the right anterior and left medial segments, and the ducts and vessels passing through these segments are at risk of damage when cholecystectomies are performed.

The cholangiogram shows the normal structure of the biliary system (Fig. 12 A). The right and left hepatic ducts join at the porta hepatis to form the common bile duct (in 90% of cases outside the liver itself). The right hepatic duct is formed by the fusion of the anterior and posterior segmental ducts, which occurs close (~1 cm) to the junction of the right and left hepatic ducts.

The right anterior segmental duct is shorter and located below the posterior segmental duct. The frontal cholangiogram shows that the bifurcation site of the anterior duct is more medial than the posterior duct. In about a third of individuals, there is a subvesical duct, which passes close to the gallbladder bed and drains into the right anterior duct. Unlike other bile ducts, it is not accompanied by a branch of the portal vein. It is not connected to the gallbladder, but can be damaged during cholecystectomy.

The left lateral superior and inferior ducts usually join at or slightly to the right of the left segmental sulcus. Bile flows into the long and thin superior duct from the apex of the left lobe, which passes into the fibrous process. In a small number of people (= 5%), the bile ducts in this appendage may persist and be a source of bile leakage when the appendage is divided to mobilize the left triangular ligament of the liver.

From the upper and lower parts of the medial segment of the left lobe, bile flows into four small ducts. When the medial and lateral segmental ducts join near the porta hepatis, the left hepatic duct is formed. Bile from the caudate part of the medial segment goes in three directions. From the rightmost section, bile usually flows into the right ductal system, from the leftmost section into the left, and from the intermediate section, with approximately equal frequency, into one of the sides.

There are several options for the location of the bile ducts inside the liver. Typically, the main left and right bile ducts join at the center of the porta hepatis (in 10% of cases, within the hepatic parenchyma). In approximately 22% of individuals, the right posterior segmental duct can cross the interlobar fissure and empty into the left hepatic duct (Fig. 12 B).

In 6% of cases, the right anterior segmental duct passes to the left side (Fig. 12 B). If the right segmental ducts are located separately, they may be damaged during cholecystectomy. It is more correct to call these ducts aberrant than accessory, since they collect bile from normal areas of the liver, and are not some kind of additional ones. On the left side, in a quarter of cases, the duct of the medial segment flows into the lower branch of the duct of the lateral segment (Fig. 12 D).

Of the peripheral ducts, the right posterior superior duct has the most consistent location. The remaining subsegmental ducts in 22% of cases have alternative drainage options.

The course of the portal vein trunks when viewed from below corresponds to the segmental structure of the liver (Fig. 13). The portal vein divides outside the liver, near the right side of the portal, and the longer left trunk crosses the portal groove. The right trunk runs close posterior to the infundibular portion of the gallbladder and is most often damaged at this location. The right trunk of the portal vein usually divides into anterior and posterior branches, going to the two main segments of the right lobe in an anterosuperior and posteroinferior direction, respectively. Sometimes this division occurs at the site of the main bifurcation of the portal vein, which thus becomes a trifurcation. During cholecystectomy, the right trunk of the portal vein may be damaged near the porta hepatis.

The left trunk of the portal vein bends anteriorly and enters the liver parenchyma in the region of the groove of the round ligament. It then divides into two branches leading to the medial and lateral segments of the left lobe. Each segmental branch feeds the upper and lower sections of its segment. Proximal branches from the main right and left trunks of the portal vein extend to the caudate lobe. Some venous outflow from the gallbladder goes into the right portal trunk, but the main amount of blood flows directly into the hepatic bed of the gallbladder.

Wind G.J.
Applied laparoscopic anatomy: abdominal cavity and pelvis