Physiology of the liver

Physiological significance of liver cancer, is involved in intermediate metabolism, is that absorbed from the intestine into the blood substances pass through P. and subjected it to chemical changes. In the liver of a number of substances (fructose, galactose, lactose, glycerin, amino acids) produces glucose from which glycogen is synthesized and stored liver cells (see Carbohydrate metabolism). In Petrograd are composed of lipids acetone bodies (mainly the lack in Petrograd glycogen and diabetes), the most part of cholesterol, bile acids, and also accumulates carotene. Here is deamination pereaminirovanie and amino acids (see Nitrogen metabolism), synthesized blood proteins (albumin, globulins, many of the coagulation factors), urea, uric acid, choline, creatine. In P. destroyed a significant part of hemoglobin; formed bilirubin (see) appears to jelchew in intestine, deposited iron (ferritin).
Ii. participates in maintaining dynamic equilibrium of many substances plasma (sugar, cholesterol, blood proteins, axerophthol, iron, water). Via P. runs about 1.5 liters of blood in 1 min and it is released V7 part of the whole energy of the body. The temperature of flowing of her blood during digestion increases by 1-2 degrees.
For the study of liver resort to delete it off the portal blood flow, the imposition unhistorically tubes on vessels, perfusion of isolated P. After removal., through 3-8 hours. comes hypoglycemia (see), leading to death.
To assess the involvement of liver cells and blood vessels in the transformation of substances submitted in one way or another in the blood, different types of ligation of vessels, including direct and inverse fistula by the Eck-Pavlov, the hepatic artery ligation and all afferent vessels P. (devascularization). Operation fistula Ekka - Pavlova is to impose an anastomosis between the portal vein and the inferior Vena veins.
After this operation and ligation of the portal vein about the liver all the blood from the intestine begins to act in the body, bypassing the liver. Thus the viability of the liver remains, as is blood: the blood flows through the hepatic artery, and flowing through arterio-venous arterio-sinusoidal anastomoses (Fig. 8).


Fig. 8. The scheme of interrelations intrahepatic vessels:
1 - arteries;
2 - bile duct;
3 - lymphatic duct;
4 - the branch of the portal vein;
5 - Central foam;
6 - liver cells;
7 - bile canaliculus;
8 - space of the thesis;
9 - sine waves;
10 - kuperovskaya cells;
11 - input sphincter;
12 - output sphincter;
13 - arteriovenous anastomoses;
14 - the confluence of arterioles in the sinusoids.


In blood portal vein in the digestive process dramatically increases the amount of ammonia, glucose, amino acids, water. If there fistula Ekka blood such composition comes in cool blood circulation, resulting in the blood and tissues of the brain with the rich content in food protein dramatically increases the amount of ammonia, develops poisoning, the animal comes coma. In P. ammonia is converted into less biologically active substance - urea, and substances such as histamine, digitalis, novocaine, iron, atropine, ergotoxin, morphine and other, to some extent, lose their toxicity. When the hepatic artery ligation after some time developing collaterals that partially ensures the delivery of arterial blood.
The liver continues to participate in metabolic processes and after gradually made devascularization. Blood kept the level of sugar, cholesterol, serum albumin somewhat reduced.
P. inactivates many hormones: adrenaline, estrogens, gonadotropic hormones, hormones crust napochechnikov, secretin, gastrin, etc. Along with the disposal of certain substances, passing through the liver, on the contrary, become more toxicity, such as colchicine becomes more poisonous substance - oxycontin; sulfonamides after acetylation in Petrograd become less soluble, therefore easily deposited in the urinary tract.
In the implementation of the protective function against foreign agents play a significant role reticuloendothelial (kuperovskaya, "coastal") cells. They have properties of fixed phagocytes, absorbing from the blood of bacteria and certain irritants. Phagocytic activity conducive to slow the blood flow in the portal sinusoids. However, these cells may play a negative role by absorbing and permanently restraining many substances, such as gum Arabic, polivinilpirrolidon that are part plasma substitutes. The result of accumulation of a large number of irritating substances occurs reactive reproduction coppersky cells, which leads to the cirrhotic process.
The liver has jelcheobrazovanie function, which in many ways is the excretory. Bile (see) in the structure contains many substances, and circulating blood (paints, antibiotics, bilirubin, hormones), and substances produced in the prostate, such as bile acids, which glycocoll and taurine form a pair connections (glikoholeva and human beings need it acids), which gives them greater solubility. Having high surface activity, they dramatically reduce the surface tension of bile, and this helps keep it in a dissolved condition of a number of substances (cholesterol, lecithin, salt, calcium). In the intestines, bile acids help emulsification and absorption of fat (see Fat metabolism); 85-95% of bile acids are absorbed from the intestine into the blood where it is captured liver cells and again excreted in the bile. This sets the enterohepatic circulation of bile acids.
In the process of formation of bile participate kuperovskaya and polygonal cells. Between blood vessels and bile canaliculi there is a direct link: sine waves are reported under helped intercellular gaps with the space of the thesis, and the latter through the pores between the liver cells are connected with bile canaliculi. Substances blood can get into the bile canals in two ways: through the intercellular space and through kuperovskaya cells.
In the process of choleresis participate and polygon liver cells, as indicated by the inclusion in the cytoplasm containing protein, gall pigments; in the education of their essential role, apparently, the Golgi apparatus. It is possible that these cells secrete the water.
The leading role in mechanism of formation of bile plays, in all probability, the active migration of substances. This is evidenced by a number of facts: choleresis can occur when low blood pressure, and also in the case when the pressure of bile in the bone more pressure of blood in the capillaries; development of individual substances selectively (e.g. sugar enters the blood, and the bile acids in the bile); choleresis falling sharply against the backdrop of oppression tissue respiration liver.


Some researchers believe that the primary process of choleresis occurs by secretion of water and dissolved salts, paints, pigments. In the future, while moving her bone establishes the equilibrium substances that can penetrate through the membrane, and all the rest, not penetrating through the membrane substance, linger in the bile. The last can get into the blood only in case of disturbed flow of bile.
In the process of choleresis the influence of humoral irritants: secretin, salts holeva acid, bile acids, acetylcholine, products of protein digestion (peptone), hormones (adrenalin, thyroxine, sex hormones, ACTH, Cortina). Nervous influence on the process of choleresis not always expressed in the same way. The effect upon stimulation wandering nerve after their transection different. Secretory effect is observed when the irritation of 4-5-th day after transection that according to the I. P. Pavlova is associated with more rapid regeneration of braking fibers. Atropine in these conditions, reduces the secretion reaction. Strengthening of choleresis was observed after stimulation of the Central end of the vagus nerve, provided the integrity of the other. Irritation of the sympathetic nerve, apparently inhibits the secretion of bile.
The difficulty clarify the mechanism of action of nerves in the process of choleresis is that it is still unknown how this effect: either nerves act directly on the secretory cells, or changing the permeability of membranes, or there are some vasomotor changes.
The process of choleresis taken study by collecting bile directly from the gallbladder. The amount of bile in the experiment varies considerably. It was found that chronic loss of bile leads to reduction of choleresis and after feeding bile secretion increased, particularly in cases where, in addition to food in intestine is entered bile. It is also shown that duct bile from enter the intestine continuously; its quantity as in the presence and in the absence of the bubble remains constant (A. Century Gubar).
Not less important function of liver - Deposit blood. The vessels of the liver can accommodate up to 20% of all blood. The delay of blood in paragraph does not mean venous congestion. The Deposit process of blood in P. contribute significantly sphincter veins and sinusoidal. Input sphincter sine wave regulates the flow, and the output is the outflow of blood. Significant Deposit blood observed during anaesthesia. P. as one of depositing bodies in the system of portal vein is a special "gateway" between the portal and the General circulation. From its functional state depends on the activities of other depositing organs (spleen, intestines). All the blood that came out of the spleen, intestines, necessarily passes through P.
The liver removes excess water from the blood that goes to education lymph and bile. In P. formed from 1/2 to 1/3 of the entire lymph with high content of protein (6%), and in average 600-700 ml of bile per day, which is poured out into the digestive tract. The blood, flowing through sine wave loses a lot of water, especially in the digestive process. In the period when increases blood flow in the portal vein, the pressure increased and is much higher than in the hepatic vein. In animals with portocaval anastomosis by the Eck water is introduced into the body in the isotonic salt solution, appears much more slowly.