What does the liver do in the human body briefly. Liver functions

The name "liver" comes from the word "oven", because. The liver has the highest temperature of all organs of the living body. What is this connected with? Most likely due to the fact that the highest amount of energy production occurs in the liver per unit mass. Up to 20% of the mass of the entire liver cell is occupied by mitochondria, the “power stations of the cell,” which continuously produce ATP, which is distributed throughout the body.

All liver tissue consists of lobules. The lobule is the structural and functional unit of the liver. The space between the liver cells is the bile ducts. There is a vein in the center of the lobule, and vessels and nerves pass through the interlobular tissue.

The liver as an organ consists of two unequal large lobes: right and left. The right lobe of the liver is much larger than the left, which is why it is so easily palpable in the right hypochondrium. The right and left lobes of the liver are separated from above by the falciform ligament, on which the liver seems to be “suspended”, and below the right and left lobes are separated by a deep transverse groove. In this deep transverse groove there are the so-called gates of the liver; at this point, vessels and nerves enter the liver, and the hepatic ducts that drain bile exit. The small hepatic ducts gradually unite into one common one. The common bile duct includes the duct of the gallbladder - a special reservoir in which bile accumulates. The common bile duct flows into the duodenum, almost in the same place where the pancreatic duct flows into it.

The blood circulation of the liver is not similar to the blood circulation of other internal organs. Like all organs, the liver is supplied with arterial blood saturated with oxygen from the hepatic artery. Venous blood, poor in oxygen and rich in carbon dioxide, flows through it and flows into the portal vein. However, in addition to this, which is normal for all circulatory organs, the liver receives a large amount of blood flowing from the entire gastrointestinal tract. Everything that is absorbed in the stomach, duodenum, small and large intestines is collected in the large portal vein and flows into the liver.

The purpose of the portal vein is not to supply the liver with oxygen and rid it of carbon dioxide, but to pass through the liver all the nutrients (and non-nutrients) that have been absorbed throughout the gastrointestinal tract. First, they pass through the portal vein through the liver, and then in the liver, having undergone certain changes, they are absorbed into the general bloodstream. The portal vein accounts for 80% of the blood received by the liver. The portal vein blood is mixed. It contains both arterial and venous blood flowing from the gastrointestinal tract. Thus, in the liver there are 2 capillary systems: the usual one, between the arteries and veins, and the capillary network of the portal vein, which is sometimes called the “miraculous network”. The normal and capillary miraculous networks are interconnected.

Sympathetic innervation

The liver is innervated by the solar plexus and branches of the vagus nerve (parasympathetic impulses).

Through sympathetic fibers, the formation of urea is stimulated and impulses are transmitted through the parasympathetic nerves, increasing bile secretion and promoting the accumulation of glycogen.

The liver is sometimes called the largest endocrine gland in the body, but this is not entirely true. The liver also performs endocrine excretory functions and also takes part in digestion.

The breakdown products of all nutrients form, to a certain extent, a common metabolic reservoir, which all passes through the liver. From this reservoir, the body synthesizes necessary substances as needed and breaks down unnecessary ones.

Carbohydrate metabolism

Glucose and other monosaccharides entering the liver are converted into glycogen. Glycogen is stored in the liver as a “sugar reserve”. In addition to monosaccharides, lactic acid, products of the breakdown of proteins (amino acids), and fats (triglycerides and fatty acids) are also converted into glycogen. All these substances begin to turn into glycogen if there are not enough carbohydrates in food.

As needed, when glucose is consumed, glycogen is converted into glucose here in the liver and enters the blood. The glycogen content in the liver, regardless of food intake, is subject to a certain rhythmic fluctuation during the day. The largest amount of glycogen is contained in the liver at night, the smallest - during the day. This is due to active energy consumption during the day and the formation of glucose. Glycogen synthesis from other carbohydrates and breakdown into glucose takes place both in the liver and in the muscles. However, the formation of glycogen from protein and fat is possible only in the liver; this process does not occur in muscles.

Pyruvic acid and lactic acid, fatty acids and ketone bodies - what are called fatigue toxins - are utilized mainly in the liver and converted into glucose. In the body of a highly trained athlete, more than 50% of all lactic acid is converted into glucose in the liver.

Only in the liver does the “tricarboxylic acid cycle” occur, which is otherwise called the “Krebs cycle” after the English biochemist Krebs, who, by the way, is still alive. He owns classic works on biochemistry, incl. and a modern textbook.

Sugar hallostasis is necessary for the normal functioning of all systems and organs. Normally, the amount of carbohydrates in the blood is 80-120 mg% (i.e. mg per 100 ml of blood), and their fluctuations should not exceed 20-30 mg%. A significant decrease in the content of carbohydrates in the blood (hypoglycemia), as well as a persistent increase in their content (hyperglycemia) can lead to serious consequences for the body.

During the absorption of sugar from the intestine, the glucose content in the blood of the portal vein can reach 400 mg%. The sugar content in the blood of the hepatic vein and in the peripheral blood increases only slightly and rarely reaches 200 mg%. An increase in blood sugar immediately turns on the “regulators” built into the liver. Glucose is converted, on the one hand, into glycogen, which accelerates, on the other hand, it is used for energy, and if after that there is excess glucose, it turns into fat.

Recently, data have appeared on the ability to form an amino acid substitute from glucose, but the process is organic in the body and develops only in the body of highly qualified athletes. When glucose levels decrease (prolonged fasting, large amounts of physical activity), glucogen is broken down in the liver, and if this is not enough, amino acids and fats are converted into sugar, which are then converted into glycogen.

The glucose-regulatory function of the liver is supported by the mechanisms of neurohumoral regulation (regulation by the nervous and endocrine systems). Blood sugar levels are increased by adrenaline, glucose, thyroxine, glucocorticoids and diabetogenic factors of the pituitary gland. Under certain conditions, sex hormones have a stabilizing effect on sugar metabolism.

Blood sugar levels are lowered by insulin, which first enters the liver through the portal vein system and only from there into the general circulation. Normally, antagonistic endocrine factors are in a state of equilibrium. With hyperglycemia, the secretion of insulin increases, with hypoglycemia - adrenaline. Glucagon, a hormone secreted by the a-cells of the pancreas, has the ability to increase blood sugar.

The glucose-static function of the liver can also be subject to direct nervous effects. The central nervous system can cause hyperglycemia both humorally and reflexively. Some experiments indicate that the liver also has a system for autonomous regulation of blood sugar levels.

Protein metabolism

The role of the liver in protein metabolism is the breakdown and “rearrangement” of amino acids, the formation of chemically neutral urea from ammonia, which is toxic to the body, as well as the synthesis of protein molecules. Amino acids, which are absorbed in the intestine and formed during the breakdown of tissue protein, constitute the body’s “reservoir of amino acids,” which can serve as both a source of energy and a building material for protein synthesis. Isotopic methods have established that in the human body, 80-100 g of protein are broken down and synthesized again. Approximately half of this protein is transformed in the liver. The intensity of protein transformations in the liver can be judged by the fact that liver proteins are renewed in about 7 (!) days. In other organs, this process occurs in at least 17 days. The liver contains the so-called “reserve protein”, which is used for the body’s needs if there is not enough protein in food. During a two-day fast, the liver loses approximately 20% of its protein, while the total protein loss of all other organs is only about 4%.

Transformation and synthesis of missing amino acids can only occur in the liver; even if 80% of the liver is removed, a process such as deamination remains. The formation of non-essential amino acids in the liver occurs through the formation of glutamic and aspartic acid, which serve as an intermediate link.

An excess amount of a particular amino acid is reduced first to pyruvic acid, and then in the Krebs cycle to water and carbon dioxide with the formation of energy stored in the form of ATP.

In the process of desemination of amino acids - the removal of amino groups from them - a large amount of toxic ammonia is formed. The liver converts ammonia into non-toxic urea (urea), which is then excreted from the body by the kidneys. Urea synthesis occurs only in the liver and nowhere else.

The synthesis of blood plasma proteins—albumin and globulins—occurs in the liver. If blood loss occurs, then with a healthy liver the content of blood plasma proteins is very quickly restored; while with a diseased liver, such recovery slows down significantly.

Fat metabolism

The liver can store much more fat than glycogen. The so-called “structural lipid” - structural lipids of the liver - phospholipids and cholesterol make up 10-16% of the dry matter of the liver. This number is fairly constant. In addition to structural lipids, the liver contains inclusions of neutral fat, similar in composition to subcutaneous fat. The content of neutral fat in the liver is subject to significant fluctuations. In general, we can say that the liver has a certain fat reserve, which, if there is a deficiency of neutral fat in the body, can be spent on energy needs. In case of energy deficiency, fatty acids can be well oxidized in the liver with the formation of energy stored in the form of ATP. In principle, fatty acids can be oxidized in any other internal organs, but the percentage will be as follows: 60% liver and 40% all other organs.

Bile secreted by the liver into the intestines emulsifies fats, and only as part of such an emulsion can fats be subsequently absorbed in the intestines.

Half of the cholesterol in the body is synthesized in the liver and only the other half is of dietary origin.

The mechanism of liver oxidation of fatty acids was elucidated at the beginning of this century. It comes down to so-called b-oxidation. Oxidation of fatty acids occurs up to the 2nd carbon atom (b-atom). The result is a shorter fatty acid and acetic acid, which is then converted to acetoacetic acid. Acetoacetic acid is converted to acetone, and the new b-oxidized acid undergoes oxidation with great difficulty. Both acetone and b-oxidized acid are collectively referred to as “ketone bodies.”

To break down ketone bodies, you need a fairly large amount of energy, and if there is a deficiency of glucose in the body (fasting, diabetes, prolonged aerobic exercise), a person’s breath may smell like acetone. Biochemists even have an expression: “fats burn in the fire of carbohydrates.” For complete combustion, complete utilization of fats into water and carbon dioxide with the formation of a large amount of ATP, at least a small amount of glucose is required. Otherwise, the process will stall at the stage of formation of ketone bodies, which shift the blood pH to the acidic side, along with lactic acid, taking part in the formation of fatigue. It’s not for nothing that they are called “fatigue toxins.”

Fat metabolism in the liver is influenced by hormones such as insulin, ACTH, diabetogenic factor of the pituitary gland, and glucocorticoids. The action of insulin promotes the accumulation of fat in the liver. The action of ACTH, diabetogenic factor, and glucocorticoids is exactly the opposite. One of the most important functions of the liver in fat metabolism is the formation of fat and sugar. Carbohydrates are a direct source of energy, and fats are the most important energy reserves in the body. Therefore, with an excess of carbohydrates and, to a lesser extent, proteins, fat synthesis predominates, and with a lack of carbohydrates, gluconeogenesis (glucose formation) from protein and fat dominates.

Cholesterol metabolism

Cholesterol molecules form the structural framework of all cell membranes without exception. Cell division is simply impossible without sufficient cholesterol. Bile acids are formed from cholesterol, i.e. essentially bile itself. All steroid hormones are formed from cholesterol: glucocorticoids, mineralocorticoids, and all sex hormones.

Cholesterol synthesis is therefore genetically determined. Cholesterol can be synthesized in many organs, but it is most intensively synthesized in the liver. By the way, the breakdown of cholesterol also occurs in the liver. Some of the cholesterol is excreted unchanged into the intestinal lumen with bile, but most of the cholesterol - 75% is converted into bile acids. The formation of bile acids is the main pathway of cholesterol catabolism in the liver. For comparison, let's say that only 3% of cholesterol is consumed for all steroid hormones taken together. A person excretes 1-1.5 g of cholesterol per day with bile acids. 1/5 of this amount is excreted from the intestines, and the rest is reabsorbed into the intestines and ends up in the liver.

Vitamins

All fat-soluble vitamins (A, D, E, K, etc.) are absorbed into the intestinal walls only in the presence of bile acids secreted by the liver. Some vitamins (A, B1, P, E, K, PP, etc.) are deposited by the liver. Many of them are involved in chemical reactions occurring in the liver (B1, B2, B5, B12, C, K, etc.). Some vitamins are activated in the liver, undergoing phosphorication there (B1, B2, B6, choline, etc.). Without phosphorus residues, these vitamins are completely inactive and often the normal vitamin balance in the body depends more on the normal state of the liver than on the sufficient intake of one or another vitamin in the body.

As we can see, both fat-soluble and water-soluble vitamins can be deposited in the liver; only the time of deposition of fat-soluble vitamins, of course, is disproportionately longer than that of water-soluble vitamins.

Hormone exchange

The role of the liver in the metabolism of steroid hormones is not limited to the fact that it synthesizes cholesterol - the basis from which all steroid hormones are then formed. In the liver, all steroid hormones are inactivated, although they are not formed in the liver.

The breakdown of steroid hormones in the liver is an enzymatic process. Most steroid hormones are inactivated by combining with glucuronic fatty acid in the liver. When liver function is impaired, the body first of all increases the content of hormones of the adrenal cortex, which are not completely broken down. This is where many different diseases arise. Aldosterone, a mineralocorticoid hormone, accumulates most in the body, the excess of which leads to sodium and water retention in the body. As a result, swelling occurs, blood pressure rises, etc.

In the liver, thyroid hormones, antidiuretic hormone, insulin, and sex hormones are largely inactivated. In some liver diseases, male sex hormones are not destroyed, but turn into female ones. This disorder occurs especially often after methyl alcohol poisoning. The excess of androgens itself, caused by the introduction of a large amount of them from the outside, can lead to increased synthesis of female sex hormones. There is, obviously, a certain threshold for the content of androgens in the body, exceeding which leads to the conversion of androgens into female sex hormones. Although, recently there have been publications that some medications can prevent the conversion of androgens into estrogens in the liver. Such drugs are called blockers.

In addition to the above hormones, the liver inactivates neurotransmitters (catecholamines, serotonin, histamine and many other substances). In some cases, even the development of mental illness is caused by the inability of the liver to inactivate certain neurotransmitters.

Microelements

The metabolism of almost all microelements directly depends on the functioning of the liver. The liver, for example, influences the absorption of iron from the intestine; it deposits iron and ensures the constancy of its concentration in the blood. The liver is a depot of copper and zinc. It takes part in the exchange of manganese, molybdenum, cobalt and other microelements.

Bile formation

Bile, produced by the liver, as we have already said, takes an active part in the digestion of fats. However, the matter is not limited to just their emulsification. Bile activates the fat-splitting enzyme liposis of pancreatic and intestinal juice. Bile also accelerates the absorption in the intestines of fatty acids, carotene, vitamins P, E, K, cholesterol, amino acids, and calcium salts. Bile stimulates intestinal motility.

The liver produces at least 1 liter of bile per day. Bile is a greenish-yellow, slightly alkaline liquid. The main components of bile: bile salts, bile pigments, cholesterol, lecithin, fats, inorganic salts. Hepatic bile contains up to 98% water. In terms of its osmotic pressure, bile is equal to blood plasma. From the liver, bile enters the hepatic duct through the intrahepatic bile ducts, from where it is directly secreted through the cystic duct and enters the gallbladder. Here the concentration of bile occurs due to the absorption of water. The density of gallbladder bile is 1.026-1.095.

Some of the substances that make up bile are synthesized directly in the liver. The other part is formed outside the liver and, after a series of metabolic changes, is excreted with bile into the intestine. Thus, bile is formed in two ways. Some of its components are filtered from the blood plasma (water, glucose, creatinine, potassium, sodium, chlorine), others are formed in the liver: bile acids, glucuronides, paired acids, etc.

The most important bile acids, cholic and deoxycholic, combine with the amino acids glycine and taurine to form paired bile acids - glycocholic and taurocholic.

The human liver produces 10-20 g of bile acids per day. Entering the intestines with bile, bile acids are broken down with the help of enzymes from intestinal bacteria, although most of them are reabsorbed by the intestinal walls and end up back in the liver.

Only 2-3 g of bile acids are released with feces, which, as a result of the decomposing action of intestinal bacteria, change their color from green to brown and change their smell.

Thus, there is a sort of hepatic-intestinal circulation of bile acids. If it is necessary to increase the excretion of bile acids from the body (for example, in order to remove large amounts of cholesterol from the body), then substances are taken that irreversibly bind bile acids, which do not allow bile acids to be absorbed in the intestines and remove them from the body along with feces. The most effective in this regard are special ion exchange resins (for example, cholestyramine), which, when taken orally, are capable of binding a very large amount of bile and, accordingly, bile acids in the intestine. Previously, activated carbon was used for this purpose.

They still use it now. Fiber in vegetables and fruits, but even more so, pectin substances, have the ability to absorb bile acids and remove them from the body. The largest amount of pectin substances is found in berries and fruits, from which jelly can be made without the use of gelatin. First of all, these are red currants, then, according to their gelling ability, they are followed by black currants, gooseberries, and apples. It is noteworthy that baked apples contain several times more pectin than fresh ones. Fresh apples contain protopectins, which turn into pectins when apples are baked. Baked apples are an indispensable attribute of all diets when you need to remove a large amount of bile from the body (atherosclerosis, liver disease, some poisoning, etc.).

Bile acids, among other things, can be formed from cholesterol. When eating meat food, the amount of bile acids increases, and when fasting, it decreases. Thanks to bile acids and their salts, bile performs its functions in the process of digestion and absorption.

Bile pigments (the main one is bilirubin) do not take part in digestion. Their secretion by the liver is a purely excretory process.

Bilirubin is formed from hemoglobin of destroyed red blood cells in the spleen and special liver cells (Kupffer cells). It’s not for nothing that the spleen is called the graveyard of red blood cells. With regard to bilirubin, the main task of the liver is its excretion, not its formation, although a considerable part of it is formed in the liver. It is interesting that the breakdown of hemoglobin to bilirubin is carried out with the participation of vitamin C. Between hemoglobin and bilirubin there are many intermediate products that can be mutually converted into each other. Some of them are excreted in urine, and some in feces.

The formation of bile is regulated by the central nervous system through various reflex influences. Bile secretion occurs continuously, increasing during meals. Irritation of the splanchnic nerve leads to a decrease in bile production, and irritation of the vagus nerve and histamines increase bile production.

Biliary excretion, i.e. The entry of bile into the intestines occurs periodically as a result of contraction of the gallbladder, depending on food intake and its composition.

Excretory (excretory) function

The excretory function of the liver is very closely related to bile formation, since substances excreted by the liver are excreted through bile and, if only for this reason, they automatically become an integral part of bile. Such substances include the thyroid hormones already described above, steroid compounds, cholesterol, copper and other trace elements, vitamins, porphyrin compounds (pigments), etc.

Substances excreted almost exclusively with bile are divided into two groups:

• Substances bound to proteins in the blood plasma (for example, hormones).
• Substances insoluble in water (cholesterol, steroid compounds).

One of the features of the excretory function of bile is that it is capable of introducing substances from the body that cannot be removed from the body in any other way. There are few free compounds in the blood. Most of the same hormones are tightly bound to transport proteins in the blood and, being firmly bound to the proteins, cannot overcome the kidney filter. Such substances are excreted from the body along with bile. Another large group of substances that cannot be excreted in urine are substances that are insoluble in water.

The role of the liver in this case is that it combines these substances with glucuronic acid and thus converts them into a water-soluble state, after which they are freely excreted through the kidneys.

There are other mechanisms that allow the liver to remove water-insoluble compounds from the body.

Neutralizing function

The liver plays a protective role not only by neutralizing and removing toxic compounds, but even by microbes that get into it, which it destroys. Special liver cells (Kupffer cells), like amoebas, capture foreign bacteria and digest them.

In the process of evolution, the liver has become an ideal organ for neutralizing toxic substances. If it cannot turn a toxic substance completely non-toxic, it makes it less toxic. We already know that toxic ammonia is converted into non-toxic urea (urea) in the liver. Most often, the liver neutralizes toxic compounds by forming paired compounds with them with glucuranic and sulfuric acid, glycine, taurine, cysteine, etc. This is how highly toxic phenols are neutralized, steroids and other substances are neutralized. A major role in neutralization is played by oxidative and reduction processes, acetylation, methylation (which is why vitamins containing free methyl radicals-CH3 are so useful for the liver), hydrolysis, etc. For the liver to perform its detoxification function, sufficient energy supply is necessary, and for this, in in turn, it requires a sufficient glycogen content and the presence of a sufficient amount of ATP.

Blood clotting

The liver synthesizes substances necessary for blood clotting, components of the prothrombin complex (factors II, VII, IX, X), the synthesis of which requires vitamin K. The liver also produces fibranogen (a protein necessary for blood clotting), factors V, XI, XII , XIII. Strange as it may seem at first glance, the synthesis of elements of the anticoagulant system occurs in the liver - heparin (a substance that prevents blood clotting), antithrombin (a substance that prevents the formation of blood clots), and antiplasmin. In embryos (fetuses), the liver also serves as a hematopoietic organ where red blood cells are formed. With the birth of a person, these functions are taken over by the bone marrow.

Redistribution of blood in the body

The liver, in addition to all its other functions, performs quite well as a blood depot in the body. In this regard, it can affect the blood circulation of the entire body. All intrahepatic arteries and veins have sphincters, which can change blood flow in the liver over a very wide range. On average, blood flow in the liver is 23 ml/kx/min. Normally, almost 75 small vessels of the liver are excluded from the general circulation by sphincters. With an increase in total blood pressure, liver vessels dilate and hepatic blood flow increases several times. On the contrary, a drop in blood pressure leads to vasoconstriction in the liver and hepatic blood flow is reduced.

Changes in body position are also accompanied by changes in hepatic blood flow. For example, in a standing position, liver blood flow is 40% lower than in a lying position.

Norepinephrine and sympathetic increase vascular resistance in the liver, which reduces the amount of blood flowing through the liver. The vagus nerve, on the other hand, reduces vascular resistance in the liver, which increases the amount of blood flowing through the liver.

The liver is very sensitive to lack of oxygen. Under conditions of hypoxia (lack of oxygen in tissues), vasodilator substances are formed in the liver, reducing the sensitivity of capillaries to adrenaline and increasing hepatic blood flow. With prolonged aerobic work (running, swimming, rowing, etc.), the increase in hepatic blood flow can reach such an extent that the liver greatly increases in volume and begins to put pressure on its outer capsule, richly supplied with nerve endings. The result is pain in the liver, familiar to every runner, and indeed to all those who engage in aerobic sports.

Age-related changes

The functional capabilities of the human liver are highest in early childhood and decrease very slowly with age.

The liver weight of a newborn child is on average 130-135 g. The liver weight reaches its maximum between the ages of 30-40 years, and then gradually decreases, especially between 70-80 years, and in men the liver weight drops more than in women. The regenerative abilities of the liver decrease somewhat in old age. At a young age, after removal of the liver by 70% (wounds, injuries, etc.), the liver restores the lost tissue by 113% (in excess) after a few weeks. Such a high ability to regenerate is not inherent in any other organ and is even used to treat severe chronic liver diseases. So, for example, in some patients with liver cirrhosis, it is partially removed and it grows back, but new, healthy tissue grows. With age, the liver no longer recovers completely. In old people, it grows only 91% (which, in principle, is also a lot).

The synthesis of albumins and globulins decreases in old age. Albumin synthesis mainly decreases. However, this does not lead to any disturbances in tissue nutrition or a drop in oncotic blood pressure, because With old age, the intensity of breakdown and consumption of proteins in plasma by other tissues decreases. Thus, the liver, even in old age, meets the body’s needs for the synthesis of plasma proteins. The ability of the liver to store glycogen also varies at different age periods. Glycogen capacity reaches its maximum by three months of age, remains for life and only slightly decreases in old age. Fat metabolism in the liver reaches its normal level also at a very early age and only slightly decreases in old age.

At different stages of the body's development, the liver produces different amounts of bile, but always covers the body's needs. The composition of bile changes somewhat throughout life. So, if a newborn child’s liver bile contains bile acids of about 11 mEq/L, then by the age of four this amount decreases almost 3 times, and by the age of 12 it increases again and reaches approximately 8 mEq/L.

The rate of emptying of the gallbladder, according to some data, is the lowest in young people, and in children and the elderly it is much higher.

In general, according to all its indicators, the liver is a low-aging organ. It serves a person well throughout his life.

If you study the structure of the liver in detail, the process of understanding the functions of the liver becomes simpler and more understandable. From the article on the structure of the liver, we already know that this organ produces bile and cleanses the blood of harmful substances. What else functions inherent liver. Of the wide variety of liver functions, which have more than 500 designations, generalized ones can be identified. So, the list of such functions includes:
- detoxification;
- excretory;
- synthetic;
— energy;
- hormonal metabolism.

Detoxification function of the liver

The detoxification function is determined by the neutralization and disinfection of harmful substances that enter there along with the blood through the portal vein from the digestive organs. The blood entering the liver through the portal vein contains, on the one hand, nutrients and toxins that arrived there after digestion of food by the gastrointestinal tract. Many different processes, including putrefactive ones, occur simultaneously in the small intestine. As a result of the flow of the latter, harmful substances are ultimately formed - cresol, indole, skatole, phenol, etc. By the way, harmful substances or, say, compounds not characteristic of our body also include pharmaceuticals, alcohol, harmful substances contained in the air near busy roads or in tobacco smoke. All these substances are harmful, they are absorbed into the blood and along with it enter the liver. The main role of the detoxification function is to process and destroy harmful substances and remove them along with bile into the intestines. This process (filtration) occurs due to the passage of various biological processes. Such processes include reduction, oxidation, methylation, acetylation, and synthesis of various protective substances. Another feature of the detoxification function is that it reduces the activity of various hormones. Once in the liver, their activity decreases.

Excretory function of the liver

The figure shows the organs of the excretory system of the human body. Among these organs is the liver. Another function of the liver is called excretory. This function is carried out due to the secretion of bile. What does bile consist of? It consists of 82% water, then 12% - bile acids, 4% - lecithin, 0.7% - cholesterol. The rest of the bile, which is approximately a little more than 1%, includes bilirubin (pigment) and other substances. Bile acids, as well as their salts, during contact break fats into small droplets, thus facilitating the process of their digestion. In addition, bile acids take an active part in the absorption of cholesterol, insoluble fatty acids, calcium salts, vitamins K, E and B vitamins. Speaking about the role of bile, it should be noted that it prevents the development of putrefaction processes in the intestines, stimulating the motility of the small intestine , participates in the process of digestion of carbohydrates and proteins, and also stimulates the secretion of juice by the pancreas, and also stimulates the bile-forming function of the liver itself. Ultimately, all toxic and harmful substances are eliminated from the body along with bile. It should be noted that complete (normal) purification of the blood from harmful substances is possible only if the bile ducts are passable - small stones in the gall bladder can impair the outflow of bile.

Synthetic functions of the liver

If we talk about the synthetic functions of the liver, then its role is in the synthesis of proteins, bile acids, activation of vitamins, metabolism of carbohydrates and proteins. During protein metabolism, amino acids are broken down as a result of which ammonia is converted into neutral urea. About half of all protein compounds that are formed in the human body undergo further qualitative and quantitative transformations in the liver. Therefore, the normal functioning of the liver determines the normal functioning of other organs and systems of the human body. Everything in the body is interconnected. For example, liver disease leads to a malfunction of the synthetic function, which may result in decreased production of certain proteins (albumin and haptoglobin). These proteins are part of the blood plasma and a violation of their concentration has an extremely negative effect on health. Due to a diseased liver, the synthesis of proteins and other substances that are responsible for the protective function of the body, for example, normal blood clotting, may decrease.

As for carbohydrate metabolism, it consists of the production of glucose, which the liver reproduces from fructose and galactose and accumulates in the form of glycogen. The liver strictly monitors the concentration of glucose and tries to maintain its level constant, and it does this constantly throughout the day. The liver carries out this process due to the reverse process of conversion of the substances mentioned above - (fructose, galactose - glycogen, and vice versa glycogen - glucose). Here I would like to note a very important detail, which is that the source of energy that ensures the vital activity of all cells of the human body is glucose. Therefore, when its level decreases, the whole body begins to suffer, but first of all this decrease affects the functioning of the brain. Brain cells differ from other cells in our body (due to their specificity) and cannot accumulate significant amounts of glucose. In addition, they do not use fats and amino acids as an energy source. Therefore, if the blood glucose level is extremely low, this can lead to muscle cramps or even loss of consciousness.

Energy function of the liver

The human body, like any other creature, consists of cells - the structural units of the body. All cells have a fundamentally identical structure, which is due to the fact that they contain information encrypted in nucleic acid, which is located in the cell nucleus. This information determines the normal functioning and development of cells, and, consequently, the entire organism. It is also important to note here that, although the cells have a fundamentally identical structure, the functions they perform are different. These functions are determined by the program embedded in their core. You have the right to ask, what does the liver have to do with it and what effect does it have on other cells? The answer is as follows: for normal functioning, cells need an external source of energy, which, as needed, could supply them with the necessary energy. The liver is such a main and backup source of energy reserves. These energy reserves are synthesized and stored in the liver in the form of glycogen, proteins and triglycerides.

Hormonal metabolism

The liver itself does not produce hormones, but is actively involved in hormonal metabolism. This participation of the liver is due to the fact that it destroys excess amounts of hormones that produce endocrine glands. With any liver disease, the level of hormones in the blood increases, which negatively affects the health of the body. Diseases such as tachycardia (increased heart rate) are caused by increased levels of thyroxine, increased sweating - exophthalmos, sodium and water retention in the body - aldosterone.

As you can see, the human body is unique and diverse. The health of the human body greatly depends on the health of the liver.

Be always healthy and happy!

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General information

As everyone knows, the liver is an unpaired organ located in the right hypochondrium. With this knowledge of anatomy, everyone who has a stabbing pain in their right side immediately diagnoses themselves with liver disease. This is a fairly massive organ, its average weight is 1.5 kg. The liver has a separate vascular network, isolated from the general blood flow. And the reason for the separate vascular network is the fact that blood flows into this organ from the entire intestinal tract. At the same time, the liver is a natural filter for the blood flowing from the intestinal walls; it performs the function of primary sorting, synthesis and distribution of nutrients in the body. Blood flows into the circulatory system of the liver from almost all organs of the abdominal cavity: intestines ( thin and thick, stomach), spleen, pancreas. Next, the blood, after being filtered in the liver tissues, returns to the systemic circulation. In order to understand how the liver functions, let’s take a closer look at its anatomical and microscopic structure.

What does liver tissue look like under a microscope?

In the lumen of the portal vein, blood from the abdominal organs moves towards the hepatic lobules.

The hepatic artery carries unidirectional blood flow from the heart to the liver tissues. This blood is enriched with nutrients and oxygen. Therefore, the main function of this network is to provide the liver tissue with energy and construction resources.

Synthesized by hepatocytes along the bile duct ( liver cells) bile flows from the hepatic lobule towards the gallbladder or the lumen of the duodenum.

Let us recall that through the portal vein there is a flow of blood to the liver mainly from the intestines, with all the substances dissolved in the blood as a result of digestion. The hepatic artery carries oxygenated and nutrient-rich blood from the heart to the liver. Inside the hepatic lobule, the vessels through which blood enters the hepatic lobule merge, forming an expanded cavity - sinusoidal capillaries.
As blood passes through sinusoidal capillaries, its speed significantly slows down. This is necessary so that hepatocytes have time to capture substances dissolved in the blood for their further processing. Nutrients are further processed and distributed through the bloodstream through the vascular network, or accumulated as reserves in the liver. Toxic substances are captured by hepatocytes and neutralized for subsequent removal from the body. After passing through the sinusoidal capillaries, the blood enters the central vein, located in the center of the hepatic lobule. The hepatic vein removes blood from the hepatic lobule towards the heart.

Liver cells are arranged in the form of single-cell plates located perpendicular to the walls of the central vein. Outwardly, it resembles a book turned 360 degrees, where the end is the central vein, and the leaves are trabeculae, between which the vessels are intertwined.

Metabolic processes in the liver - how do they occur?

With regard to proteins, fats and carbohydrates, the important fact is that these substances can be synthesized in the liver. Moreover, carbohydrates can be synthesized from fats or amino acids. Fats can be synthesized from the breakdown products of carbohydrates and amino acids. And only amino acids cannot be synthesized from carbohydrates or fats. Vitamins are also not synthesized in our body. Therefore, without a constant supply of amino acids and vitamins from food, it is impossible to feel healthy for a long time.

So, during the digestion process, in the blood flowing from the intestinal walls there are many fatty particles broken down to the level of the smallest ( chylomicrons). This blood contains fats, forming an emulsion that resembles milk in appearance. Carbohydrates enter the blood in the form of molecules of different structures ( fructose, maltose, galactose, etc.).

Amino acids- these are structural units of protein that enter our body in the form of individual molecules or in the form of short chains of particles attached to each other.
Amino acids - these important substances for our body are used with particular frugality by liver cells. From them enzymes and blood proteins are synthesized. Some of the synthesized protein molecules return to the blood for transport to organs and tissues in the form of amino acids or blood plasma protein - albumin. Some amino acids are broken down to build other amino acid molecules or other organic substances.

Vitamins– these substances enter our body during the digestion process, some of them are synthesized by the intestinal microflora. However, they all enter the body after passing through the liver tissue. Vitamins are essential substances that enter the liver tissue through the bloodstream. Vitamins are actively absorbed by the cells of the organ. Some vitamins are immediately incorporated into synthesized enzymes, some are stored by liver cells, and some are redirected with the blood flow flowing from this organ to peripheral tissues. When passing through the hepatic sinuses, organic substances and vitamins are captured by the liver cells and move inside the hepatocyte. Further, depending on the state of the body, processes of transformation and distribution occur.

Carbohydrates are most actively processed in the liver. The various forms of carbohydrates are converted into a single form - glucose. Next, glucose can be released into the bloodstream and rush through the central vein into the systemic circulation, go to the energy needs of the liver, or be broken down to produce substances necessary for the body, or accumulate in the form of glycogen.

Fats– enter the liver in the form of an emulsion. When they enter the hepatocyte, they are broken down, fats are broken down into their component parts glycerol and fatty acids. Subsequently, transport forms are formed from the newly synthesized fats - lipoproteins from cholesterol, lipid and protein molecules. It is these lipoproteins, entering the bloodstream, that deliver cholesterol to peripheral tissues and organs.

The liver as a factory for collecting complex proteins, carbohydrates and fats

Albumen is a low molecular weight protein with a molecular weight of 65,000. Serum albumin is synthesized exclusively by the liver. The amount of albumin contained in a liter of blood serum reaches 35 - 50 grams. Albumin performs many functions of blood: it is one of the transport forms of protein in the body, carries on its surface some hormones, organic substances and medications, and provides oncotic blood pressure ( this pressure prevents the liquid part of the blood from leaving the vascular bed).

Fibrin is a low-molecular blood protein that is formed in the liver due to enzymatic treatment and ensures blood clotting and blood clot formation.

Glycogen is a molecular compound that unites carbohydrate molecules in a chain. Glycogen acts as a carbohydrate depot for the liver. When energy resources are needed, glycogen is broken down and glucose is released.

The liver is an organ in which there is a constant high concentration of basic structural elements: proteins, fats, carbohydrates. To transport or store them in the tissues of a given organ, it is necessary to synthesize more complex molecules. Some of the synthesized molecules and microscopic structures are only transport forms of proteins ( albumin, amino acids, polypeptides), fats ( low density lipoproteins), carbohydrates ( glucose).

Bile is one of the main factors in the breakdown of fats

The liver is an indispensable conveyor belt of the body

The human organ is the liver. It is unpaired and located on the right side of the abdominal cavity. The liver performs about 70 different functions. All of them are so important for the functioning of the body that even a slight disruption in its functioning leads to serious illnesses. In addition to participating in digestion, it cleanses the blood of poisons and toxins, is a storehouse of vitamins and minerals, and performs many other functions. To help this organ work without interruption, you need to know what the role of the liver is in the human body.

Basic information about this body

The liver is located in the right hypochondrium and takes up a lot of space in the abdominal cavity because it is the largest internal organ. Its weight ranges from 1200 to 1800 grams. Its shape resembles a convex mushroom cap. It got its name from the word “furnace”, since the temperature in this organ is very high. The most complex chemical processes constantly take place there, and work goes on without interruption.

It is impossible to unambiguously answer the question of what the role of the liver is in the human body, because all the functions that it performs are vital for it. Therefore, this organ has regenerative abilities, that is, it can repair itself. But the cessation of its activities leads to the death of a person within a couple of days.

Protective function of the liver

More than 400 times a day, all the blood passes through this organ, cleansing itself of toxins, bacteria, poisons and viruses. The barrier role of the liver is that its cells break down all toxic substances, process them into a harmless water-soluble form and remove them from the body. They work like a complex chemical laboratory, neutralizing toxins that enter the body with food and air and are formed as a result of metabolic processes. What toxic substances does the liver cleanse the blood of?

From preservatives, dyes and other additives found in food products.

From bacteria and microbes entering the intestines, and from the products of their vital activity.

From alcohol, drugs and other toxic substances that enter the bloodstream with food.

From exhaust gases and heavy metals from the surrounding air.

From excess hormones and vitamins.

From toxic products resulting from metabolism, such as phenol, acetone or ammonia.

Digestive function of the liver

It is in this organ that proteins, fats and carbohydrates coming from the intestines are converted into an easily digestible form. The role of the liver in the digestion process is enormous, because it is there that cholesterol, bile and many enzymes are formed, without which this process is impossible. They are released into the intestines through the duodenum and help in the digestion of food. The role of bile is especially important, which not only breaks down fats and promotes the absorption of proteins and carbohydrates, but also has a bactericidal effect, destroying pathogenic microflora in the intestines.

The role of the liver in metabolism

Carbohydrates supplied with food are converted into glycogen only in this organ, which enters the blood in the form of glucose as needed. The process of gluconeogenesis provides the body with the required amount of glucose. The liver controls the level of insulin in the blood depending on the person's needs.

This organ is also involved in protein metabolism. It is in the liver that albumin, prothrombin and other proteins important for the functioning of the body are synthesized. Almost all of the cholesterol involved in the breakdown of fats and the formation of certain hormones is also formed there. In addition, the liver takes an active part in water and mineral metabolism. It can accumulate up to 20% of blood and

serves as a repository of many minerals and vitamins.

Participation of the liver in the process of hematopoiesis

This organ is called the “blood depot”. In addition to the fact that up to two liters of it can be stored there, hematopoiesis processes take place in the liver. It synthesizes globulins and albumins, proteins that ensure its fluidity. The liver is involved in the formation of iron, which is necessary for the synthesis of hemoglobin. In addition to toxic substances, this organ breaks down red blood cells, resulting in the production of bilirubin. It is in the liver that proteins are formed that perform transport functions for hormones and vitamins.

Storage of useful substances

Speaking about the role of the liver in the human body, it is impossible not to mention its function of accumulating substances necessary for life. What is this organ a repository of?

1. This is the only place where glycogen is stored. The liver stores it and releases it into the blood as glucose as needed.

2. About two liters of blood are kept there and are only used in cases of severe blood loss or shock.

3. The liver is a repository of vitamins necessary for the normal functioning of the body. It contains especially a lot of vitamins A and B12.

4. This organ forms and accumulates cations of metals necessary for the body, such as iron or copper.

What can lead to liver dysfunction?

If for some reason this organ cannot work correctly, then various diseases occur. You can immediately understand what the role of the liver is in the human body if you see what disruptions in its work lead to:

Decreased immunity and constant colds;

Blood clotting disorders and frequent bleeding;

Severe itching, dry skin;

Hair loss, acne;

The emergence of diabetes and obesity;

Various gynecological diseases, such as early menopause;

Digestive disorders, manifested by frequent constipation, nausea and loss of appetite;

Nervous disorders - irritability, depression, insomnia and frequent headaches;

Disorders of water metabolism, manifested by edema.

Very often the doctor treats these symptoms without noticing that the cause is liver destruction. There are no nerve endings inside this organ, so a person may not experience pain. But everyone should know the role the liver plays in their life and try to support it. You need to give up alcohol, smoking, spicy and fatty foods. Limit the use of medications, products containing preservatives and dyes.

Every person should understand what functions the liver performs. The stable functioning of the body directly depends on the health of this organ. The liver performs the functions of neutralizing toxins and is also responsible for proper hematopoiesis. The role of this gland in the digestive system is great: the liver consists of 80% hepatocytes, due to which part of the cholesterol is converted into bile acids, which gradually emulsify into lipids and promote the absorption of beneficial fat-soluble vitamins.

Description

Medical reference books contain a lot of information about what functions the human liver performs. This body acts as a central chemical laboratory. Since as a result of the intensive work of this organ, bile is released, which is necessary for the digestion of food, it is classified as the digestive system. The gland is responsible for the production of those enzymes that are necessary for the uniform absorption of food, simultaneously destroying toxins.

The main functions of the liver in the human body include all types of metabolism:

• Protein.
• Fat.
• Water.
• Carbohydrate.
• Pigmentary.

Despite the fact that bile produces several types of hormones, it is not considered part of the endocrine system.

Anatomy

The liver is the largest gland in the human digestive system. Depending on the physiological characteristics, its weight can vary from one to 2 kilograms. The organ is located in the right, as well as a smaller part of the left hypochondrium of the body. The principle of the structure of the liver is distinguished by its division into 2 lobes. There is a fold between the two halves.

The structure and functions of the liver depend on the condition of individual lobules. This term is usually understood as a small area in the form of a hexagonal prism 1.7 mm wide and 2.6 mm high. The organ itself consists of more than 500 thousand of these lobules, which perform all liver functions. The role of partitions is played by the thinnest triangular films in which the bile ducts are hidden. The central vein is located in the middle of the organ.

Main functions

Stable functioning of the human body is simply impossible without the liver. It performs functions that help cleanse the blood, promote good digestion, and also control the functioning of the gastrointestinal tract. That is why it is important to monitor the condition of this organ.

Initially, you need to understand what functions the liver performs:

1. High-quality biosynthesis of urea.
2. Removing toxins, xenobiotics, poisons, biogenic amines from the body.
3. Metabolism of carbohydrates, proteins, nucleic acids, lipoproteins, vitamins, lipids.
4. Secretion of bile by hepatocytes.
5. In the body, the liver performs functions that are of the catabolic type. The liver is responsible for the production of hormones, as well as the breakdown of hemoglobin.
6. Biosynthetic function. The glandular organ is responsible for the synthesis of those substances that are necessary for the stable functioning of the whole organism: triacylglycerol, glucose, phospholipids, lipoproteins, higher fatty acids.
7. Accumulation of valuable vitamins and microelements: glycogen, iron, fat-soluble vitamins.
8. Kupffer cells in the liver are involved in phagocytosis.
9. Biosynthesis of proteins of the coagulation system.
10. Excretion of bilirubin, cholesterol, bile acid, iron with bile.

Digestive system

The liver is a multifunctional organ, the main task of which is the production of bile. This liquid has a characteristic yellowish-green tint, which ensures a change from gastric to intestinal digestion. The liver continuously generates bile pigments through the cellular breakdown of hemoglobin.

Before using this or that medicine, you need to familiarize yourself with what liver functions are necessary for normal digestion:

• Significant increase in the activity of intestinal enzymes.
• High-quality emulsification of fats with a gradual increase in their area for joint hydrolysis by lipase.
• It is bile that is responsible for the absorption of amino acids, cholesterol and salts.
• Dissolution of lipid hydrolysis products.
• Supports normal intestinal motility.
• Normalization of gastric juice acidity.

If a person neglects to eat regularly, this leads to bile accumulating in the bladder with increased concentration. Of course, this fluid is secreted differently in each person. But the sight of food, its smell and the intake itself always cause relaxation of the gallbladder, followed by contraction.

Malfunctions

If the liver does not perform the functions on which the performance of other organs depends, then various ailments begin to develop in the body. In medical practice, there are many different cases of disease of the gland itself. All these diseases can be divided into several main groups:

• Impaired blood supply to the hepatic vessels.
• Damage to gland cells by purulent or inflammatory processes.
• Development of cancer diseases.
• Various mechanical damages.
• Damage to the bile ducts.
• Pathological or abnormal changes in the liver.
• Complex infectious diseases.
• Structural damage to organ tissue, which can cause liver failure, cirrhosis.
• Diseases arising from exposure to autoimmune viruses.

It is worth noting that any of the above ailments will be accompanied by liver failure and pain, and this is fraught with cirrhosis.

Symptoms

The coordinated functioning of many body systems directly depends on what functions the liver performs. If this organ is damaged, then this is fraught with serious consequences. Most often, people suffer from diseases of the stomach, pancreas and other organs. If you do not seek qualified medical help in a timely manner, a person’s quality of life may deteriorate.

Experts recommend following several rules. The liver will perform all its functions only if a person can identify the disease in the early stages and get rid of it. All pathologies of this glandular organ at the primary stage are manifested by standard symptoms:

• Liquid stool consistency.
• Acute pain in the liver area, indicating an enlarged organ and the presence of viral hepatitis.
• A small rash on the face or chest.
• Changes in skin and eye color (characteristic yellow color).
• Clearly visible problems with blood vessels.

If at least one symptom appears, you should immediately consult a doctor. Only after a thorough examination and all tests will a specialist be able to determine an accurate diagnosis.

Preventive methods

In order for the liver to perform all functions for the normal functioning of the digestive tract, you need to follow a few basic recommendations. A balanced diet has real healing properties: the patient must completely exclude fried, fatty, smoked, salty, too sweet and alcohol from his diet. Be sure to eat fresh fruits and vegetables. It is advisable to replace butter with vegetable or olive oil. You need to drink at least a liter of pure still water per day.

The liver functions better if a person drinks fresh juices daily. Medicines can only be used after being prescribed by a specialist. Only after consulting a doctor can you resort to effective traditional medicine recipes. Thanks to this, you can cleanse the liver. Yoga also has a positive effect on the organ.

Unfavorable factors

The importance of the liver for a person’s full life is simply priceless. But this organ is very sensitive to various unfavorable factors. Numerous studies have shown that iron suffers most from the following factors:

Long-term exposure to one or several of the above factors leads to dysfunction of the organ. If the patient neglects timely treatment, then the death of liver cells is simply inevitable, and this attitude towards health will end in hepatitis or cirrhosis.

Regenerative capabilities

Few citizens thought about the importance of each organ. The liver performs numerous functions on which not only a person’s well-being depends, but also the performance of all other body systems. But until serious health problems appear, preventive measures are most often forgotten.

The liver has a unique property: it is capable of regeneration, even if specialists managed to save only 20-25% of the entire share. There is a lot of information in medical reference books that after resection (removal of the diseased area), restoration of the original size of the organ was repeatedly observed. Of course, this process is quite slow, as it can take anywhere from two months to several years. It all depends on the age and lifestyle of a particular person.

The liver often reacts to excess and undersize. Qualified doctors have repeatedly observed patients who have undergone organ transplantation. It is considered interesting that after the patient’s native gland recovered and was restored to the required size, the donor part gradually atrophied. Of course, even numerous studies have not been able to fully explain all the features of regeneration. But recovery always occurs only after healthy liver cells begin to divide. It is surprising that after removing 90% of the affected tissue, the reproduction of hepatocytes is simply impossible. If less than 40% of the organ was resected, then there will be no cell division either.