The human liver comes into contact with the following organs:

• diaphragm - a muscle that separates the chest and abdominal cavity;
• stomach;
• gallbladder;
• duodenum;
• right kidney and right adrenal gland;
• transverse colon.

The liver is located on the right under the ribs and has a wedge-shaped shape.

The organ has two surfaces:

• Diaphragmatic (upper) – convex, dome-shaped, corresponding to the concavity of the diaphragm.
• Visceral (lower) - uneven, with impressions of adjacent organs, with three grooves (one transverse and two longitudinal), forming the letter H. In the transverse groove is the portal of the liver, through which nerves and vessels enter and lymph vessels and bile ducts exit. In the middle of the right longitudinal groove is the gallbladder, in the posterior part is the IVC (inferior vena cava). The umbilical vein passes through the anterior part of the left longitudinal groove; the remainder of the ductus venosus of Aranti is located in the posterior part.

The liver has two edges - a sharp lower edge and a blunt upper-posterior edge. The upper and lower surfaces are separated by a lower sharp edge. The superior posterior margin looks almost like the posterior surface.

The structure of the human liver

It consists of very soft fabric, its structure is granular. It is located in a Glissonian capsule made of connective tissue. In the area of ​​the hilum of the liver, the Glissonian capsule is thicker and is called the hilar plate. On top, the liver is covered with a layer of peritoneum, which tightly fuses with the connective tissue capsule. There is no visceral layer of peritoneum at the site of attachment of the organ to the diaphragm, at the site of entry of blood vessels and exit of the biliary tract. The peritoneal layer is absent in the posterior area adjacent to the retroperitoneal tissue. At this point, access to the posterior parts of the liver is possible, for example, to open abscesses.

In the center of the lower part of the organ there is Glisson's gate - the exit of the biliary tract and the entrance of large vessels. Blood enters the liver through the portal vein (75%) and the hepatic artery (25%). The portal vein and hepatic artery in approximately 60% of cases are divided into right and left branches.

The falciform and transverse ligaments divide the organ into two unequal-sized lobes - right and left. These are the main lobes of the liver; in addition to them, there is also the caudal and quadrate lobes.

The liver consists of parenchyma and stroma

Parenchyma is formed from lobules, which are its structural units. In their structure, the lobules resemble prisms inserted into each other.

The stroma is a fibrous membrane, or Glissonian capsule, of dense connective tissue with septa of loose connective tissue that penetrate the parenchyma and divide it into lobules. It is pierced by nerves and blood vessels.

The liver is usually divided into tubular systems, segments and sectors (zones). Segments and sectors are separated by depressions - grooves. Division is determined by the branching of the portal vein.

Tubular systems include:

• Arteries.
• Portal system (portal vein branches).
• Caval system (hepatic veins).
• Biliary tract.
• Lymphatic system.

Tubular systems, except for the portal and caval veins, run next to the branches of the portal vein parallel to each other and form bundles. Nerves join them.

The photo shows tubular systems according to Sinelnikov: 1 – inferior vena cava; 2 – right lobe of the liver; 3 – common hepatic duct; 4 – portal vein; 5 – lymphatic vessels; 6 – common hepatic artery; 7 – left lobe of the liver; 8 – hepatic veins

Segments are sections of the parenchyma that are pyramid-shaped and adjacent to the branches of the second-order portal vein, branches of the hepatic duct, and branches of the hepatic artery. They are located around the gates in radii.

There are eight segments (from right to left counterclockwise from I to VIII):

• Left lobe: caudate – I, posterior – II, anterior – III, quadrate – IV.
• Right lobe: middle upper anterior – V, lateral inferoanterior – VI and lateral inferoposterior – VII, middle upper posterior – VIII.

Segments form larger areas - sectors (zones). There are five of them. They are formed by certain segments:

• Left lateral (segment II).
• Left paramedian (III and IV).
• Right paramedian (V and VIII).
• Right lateral (VI and VII).
• Left dorsal (I).

The outflow of blood occurs through three hepatic veins, which come together on the posterior surface of the liver and flow into the inferior cava, which lies on the border of the right part of the organ and the left.

The bile ducts (right and left), which remove bile, merge into the hepatic duct at the Glissonian hilum.

The outflow of lymph from the liver occurs through the lymph nodes of the Glissonian hilum, the retroperitoneal space and the hepatoduodenal ligament. There are no lymphatic capillaries inside the hepatic lobes; they are located in the connective tissue and flow into the lymphatic vascular plexuses that accompany the portal vein, hepatic arteries, biliary tract and hepatic veins.

The liver is supplied with nerves from the vagus nerve (its main trunk is the Lattarget nerve).

The ligamentous apparatus, consisting of the semilunar, falciform and triangular ligaments, attaches the liver to the posterior wall of the peritoneum and the diaphragm.

The liver is located on the right side under the diaphragm. It occupies most of the upper abdominal cavity. A small part of the organ extends beyond the midline into the left part of the subphrenic region and reaches the left hypochondrium. From above it is adjacent to the lower surface of the diaphragm, a small part of the anterior surface of the liver is adjacent to the anterior wall of the peritoneum.

Most of the organ is located under the right ribs, a small part in the epigastric zone and under the left ribs. The midline coincides with the border between the lobes of the liver.

The liver has four boundaries: right, left, upper, lower. The organ is projected onto the anterior wall of the peritoneum. The upper and lower boundaries are projected onto the anterolateral surface of the body and converge at two points - on the right and left sides.

The location of the upper border of the liver is the right nipple line, the level of the fourth intercostal space.

The apex of the left lobe is the left parasterial line, the level of the fifth intercostal space.

The anterior lower edge is the level of the tenth intercostal space.

The anterior edge is the right nipple line, the costal edge, then it departs from the ribs and stretches obliquely upward to the left.

The anterior contour of the organ has a triangular shape.

The lower edge is not covered with ribs only in the epigastric zone.

In diseases, the anterior edge of the liver protrudes beyond the edge of the ribs and is easily palpable.

Functions of the liver in the human body

The role of the liver in the human body is great; gland is one of the vital organs. This gland performs many different functions. The main role in their implementation is given to structural elements - hepatocytes.

How does the liver work and what processes occur in it? It takes part in digestion, in all types of metabolic processes, performs a barrier and hormonal function, as well as hematopoietic during embryonic development.

What does the liver do as a filter?

It neutralizes toxic products of protein metabolism that come with the blood, that is, it disinfects toxic substances, turning them into less harmless ones that are easily removed from the body. Thanks to the phagocytic properties of the endothelium of the liver capillaries, substances absorbed in the intestinal tract are neutralized.

It is responsible for removing excess vitamins, hormones, mediators, and other toxic intermediate and end products of metabolism from the body.

What is the role of the liver in digestion?

It produces bile, which then enters the duodenum. Bile is a yellow, greenish or brown jelly-like substance with a specific odor and a bitter taste. Its color depends on the content of bile pigments, which are formed during the breakdown of red blood cells. It contains bilirubin, cholesterol, lecithin, bile acids, mucus. Thanks to bile acids, fats are emulsified and absorbed in the gastrointestinal tract. Half of all the bile produced by liver cells goes into the gallbladder.

What is the role of the liver in metabolic processes?

It is called the glycogen depot. Carbohydrates that are absorbed by the small intestine are converted into glycogen in the liver cells. It is deposited in hepatocytes and muscle cells and, when there is a deficiency of glucose, begins to be consumed by the body. Glucose is synthesized in the liver from fructose, galactose and other organic compounds. When accumulated in excess in the body, it turns into fat and settles throughout the body in fat cells. The deposition of glycogen and its breakdown to release glucose is regulated by insulin and glucagon, the hormones of the pancreas.

The liver breaks down amino acids and synthesizes proteins.

It neutralizes ammonia released during the breakdown of proteins (it turns into urea and leaves the body with urine) and other toxic substances.

Phospholipids and other fats needed by the body are synthesized from fatty acids obtained from food.

What function does the fetal liver perform?

During embryonic development, it produces red blood cells - erythrocytes. The placenta plays a neutralizing role during this period.

Due to the variety of functions, it is not entirely clear which organ system the liver belongs to. This is an exocrine gland and is considered an auxiliary organ of the digestive tract.

Pathologies

Liver diseases are caused by its functions. Since one of its main tasks is the neutralization of foreign agents, the most common diseases of the organ are infectious and toxic lesions. Despite the fact that liver cells are able to quickly recover, these capabilities are not unlimited and can quickly be lost during infectious lesions. With prolonged exposure to pathogens, fibrosis can develop, which is very difficult to treat.

Diseases can appear not only as a result of direct exposure to harmful factors on hepatocytes, but as a result of poor nutrition, circulatory disorders, and other things.

Pathologies usually develop in the form of dystrophy, bile stagnation, inflammation, and liver failure. Further disturbances in metabolic processes: protein, carbohydrate, fat, hormonal, enzymatic depend on the degree of damage to the liver tissue.

Diseases can occur in a chronic or acute form, changes in the organ can be reversible or irreversible.

Characterized by disruption of the organ. One function, several or all at once may decrease. There are acute and chronic insufficiency, based on the outcome of the disease - non-fatal and fatal.

The most severe form is acute. In acute renal failure, the production of blood coagulation factors and albumin synthesis are disrupted.

If one liver function is impaired, there is partial failure, if several - subtotal, if all - total.

If carbohydrate metabolism is disturbed, hypo- and hyperglycemia may develop.

If fat is disturbed, cholesterol plaques are deposited in blood vessels and atherosclerosis develops.

If protein metabolism is disrupted, bleeding, swelling, delayed absorption of vitamin K in the intestine.

Portal hypertension

This is a severe complication of liver disease, characterized by increased pressure in the portal vein and blood stagnation. Most often it develops with cirrhosis, as well as with congenital anomalies or thrombosis of the portal vein, when it is compressed by infiltrates or tumors. Blood circulation and lymph flow in the liver with portal hypertension worsens, which leads to disturbances in the structure and metabolism in other organs.

Diseases

The most common diseases are hepatosis, hepatitis, and cirrhosis.

Hepatitis is an inflammation of the parenchyma (the suffix -itis indicates inflammation). There are infectious and non-infectious. The first include viral ones, the second - alcoholic, autoimmune, and medicinal. Hepatitis occurs acutely or chronically. They can be an independent disease or secondary - a symptom of another pathology.

There are several types of viral hepatitis

Hepatosis is a dystrophic lesion of the parenchyma (the suffix -oz indicates degenerative processes). The most common is fatty hepatosis, or steatosis, which usually develops in people suffering from alcoholism. Other causes of its occurrence are the toxic effects of drugs, diabetes mellitus, Cushing's syndrome, obesity, and long-term use of glucocorticoids.

Cirrhosis is an irreversible process and the final stage of liver disease. The most common cause is alcoholism. Characterized by degeneration and death of hepatocytes. With cirrhosis, nodules are formed in the parenchyma, surrounded by connective tissue. As fibrosis progresses, the circulatory and lymphatic systems deteriorate, liver failure and portal hypertension develop. With cirrhosis, the spleen and liver increase in size, gastritis, pancreatitis, stomach ulcers, anemia, dilation of the esophageal veins, and hemorrhoidal bleeding may develop. Patients become exhausted, they experience general weakness, itching of the entire body, and apathy. The functioning of all systems is disrupted: nervous, cardiovascular, endocrine and others. Cirrhosis is characterized by high mortality.

Developmental defects

This type of pathology is rare and is expressed by an abnormal location or abnormal shape of the liver.

Incorrect location is observed with a weak ligamentous apparatus, resulting in prolapse of the organ.

Abnormal forms are the development of additional lobes, changes in the depth of the grooves or the size of parts of the liver.

Congenital defects include various benign formations: cysts, cavernous hemangiomas, hepatoadenomas.

The importance of the liver in the body is enormous, so you need to be able to diagnose pathologies and treat them correctly. Knowledge of the anatomy of the liver, its structural features and structural division makes it possible to find out the location and boundaries of the affected foci and the degree of coverage of the organ by the pathological process, determine the volume of its part to be removed, and avoid disruption of the outflow of bile and blood circulation. Knowledge of the projections of liver structures onto its surface is necessary for performing operations to remove fluid.

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 that form 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 liver is a voluminous glandular organ. Given the complex structure and functions of the liver, it is impossible to say exactly which system it belongs to. It is an exocrine gland, but at the same time an auxiliary organ of the digestive tract.

Anatomy

Basic moments:

• The liver is distinguished: 2 surfaces and 2 edges, 4 lobes, 5 sectors and 8 segments. Such a diverse division is arbitrary and serves as guidelines for the ease of diagnostic and surgical procedures.
• Surfaces: upper convex (diaphragmatic) and lower concave (visceral),
• Edges: posterior blunt and anterior sharp.
• Sectors: right – paramedian (V and VIII) and lateral (VI and VII), left – dorsal (I), lateral (II) and paramedian (III and IV). A sector is a section of the liver into which a branch of the portal vein enters, a corresponding branch of the hepatic artery, nerves, and the sectoral bile duct exits.
• Connective tissue and peritoneal ligaments. They hold the liver in a certain position.
• Blood flow: hepatic artery and portal vein.
• Outflow: hepatic veins.
• The shape resembles a triangle.
• Location: from the fifth intercostal space to the costal arch, mainly to the right of the midline. It is adjacent to the diaphragm above, to the stomach and duodenum below.
• Almost completely covered by visceral peritoneum, except for the posterior part of the diaphragmatic surface and the gall bladder bed.
• The functional and structural unit is the hepatic lobule, consisting of glandular cells (in humans there are approximately 500,000 lobules)

Structure

The liver consists of two lobes, which are separated by the falciform ligament on top and longitudinal (left and right) and transverse grooves on the lower surface. Another name for the transverse groove is the porta hepatis. Nerves, portal vein, hepatic artery, hepatic bile duct and lymphatic vessels pass through the hilum.

The right longitudinal groove is the bed of the gallbladder, the inferior vena cava also passes there. The left groove contains the round ligament of the liver and the umbilical vein. The caudal and quadrate lobes, which were previously included in the right lobe, are also distinguished.

Each lobe is conventionally divided into 4 segments. The segment is a branch of the portal branch, the corresponding branch of the hepatic artery and the bile duct, surrounded by a section of liver parenchyma.

Under the serous membrane of the liver there is a thin fibrous membrane, which, together with the vessels, enters into the connective tissue layers surrounding the liver lobules.

The connective tissue layers have a high density, but they are thin and inelastic. Because of this, the liver is a very delicate organ - the slightest mechanical impact can lead to damage.

Ligaments

All ligaments, except the hepatorenal ligament, are two layers of peritoneum. They are formed at the transition points of the peritoneum covering the liver to nearby organs (peritoneal) and tissues (connective tissue).

Peritoneal: hepatic-duodenal, hepatic-gastric, hepatic-renal.

Connective tissue:

• Round ligament of the liver - extends from the left longitudinal groove to the anterior abdominal wall near the umbilicus
• Crescent - from the diaphragm to the liver. It divides the liver into right and left lobes and is connected to two others: round and coronal.
• Coronary - on the left lobe it is represented by two leaves, on the right - the leaves of the peritoneum diverge from the level of the inferior vena cava. An open area of ​​the liver remains, not covered by peritoneum.
• Triangular. To the left of the diaphragm and the left lobe of the liver, it is divided into 2 parts. On the left side it ends with a free edge, on the right it is a continuation of the coronary ligament. Right - from the diaphragm to the right lobe of the liver.

Liver functions

• Formation and secretion of bile.
• Barrier function.
• Detoxification (macrophages)
• Depot of glycogen, some vitamins and microelements and even blood (up to 1 liter)
• Participates in all types of exchanges
• Hematopoietic (in the embryonic period)

Features of anatomy

• The location of the liver changes depending on the position of the body. When standing, it goes down, while lying down, it goes up. It’s the same in the process of breathing: when you inhale, it rises, when you exhale, it falls. During the deep inspiration phase, it is possible to determine its lower edge.
• There are two vein systems in the liver: portal - formed by the branches of the portal vein, through which blood flows into the organ through its gates, and caval - branches of the hepatic vein - carrying blood from the liver to the inferior vena cava.

Unlike other organs, not only arterial blood flows into the liver (through the hepatic artery), but also venous blood (through the portal). And it flows through the hepatic veins. Portal blood, unlike the venous blood of the caval system, contains food breakdown products and toxic substances absorbed in the intestine

• Each half of the liver is independently supplied with blood and also has its own outflow of bile and blood. The border between these halves conventionally passes through the upper part of the gallbladder and the inferior vena cava. And they, in turn, are divided into 4 segments with an identical blood supply system. Every 2 minutes, all the blood passes through both sections.

Role in the body

• First of all, this is the formation of bile by hepatocytes (choleresis) and its secretion (cholekinesis). This alone makes a significant contribution to the digestive process.
• Choleresis occurs continuously, but food intake enhances this process.
• Cholekinesis occurs periodically - only with food. On an empty stomach, bile enters the gallbladder. And in the process of eating, bile enters the duodenum.

Strong stimulators of bile secretion are milk, meat, fats, and egg yolk.

Bile meaning:

• Emulsifies fats, resulting in an increase in the surface area on which they are hydrolyzed by lipase.
• Dissolves fat hydrolysis products, helping their absorption and resynthesis of triglycerides in enterocytes.
• Increases the activity of liver and intestinal enzymes, especially lipase.
• Enhances hydrolysis and absorption of carbohydrates and proteins, absorption of fat-soluble vitamins (A, D, E, K), cholesterol and calcium salts.
• It itself is a stimulator of bile formation and bile excretion.
• Promotes motor and secretory activity of the small intestine, proliferation of enterocytes, apoptosis.
• Neutralizes hydrochloric acid in the duodenum.
• Stimulates intestinal motility.
• Removes toxins and metabolites from the body, such as bilirubin.

The role of the liver in neutralizing toxic substances is no less important.

• Chemicals are neutralized in 2 stages: Enzymatic oxidation, reduction, methylation, acetylation, hydrolysis. Subsequent conjugation with glycine, taurine, sulfuric, acetic, glucuronic acid.
• Soluble conjugates are excreted in bile and urine.
• Toxic ammonia is inactivated by urea and creatinine.
• Microorganisms are neutralized through phagocytosis and lysis.
• Also takes part in ensuring homeostasis. The same bile in its composition releases a number of substances from the blood that are transformed in the liver.
• Depositing blood. In case of blood loss or shock, this blood is released into the vascular bed.
• Inactivates: hormones (glucocorticosteroids, aldosterone, androgens, estrogens, glucagon, some gastrointestinal hormones), biogenic amines (catecholamines, histamine, serotonin).
• Participates in erythrokinetics: in the destruction of aging forms of red blood cells, heme degradation and the formation of bilirubin. Supplier of iron to red bone marrow.
• Regulatory influence of bile on the secretion of the stomach and small intestine. Evacuation activity of the gastroduodenal complex and intestinal motility
• Finally, it participates in all types of exchange.

In protein metabolism

What happens in the liver:

• synthesis of blood proteins: all fibrinogen, most albumins and globulins, factors of the coagulation and anticoagulation system of the blood. Therefore, the liver takes part in blood clotting, and, conversely, in slowing down this process.
• Transamination of amino acids – i.e. the formation of new proteins from the breakdown products of proteins that enter the intestines with food.
• Another task: transport of substances in the blood. It forms protein complexes with fats, carbohydrates, and carrier complexes - for example, transferrin - an iron carrier.
• The breakdown of proteins to their final products: ammonia and urea.
• Ammonia is toxic. The accumulation of ammonia in the blood and nervous system leads to psychopathology, up to coma - a complete shutdown of the nervous system. That is why the role of this organ is important; it neutralizes ammonia to low-toxic urea, which is excreted by the kidneys.

In lipid metabolism

The role of the liver is that fats are broken down into trilycerides, and phospholipids, bile acids, lipoproteins, and acetone bodies are formed.

Short chain fatty acids are synthesized only in this organ. They are the source of a significant proportion of energy and heat in the body and are used for the full functioning of skeletal and cardiac muscles.

In carbohydrate metabolism

Participation is determined by the synthesis, breakdown and deposition of glycogen, the conversion of galactose and fructose into glucose, and its oxidation. Those. Excess glucose is converted into glycogen and stored in the liver, and if there is a lack of sugar in the blood, it is again converted into glucose.

In vitamin metabolism

Participation in the absorption, formation of vitamins and their bioactive forms, deposition and removal of their excess from the body.

In the exchange of microelements and electrolytes

Maintaining plasma oncotic pressure, regulating plasma sodium and potassium levels by influencing aldosterone levels.

LIVER
the largest gland in the body of vertebrates. In humans, it makes up about 2.5% of body weight, on average 1.5 kg in adult men and 1.2 kg in women. The liver is located in the upper right part of the abdominal cavity; it is attached by ligaments to the diaphragm, abdominal wall, stomach and intestines and is covered with a thin fibrous membrane - Glisson's capsule. The liver is a soft but dense organ of a red-brown color and usually consists of four lobes: a large right lobe, a smaller left lobe and much smaller caudate and quadrate lobes that form the posterior lower surface of the liver.

LIVER is the largest gland in the human body, performing many functions. Ligaments fix its position in the upper right part of the abdominal cavity. The structure of the liver includes several lobes, each of which consists of functional units - lobules. Liver cells secrete bile needed for digestion into intralobular bile canaliculi. Through the common bile duct, bile is transported to the intestines or gallbladder, where it is stored for later use. Nutrition of the liver tissue is provided by blood flowing through the hepatic artery. The portal vein brings blood containing absorbed digestive products, which are further processed in the liver. All incoming blood enters the lobular capillaries - sinusoids. Flowing through them, it washes the liver cells and exits through the central, then interlobular, and then hepatic veins into the inferior vena cava.

Functions. The liver is an essential organ for life with many different functions. One of the main ones is the formation and secretion of bile, a transparent liquid of orange or yellow color. Bile contains acids, salts, phospholipids (fats containing a phosphate group), cholesterol and pigments. Bile salts and free bile acids emulsify fats (i.e. break them into small droplets), making them easier to digest; convert fatty acids into water-soluble forms (which is necessary for the absorption of both the fatty acids themselves and fat-soluble vitamins A, D, E and K); have an antibacterial effect. All nutrients absorbed into the blood from the digestive tract - products of the digestion of carbohydrates, proteins and fats, minerals and vitamins - pass through the liver and are processed there. At the same time, some amino acids (protein fragments) and some fats are converted into carbohydrates, so the liver is the largest “depot” of glycogen in the body. It synthesizes blood plasma proteins - globulins and albumin, and also undergoes amino acid conversion reactions (deamination and transamination). Deamination - the removal of nitrogen-containing amino groups from amino acids - allows the latter to be used, for example, for the synthesis of carbohydrates and fats. Transamination is the transfer of an amino group from an amino acid to a keto acid to form another amino acid (see METABOLISM). The liver also synthesizes ketone bodies (products of fatty acid metabolism) and cholesterol. The liver is involved in regulating glucose (sugar) levels in the blood. If this level increases, liver cells convert glucose into glycogen (a substance similar to starch) and store it. If the blood glucose level drops below normal, glycogen is broken down and glucose enters the bloodstream. In addition, the liver is capable of synthesizing glucose from other substances, such as amino acids; this process is called gluconeogenesis. Another function of the liver is detoxification. Medicines and other potentially toxic compounds can be converted into a water-soluble form in liver cells, which allows them to be excreted in bile; they can also be destroyed or conjugate (combine) with other substances to form harmless products that are easily excreted from the body. Some substances are temporarily deposited in Kupffer cells (special cells that absorb foreign particles) or in other liver cells. Kupffer cells are particularly effective at removing and destroying bacteria and other foreign particles. Thanks to them, the liver plays an important role in the body's immune defense. Possessing a dense network of blood vessels, the liver also serves as a blood reservoir (it constantly contains about 0.5 liters of blood) and is involved in the regulation of blood volume and blood flow in the body. In general, the liver performs more than 500 different functions, and its activity cannot yet be reproduced artificially. Removal of this organ inevitably leads to death within 1-5 days. However, the liver has a huge internal reserve, it has an amazing ability to recover from damage, so humans and other mammals can survive even after 70% of the liver tissue is removed.
Structure. The complex structure of the liver is perfectly adapted to perform its unique functions. The lobes consist of small structural units - lobules. In the human liver there are about one hundred thousand of them, each 1.5-2 mm long and 1-1.2 mm wide. The lobule consists of liver cells - hepatocytes, located around the central vein. Hepatocytes are united into layers one cell thick - the so-called. liver plates. They diverge radially from the central vein, branch and connect with each other, forming a complex system of walls; the narrow gaps between them, filled with blood, are known as sinusoids. Sinusoids are equivalent to capillaries; passing one into another, they form a continuous labyrinth. The hepatic lobules are supplied with blood from the branches of the portal vein and the hepatic artery, and the bile formed in the lobules enters the tubular system, from them into the bile ducts and is excreted from the liver.

The hepatic portal vein and hepatic artery provide the liver with an unusual, dual blood supply. Nutrient-rich blood from the capillaries of the stomach, intestines and several other organs is collected in the portal vein, which, instead of carrying blood to the heart like most other veins, carries it to the liver. In the liver lobules, the portal vein breaks up into a network of capillaries (sinusoids). The term “portal vein” indicates an unusual direction of blood transport from the capillaries of one organ to the capillaries of another (the kidneys and pituitary gland have a similar circulatory system). The second source of blood supply to the liver, the hepatic artery, carries oxygenated blood from the heart to the outer surfaces of the lobules. The portal vein provides 75-80%, and the hepatic artery 20-25% of the total blood supply to the liver. In general, about 1500 ml of blood passes through the liver per minute, i.e. a quarter of cardiac output. Blood from both sources ultimately enters the sinusoids, where it mixes and flows to the central vein. From the central vein, the outflow of blood to the heart begins through the lobar veins into the hepatic vein (not to be confused with the portal vein of the liver). Bile is secreted by liver cells into the smallest tubules between the cells - bile capillaries. It is collected through the internal system of tubules and ducts into the bile duct. Some bile goes directly into the common bile duct and is released into the small intestine, but most of it travels through the cystic duct back for storage in the gallbladder, a small, muscular-walled sac attached to the liver. When food enters the intestines, the gallbladder contracts and releases the contents into the common bile duct, which opens into the duodenum. The human liver produces about 600 ml of bile per day.
Portal triad and acini. The branches of the portal vein, hepatic artery and bile duct are located nearby, at the outer border of the lobule and form the portal triad. At the periphery of each lobule there are several such portal triads. The functional unit of the liver is the acinus. This is the part of tissue that surrounds the portal triad and includes lymphatic vessels, nerve fibers and adjacent sectors of two or more lobules. One acini contains about 20 liver cells located between the portal triad and the central vein of each lobule. In a two-dimensional image, a simple acinus looks like a group of vessels surrounded by adjacent sections of lobules, and in a three-dimensional image it looks like a berry (acinus - lat. berry) hanging on a stalk of blood and bile vessels. The acini, the microvascular framework of which consists of the above-mentioned blood and lymphatic vessels, sinusoids and nerves, is the microcirculatory unit of the liver. Liver cells (hepatocytes) have the shape of polyhedra, but they have three main functional surfaces: sinusoidal, facing the sinusoidal channel; tubular - involved in the formation of the wall of the bile capillary (it does not have its own wall); and intercellular - directly adjacent to neighboring liver cells.
Liver dysfunction. Since the liver has many functions, its functional disorders are extremely diverse. Liver disease increases the load on the organ and can damage its structure. The process of restoration of liver tissue, including the regeneration of liver cells (formation of regeneration nodes), has been well studied. It has been discovered, in particular, that with liver cirrhosis, perverted regeneration of liver tissue occurs with an incorrect arrangement of vessels formed around cell nodes; As a result, blood flow in the organ is disrupted, which leads to the progression of the disease. Jaundice, manifested by yellowness of the skin, sclera (the white of the eyes; this is where the color change is usually most noticeable), and other tissues, is a common symptom in liver disease, reflecting the accumulation of bilirubin (the reddish-yellow pigment of bile) in body tissues.
see also
HEPATITIS;
JAUNDICE;
GALL BLADDER ;
CIRRHOSIS.
Animal liver. If the human liver has 2 main lobes, then in other mammals these lobes can be divided into smaller ones, and there are species in which the liver consists of 6 and even 7 lobes. In snakes, the liver is represented by one elongated lobe. The liver of fish is relatively large; in those fish that use liver oil to increase buoyancy, it is of great economic value due to its significant content of fats and vitamins. Many mammals, such as whales and horses, and many birds, such as pigeons, lack a gallbladder; however, it is present in all reptiles, amphibians and most fish, with the exception of a few species of sharks.
LITERATURE
Green N., Stout W., Taylor D. Biology, vol. 2. M., 1996 Human Physiology, ed. Schmidt R., Tevsa G., vol. 3. M., 1996

Collier's Encyclopedia. - Open Society. 2000 .

Synonyms:

See what "LIVER" is in other dictionaries:

Liver- (hepar) (Fig. 151, 158, 159, 165, 166) is the largest gland of the human body, its weight reaches 1.5-2 kg, and its size is 25-30 cm. It is located in the upper abdominal cavity under the dome of the diaphragm, occupying mainly... ... Atlas of Human Anatomy

LIVER- LIVER. Contents: I. Liver ashtomia............... 526 II. Liver histology......................... 542 III. Normal liver physiology...... 548 IV. Pathological physiology of the liver..... 554 V. Pathological anatomy of the liver...... 565 VI.… … Great Medical Encyclopedia

- (hepar), digestive gland of some invertebrates and all vertebrates. Among invertebrates, it is found in horseshoe crabs, arachnids, crustaceans, mollusks, and a number of echinoderms (starfish and lilies). Represents a hollow outgrowth of the average... ... Biological encyclopedic dictionary

liver- - is the most voluminous of the glands of the appendages of the digestive tract: indeed, its weight is 1500 grams. It is located on the highest tier of the right side of the abdominal cavity and extends into the epigastric region. Through the underside of the liver... ... Universal additional practical explanatory dictionary by I. Mostitsky

Liver- person. LIVER, a large gland in the abdominal cavity. Participates in the metabolism of proteins (synthesizes many blood proteins), lipids, carbohydrates (regulates blood sugar levels), in water and salt metabolism, in the synthesis of vitamins A and B12, in detoxification... ... Illustrated Encyclopedic Dictionary

PECHENKIN LIVER PECHENITSYN PECHENIKOV PECHINKIN LIVER PECHENKIN LIVER PECHENITSYN PECHENIN PECHENIKOV PECHINKIN From the name of the organ of the human body liver (E) More correctly from the nickname Liver, possibly a person similar to the liver of an animal... Russian surnames

Large gland in animals and humans; participates in the processes of digestion, metabolism, blood circulation; ensures the constancy of the internal environment of the body. In vertebrates and humans, liver cells synthesize bile. Happens in the liver... Big Encyclopedic Dictionary

LIVER, a large organ located in the upper right part of the abdominal cavity of vertebrates. In adults it weighs up to 2 kg. Divided into four parts. Performs many functions. It is very important for monitoring the internal state of the body (HOMEOSTASIS).... ... Scientific and technical encyclopedic dictionary

Liver, offal, gland Dictionary of Russian synonyms. liver noun, number of synonyms: 6 voex (2) iron... Synonym dictionary

LIVER, liver, pl. no, female (anat.). The largest gland in the body, lying under the abdominal barrier in the right hypochondrium and producing bile. Liver diseases. Ushakov's explanatory dictionary. D.N. Ushakov. 1935 1940 ... Ushakov's Explanatory Dictionary

LIVER, and, female. A large gland in animals and humans that produces bile and is involved in the processes of digestion, blood circulation, and metabolism. | adj. liver, oh, oh. Liver colic. Ozhegov's explanatory dictionary. S.I. Ozhegov, N.Yu. Shvedova... ... Ozhegov's Explanatory Dictionary

Books

• Liver. Cleansing and prevention of diseases, M. M. Burov, It is no coincidence that the liver is considered one of the most important organs of the human body, sometimes it is even called the “second heart”. Indeed, the liver performs not one, not two, but several... Category:

Liver- one of the main organs of the human body. Interaction with the external environment is ensured with the participation of the nervous system, respiratory system, gastrointestinal tract, cardiovascular, endocrine and musculoskeletal systems.

The variety of processes occurring inside the body is carried out due to metabolism, or metabolism. The nervous, endocrine, vascular and digestive systems are of particular importance in ensuring the functioning of the body. In the digestive system, the liver occupies one of the leading positions, performing the functions of a center for chemical processing, the formation (synthesis) of new substances, a center for the neutralization of toxic (harmful) substances and an endocrine organ.

The liver is involved in the processes of synthesis and breakdown of substances, in the interconversion of some substances into others, in the exchange of the main components of the body, namely in the exchange of proteins, fats and carbohydrates (Sugars), and at the same time it is an endocrine-active organ. We especially note that in the liver there occurs the breakdown, synthesis and deposition (deposition) of carbohydrates and fats, the breakdown of proteins to ammonia, the synthesis of heme (the basis for hemoglobin), the synthesis of numerous blood proteins and intensive amino acid metabolism.

Food components prepared in previous stages of processing are absorbed into and delivered primarily to the liver. It is appropriate to note that if toxic substances are supplied with food components, then they first of all enter the liver. The liver is the largest primary chemical processing factory in the human body, in which metabolic processes occur that affect the entire body.

The liver is one of the largest organs, weighs about 1.5 kilograms and is, figuratively speaking, the main laboratory of the body. The functions of the liver are very diverse.

1.Barrier (protective) and neutralizing functions consist in the destruction of toxic products of protein metabolism and harmful substances absorbed in the intestines.

2. Liver- a digestive gland that produces bile, which enters the duodenum through the excretory duct.

3.Participation in all types of metabolism in the body.

Let's consider the role of the liver in the metabolic processes of the body.

1. Amino acid (protein) metabolism. Synthesis of albumins and partially globulins (blood proteins). Among the substances coming from the liver into the blood, proteins can be placed in first place in terms of their importance for the body. The liver is the main site of formation of a number of blood proteins that provide a complex blood coagulation reaction.

The liver synthesizes a number of proteins that take part in the processes of inflammation and transport of substances in the blood. That is why the condition of the liver significantly affects the state of the blood coagulation system, the body’s response to any impact accompanied by an inflammatory reaction.

Through the synthesis of proteins, the liver takes an active part in the immunological reactions of the body, which are the basis for protecting the human body from the action of infectious or other immunologically active factors. Moreover, the process of immunological protection of the mucous membrane of the gastrointestinal tract includes the direct participation of the liver.

In the liver, protein complexes are formed with fats (lipoproteins), carbohydrates (glycoproteins) and carrier complexes (transporters) of certain substances (for example, transferrin - an iron transporter).

In the liver, the breakdown products of proteins entering the intestines with food are used to synthesize new proteins that the body needs. This process is called transamination of amino acids, and the enzymes involved in the exchange are called transaminases;

2. Participation in the breakdown of proteins to their final products, i.e. ammonia and urea. Ammonia is a constant product of protein breakdown, but at the same time it is toxic to the nervous system. systems matter. The liver ensures a constant process of converting ammonia into a low-toxic substance, urea, which is excreted by the kidneys.

When the liver's ability to neutralize ammonia decreases, it accumulates in the blood and nervous system, which is accompanied by mental disorders and ends in a complete shutdown of the nervous system - coma. Thus, we can safely say that there is a pronounced dependence of the state of a person’s brain on the correct and complete functioning of his liver;

3. Lipid (fat) metabolism. The most important processes are the breakdown of fats into triglycerides, the formation of fatty acids, glycerol, cholesterol, bile acids, etc. In this case, short-chain fatty acids are formed exclusively in the liver. Such fatty acids are necessary for the full functioning of skeletal muscles and cardiac muscle as a source of a significant portion of energy.

These same acids are used to produce heat in the body. Of fats, 80–90% of cholesterol is synthesized in the liver. On the one hand, cholesterol is a substance necessary for the body, on the other hand, if there is a disturbance in its transport, cholesterol is deposited in the vessels and causes the development of atherosclerosis. All of the above makes it possible to trace the connection of the liver with the development of diseases of the vascular system;

4. Carbohydrate metabolism. Synthesis and breakdown of glycogen, conversion of galactose and fructose into glucose, oxidation of glucose, etc.;

5. Participation in assimilation, storage and education, especially A, D, E and groups B;

6. Participation in the metabolism of iron, copper, cobalt and other trace elements necessary for hematopoiesis;

7. Participation of the liver in the removal of toxic substances. Toxic substances (especially those from outside) are distributed, and they are distributed unevenly throughout the body. An important stage of their neutralization is the stage of changing their properties (transformation). Transformation leads to the formation of compounds with less or greater toxic ability compared to the toxic substance entering the body.

Elimination

The next important stage in the neutralization of toxic substances in the body is their removal from the body (elimination). Elimination- this is a complex of processes aimed at removing a toxic substance from the body through the available natural routes of elimination. Toxic substances can be removed either in transformed or unchanged form.

1. Bilirubin exchange. Bilirubin is often formed from breakdown products of hemoglobin released from aging red blood cells. Every day in the human body, 1–1.5% of red blood cells are destroyed, in addition, about 20% of bilirubin is formed in liver cells;

Impaired bilirubin metabolism leads to an increase in its content in the blood - hyperbilirubinemia, which is manifested by jaundice;

2. Participation in blood clotting processes. Liver cells produce substances necessary for blood clotting (prothrombin, fibrinogen), as well as a number of substances that slow down this process (heparin, antiplasmin).

The liver is located under the diaphragm in the upper part of the abdominal cavity on the right and is normally not palpable in adults, as it is covered by the ribs. But in young children it can protrude from under the ribs. The liver has two lobes: the right (larger) and the left (smaller) and is covered with a capsule.

The upper surface of the liver is convex, and the lower is slightly concave. On the lower surface, in the center, there is a kind of gate of the liver, through which vessels, nerves and bile ducts pass. The recess under the right lobe houses the gallbladder, which stores bile produced by liver cells called hepatocytes. The liver produces from 500 to 1200 milliliters of bile per day. Bile is produced continuously, and its entry into the intestines is associated with food intake.

Bile

Bile is a yellow liquid that consists of water, bile pigments and acids, cholesterol, and mineral salts. It is released into the duodenum through the common bile duct.

The release of bilirubin by the liver through bile ensures the removal from the blood of bilirubin, which is toxic to the body and is formed as a result of the constant natural breakdown of hemoglobin - a protein in red blood cells). In case of violations. At any of the stages of bilirubin secretion (in the liver itself or the secretion of bile through the hepatic ducts), bilirubin accumulates in the blood and tissues, which manifests itself in the form of a yellow color of the skin and sclera, i.e. in the development of jaundice.

Bile acids (cholates)

Bile acids (cholates), together with other substances, ensure a steady-state level of cholesterol metabolism and its excretion with bile, while cholesterol in bile is dissolved, or rather, enclosed in tiny particles that ensure cholesterol excretion. A disturbance in the metabolism of bile acids and other components that ensure the removal of cholesterol is accompanied by the loss of cholesterol crystals in the bile and the formation of gallstones.

Not only the liver, but also the liver is involved in maintaining a stable exchange of bile acids. In the right sections of the large intestine, cholates are reabsorbed into the blood, which ensures the circulation of bile acids in the human body. The main reservoir of bile is the gallbladder.

Gallbladder

When its function is impaired, there are also disturbances in the secretion of bile and bile acids, which is another factor contributing to the formation of gallstones. At the same time, bile substances are necessary for the complete digestion of fats and fat-soluble vitamins.

With a long-term lack of bile acids and some other bile substances, a deficiency of vitamins (hypovitaminosis) occurs. Excessive accumulation of bile acids in the blood due to disturbances in their excretion with bile is accompanied by painful itching of the skin and changes in the pulse rate.

A feature of the liver is that it receives venous blood from the abdominal organs (stomach, pancreas, intestines, etc.), which, entering through the portal vein, is cleared of harmful substances by liver cells and enters the inferior vena cava, going to heart. All other organs of the human body receive only arterial blood, and give away venous blood.

The article uses materials from open sources: