Functions of the liver
Last reviewed: 23.04.2024
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The liver is the largest organ of man. Liver functions are diverse. It participates in the processes of digestion, hematopoiesis and performs numerous functions in the metabolism.
The liver is located in the right hypochondrium and in the epigastric region; has a diaphragmatic and visceral surface. These surfaces converge with each other, forming an acute lower edge of the liver. Isolate the left (smaller) and right (large) portion of the liver, consisting of a square and a caudate lobe. To the diaphragmatic surface of the liver from the diaphragm and the anterior abdominal wall there is a sickle ligament, dividing the right and left lobes from the front. At the back they are separated by a slit in which there is a venous ligament (overgrown venous duct, which connected the fetus with a nocturnal vein with the inferior vena cava).
From below, the lobe of the liver is divided by a gap, where a round ligament of the liver passes (overgrown umbilical vein). At the level of the posterior edge of the slit of the circular ligament and the fossa of the gallbladder are the gates of the liver. They include the portal vein, the hepatic artery, nerves; of them come out the common hepatic duct and lymphatic vessels.
[Digestive function of the liver
Bile produced by the liver plays an important role in digestion processes, providing a change of gastric digestion to the intestinal (IP Pavlov). Bile inactivates pepsin, neutralizes hydrochloric acid found in gastric contents, and enhances the activity of pancreatic enzymes. Salts of bile acids emulsify fats, which leads to their further digestion. Bile promotes active work of enterocytes and their regeneration
In addition, it is involved in stimulating intestinal motility, and also inhibits the growth of opportunistic microflora, which prevents the development of putrefactive processes in the intestine.
On the day the liver of a healthy adult produces 0.6-1.5 l of bile, 2/3 of which is formed as a result of the activity of hepatocytes and 1/3 of the epitheliocytes of the bile ducts. The bile contains bile acids, bile pigments, cholesterol, inorganic salts, soaps, fatty acids, neutral fats, lecithin, urea, vitamins A, B, C and a small amount of amylase, phosphatase, protease, catalase, oxidase.
In the production of bile by hepatocytes, two mechanisms participate: dependent and independent of bile ducts; acids. The final formation of primary bile occurs in the bile ducts. Hepatic bile in its composition differs from vesicular because bile in the gallbladder is exposed to its epithelium. Reabsorption of water and some ions occurs, which leads to an increase in the concentration of gall bladder. That's why, although the volume of the adult gallbladder is normal - 50-60 ml, it can contain the bile produced by the liver for about half a day. At the same time, the pH of the gallbladder usually decreases to 6.5 compared to 7.3-8.0 of the gall bladder. The formation of bile (choleresis) occurs continuously, including during fasting.
Bile excretion (cholekinesis) is regulated by the work of biliary tract sphincters and gallbladder musculature. Out of the digestive process, bile accumulates in the gallbladder, as the sphincter of the common bile duct (Oddi) is closed, and bile can not enter the duodenum. Then the sphincter Mirizzi, located at the junction of the common hepatic and vesicular duct, and the Lutkens sphincter in the neck of the gallbladder are open. After eating, the sphincter of Oddi opens, and the contractile activity of the gallbladder and bile ducts increases. Initially, the duodenum comes in a bubble, then mixed, and then - liver bile.
Non-digestive liver function
An exceptional role of the liver in providing specific reactions of protein, carbohydrate, fat, and mineral metabolism.
In the liver, proteins are synthesized - fibrinogen, prothrombin, other factors that provide mechanisms of hemostasis and anti-coagulation, almost all albumins, globulins, and glycogen. With an increase in the energy expenditure of the body, glycogen is cleaved with the formation of glucose. The involvement of the liver in maintaining blood glucose concentration at the optimal level is associated with increased glycogen degradation in hepatonites under the influence of the sympathetic nervous system, epinephrine, glucagon. In hepatocytes, fat splits to form fatty acids. Short-chain fatty acids are converted here to higher fatty acids.
The liver serves as a depot of proteins, carbohydrates, fats, microelements, vitamins A, D1, D2, K, C, PP.
The liver realizes the barrier function, detoxifying the toxic substances entering the blood from the intestine (indole, phenol, skatole), foreign substances that are not involved in either the plastic or energy processes of the organism (xenobiotics), through the reactions of oxidation, reduction, hydrolysis, as well as reactions of the compound with glucuronic acid, sulfuric acid, clay, glutamine (conjugation reaction). As is known, with deamination of amino acids, nucleotides, other intermediate products of protein metabolism, ammonia is formed in the liver, which is a highly toxic compound. Detoxification of ammonia is carried out during the synthesis of urea, which is then released by the kidneys.
The physiological activity of the liver is interrelated with the metabolism of hormones - protein-peptide, steroid, amino acid derivatives. Protein-peptide hormones are inactivated in the liver by proteinases, steroid-by hydroxylases, catecholamines (adrenaline, noradrenadine, dopamine) are deaminated with the participation of monoamine oxidase.
The liver performs blood depot functions, participates in the destruction of erythrocytes, biochemical transformations of heme with the formation of bile pigments, the liver participates in immune reactions of the body.
Summarizing the above, the functions of the liver can be represented as follows.
- The function of nutrition - the production, processing and accumulation of nutrients (amino acids, fatty acids, carbohydrates, cholesterol and vitamins), absorbed in the digestive tract, the release of metabolites.
- Synthesis of substances - the production of plasma proteins (albumins, coagulation factors, grandsport proteins), the synthesis of binding proteins, modulating the concentration of ions and drugs in the blood.
- Immunological function - participation in the process of transport of immunoglobulins, clearance of antigens in Kupffer cells.
- Hematologic function - synthesis and isolation of coagulation factors, clearance of activated coagulation factors.
- Detoxifying function: the liver is the main site of metabolic transformations of endogenous and exogenous substances.
- The excretory function is the metabolism of bile acids (the synthesis of bile acids from cholesterol, the secretion of bile acids into the intestines, as a result of which their flasks are regulated and effective emulsification and absorption of dietary fats are ensured).
- Endocrine function of the liver - catabolism of a number of hormones (including thyroid and steroid), the metabolism of insulin.