Physiological functions of the liver. Examination of the liver and gallbladder

The liver is the largest organ. The weight of an adult is 2.5% of the total body weight. For 1 minute, the liver receives 1350 ml of blood and this is 27% of the minute volume. The liver receives both arterial and venous blood.

• Arterial blood flow - 400 ml per minute. arterial blood enters through the hepatic artery
• Venous blood flow - 1500 ml per minute. Venous blood flows through the portal vein from the stomach small intestine, pancreas, spleen and part of the colon. It is through the portal vein that nutrients and vitamins from the digestive tract enter. The liver captures these substances and then distributes them to other organs.

An important role of the liver belongs to carbon metabolism. It maintains blood sugar levels by being a depot of glycogen. Regulates the content of lipids in the blood and especially the low density lipoproteins that it secretes. An important role in the protein department. All plasma proteins are made in the liver.

The liver performs a neutralizing function in relation to toxic substances and drugs.

It performs a secretory function - the formation of bile by the liver and the excretion of bile pigments, cholesterol, and medicinal substances.

Carries out endocrine function.

The functional unit is hepatic lobule, which is built from hepatic beams formed by hepatocytes. In the center of the hepatic lobule is the central vein, into which blood flows from the sinusoids. Collects blood from capillaries of a portal vein and capillaries of a hepatic artery. The central veins, merging with each other, gradually form the venous system of outflow of blood from the liver. And the blood from the liver flows through the hepatic vein, which flows into the inferior vena cava. In the hepatic beams, upon contact of neighboring hepatocytes, bile ducts. They are separated from the intercellular fluid by tight junctions, which prevents the mixing of bile and extracellular fluid. The bile formed by hepatocytes enters the tubules, which gradually merge to form the system of intrahepatic bile ducts. It eventually enters the gallbladder or through the common duct into the duodenum. The common bile duct connects to Persungov pancreatic duct and together with it opens at the top Vaterova pacifier. There is a sphincter at the exit of the common bile duct. Oddy, which regulate the flow of bile into the 12th duodenum.

Sinusoids are formed by endothelial cells that lie on the basement membrane, around - perisinusoidal space - space Disse. This space separates sinusoids and hepatocytes. Hepatocyte membranes form numerous folds, villi, and they protrude into the peresinusoidal space. These villi increase the area of ​​contact with the peresophageal fluid. Weak expression of the basement membrane, sinusoid endothelial cells contain large pores. The structure resembles a sieve. Pores pass substances from 100 to 500 nm in diameter.

The amount of proteins in the peresinusoidal space will be greater than in plasma. There are macrocytes of the macrophage system. These cells, through endocytosis, ensure the removal of bacteria, damaged erythrocytes, and immune complexes. Some sinusoid cells in the cytoplasm may contain droplets of fat - cells Ito. They contain vitamin A. These cells are associated with collagen fibers, their properties are close to fibroblasts. They develop with cirrhosis of the liver.

Production of bile by hepatocytes - the liver produces 600-120 ml of bile per day. Bile performs 2 important functions -

ü It is necessary for the digestion and absorption of fats. Due to the presence of bile acids - bile emulsifies fat and turns it into small droplets. The process will promote a better action of lipases, for better breakdown into fats and bile acids. Bile is necessary for the transport and absorption of cleavage products.

ü Excretory function. It removes bilirubin and cholesterol. The secretion of bile occurs in 2 stages. Primary bile is formed in hepatocytes, it contains bile salts, bile pigments, cholesterol, phospholipids and proteins, electrolytes, which are identical in content to plasma electrolytes, except bicarbonate anion, which is more in bile. This is what gives the alkaline reaction. This bile comes from hepatocytes to the bile ducts. At the next stage, bile moves along the interlobular, lobar duct, then to the hepatic and common bile duct. As the bile progresses, epithelial cells ducts, secrete sodium and bicarbonate anions. This is essentially a secondary secretion. The volume of bile in the ducts can increase by 100%. Secretin increases bicarbonate secretion to neutralize hydrochloric acid from the stomach.

Outside of digestion, bile accumulates in gallbladder where it enters through the cystic duct.

Secretion of bile acids

Liver cells secrete 0.6 acids and their salts. Bile acids are formed in the liver from cholesterol, which enters the body either with food, or can be synthesized by hepatocytes during salt metabolism. When carboxyl and hydroxyl groups are added to the steroid nucleus, primary bile acids-

• Holeva
• Chenodeoxycholic

They combine with glycine, but to a lesser extent with taurine. This leads to the formation of glycocholic or taurocholic acids. When interacting with cations, sodium and potassium salts are formed. Primary bile acids enter the intestine and in the intestine, intestinal bacteria convert them into secondary bile acids

• Deoxycholic
• Litocholic

Bile salts are more ion-forming than the acids themselves. Bile salts are polar compounds, which reduces their penetration through the cell membrane. Therefore, absorption will decrease. By combining with phospholipids and monoglycerides, bile acids contribute to the emulsion of fats, increase the activity of lipase and convert the products of fat hydrolysis into soluble compounds. Since bile salts contain hydrophilic and hydrophobic groups, they take part in the formation with cholesterols, phospholipids and monoglycerides to form cylindrical discs, which will be water-soluble micelles. It is in such complexes that these products pass through the brush border of enterocytes. Up to 95% of bile salts and acids are reabsorbed in the intestine. 5% will be excreted in the feces.

Absorbed bile acids and their salts combine in the blood with high-density lipoproteins. Through the portal vein, they again enter the liver, where 80% are again captured from the blood by hepatocytes. Thanks to this mechanism, a reserve of bile acids and their salts is created in the body, which ranges from 2 to 4 g. There, the enterohepatic cycle of bile acids takes place, which promotes the absorption of lipids in the intestine. For people who do not eat much, this turnover occurs 3-5 times a day, and for people who eat a lot of food, such a cycle can increase up to 14-16 times a day.

Inflammatory conditions of the small intestine mucosa reduce the absorption of bile salts, which impairs the absorption of fats.

Cholesterol - 1.6-8, mmol/l

Phospholipids - 0.3-11 mmol / l

Cholesterol is considered as a by-product. Cholesterol is practically insoluble in clean water, but when combined with bile salts in micelles, it turns into a water-soluble compound. For some pathological conditions cholesterol is precipitated, calcium is deposited in it, and this causes the formation of gallstones. Gallstone disease is a fairly common disease.

• The formation of bile salts is facilitated by excessive absorption of water in the gallbladder.
• Excessive absorption of bile acids from bile.
• Increase in cholesterol in bile.
• Inflammatory processes in the gallbladder mucosa

The capacity of the gallbladder is 30-60 ml. In 12 hours, the gallbladder can accumulate up to 450 ml of bile, and this happens due to the process of concentration, while water, sodium and chloride ions, other electrolytes are absorbed, and usually the bile is concentrated in the bladder 5 times, but the maximum concentration is 12-20 times. Approximately half of the soluble compounds in gallbladder bile are bile salts, and high concentrations of bilirubin, cholesterol and leucitin are also achieved here, but the electrolyte composition is identical to plasma. The emptying of the gallbladder occurs during the digestion of food and especially fat.

The process of emptying the gallbladder is associated with the hormone cholecystokinin. It relaxes the sphincter Oddy and helps to relax the muscles of the bladder itself. Peristaltic contractions of the bladder then go to the cystic duct, the common bile duct, which leads to the removal of bile from the bladder into the duodenum. The excretory function of the liver is associated with the excretion of bile pigments.

Bilirubin.

Monocyte - macrophage system in the spleen bone marrow, liver. 8 g of hemoglobin breaks down per day. When hemoglobin breaks down, 2-valent iron is split off from it, which combines with protein and is deposited in reserve. From 8 g Hemoglobin => biliverdin => bilirubin (300 mg per day) The norm of bilirubin in the blood serum is 3-20 μmol / l. Above - jaundice, staining of the sclera and mucous membranes of the oral cavity.

Bilirubin binds to a transport protein blood albumin. it indirect bilirubin. Bilirubin from blood plasma is captured by hepatocytes and in hepatocytes bilirubin combines with glucuronic acid. Bilirubin glucuronil is formed. This form enters the bile ducts. And already in the bile this form gives direct bilirubin. It enters the intestine through the bile duct system. In the intestine, intestinal bacteria split off glucuronic acid and convert bilirubin into urobilinogen. Some of it undergoes oxidation in the intestines and enters stool and is already called stercobilin. The other part will be absorbed and enter the bloodstream. From the blood it is captured by hepatocytes and again enters the bile, but some will be filtered in the kidneys. Urobilinogen enters the urine.

Prehepatic (hemolytic) jaundice caused by a massive breakdown of red blood cells as a result of the Rh conflict, the entry into the blood of substances that cause the destruction of red blood cell membranes and some other diseases. With this form of jaundice, the content of indirect bilirubin in the blood is increased, the content of stercobilin in the urine is increased, bilirubin is absent, and the content of stercobilin in the feces is increased.

Hepatic (parenchymal) jaundice caused by damage to liver cells during infections and intoxications. With this form of jaundice, the content of indirect and direct bilirubin is increased in the blood, the content of urobilin is increased in the urine, bilirubin is present, and the content of stercobilin in the feces is reduced.

Subhepatic (obstructive) jaundice caused by a violation of the outflow of bile, for example, when the bile duct is blocked by a stone. With this form of jaundice, the content of direct bilirubin (sometimes indirect) is increased in the blood, there is no stercobilin in the urine, bilirubin is present, and the content of stercobilin in the feces is reduced.

Regulation of bile formation

Regulation is based on feedback mechanisms based on the level of concentration of bile salts. The content in the blood determines the activity of hepatocytes in the production of bile. Outside the period of digestion, the concentration of bile acids decreases and this is a signal for increased formation of hepatocytes. The excretion into the duct will decrease. After eating, there is an increase in the content of bile acids in the blood, which, on the one hand, inhibits the formation in hepatocytes, but at the same time enhances the release of bile acids in the tubules.

Cholecystokinin is produced under the action of fatty and amino acids and causes bladder contraction and sphincter relaxation - i.e. stimulation of bladder emptying. Secretin, which is released by the action of hydrochloric acid on C cells, enhances tubular secretion and increases the content of bicarbonate.

Gastrin affects hepatocytes and enhances secretory processes. Indirectly, gastrin increases the content of hydrochloric acid, which then increases the content of secretin.

Steroid hormones- Estrogens and some androgens inhibit the formation of bile. The mucosa of the small intestine produces motilin- It promotes the contraction of the gallbladder and the excretion of bile.

Influence nervous system - through the vagus nerve - enhances bile formation and the vagus nerve contributes to the contraction of the gallbladder. Sympathetic influences are inhibitory in nature and cause relaxation of the gallbladder.

Intestinal digestion.

In the small intestine - the final digestion and absorption of the products of digestion. The small intestine receives 9 liters daily. Liquids. We absorb 2 liters of water with food, and 7 liters come from the secretory function of the gastrointestinal tract, and of this amount, only 1-2 liters will enter the large intestine. The length of the small intestine to the ileocecal sphincter is 2.85 m. The corpse is 7 m.

The mucous membrane of the small intestine forms folds that increase the surface by 3 times. 20-40 villi per 1 sq. mm. This increases the area of ​​the mucosa by 8-10 times, and each villus is covered with epitheliocytes, endotheliocytes, containing microvilli. These are cylindrical cells, on the surface of which there are microvilli. From 1.5 to 3000 on 1 cell.

The length of the villi is 0.5-1 mm. The presence of microvilli increases the area of ​​the mucosa and it reaches 500 sq.m. Each villus contains a blindly ending capillary, a feeding arteriole approaches the villus, which breaks up into capillaries that pass at the top into venous capillaries and produce blood outflow through the venules. The blood flow is venous and arterial in opposite directions. Rotary-countercurrent systems. Wherein a large number of oxygen passes from arterial to venous blood without reaching the top of the villus. It is very easy to create conditions under which the tops of the villi will receive less oxygen. This can lead to the death of these areas.

glandular apparatus - Bruner's glands in the duodenum. Liberty glands in the jejunum and ileum. There are goblet cells that produce mucus. The glands of the 12th duodenum resemble the glands of the pyloric part of the stomach and they secrete a mucous secret for mechanical and chemical irritation.

Them regulation takes place under the influence vagus nerves and hormones especially secretin. The mucous secretion protects the duodenum from the action of hydrochloric acid. The sympathetic system reduces the production of mucus. When we experience striving, we have an easy opportunity to get a duodenal ulcer. By reducing the protective properties.

The secret of the small intestine formed by enterocytes, which begin their maturation in the crypts. As the enterocyte matures, they begin to move towards the top of the villi. It is in the crypts that the cells actively transport chlorine and bicarbonate anions. These anions create a negative charge that attracts sodium. Osmotic pressure is created, which attracts water. Some pathogenic microbes - dysentery bacillus, cholera vibrio increase the transport of chloride ions. This leads to a large release of fluid in the intestine up to 15 liters per day. Normally 1.8-2 liters per day. Intestinal juice is a colorless liquid, cloudy due to the mucus of epithelial cells, has an alkaline reaction ph7.5-8. Intestinal juice enzymes accumulate inside enterocytes and are released along with them when they are rejected.

intestinal juice contains a complex of peptidases, which is called eryxin, which ensures the final breakdown of protein products to amino acids.

4 aminolytic enzymes- sucrase, maltase, isomaltase and lactase. These enzymes break down carbohydrates into monosaccharides. There is intestinal lipase, phospholipase, alkaline phosphatase and enterokinase.

The liver is involved in the process of digestion, circulation and metabolism. The liver performs a specific protective and excretory function, thanks to which it maintains the constancy of the internal environment of the body.

Anatomy of the liver and gallbladder

Location of the liver in the human body

The liver is located directly below the diaphragm. If a abdominal cavity conditionally divided into four squares, then the bulk of the liver will be in the upper right part of the abdomen, and only a small part of its left lobe will pass beyond median line to the next square. The upper border of the liver is at the level of the nipples, its lower border protrudes 1-2 cm from under the costal arch. The upper edge of the liver is convex and repeats the concavity of the diaphragm. The right edge of the liver is smooth, blunt, descends vertically down by 13 cm. The left edge of the liver is sharp, its height does not exceed 6 cm. The lower edge of the liver has concavities from contact with nearby abdominal organs.

Liver - ventral view (inner surface)

The liver is formed by a large right and 6 times smaller left lobes, which are separated by a sheet of peritoneum. The mass of the liver is 1.5-2 kg - this is the largest glandular organ in the human body.

On the inner hepatic surface, approximately in its middle part, there are gates of the liver, through which the hepatic artery enters and the portal vein exits, as well as the common hepatic duct, which removes bile from the liver.

The basic structural unit of the liver is the hepatic lobule. It is formed due to the separation of the liver tissue by a connective tissue capsule penetrating deep into the organ. The hepatic lobule is made up of liver cells called hepatocytes, which are interconnected in tiers, surrounding the bile ducts, venules and arterioles.

The structure of the gallbladder

The gallbladder is located under the gate of the liver. It extends to the outer edge of the liver and lies on the duodenum. The gallbladder is pear-shaped, its length is 12-18 cm. Anatomically, the gallbladder is divided into a wider part - the bottom, the middle part - the body and a tapering part - the neck. The neck of the bladder passes into the common cystic duct.

bile ducts

The bile ducts, leaving the hepatic lobule, form the bile ducts, which merge into the right and left, then into the common hepatic duct. Further, the hepatic duct is divided into two parts, one of which passes into the common bile duct and opens into the duodenum, and the other part passes into the cystic duct and ends with the gallbladder.

Physiology of the liver and gallbladder

Liver functions

The liver is involved in the process of digestion of food, releasing bile. Bile enhances intestinal motility, promotes the breakdown of fats, increases the activity of intestinal and pancreatic enzymes, and neutralizes the acidic environment of gastric contents. Bile ensures the absorption of amino acids, cholesterol, fat-soluble vitamins and calcium salts, inhibits the reproduction of bacteria.

The liver takes part in all types of metabolism. Participating in protein metabolism, the liver destroys and rebuilds blood proteins, with the help of enzymes it converts amino acids into a reserve source of energy and material for the synthesis of its own proteins in the body, from which blood plasma proteins (albumin, globulin, fibrinogen) are formed.

In carbohydrate metabolism, the function of the liver is the formation and accumulation of glycogen, the reserve energy substrate of the body. Glycogen is created as a result of the processing of glucose and other monosaccharides, lactic acid, breakdown products of fats and proteins.

The liver takes part in fat metabolism, splitting fats into fatty acids and ketone bodies with the help of bile. The liver also produces cholesterol and stores fat in the body.

The liver regulates the balance of proteins, fats and carbohydrates. With a lack of intake of carbohydrates from food, for example, the liver begins to synthesize them from protein, and with an excess of carbohydrates and proteins in food, it processes their excess into fats.

The liver contributes to the synthesis of hormones of the adrenal glands, pancreas and thyroid gland. It is involved in the synthesis of anticoagulants (substances that prevent blood clotting), the metabolism of trace elements by regulating the absorption and deposition of cobalt, iron, copper, zinc and manganese.

The liver performs a protective function, being a barrier to toxic substances. One of the main tasks of the liver is blood purification, it is here that the neutralization of all poisons that enter the body from the outside takes place.

The liver controls the balance of homeostasis (the constancy of the internal environment of the body) is ensured by the biotransformation of foreign compounds into water-soluble non-toxic substances that are excreted from the body by the intestines, kidneys and through the skin.

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bile production

Bile is produced in the lobules of the liver. The bile then travels through the hepatic and bile ducts to the gallbladder, where it is stored. The gallbladder can collect up to 60 ml of bile.

To participate in digestion, bile passes through the ducts from the bladder into the duodenum. The bladder sphincter (pulp), located in the neck of the gallbladder, and the sphincter of Oddi, located at the entrance to the duodenum, regulate the release of bile. The main signal for the release of bile is the intake of food and its entry into the stomach. When there is not enough gallbladder bile to digest food (for example, overeating or eating too much fatty foods), bile from the hepatic duct enters directly into the duodenum, bypassing the gallbladder.

The composition of bile

Distinguish between hepatic and cystic bile. Hepatic bile produces 800-1000 ml per day. It is liquid in consistency and light brown in color. The bile that enters the gallbladder is concentrated due to the reabsorption of the liquid part into the blood, therefore it becomes thick and dark brown in color.

Bile contains water, bile acids (taurocholic and glycocholic sodium salts), bile pigments (bilirubin, biliverdin), fats. It also contains lecithin, cholesterol, mucus, salts of potassium, sodium, magnesium, calcium and the enzyme - phosphatase. From bile pigments, fecal pigments (stercobilin) ​​and urine pigments (urobilin) ​​are formed.

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The physiological significance of the liver as a gland involved in interstitial metabolism is determined by the fact that substances absorbed from the intestine into the blood pass through the liver and undergo chemical changes in it. In the liver, glucose is formed from a number of substances (fructose, galactose, lactose, glycerol, amino acids), from which glycogen is synthesized and deposited by liver cells (see Carbohydrate metabolism). In the liver, acetone bodies are formed from lipids (mainly with a lack of glycogen in the liver and diabetes), most of the cholesterol, bile acids, and carotene also accumulates. Here, deamination and transamination of amino acids take place (see Nitrogen metabolism), blood proteins (albumins, globulins, many blood coagulation factors), urea, uric acid, choline, and creatinium are synthesized. A significant part of hemoglobin is destroyed in the liver; the resulting bilirubin (see) is excreted in the bile into the intestine, iron (ferritin) is deposited.

The liver is involved in maintaining the dynamic balance of many plasma substances (sugar, cholesterol, blood proteins, axerophthol, iron, water). About 1.5 liters of blood flows through the liver per minute. and 1/7 of the entire energy of the body is released in it. The temperature of the blood flowing from it during digestion increases by 1-2 °.

To study the functions of the liver, they resort to removing it, turning off the portal blood flow, applying angiostomy tubes to the vessels, and perfusion of the isolated liver. After removal of the liver after 3-8 hours. comes hypoglycemia (see), leading to death.

To study the participation of hepatic cells and blood vessels in the transformation of substances that have entered the blood in one way or another, various options for ligation of vessels are used, including direct and reverse fistulas according to Eck-Pavlov, ligation of the hepatic artery and all afferent vessels of the liver (devascularization). The operation of the Eck-Pavlov fistula consists in the imposition of an anastomosis between the portal and inferior vena cava.

After such an operation and ligation of the portal vein near the liver, all blood from the intestine begins to enter the body, bypassing the liver. At the same time, the viability of the liver is preserved, since its blood supply is preserved: blood enters through the hepatic artery, and flows out through arteriovenous and arterio-sinusoid anastomoses (Fig. 8).

Rice. 8. Scheme of the relationship of intrahepatic vessels:
1 - arteries;
2 - bile duct;
3 - lymphatic duct;
4 - branch of the portal vein;
5 - central foam;
6 - liver cells;
7 - bile duct;
8 - Disse space;
9 - sinusoid;
10 - Kupffer cells;
11 - input sphincter;
12 - output sphincter;
13 - arteriovenous anastomosis;
14 - confluence of the arteriole into the sinusoid.

In the blood of the portal vein during digestion, the amount of ammonia, glucose, amino acids, and water increases sharply. In the presence of Eck's fistula, blood of this composition enters the blood circulation, as a result of which, in the blood and brain tissues, with a high content of protein in food, the amount of ammonia increases sharply, poisoning develops, and the animal develops a coma. In the liver, ammonia is converted into less biologically active substance- urea, and substances such as histamine, foxglove, novocaine, iron, atropine, ergotoxin, morphine and others, to some extent lose their toxicity. When the hepatic artery is ligated, collaterals develop after some time, which partially ensures the delivery of arterial blood.

The liver continues to take part in metabolic processes even after a staged devascularization. The level of sugar and cholesterol is maintained in the blood, serum albumin is somewhat reduced.

The liver inactivates many hormones: adrenaline, estrogens, gonadotropic hormones, hormones of the adrenal cortex, secretin, gastrin, etc. Along with neutralization, some substances, having passed through the liver, on the contrary, become more toxic, for example, colchicine turns into a more toxic substance - oxycolchicine; sulfamides after acetylation in the liver become less soluble, as a result of which they are easily precipitated in the urinary tract.

In the implementation of the protective function against foreign agents, reticuloendothelial (Kupffer, "coastal") cells play a significant role. They have the properties of fixed phagocytes that absorb bacteria from the blood, as well as some irritating substances. Phagocytic activity is favored by slow blood flow in the portal sinusoids. However, these cells can also play a negative role, absorbing and retaining for a long time many substances, such as gum arabic, polyvinylpyrrolidone, which are part of plasma substitutes. As a result of the accumulation of a large amount of irritating substances, reactive multiplication of Kupffer cells occurs, which leads to a cirrhotic process.

The liver has a bile-forming function, which is largely excretory. Bile (see) in its composition contains many substances circulating in the blood (dyes, antibiotics, bilirubin, hormones), as well as substances formed in the gland itself, for example, bile acids, which form paired compounds with glycocol and taurine (glycocholic and taurocholic acids), which makes them more soluble. Possessing high surface activity, they sharply reduce the surface tension of bile, and this helps to keep a number of substances in it in a dissolved state (cholesterol, lecithin, calcium salts). In the intestines, bile acids help emulsify and absorb fat (see Fat Metabolism); 85-95% of bile acids are absorbed from the intestines into the blood, from where they are captured by the liver cells and again excreted into the bile. Thus, enterohepatic circulation of bile acids is established.

Kupffer and polygonal cells take part in the process of bile formation. There is a direct connection between the blood vessels and the bile ducts: the sinusoids communicate with the help of the intercellular gaps with the spaces of Disse, and the latter through the pores between the liver cells are connected to the bile ducts. Blood substances can enter the bile ducts in two ways: through the intercellular spaces and through the Kupffer cells.

Polygonal liver cells also participate in the process of bile formation, as evidenced by inclusions in the protoplasm containing proteins, bile pigments; apparently, the Golgi apparatus plays a significant role in their formation. It is possible that these same cells secrete water.

The leading role in the mechanism of bile formation is played, in all likelihood, by the active transport of substances. This is evidenced by a number of facts: bile formation can occur at low blood pressure, as well as in the case when the pressure of bile in the tubules is greater than the pressure of blood in the capillaries; the excretion of certain substances is selective (for example, sugar enters the blood, and bile acids enter the bile); bile formation is sharply reduced against the background of oppression of tissue respiration of the liver.

Some researchers believe that primary process bile formation occurs by the secretion of water and salts, dyes, pigments dissolved in it. Later, when it moves through the tubules, an equilibrium of substances that can penetrate the membranes is established, and all other substances that do not penetrate the membranes are retained in the bile. The latter can enter the blood only if the outflow of bile is disturbed.

The process of bile formation is affected by the influence of humoral stimuli: secretin, cholic acid salts, bile acids, acetylcholine, protein digestion products (peptones), hormones (adrenaline, thyroxine, sex hormones, ACTH, cortine). Nervous influences on the process of bile formation are not always expressed in the same way. The effect of irritation of the vagus nerves after their transection is different. The secretory effect is observed when they are irritated only on the 4-5th day after transection, which, according to IP Pavlov's ideas, is associated with a more rapid degeneration of inhibitory fibers. Atropine under these conditions reduces the secretory reaction. Increased bile formation was also observed after stimulation of the central end vagus nerve subject to the integrity of the other. Irritation of the sympathetic nerve, apparently, inhibits the secretion of bile.

The difficulty in elucidating the mechanism of action of nerves on the process of bile formation is that it is still unknown how this effect is carried out: either nerves act directly on secretory cells, or membrane permeability changes, or some vasomotor changes occur.

The process of bile formation is usually studied by collecting bile directly from the gallbladder. The amount of bile in the experimental conditions varies significantly. At the same time, it was found that chronic loss of bile leads to a decrease in bile formation, and after feeding, bile secretion increases, especially in cases where, in addition to food, bile is introduced into the intestine. It is also shown that bile from the duct enters the intestine continuously; its quantity, both in the presence and in the absence of a bubble, remains constant (A. V. Gubar).

An equally important function of the liver is the deposition of blood. The vessels of the liver can hold 20% of all blood. Retention of blood in the liver does not mean venous congestion. The process of deposition of blood in the liver is greatly facilitated by the sphincters of the veins and sinusoids. The input sphincter sinusoid regulates the inflow, and the output - the outflow of blood. Significant deposition of blood is observed during anesthesia. The liver, as one of the depositing organs in the portal vein system, is a special "gateway" between the portal and general circulation. The activity of other depositing organs (spleen, intestines) depends on its functional state. All blood that comes out of the spleen, intestines, necessarily passes through the liver.

The liver removes excess water from the blood, which goes to the formation of lymph and bile. From 1/2 to 1/3 of all lymph with a high protein content (6%) is formed in the liver, as well as an average of 600-700 ml of bile per day, which is poured into the digestive tract. Blood, flowing through the sinusoids, loses a large amount of water, especially during digestion. During the period when blood flow to the portal vein increases, the pressure in it rises and becomes much higher than in the hepatic vein. In animals with porto-caval anastomosis according to Eck, water introduced into the body in the form of isotonic saline solution, is rendered much more slowly.

The liver is polyfuctional (?) Its functions are:

1. Participates in protein metabolism. This function is expressed in the splitting and (?) in the liver, deamination of amino acids occurs with the help of enzymes. The liver plays a crucial role in the synthesis of plasma proteins (albumins, globulins, fibrinogen). The liver contains a reserve protein, which is used when there is a limited intake of protein from food.

2. The liver is involved in the metabolism of carbohydrates, glucose and other monosaccharides that enter the liver are converted into glycogen, which turns out to be a reserve of sugar. Lactic acid and the breakdown products of proteins and fats are converted into glycogen. When glucose is consumed, liver glycogen is converted into (?), which enters the bloodstream.

3. The liver is involved in fat metabolism by acting (?) through the synthesis of lipoids (cholesterol) and the breakdown of fats with the formation of ketone bodies. Oxidation (?) of the most important functions of the liver occurs in the liver - the formation of fat from sugar. At (?)

protein glycogenesis. The liver is a depot of fat.

4. The liver is involved in the metabolism of vitamins. All fat soluble vitamins. .. intestines only in the presence of bile acids secreted by the liver. Some vitamins are stored in the liver. Part of the vitamins is activated in the liver, undergoing phosphorylation.

5. The liver takes part in the exchange of steroid hormones and other biologically active substances. Cholesterol is produced in the liver. Steroid hormones. It is broken down in the liver and...

6. The liver plays an important role in maintaining homeostasis due to its participation in hormone metabolism.

7. The liver is involved in the exchange of trace elements. It influences (?) bile in the intestines and deposits it. The liver is a depot of copper and zinc. It takes part in the exchange of manganese, cobalt, etc.

8. The protective (barrier) function of the liver is manifested in the following. Firstly, microbes in the liver undergo phagocytosis, and secondly ... ... substances of an endogenous and exogenous nature. The whole ….. intestinal tract…. through the portal vein enters the liver.

… neutralization of substances such as ammonia (turns into ……

compounds (indole, skatole, phenol).

9. Substances involved in ... .. components of the anticoagulant system are synthesized in the liver.

ten. …. Liver substances are part of the bile. to such substances.

11. The liver is a blood depot.

12. The liver is one of the most important organs of heat production.

13. Participation of the liver in the processes of digestion is provided mainly by bile, which is synthesized by liver cells, bile…….. functions.

Participates in the processes of digestion:

* emulsifies fats, thereby increasing the surface for their hydrolysis….

* dissolves the products of fat hydrolysis, which contributes to their absorption.

* increases the activity of enzymes (pancreatic and intestinal), especially ...

* Neutralizes acidic stomach contents.

* inactivates pepsins.

* promotes the absorption of fat-soluble ……… and calcium salts.

* participates in parietal digestion, facilitating f(?) enzymes. And enhances the motor and secretory function of the small intestine.

Stimulates bile formation and bile excretion.

Participates in the hepato-intestinal circulation of bile components - bile components enter the intestine, ...... bile composition.

Bile has a bacteriostatic effect……. microbes,

bile formation e. A person develops in a day ... ..

….. formation of bile – bile secretion – goes on continuously, and bile secretion…….

... eating. On an empty stomach, almost no bile enters the intestines, ......

..... which are somewhat different in composition. During the passage of bile……. There is a concentration of bile, it is added ...... bile acids and absorption of bicarbonates.

The formation of bile is carried out by the following mechanisms:

* active secretion of bile components (bile acids) by hepatocytes

* active and passive transport of certain substances from the blood (water, glucose, electrolytes, vitamins, hormones, etc.)

* reabsorption of water and certain substances from the bile capillaries, ducts and gallbladder.

The process of bile formation is carried out continuously (?) ... receptors of the gastrointestinal tract and internal organs, as well as conditioned reflex.

Humoral stimuli of bile formation are: bile itself, secretin, gastrin, cholecystokinin-pancreozymin.

Proteins increase bile formation and excretion with it ....

Bile secretion. The movement of bile in the biliary apparatus is due to ... .... its parts and in duodenum, as well as the state of ... ..

Dedicated and bile again begins to accumulate in the gallbladder.

Reflex effects on the bile duct………

Including from the receptors of the oral cavity, stomach and duodenum

.... the hormone cholecystokinin-pancreozymin, which ... ..

Details

The liver is the largest human gland- its mass is about 1.5 kg. The metabolic functions of the liver are extremely important for maintaining the viability of the body. Metabolism of proteins, fats, carbohydrates, hormones, vitamins, neutralization of many endogenous and exogenous substances. excretory function - bile secretion necessary for the absorption of fats and stimulation of intestinal motility. Approximately released per day 600 ml bile.

Liver is the body that plays the role blood depot. It can deposit up to 20% of the total mass of blood. In embryogenesis, the liver performs a hematopoietic function.
The structure of the liver. In the liver, epithelial parenchyma and connective tissue stroma are distinguished.

The hepatic lobule is the structural and functional unit of the liver.

Structural and functional units of the liver are hepatic lobules about 500 thousand in number. The liver lobules are shaped like hexagonal pyramids with a diameter of up to 1.5 mm and a slightly greater height, in the center of which is the central vein. Due to the peculiarities of hemomicrocirculation, hepatocytes in different parts of the lobule are in different conditions of oxygen supply, which affects their structure.

That's why in the lobule are central, peripheral and between them intermediate zone. The peculiarity of the blood supply of the hepatic lobule is that the intralobular artery and vein extending from the perilobular artery and vein merge and then the mixed blood moves through the hemocapillaries in the radial direction towards the central vein. Intralobular hemocapillaries run between the hepatic beams (trabeculae). They have a diameter of up to 30 microns and belong to the sinusoidal type of capillaries.

Thus, mixed blood (venous - from the portal vein system and arterial - from the hepatic artery) flows through the intralobular capillaries from the periphery to the center of the lobule. Therefore, hepatocytes of the peripheral zone of the lobule are more favorable conditions supply of oxygen than those in the center of the lobule.
By interlobular connective tissue, normally poorly developed, pass circulatory and lymphatic vessels and excretory bile ducts. As a rule, the interlobular artery, interlobular vein and interlobular excretory duct go together, forming the so-called hepatic triads. Collecting veins and lymphatic vessels pass at some distance from the triads.

Hepatocytes. The epithelium of the liver.

Epithelium the liver is made up of hepatocytes, constituting 60% of all liver cells. Associated with the activity of hepatocytes performing most of the functions characteristic of the liver. At the same time, there is no strict specialization between hepatic cells, and therefore the same hepatocytes produce both exocrine secretion (bile), and by type endocrine secretion numerous substances entering the bloodstream.

Hepatocytes are separated by narrow slits (space of Disse)- filled with blood sinusoids, in the walls of which there are pores. From two neighboring hepatocytes, bile is collected into bile capillaries>tubules of Genirg>interlobular tubules>hepatic duct. Departs from him cystic duct to gallbladder. Hepatic + cystic duct = common bile duct into the duodenum.

Composition and functions of bile.

Excreted with bile metabolic products: bilirubin, drugs, toxins, cholesterol. Bile acids are needed for emulsification and absorption of fats.. Bile is produced by two mechanisms: FA dependent and independent.

Hepatic bile: isotonic to blood plasma (HCO3, Cl, Na). Bilirubin ( yellow). Bile acids (can form micelles, detergents), cholesterol, phospholipids.
AT bile ducts bile is modified.

Cystic bile: water is reabsorbed in the bladder> ^ concentration of org. substances. Active transport of Na, followed by Cl, HCO3.
Bile acids circulate (economy). They are isolated in the form of micelles. Absorbed passively in the intestine, actively in the ileum.
» Bile is produced by hepatocytes

The components of bile are:
Bile salts (= steroids + amino acids) Detergents capable of reacting with water and lipids to form water-soluble fatty particles
Bile pigments (result of degradation of hemoglobin)
Cholesterol

Bile is concentrated and deposited in the gallbladder and released from it during contraction.
- Bile release is stimulated by vagus, secretin and cholecystokinin

BILE PRODUCTION AND BILE EXECUTION.

Three important notes:

• bile is formed constantly, and is secreted periodically (because it accumulates in the gallbladder);
• bile does not contain digestive enzymes;
• bile is both a secret and an excretion.

COMPOSITION OF BILE: bile pigments (bilirubin, biliverdin - toxic products of hemoglobin metabolism. Excreted from the internal environment of the body: 98% with bile from the gastrointestinal tract and 2% by the kidneys); bile acids (secreted by hepatocytes); cholesterol, phospholipids, etc. Hepatic bile is slightly alkaline (due to bicarbonates).
In the gallbladder, the bile is concentrated, becoming very dark and thick. Bubble volume 50-70 ml. The liver produces 5 liters of bile per day, and 500 ml is secreted into the duodenum. Bladder and duct stones form (A) with excess cholesterol and (B) lower pH when bile stasis in the bladder (pH<4).

VALUE OF BILE:

1. emulsifies fats
2. increases the activity of pancreatic lipase,
3. promotes the absorption of fatty acids and fat-soluble vitamins A, D, E, K,
4. neutralizes HC1,
5. has a bactericidal effect
6. performs an excretory function
7. stimulates motility and absorption in the small intestine.

BILE ACIDS CYCLE: bile acids are used repeatedly: they are absorbed in the distal ileum (ileum), enter the liver with blood flow, are captured by hepatocytes and are again excreted into the intestine as part of bile.

REGULATION OF BIOL FORMATION: neuro-humoral mechanism. The vagus nerve, as well as gastrin, secretin, bile acids increase the secretion of bile.

BILARY REGULATION: neuro-humoral mechanism. The vagus nerve and cholecystokinin cause the gallbladder to contract and the sphincter to relax. Sympathetic nerves cause bladder relaxation (accumulation of bile).

NONDIGESTIVE LIVER FUNCTIONS:

1. protective (detoxification of various substances, synthesis of urea from ammonia),
2. participation in the metabolism of proteins, fats and carbohydrates,
3. hormone inactivation,
4. blood depot, etc.