Acute renal and liver failure

Anatomical and physiological features of the liver

The weight of the liver is 1.5-2 kg. It is divided into right and left lobes. In this case, the right lobe is larger than the left. The liver receives 1.5 liters of blood per minute, which is about 25% of cardiac output, and uses only 20% of the total amount of oxygen consumed by the body.

The liver has a dual circulatory system: through the portal vein and the common hepatic artery. The hepatic artery is a high-pressure vessel and has high peripheral resistance. The portal hepatic vein does not have a valve apparatus. Hepatic blood flow is regulated by the sympathetic part of the autonomic nervous system. Hypersympathicotonia is accompanied by a decrease in the intensity of blood flow in the liver. As a result, in shock and other conditions accompanied by an increase in the tone of the sympathetic part of the autonomic nervous system, the blood of the liver vessels is a reserve for replenishing the volume of circulating blood.

The liver consists of stroma and parenchyma. The parenchyma is formed by glandular cells-hepatocytes. The main functional and morphological unit of the liver is the hepatic lobule (Scheme 6).

The liver lobules are connected to each other by stroma. The hepatic lobule is conventionally divided into central, intermediate and peripheral zones. Between the lobules there is a portal triad, which is formed by the interlobular bile ducts, interlobular arteries and veins (belonging to the hepatic portal vein system). The radial spaces between hepatocytes are called sinusoids. They direct mixed blood from the common hepatic artery and hepatic portal vein to the center of the lobule, from where it drains into the central veins. The central veins unite with each other and form the hepatic veins, which flow into the inferior vena cava.

Hepatocytes are glandular liver cells measuring 18-40 microns. Their sizes can change during the day depending on the degree of filling of the vascular bed with blood and the intensity of metabolic processes. Hepatocytes in the peripheral parts of the liver lobules perform a storage function and take part in detoxification processes. In the hepatocytes of the central parts of the liver, the processes of metabolism and excretion of substances of exo- and endogenous origin into the bile ducts are carried out.

Each liver cell participates in the formation of several bile canaliculi. In the biliary section of hepatocytes, substances are excreted into the bile ducts. More than 10 % The liver masses are made up of stellate reticuloendotheliocytes (the so-called Kupffer cells). Biotransformation of drugs, toxins and metabolic products occurs in the smooth endoplasmic reticulum of hepatocytes, regardless of their localization in the lobule. The process of bile excretion is disrupted when hepatocytes are damaged and parenchymal hepatitis develops, which leads to jaundice. Direct damage to the structural elements of the liver (at the level of the genetic apparatus, due to hypoxia, circulatory disorders, intoxication, purulent-septic diseases, infections, obstruction of the bile ducts) predetermines the development of liver diseases and acute liver failure.

Basic liver functions

Main functions of the liver:

Metabolism of carbohydrates, proteins and fats.

Neutralization of drugs and toxins.

Depot of glycogen, vitamins A, B, C, E, as well as iron and copper.

Blood reservoir.

Bacteria filtration, endotoxin degradation, lactate metabolism.

Excretion of bile and urea.

Immunological function with the synthesis of immunoglobulins and phagocytic activity due to Kupffer cells.

Hematopoiesis in the fetus.

Protein metabolism. The liver plays a major role in the metabolism and anabolism of proteins, removes amino acids from the blood for their subsequent participation in the processes of gluconeogenesis and protein synthesis, and also releases amino acids into the blood for use by peripheral cells. Therefore, the liver is of great importance in the processes of utilization of amino acids and removal of nitrogen from the body in the form of urea. It synthesizes such important proteins as albumins (which maintain colloid-osmotic pressure in the circulatory system), globulins - lipoproteins and glycoproteins that perform a transport function (ferritin, ceruloplasmin, a 1 -antitrypsin, a 2 -macroglobulin), complement factors and haptoglobins, binding and stabilizing free hemoglobin. Also, under conditions of physiological stress, acute phase proteins are synthesized in the liver: antithrombin III, a-glycoprotein and C-reactive protein. Almost all blood clotting factors are synthesized in the liver. Coagulopathies can occur both with insufficiency of the synthetic function of the liver and with insufficiency of bile excretion, which leads to a decrease in the absorption of vitamin K, which is involved in the synthesis of factors II (prothrombin), VII, IX, X.

Protein catabolism. Amino acids are decomposed by transamination, deamination and decarboxylation. The product of this decomposition is acetyl coenzyme A, which is included in the citric acid formation cycle. The end product of amino acid metabolism is ammonia. It is toxic, therefore it is excreted from the body in the form of a non-toxic product - urea. Urea is synthesized from ammonia in the ornithine cycle, which is an endothermic process (Scheme 7).

Creatinine is also synthesized in the liver from methionine, glycine and arginine. Phosphocreatinine, which is synthesized in muscles, serves as an energy source for ATP synthesis. Creatinine is formed from phosphocreatinine and is excreted in the urine.

During fasting, the liver maintains glucose homeostasis through gluconeogenesis and the production of ketone bodies. Also functions as a glycogen depot. Glycogenolysis and gluconeogenesis occur in it when glycogen stores are depleted.

Metabolism of fats. The liver synthesizes fatty acids and lipoproteins; it is also the organ in which the synthesis of endogenous cholesterol and prostaglandin occurs.

Metabolism of bilirubin . Hemoglobin is broken down into heme and globin during metabolism. Globin enters the pool of amino acids. The tetrapyrole ring of heme breaks, as a result of which an iron atom is released from it, and the heme is converted into biliverdin. Next, the enzyme biliverdin reductase converts biliverdin into bilirubin. This bilirubin remains bound to albumin in the blood as unconjugated, or free, bilirubin. It then undergoes glucuronidation in the liver, and in the process, conjugated bilirubin is formed, most of which enters the bile. The remainder of the conjugated bilirubin is partially reabsorbed into the circulation and excreted by the kidneys as urobilinogen, and partially excreted in the feces as stercobilin and stercobilinogen (Scheme 8).

Bile production. During the day, the liver produces about 1 liter of bile, which enters the gallbladder and is concentrated in it to 1/5 of its primary volume. Bile consists of electrolytes, proteins, bilirubin, bile acids and their salts. Bile acids are formed in the liver from cholesterol. In the intestinal contents, with the participation of bacteria, they are converted into secondary bile acids, which are then bound into bile salts. Bile salts emulsify fats and fat-soluble vitamins A, E and K to ensure their subsequent absorption.

Acute liver failure is a pathological condition that occurs as a result of the action of various etiological factors, the pathogenesis of which is hepatocellular necrosis and inflammation with further impairment or loss of basic liver functions. Acute liver failure is one of the most severe complications of therapeutic, infectious and surgical diseases, as well as acute poisoning as a component of multiple organ failure syndrome in any critical condition, in particular with exacerbation of chronic liver disease. The survival rate for children under 14 years of age with acute liver failure is 35%, for those over 15 years of age - 22%, and for adults over the age of 45 years - 5%.

Regardless of the cause of liver failure, its main manifestations are always the same, since it affects one or more of the following basic liver functions:

1) protein-synthetic (production of albumins, amino acids, immunoglobulins, blood clotting factors);

2) metabolism of carbohydrates (glycogenesis, glycogenolysis, gluconeogenesis) and fats (synthesis and oxidation of triglycerides, synthesis of phospholipids, lipoproteins, cholesterol and bile acids);

3) detoxifying (neutralization of ammonia, toxins and medicinal substances);

4) maintaining the acid-base state in the body through lactate metabolism and pigment metabolism (synthesis of bilirubin, conjugation and excretion into bile);

5) exchange of biologically active substances (hormones, biogenic amines), vitamins (A, D, E, K) and microelements.

Depending on the time of onset of symptoms, they are distinguished:

fulminant form of liver failure(its main symptoms of deficiency develop no less than 4 weeks before its full clinical manifestation);

acute liver failure(forms against the background of various diseases of the liver and biliary tract for 1-6 months);

chronic liver failure (develops gradually as a result of acute and chronic liver diseases or hepatic ducts for more than 6 months).

Acute liver failure occurs when 75-80% of the liver parenchyma is affected.

There are three types of acute liver failure:

1) acute hepatocellular (hepatocellular) failure, which is based on dysfunction of hepatocytes and the drainage function of the biliary system;

2) acute portocaval (“shunt”) insufficiency resulting from portal hypertension;

3) mixed acute liver failure.

The liver is one of the most important human organs, but very few people know what functions it performs. Some have heard that the liver “cleanses the body,” others know a little about bile.

Meanwhile, the liver is a true “universal soldier” that performs more than 500 different functions in our body!
Conventionally, all the functions of this important and, by the way, the largest internal organ can be divided into three large “blocks”:

- external function – formation and secretion of bile;

Internal function - metabolism and hematopoiesis;

Barrier function – protecting the body from toxins and other harmful substances.

External function. Bile plays an important role in digestion - without its participation, most foods could not be digested. And the liver is a “factory” for the production of bile, which works non-stop: during the day, 500 ml is secreted. up to 1.2 l. bile. When the digestion process is absent, it accumulates in a very concentrated form in the gallbladder.

Internal function. The liver has a lot of internal functions: from the metabolism of proteins and carbohydrates to the breakdown of hormones and blood clotting:

1. Protein metabolism - thanks to enzymes, the liver breaks down, processes and rearranges amino acids. And if an insufficient amount of protein enters the human body, the liver secretes reserve protein “for general needs.”

2. Carbohydrate metabolism: the liver processes glucose, lactic acid and substances formed during the breakdown of proteins and fats into glycogen. As soon as the body needs glucose, the liver converts stored glycogen back into glucose and “feeds” it into the blood.

3. Metabolism of vitamins - the liver secretes bile acids, due to which fat-soluble vitamins are transported to the intestines. Certain vitamins are retained as “reserves” in the liver until the body’s deficiency period.

4. Metabolism of microelements: the liver promotes the metabolism of manganese and cobalt, zinc and copper.

5. The liver breaks down the following hormones: thyroxines, aldosterones, blood pressure, and insulin. In addition, the liver functions as a stabilizer of the body’s hormonal balance.

6. The liver synthesizes substances that affect the blood clotting process.

7. The liver is the main source of blood enrichment, as well as a blood reserve, its “depot”.

Barrier function. One of the key purposes of cookies is to “protect” our body. It's hard to imagine, but every moment the body is constantly exposed to toxins, and the liver continuously functions as a filter throughout life, repelling these attacks.

Good liver function is the key to the health of the whole body. But the liver, as the main “workaholic”, needs our support. To help the process of strengthening and restoring the functioning of liver cells, doctors often prescribe a course of hepatoprotector. The main active ingredient of this drug is obtained from the liver of young cattle.

The important components of this combined hepatoprotector are choline, cysteine, myo-inositol, as well as microelements - magnesium, zinc, chromium and selenium - in combination they promote the transport and metabolism of fats in the liver and affect carbohydrate metabolism.

Modern hepatoprotectors also regulate the level of insulin in the blood, support energy metabolism, have an antioxidant effect, help preserve and restore cell structure, protect the liver from the effects of alcohol, smoking, and toxic substances.

Inflammatory processes in the liver lead to the destruction of hepatocytes - the cells of this organ. The problem can be solved by taking complex preparations based on glycyrrhizic acid and phospholipids. Positive treatment results can be achieved thanks to drugs based on active ingredients that have undergone numerous clinical studies. “Phosphogliv” is an example of a modern combination drug that can help at all stages of liver damage:

• optimal composition of active components;
• anti-inflammatory effect;
• favorable safety profile;
• over-the-counter release from pharmacies.

An integrated approach to liver treatment is not only eliminating the cause of damage to hepatocytes, but also their restoration.

The human liver: where is it located, what functions does it perform and why is the prevention of diseases of this organ so important?

One of the most important organs of our body is the liver. It performs many functions. That is why the manifestations of liver diseases are so varied. At the same time, non-specialists, as a rule, have little idea of ​​the role of the organ and the consequences of failures in its operation. The heart pumps blood, we breathe through the lungs, food is digested in the stomach, and what is the liver doing at this time? Let's try to understand the tasks of the organ and understand what can cause it to fail.

The structure and location of the human liver

The liver is a fairly large organ: its weight is 1/40 of the body weight of an adult and 1/20 of a newborn. The liver is located under the diaphragm and occupies almost the entire upper right part of the abdominal cavity. Therefore, diseases of the organ manifest themselves as pain and discomfort in the right hypochondrium. It is worth saying that the liver does not have pain receptors, so all the unpleasant sensations in the area where the organ is located are associated with an increase in its size and stretching of the liver capsule, caused by various lesions.

The functions of the liver in producing bile are closely related to the work of the gallbladder, a small sac located directly under the liver. It stores the unused part of the bile.

Functions of the organ

The liver performs about 70 important functions. It is involved in 97% of all processes in the body. It is difficult to list everything in one article, so we will limit ourselves to the main ones:

• Protecting the body from toxins . The liver filters the blood and neutralizes all toxins that enter our body from the outside or are formed as a result of decay reactions.
• Participation in the regulation of hormonal levels . The human liver is involved in the synthesis of hormones, as well as in the elimination of their excess.
• Participation in digestion . The liver produces bile, without which digestion is impossible. Thanks to it, fats are broken down in the intestines. Nutrient storage . A healthy human liver can store vitamins and minerals and use them when the need arises. In addition, it itself converts some substances into vitamins - for example, carotene - into vitamin A.
• Protecting the body from infections and bacteria . The liver is one of the main outposts on the path of pathogenic microorganisms. It passes all the blood of our body through itself, and during the filtration process, special cells of the immune system neutralize most bacteria.
• Participation in exchange processes . The liver is involved in the metabolism of fats, proteins and carbohydrates.

Major diseases

The most common liver diseases include hepatosis, hepatitis (inflammation in the liver) And cirrhosis.

Hepatosis, or, as it is also called, fatty degeneration, is a disease caused by the accumulation of fat in the liver. Most often, people aged 40 to 56 years suffer from this disease. Very often, hepatosis develops against the background of obesity and diabetes. The risk group also includes overweight people and those who do not adhere to a healthy diet, leaning on fatty and fried foods, as well as drinkers. Hepatosis develops unnoticed and can manifest itself as heaviness in the right side, nausea, heartburn, weakness, and problems with stool. According to statistics, fatty hepatosis in 40% of cases subsequently develops into hepatitis, fibrosis and cirrhosis.

Hepatitis- a term that combines acute and chronic inflammatory liver diseases of various etiologies. Most often, the cause of hepatitis is a viral infection (hepatitis A, B and C) or toxic liver damage, including alcohol. The most dangerous is hepatitis C, which is difficult to cure completely. There are no characteristic signs of hepatitis. However, it may be accompanied by pain in the right side, yellow discoloration of the skin and whites of the eyes, and changes in the color of urine and feces. The Russian Ministry of Health characterizes the epidemic situation in the country regarding viral hepatitis as unfavorable.

Cirrhosis- the disease is even more serious. In cirrhosis, liver cells die and are replaced by fibrous connective tissue. The prognosis is alarming - the liver increases in size or, conversely, shrinks, blood circulation is disrupted and ultimately the liver ceases to function. According to statistics, 15–40 people per 100 thousand die from liver cirrhosis every year in different countries, and up to 40 million people die from cirrhosis every year in the world. Cirrhosis is especially dangerous because in 80% of cases it is asymptomatic and manifests itself only when the situation becomes critical.

Due to the deplorable situation regarding liver diseases, doctors believe that in the next 10–20 years the number of patients with liver cirrhosis will increase by 60%, liver cancer - by 68%, and mortality from other liver diseases will double. And this is also a relatively optimistic forecast, suggesting that the rate of spread of diseases will remain the same or slow down.

Important!
According to statistics, cirrhosis sooner or later develops in 5% of overweight people, and fatty liver in 65% of cases.

Causes of pathological processes

A variety of factors can destroy the liver (and at the same time your health). Here are the most common ones:

Alcohol and toxins

Alcohol and toxic injuries account, according to various estimates, from 40 to 50% of all human liver pathologies. Alcohol is broken down in the liver, but if consumed excessively, this organ simply does not have time to cope with the amount of work. For liver cells, ethyl alcohol is a highly toxic poison. It promotes the growth of connective tissue, which leads to liver fibrosis. The most common causes of alcohol are fatty liver disease, alcoholic hepatitis and fibrosis. Without timely treatment, all these diseases can outgrow cirrhosis - even if the person refuses to drink.

There are a lot of myths around alcohol and its effects on the liver, and they should be discussed separately. You can often hear from various “experts” that the main thing is to drink wisely, drink certain drinks, or carry out “rehabilitation” after a party with brine, broth and a shot of vodka. These are all myths and nothing more. For the liver, the concept of a “safe dose” does not exist. WHO has calculated a conditionally safe daily dose, and it is approximately 20 grams of ethyl alcohol per day (±5 grams depending on a person’s height, weight, age and even nationality), provided that the alcohol is of the highest quality, liver and all other systems the body is ideally healthy, the person leads a healthy lifestyle and does not drink alcohol at all at least 2 days a week. This dose is equivalent to one small glass of vodka or cognac, a glass of wine or a small bottle of beer. For women, the generally safe dose is half as much. “Conditionally safe” does not in any way mean “useful”. For the liver, even a teaspoon of vodka is already additional work and unnecessary harm. But if she can still cope with one glass as usual, then two or three is already an emergency mode, an overload and, as a result, the death of liver cells. It doesn’t matter at all whether you feel intoxicated or not.

Infections

Viral hepatitis is a common cause of viral liver disease. Hepatitis A is transmitted through dirty water or food; this type of hepatitis is easily treated and does not cause irreversible damage to the liver. Hepatitis B and C spread through the blood and other body fluids; they often become chronic and lead to cirrhosis. In the case of hepatitis C, the main goal of therapy is eradication (removal) of the virus from the body.

Poor nutrition

Fast food, an abundance of fatty and fried foods, an addiction to spicy and salty foods, a poor diet - all this leads to excess weight gain and a lack of vitamins B, C, E, D and A necessary for the liver. Not only excess weight can cause harm, but also its sudden loss - the body considers this situation as an emergency, and the liver begins to accumulate carbohydrates and fats, as it receives a signal from the brain: “hunger has come!” Let's stock up on nutrients!"

Diabetes mellitus

Common companions of diabetes are fatty hepatosis and liver failure. Fatty liver in diabetes is caused by the process of fat breakdown getting out of control and causing fat to accumulate in the liver cells.

Signs of a diseased liver

Only a doctor can determine the presence of liver disease, and only after a blood test and instrumental studies - for example, ultrasound, CT and MRI. But the patient himself may suspect liver damage based on some signs.

Asthenic symptoms . Weakness, fatigue, constant drowsiness are the first “bells” of a diseased liver. These symptoms are a consequence of impaired neutralization of nitrogen metabolism products in the liver.

Pain . There are no nerve cells in the liver, and it cannot hurt on its own. But with lesions, it increases in size and puts pressure on the capsule surrounding it - but in this capsule there are already pain receptors. Therefore, disturbances in liver function are accompanied by extremely unpleasant sensations. How does a person’s liver hurt? It all starts with a feeling of heaviness in the right hypochondrium, which is replaced by a dull aching pain. After eating, the discomfort intensifies. Pain that increases every day is a sign of a tumor or cyst. A sharp, almost unbearable pain, called hepatic colic, means that one of the ducts is blocked by a stone. Digestive disorders. People with liver disease often complain of flatulence, diarrhea, nausea or even vomiting, decreased appetite and a bitter taste in the mouth.

Jaundice . Yellowing of the skin and whites of the eyes is a sure sign of a diseased liver. This is due to a violation of bile transport or bilirubin metabolism.

Bad skin . A diseased human liver cannot properly protect the body from toxins and bacteria. The attack of poisons and pathogenic microorganisms is instantly reflected on the skin - pimples and rashes appear. Liver diseases are also characterized by the appearance of spider veins - they appear due to the fact that the vessels become fragile and blood clotting is impaired.

By the way
The number of people in the world suffering from liver diseases is 200 million. Liver disorders are among the top 10 most common causes of death. In most cases, the liver suffers due to viruses and toxins.

Prevention of liver diseases

What can be done to protect the liver and help this vital organ cope with its responsibilities?

First, review your diet and give up foods that negatively affect liver function - first of all, fatty and fried foods, trans fats (margarine, etc.), hot spices, vinegar, marinades, white bread and pastries, mushrooms, many fatty foods dairy products. The majority of the diet should consist of a variety of vegetables, cereals and pasta, lean boiled or baked meat and fish, and wholemeal bread. It has been noticed that Asian peoples, who eat mainly vegetables and rice with a small amount of chicken or seafood, suffer from liver diseases much less often than Europeans. Needless to say, alcohol and a healthy liver are incompatible?

Secondly, you should monitor your body weight, without justifying your laziness by saying that “there should be a lot of good people.” Slimness is a matter not only of attractiveness, but also of health and, ultimately, life expectancy.

Thirdly, never take medications without a doctor's prescription. Many seemingly harmless pills for colds, migraines and other ailments create a serious burden on the liver, which only increases if you take several medications at the same time. Antibiotics should be taken with extreme caution.

Fourth, protect yourself from exposure to toxins. Sources of poisons can be the most common things - household chemicals, low-quality repair and finishing materials, synthetic fabrics and plastic products. Buy only safe products that have all the necessary certificates of conformity, do not walk along roads and be careful when working with potentially dangerous chemicals - acetone, chlorine, solvents, paints and enamels.

And finally, if you have risk factors, you can help your liver by taking hepatoprotective medications. This will strengthen the liver cells and minimize the damage that we cause to this organ every day.

Prophylactic drugs

Hepatoprotectors - means for preventing liver diseases and improving its activity - are very widespread today. They have proven their effectiveness and saved the health of many people. The hepatoprotector market is very large and includes hundreds of items. Particularly popular are hepatoprotectors, which contain phospholipids - substances of plant origin, which in the human body are the main component of cell walls, including liver cells. Medicines with phospholipids help restore damaged liver cells and stimulate their regeneration. However, phospholipids alone cannot combat inflammation, which is a common cause of liver disease. That is why pharmacists around the world are looking for a combination of substances that would simultaneously stop inflammatory processes and protect liver cells from destruction. Today, one of the most effective combinations is phospholipids with glycyrrhizic acid. Glycyrrhizic acid, which occurs naturally in licorice root, not only eliminates inflammation, but has antioxidant and antifibrotic effects. The effectiveness of glycyrrhizic acid and essential phospholipids has been proven in clinical studies and in practice. That is why the combination based on glycyrrhizic acid and essential phospholipids is the only one included in the list of vital and essential medicines in the section “Drugs for the treatment of liver diseases”, annually approved by the Government of the Russian Federation. Thanks to its inclusion in this list, its price is regulated by the state.

Tuesday, 04/10/2018

Editorial opinion

Hepatoprotectors are drugs whose effect appears gradually. You need to take such drugs in a course (usually from 3 months, depending on the condition of the liver). The vast majority of hepatoprotectors are safe and are sold in pharmacies without a prescription, however, some of them have contraindications, so you should consult your doctor before taking them.

The liver is an abdominal glandular organ in the digestive system. It is located in the right upper quadrant of the abdomen under the diaphragm. The liver is a vital organ that supports almost every other organ to one degree or another.

The liver is the second largest organ of the body (the skin is the largest organ), weighing about 1.4 kilograms. It has four lobes and a very soft structure, pink-brown color. Also contains several bile ducts. There are a number of important liver functions that will be discussed in this article.

The liver is an abdominal glandular organ in the digestive system

Physiology of the liver

Human liver development begins during the third week of pregnancy and reaches mature architecture before age 15. It reaches its largest relative size, 10% of the fetal weight, around the ninth week. This is about 5% of the body weight of a healthy newborn. The liver makes up about 2% of an adult's body weight. Weighs about 1400 g for an adult woman and about 1800 g for a man.

It is located almost entirely behind the chest, but the lower edge can be felt along the right costal arch during inspiration. A layer of connective tissue called Gleason's capsule covers the surface of the liver. The capsule extends to all but the smallest vessels in the liver. The falciform ligament attaches the liver to the abdominal wall and diaphragm, dividing it into a large right lobe and a small left lobe.

In 1957, French surgeon Claude Couinaud described 8 liver segments. Since then, radiographic studies have described an average of twenty segments based on the distribution of the blood supply. Each segment has its own independent vascular branches. The excretory function of the liver is represented by bile branches.

What is each of the liver lobes responsible for? They serve arterial, venous and biliary vessels in the periphery. The lobules of the human liver have small connective tissue separating one lobule from the other. Insufficiency of connective tissue makes it difficult to determine the portal tracts and the boundaries of individual lobules. Central veins are easier to identify because of their large lumen and because they lack the connective tissue that envelops the portal triad vessels.

1. The role of the liver in the human body is diverse and performs more than 500 functions.
2. Helps maintain blood glucose and other chemical levels.
3. Bile secretion plays an important role in digestion and detoxification.

Because of its many functions, the liver is susceptible to rapid damage.

The liver plays an important role in the functioning of the body, detoxification, metabolism

What functions does the liver perform?

The liver plays an important role in the functioning of the body, detoxification, metabolism (including regulation of glycogen storage), hormone regulation, protein synthesis, breakdown and breakdown of red blood cells, in a nutshell. The liver's main function is to produce bile, a chemical that breaks down fats and makes them more easily digestible. Carries out the production and synthesis of several important elements of plasma, and also stores several vital nutrients, including vitamins (especially A, D, E, K and B-12) and iron. The liver's next function is to store the simple sugar glucose and convert it into useful glucose if blood sugar levels drop. One of the liver's best known functions is as a detoxification system, removing toxic substances from the blood such as alcohol and drugs. It also destroys hemoglobin, insulin and maintains hormone levels in balance. In addition, it destroys old blood cells.

What other functions does the liver perform in the human body? The liver is vital for healthy metabolic function. It converts carbohydrates, lipids and proteins into useful substances such as glucose, cholesterol, phospholipids and lipoproteins, which are then used in various cells throughout the body. The liver breaks down unusable parts of proteins and converts them into ammonia and eventually urea.

Exchange

What is the metabolic function of the liver? It is an important metabolic organ, and its metabolic function is controlled by insulin and other metabolic hormones. Glucose is converted to pyruvate through glycolysis in the cytoplasm, and pyruvate is then oxidized in the mitochondria to produce ATP through the TCA cycle and oxidative phosphorylation. In this state, glycolytic products are used for the synthesis of fatty acids through lipogenesis. Long chain fatty acids are incorporated into triacylglycerol, phospholipids and/or cholesterol esters in hepatocytes. These complex lipids are stored in lipid droplets and membrane structures or secreted into the circulation as low-density lipoprotein particles. In a fasted state, the liver tends to release glucose through glycogenolysis and gluconeogenesis. During short fasting, hepatic gluconeogenesis is the main source of endogenous glucose production.

Fasting also promotes lipolysis in adipose tissue, which leads to the release of non-esterified fatty acids, which are converted to ketone bodies in liver mitochondria, despite β-oxidation and ketogenesis. Ketone bodies provide metabolic fuel for extrahepatic tissues. Based on human anatomy, liver energy metabolism is closely regulated by neural and hormonal signals. While the sympathetic system stimulates metabolism, the parasympathetic system suppresses hepatic gluconeogenesis. Insulin stimulates glycolysis and lipogenesis but inhibits gluconeogenesis, and glucagon opposes the action of insulin. Multiple transcription factors and coactivators, including CREB, FOXO1, ChREBP, SREBP, PGC-1α, and CRTC2, control the expression of enzymes that catalyze key steps in metabolic pathways, thereby controlling energy metabolism in the liver. Aberrant energy metabolism in the liver contributes to insulin resistance, diabetes, and nonalcoholic fatty liver disease.

The barrier function of the liver is to provide protection between the portal vein and systemic circulations

Protective

The barrier function of the liver is to provide protection between the portal vein and systemic circulations. In the reticuloendothelial system it is an effective barrier against infection. Also acts as a metabolic buffer between highly variable intestinal contents and portal blood, and tightly controls systemic circulation. By absorbing, storing and releasing glucose, fat and amino acids, the liver plays a vital role in homeostasis. It also stores and releases vitamins A, D and B12. Metabolizes or detoxifies most biologically active compounds absorbed from the intestines, such as drugs and bacterial toxins. Performs many of the same functions when administering systemic blood from the hepatic artery, processing a total of 29% of cardiac output.

The liver's protective function is to remove harmful substances (such as ammonia and toxins) from the blood and then neutralize them or convert them into less harmful compounds. In addition, the liver converts most hormones and changes them into other more or less active products. The barrier role of the liver is represented by Kupffer cells - absorbing bacteria and other foreign substances from the blood.

Synthesis and cleavage

Most plasma proteins are synthesized and secreted by the liver, the most abundant of which is albumin. The mechanism of its synthesis and secretion has recently been presented in more detail. Synthesis of the polypeptide chain is initiated on free polyribosomes with methionine as the first amino acid. The next segment of the protein produced is rich in hydrophobic amino acids, which likely mediate the binding of albumin-synthesizing polyribosomes to the endoplasmic membrane. Albumin, called preproalbumin, is transported into the interior of the granular endoplasmic reticulum. Preproalbumin is reduced to proalbumin by hydrolytic cleavage of 18 amino acids from the N-terminus. Proalbumin is transported to the Golgi apparatus. Finally, it is converted to albumin just before secretion into the bloodstream by removing six more N-terminal amino acids.

Some of the metabolic functions of the liver in the body are protein synthesis. The liver is responsible for many different proteins. Endocrine proteins produced by the liver include angiotensinogen, thrombopoietin, and insulin-like growth factor I. In children, the liver is primarily responsible for heme synthesis. In adults, the bone marrow is not the heme production apparatus. However, the adult liver carries out 20% of heme synthesis. The liver plays a critical role in the production of almost all plasma proteins (albumin, alpha-1-acid glycoprotein, most of the coagulation cascade and fibrinolytic pathways). Notable exceptions: gamma globulins, factor III, IV, VIII. Proteins produced by the liver: protein S, protein C, protein Z, plasminogen activator inhibitor, antithrombin III. Vitamin K-dependent proteins synthesized by the liver include: Factors II, VII, IX and X, protein S and C.

Endocrine

Every day, the liver secretes about 800-1000 ml of bile, which contains bile salts necessary for digesting fats in the diet.

Bile is a medium for the excretion of certain metabolic wastes, drugs and toxic substances

Bile is also a medium for the excretion of certain metabolic wastes, drugs and toxic substances. From the liver, a system of channels carries bile to the common bile duct, which empties into the duodenum of the small intestine and connects to the gallbladder, where it is concentrated and stored. The presence of fat in the duodenum stimulates the flow of bile from the gallbladder into the small intestine.

The endocrine functions of the human liver include the production of very important hormones:

• Insulin-like growth factor 1 (IGF-1). Growth hormone released from the pituitary gland binds to receptors on liver cells, causing them to synthesize and release IGF-1. IGF-1 has insulin-like effects because it can bind to the insulin receptor and also stimulates body growth. Almost all cell types respond to IGF-1.
• Angiotensin. It is a precursor of angiotensin 1 and is part of the Renin-Angiotensin-Aldosterone system. It is converted to angiotensin by renin, which in turn is converted to other substrates that act to increase blood pressure during hypotension.
• Thrombopoietin. The negative feedback system works to maintain this hormone at the appropriate level. Allows bone marrow progenitor cells to develop into megakaryocytes, the precursors of platelets.

Hematopoietic

What functions does the liver perform in the process of hematopoiesis? In mammals, soon after liver progenitor cells invade the surrounding mesenchyme, the fetal liver is colonized by hematopoietic progenitor cells and temporarily becomes the primary hematopoietic organ. Research in this area has shown that immature liver progenitor cells can generate an environment that supports hematopoiesis. However, when liver progenitor cells are induced to mature, the resulting cells can no longer support blood cell development, consistent with the movement of hematopoietic stem cells from the fetal liver to the adult bone marrow. These studies indicate that there is a dynamic interaction between the blood and parenchymal compartments within the fetal liver that controls the timing of both hepatogenesis and hematopoiesis.

Immunological

The liver is a critical immunological organ with high exposure to circulating antigens and endotoxins from the gut microbiota, especially enriched in innate immune cells (macrophages, innate lymphoid cells, mucosal-associated invariant T cells). In homeostasis, many mechanisms provide suppression of immune responses, which leads to addiction (tolerance). Tolerance is also relevant for chronic persistence of hepatrotropic viruses or allograft ingestion after liver transplantation. The detoxifying function of the liver can quickly activate the immune system in response to infections or tissue damage. Depending on the underlying liver disease, such as viral hepatitis, cholestasis, or nonalcoholic steatohepatitis, different triggers mediate immune cell activation.

Conserved mechanisms, such as molecular danger patterns, toll-like receptor signaling, or inflammasome activation, initiate inflammatory responses in the liver. Excitatory activation of hepatocellulose and Kupffer cells leads to chemokine-mediated infiltration of neutrophils, monocytes, natural killer (NK) cells, and natural killer T (NKT) cells. The ultimate outcome of the intrahepatic immune response to fibrosis depends on the functional diversity of macrophages and dendritic cells, but also on the balance between pro-inflammatory and anti-inflammatory T cell populations. Tremendous advances in medicine have helped to understand the fine-tuning of immune responses in the liver from homeostasis to disease, indicating promising targets for future treatments for acute and chronic liver diseases.

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Structure and functions of the liver.

Good liver function guarantees the health of the entire body.

The functions of the liver are numerous, but there are two irreplaceable ones: it purifies all the blood that saturates every cell of our body, and, by taking part in the digestion process, it helps to obtain the energy necessary for life. Moreover, both functions of the liver are not performed simultaneously, but in accordance with natural biological rhythms. Cleansing the blood of toxins and their accumulation in bile occurs at night, when all other body systems are resting. Therefore, if a person has breakfast between 5 and 7 o’clock in the morning or at least drinks half a glass of juice or herbal decoction, the toxic bile at night will be released into the digestive system, and then the toxins will not poison him all day.

This way you can prevent constipation, hemorrhoids, gastritis, biliary dyskinesia, cholelithiasis, cholangitis, and uric acid diathesis.

Every day, the liver secretes from half a kilo to a kilogram of bile, which is simply necessary for digestion.
The liver also serves as a link connecting two systems - circulatory and digestive. If this complex mechanism is upset, the heart, stomach and intestines become ill.

When a pregnant woman drinks a lot of coffee, drinks alcohol, smokes, or takes antibiotics, she runs the risk of giving birth to a child with an already diseased liver.

These are just the basic functions of the liver. And in total there are more than five hundred of them!

Metabolism regulation

It takes part in the processing of fats and proteins, and stores nutrients in it, including glycogen, which is necessary during stress. For other systems, it seems to serve as a “cover” from a strong release of norepinephrine and adrenaline.

The protective functions of the liver are indispensable in the processes of food digestion and metabolism. Complex chemical reactions take place in it. The liver retains, processes, distributes, assimilates and destroys substances entering it from various organs (spleen, intestines) and tissues. At the same time, from these substances it produces new products needed by the body.

Bile, which is produced by the liver, plays an important role in digestion. Bile is produced non-stop: during the day, at least 500 ml and maximum 1.2 liters are released. When the digestion process is absent, it accumulates in a very concentrated form in the gallbladder. Its saturation is explained by the very small volume of the gallbladder: no more than 30-40 ml. In liver cells, bile is formed from substances that come from the blood. In other words, bile pigments are the result of the breakdown of hemoglobin. Both bile pigments and acids are the most important components that make up bile. In addition, it contains mucin, cholesterol, soaps, lecithin, inorganic salts and fats.

Bile formation is also stimulated by humoral factors. These include those products that are obtained as a result of the processing of fats and proteins, gastrin, as well as bile itself.
The excretion of bile is regulated by humoral and neuroreflex mechanisms. The vagus and sympathetic nerves transmit the influence of stimuli (conditioned and unconditioned) to the bladder and its ducts. When the vagus nerve is slightly irritated, then the sphincter in the common bile duct relaxes and the bladder muscles contract. Only after this can bile enter the duodenum.

When the vagus nerve is more irritated, it leads to the opposite effect - the sphincter contracts, and the muscles of the bladder relax and bile accumulates in it. Artificial stimulation of the sympathetic nerve produces the same effect as stimulation of the vagus nerve.

The most important humoral regulator of bile excretion, cholecystokinin, is formed in the duodenum, in its mucous membrane. Thanks to it, the gallbladder contracts and empties during digestion.
The flow of bile begins five to ten minutes after eating. The gallbladder is completely empty three to five hours after the last meal. Small portions of bile from it enter the intestines every hour or two. Its secretion increases significantly during the simultaneous entry of food into the intestines and depends on the nature of the nutrients.

The functional purpose of bile is that it activates lipase (enzyme), emulsifies fats (lipase affects already emulsified fats), while increasing the area of ​​their collision with the enzyme, due to which its effect is significantly enhanced.

Absorption and breakdown of fats

Bile is important in the absorption of fats. One of the products of their breakdown is fatty acids. They can be absorbed only after they combine with bile acids. The absorption of these compounds is explained by their good solubility in water. The motor function of the intestines is also stimulated by bile.

Regulating Blood Glucose Levels

Participation in the process of metabolism of fats, carbohydrates and proteins is also included in the functions of the liver. It regulates the stability of blood sugar levels. When the concentration of glucose in the blood increases, glycogen is formed from it in the liver and then deposited. As soon as the blood sugar level drops, glycogen is broken down in the liver into glucose, which again returns to the blood, and thus the sugar content in it returns to normal.

Protein metabolism

The functions of the liver also include influence on protein metabolism. It retains more protein than other organs (30-60%). There are also protein substances that, coming from the digestive canal to the portal vein, are processed in it and degreased. Blood plasma proteins - albumin, fibrinogen and others - are also formed in the liver. It produces antithrombin and prothrombin, which are necessary for blood clotting. Therefore, with a liver ulcer, the blood clotting process is disrupted.

Vitamin synthesis

Liver functions are directly related to participation in vitamin metabolism. Vitamin A is synthesized in this organ, nicotinic acid and vitamin K are deposited.

Water-salt metabolism

Water-salt metabolism also does not occur without the participation of the liver. It is in it that ions of iron, chlorine, and bicarbonates are retained.
It also participates in fat metabolism. Fat is deposited in it, which first enters the portal vein, and then passes into an unsaturated form, which is easily oxidized. From the number of fatty acids in this organ, substances such as acetone, glucose, and ketone bodies are formed. It also synthesizes cholesterol and lecithin from fatty acids.
During embryonic development, the liver plays the role of an organ that produces blood.

Protective functions

The protective functions of the liver lie in the ability to neutralize nitrogenous toxic products resulting from the breakdown of proteins - indole, phenol, ammonia and skatole. They turn into urea and are excreted in the urine. Thanks to the ability of phagocytosis, capillary stellate cells fight microbes that enter the body. It was found that after the introduction of microbes into the blood, only half a percent accumulates in the brain tissues, six percent in the lungs, and eighty percent in the liver. It should be noted that the neutralizing effect of the liver is especially pronounced when it is saturated with glycogen. If its level drops, the protective functions of the liver also decrease.