Traditional medicine

Bile physical properties chemical composition. Functions of bile in the human body

Not a single process of complete digestion is complete without a special liquid produced by our body - bile. Its deficiency leads to impaired absorption of food, especially fat, and excess can even affect brain activity: in a sense, the expression “bilious person” sometimes has a purely physiological basis.

What is bile, where is it produced, its composition

Bile is a greenish or yellow-brown biological fluid that is produced by liver cells.

Bile is a biological fluid with a specific odor. It can be of varying thickness, yellow-brown or greenish in color and has a distinct bitter taste.

Bile is produced in liver cells - hepatocytes. It is quite liquid and has a light shade, for example, yellow. The liver continuously produces bile. Then it flows through special ducts into the reservoir - the gallbladder, which is a hollow sac with a capacity of 80-120 ml. Here it becomes more concentrated and viscous, and its color changes to darker, for example, brown or green. Due to the fact that bile produced directly in the liver differs in its physicochemical characteristics from that stored in the gallbladder, in medicine it is customary to separate hepatic and gallbladder bile separately.

The main differences between cystic and hepatic bile:

In addition, bile contains various proteins, metal ions, enzymes and other biologically active substances.

Food stimulates the contraction of the gallbladder, as a result of which bile flows through the common bile duct into the duodenum, where it mixes with the rest of the intestinal juice and pancreatic secretions.

Individual components that make up bile

Bilirubin and biliverdin. is formed from hemoglobin molecules that enter the blood after the death of red blood cells. It is he who gives the appropriate color to the bile, because it itself has a red-yellow color. Biliverdin has a green tint and is found in bile in small quantities. Oxidizing in the intestines, bile pigments turn stool brown.

If for some reason a lot of bilirubin accumulates in the blood, it gives a yellow tint to the skin, eyeballs and changes the color of urine, which becomes similar to beer. In the body, bilirubin is present in two main forms - bound and unbound with glucuronic acid. Unbound (indirect) bilirubin in large quantities can penetrate the brain cells, staining its various parts and leading to a change in mental state in adults and a decrease in mental abilities in newborns.

Bile acids. This is a series of organic acids that are necessary to emulsify fats. Without emulsification, the process of their absorption in the intestines is impossible. Excreted during the day in the amount of 15-30 g, the overwhelming amount of these acids is absorbed back, and only 0.5 g is excreted in the feces.

Pathological inclusions

Microorganisms and protozoa. Normally, bile is sterile. However, in some diseases, microorganisms or protozoa penetrate primarily from the intestines. The result is inflammation of the gallbladder. In this case, Proteus, Enterobacteriaceae, Klebsiella, Escherichia coli and even can be detected.

Microliths and stones. They are formed if the chemical composition of bile is disrupted: it should become more concentrated and saturated with cholesterol and bile salts.

Leukocytes, cells of the mucous membranes (epithelium). Normally present in small quantities. Their increase indicates inflammation of the gallbladder.

Functions of bile

Stagnation of bile in the gallbladder and insufficient release into the duodenum can lead to abdominal pain.

The main functions of bile:

fat emulsification;
increased activity of pancreatic enzymes;
normalization of fat absorption;
increased absorption of proteins and carbohydrates;
stimulation of intestinal motility;
participation in the renewal of cells of the intestinal mucosa;
neutralization of the action of gastric juice, including pepsin;
participation in the absorption of cholesterol, calcium salts, fat-soluble vitamins, amino acids.

In case of disruption of the production and flow of bile into the intestines, the following digestive disorders are observed:

varying intensity (due to poor neutralization of gastric juice, it occurs, which causes pain);
bloating;
vitamin deficiency;
general weakness.

A striking example of such a condition is that which occurs after removal of the gallbladder.

How is bile examined?

To find out your bile composition, you should undergo duodenal intubation. To do this, after special preparation of the patient, a probe is inserted into the duodenum and the contents of the lumen of this intestine are taken for analysis, which is extracted in 5 phases:

Fraction “A” is a mixture of bile with duodenal juice (20-30 minutes).
Closing phase of the sphincter of Oddi. There is no bile in the contents (up to 6 minutes).
Bile flow from extrahepatic bile ducts (3-4 minutes).
Portion “B” – bladder bile (20-30 minutes).
Portion “C” – liver bile (remaining time after the end of phase No. 4).

As a rule, a referral for duodenal intubation can be obtained from a general practitioner, family doctor, gastroenterologist or surgeon.

At the discretion of the doctor, this procedure is usually prescribed for diseases of the liver, gall bladder, gastroduodenitis, etc. It must also be undergone in a comprehensive examination with ultrasound or MRI if the following complaints appear:

pain in the right hypochondrium;
change in color of stool;
appearance of skin, sclera, palms;
digestive disorders - bloating, flatulence;
, nausea, belching, etc.

Bile and character

Ancient scientists considered bile to be as important a fluid in the body as blood. They believed that an excess of light bile in the blood leads to a person becoming unbalanced and hot-tempered (choleric), and dark bile leads to depression and a gloomy mood (melancholy). Of course, such views turned out to be wrong.

However, if one of the components of bile, unconjugated bilirubin, enters the blood in large quantities, it can cause a number of pathological effects:

strong ;
discolored stool, dark urine;
change in the general condition of a person - irritability, increased weakness and fatigue.

In severe cases, toxic encephalopathy may develop, manifested by inhibition of all brain functions up to the development of coma.

How lifestyle can affect the composition of bile

With an increased level of bile components in the blood of a person, painful itching of the skin bothers him.

If bile remains in the gallbladder for a long time, it becomes more concentrated, and under unfavorable circumstances the risk increases

The most interesting biochemical processes occur in human organ systems. They are designed to ensure homeostasis in the body, that is, they preserve and maintain the internal environment. Some processes maintain body temperature, some maintain blood pressure, and some are responsible for metabolism. But it is difficult to imagine the functioning of the digestive system without the production of bile. What is this? Where and how is it formed? And why does it play such an important role? The answers to these questions are presented in the article.

General information

The process of bile secretion is continuous. In this case, bile gradually accumulates in the bladder. Bile excretion is possible only at the time of eating. It begins 5-12 minutes after the start of the meal.

Two types of bile accumulate in the body - liver and bladder. The liver secretion is “young”; part of it is immediately transported to the duodenum, the rest to the gallbladder. And bladder bile is more mature. Liquids vary in color, density, and composition.

Compound

Liver bile is characterized by a yellow or slightly greenish color. Bladder bile is darker, almost brown. The acidity (pH) of liver secretion is 7-8. During the absorption of bicarbonates, the acidity of gallbladder bile decreases - 6-7. The relative density of the liver secretion is 1.008-1.015, and the gallbladder bile is somewhat denser - 1.025-1.048.

Approximately 98% of the composition of bile is water, 2% is dry residue. The dry residue contains bile salts, a certain amount of bilirubin and biliverdin (bile pigments). There is also cholesterol, fatty acids, electrolytes, lecithin and cholesterol. In gallbladder bile the concentration of substances is much higher.

All dry residue substances are conventionally divided into 2 groups:

entering the filtration line from the blood (Na, Ka, creatinine, cholesterol and others);
formed during secretion by hepatocytes (bile acids, pigments).

Given the importance of the function of bile, the body produces approximately 10-15 ml of it for every kilogram of body weight. It turns out that an adult with normal weight produces about 600-1500 ml of bile per day. Despite the continuity of the process, its intensity fluctuates depending on the time of day.

Functions

Bile performs functions related to digestion, fermentation, peristalsis, and so on. All of them are equally important for human well-being. Any changes in the functioning of the gallbladder lead to the development of serious diseases that require drug treatment. If we consider in more detail, we can describe the functions of bile as follows:

Together with gastric juice, bile neutralizes the acidic chyme (food bolus) coming from the stomach. During the neutralization process, a reaction occurs between carbonates and HCI, releasing carbon dioxide. As a result, the chyme loosens, which facilitates the digestion process.
Bile is involved in the digestion of fats. Due to the action of bile acids in combination with fatty acids and monoacylglycerols, fats are emulsified (mixed with water), after which lipase can act on them.
Bile helps reduce surface tension, which prevents fat droplets from draining.
The secretion influences the formation of individual particles (micelles) adapted to absorption.
One of the functions of bile is the absorption of fat-soluble vitamins (A, D, K, E).
The enzymes that make up the secretion activate intestinal peristalsis.
Bile stops the action of gastric juice in the small intestine by inactivating pepsin.
Normalizes intestinal microflora, providing bactericidal and bacteriostatic effects. Prevents putrefactive processes.
It has an excretory function for substances that the kidneys are not able to filter (cholesterol, bilirubin, glutathione, steroids, metals, some drugs), excreting them from the body with feces. In this case, cholesterol is excreted from the body only with bile. Excretion of 1-2 g is possible per day.

The functions of bile in digestion, as you noticed, are very diverse. If you exclude it from the digestive process, the digestion and absorption of fats will be completely disrupted.

The effect of bile on health

Let's consider what happens to a person whose body lacks bile. First, his stool will lighten in color and become greasy, leading to a deficiency of fat-soluble vitamins. There will be a lack of fatty acids, as a result of which the condition of the skin will worsen, problems will arise in the functioning of the cardiovascular system, weakness will occur and metabolism will be disrupted.

If there is insufficient bile production, pathologies of the large intestine cannot be avoided. The fact is that it is not able to independently cope with large amounts of fat in the chyme, and the breakdown of fats is one of the main functions of bile.

If there is a lack of secretion, the digestion process will be disrupted, which can lead to the accumulation of fats in the fascia of the internal organs. Patients with gallbladder disease often suffer from internal obesity, which impairs the functioning of the heart, liver, spleen and intestines.

How can you influence bile?

If it is necessary to increase the concentration of bile acids, then patients are prescribed choleretics. These are choleretic agents containing elements of ox bile (Allohol, Cholenzym). It is also possible to prescribe plant sterols using choleretic herbs; such drugs include Liv 52 and Holosas. Medicinal herbs to influence the level of bile acids include immortelle flowers, string, arnica, wormwood, parsley, rose hips and dry corn silk.

To reduce the toxicity of bile acids, drugs containing ursodeoxycholic or chenodeoxycholic bile acid are used.

Bile is a specific liquid with a characteristic odor and bitter taste that is produced. Performs a main function in the digestion of fats and prevents the accumulation of cholesterol. Without this substance, normal digestion is impossible. Changes in the quality of bile or its deficiency cause the appearance of stones in the liver and bladder. Problems lead to metabolic disorders and the development of dangerous pathologies of the digestive system.

Where is bile produced and where is it stored?

Bile, as a multifunctional, biologically active medium, is of particular value for the body. The idea of which organ produces bile and how secretion occurs leads to an understanding of the mechanism of bile secretion:

Bile is produced in liver cells - hepatocytes. It looks like an amber-golden liquid.
The liver produces bile almost continuously. At this stage she is called young. The liver is the only organ in which bile is formed. The amount of bile per day can reach up to 1 liter.
The secretion is collected through the capillaries into the liver ducts. Here it is concentrated and enriched with certain components. The color changes - it becomes darker.
Through the common hepatic duct, bile flows to the place of storage - in. In composition and consistency it is not identical to liver. The bladder acquires the status of mature bile.
The gallbladder is a storage facility from which bile is taken to participate in metabolic processes. The process of bile secretion occurs reflexively at the moment a bolus of food enters the intestine.
If necessary, some part of the liver secretion is immediately delivered to the duodenum, where it performs the function of digesting fatty foods.
In the duodenum, the “dormant” enzymes of the pancreas are activated, which does not produce bile. However, thanks to its stimulation, it actively participates in the breakdown of proteins, fats and carbohydrates.

Thus, bile is produced in the largest gland of the body - the liver, and is stored in a small pouch - the gallbladder.

The process of constant bile secretion occurs due to pressure changes in the parts of the digestive system. This is ensured by a system of reflexes that regulate the function of normal digestion. Commands are issued from the brain.

What does it consist of?

The composition and properties of bile are associated with its leading function in the breakdown of fats. The most important active substances are primary and secondary bile acids. Without water they make up 70% among other components. Primary acids are formed in cells, and secondary acids come from primary bile acids. These transformations occur in the intestines, where local enzymes act on them accordingly. In the composition of bile, these acids are in a bound state and are called “bile salts.”

In addition to salts, a significant part in the structure is occupied by potassium and sodium ions. This explains the alkaline environment of bile masses.

Depending on the color of a person’s bile, classification is made.

The following types of bile are distinguished:

Hepatic (young) - goes to the intestines directly from the liver. Due to its high water content, it is an almost transparent liquid of straw-golden color.
Cystic (mature) - secreted from the gall bladder. More concentrated, semi-viscous consistency. The smell is specific and more pronounced. Color varies from dark green to brown.

Thanks to its multicomponent composition, the digestive juice of the liver performs a whole range of vital functions in the body.

The consistency of liver bile is more liquid, but is no different from cystic bile in content. The composition includes the following components:

water – its content in the liver bile reaches 80%;
bile salts - compounds of bile acids with taurine and glycine;
phospholipids – content reaches 20%;
– enter the secretion after the breakdown of red blood cells, they are the ones who influence its color;
mucus - contains substances necessary to activate certain intestinal enzymes;
cholesterol – excreted from the body thanks to bile;
proteins and vitamins are present as necessary biologically active substances.

Why is bile needed?

The formation of bile occurs continuously - such is the importance of liver secretion for the body. The diverse properties of bile characterize it as a special component in the hierarchy of biologically active substances. The function of bile secreted by the liver can be seen through numerous metabolic reactions.

Bile plays the most important role in digestion:

Performs the function of breaking down lipids (fats) and their further complete absorption. In the intestines, thanks to bile acids, fats are broken down into small droplets - emulsified. Under the influence of enzymes, they transform into a digestible form and are easily absorbed by the walls of the small intestine.
Accelerates the breakdown of proteins and carbohydrates. Takes on the function of activating pancreatic enzymes that enter the duodenum in an inactive state.
It has the function of neutralizing gastric acids, changing digestion from gastric to intestinal, since the acidic environment of the stomach suppresses the action of duodenal enzymes. The action of bile juice creates an alkaline environment and stimulates digestion.
Strengthens intestinal motility. Bile components stimulate the function of mucus secretion, promoting the movement of the food bolus (chyme).
Neutralizes the destructive effect of pepsin on pancreatic cells, activates the work of its hormones and enzymes.

No less significant in the human body are the adsorbent and excretory functions of bile, aimed at:

accumulation and removal from the body of toxins and decay products - everything that cannot be removed with urine (products of the breakdown of fats, red blood cells, cholesterol) is dissolved in it and excreted with feces;
neutralization of microorganisms that enter the body with food - thanks to the antiseptic properties of bile, bacteria that accidentally enter the gastrointestinal tract are destroyed.

What diseases are associated with improper production of bile and its excretion?

Disturbances in the mechanism of bile secretion against the background of diseases associated with the liver and disorders of the excretory function of the bile can provoke conditions dangerous to the body. These include:

(cholestasis) – occurs when liver cells do not function sufficiently to produce its components; due to a violation of the flow of bile into the lumen of the duodenum from the bladder. It can have an acute and chronic form. Without qualified treatment it is fraught.
– occurs as a result of an imbalance in the composition of liver secretions. The formation of stones is provoked by the substance present in the components. Combining with calcium and bilirubin, it turns into solid inclusions. Stones can settle in the gallbladder and even the liver. Against this background, blockage of the ducts is possible. Often with the threat of rupture. The solution to the problem is most often done by.
Biliary reflux gastritis. The disease occurs due to insufficient valve function and is associated with the reflux of bile into the duodenum and. Bile acids destroy the mucous membrane of these structures and disrupt the digestion process.
Steatorrhea is a dysfunction of fat absorption. They are excreted from the body during bowel movements in an undigested form. The stool becomes fat and has a characteristic color. The microflora of the lower gastrointestinal tract changes for the worse. Develops against the background of insufficient liver function or a complete lack of bile production. The body lacks vital substances.

The occurrence of these conditions is often associated with a person’s lifestyle and diet.

Inactivity, an unbalanced diet, bad habits, and stress can provoke a disorder of bile secretion.

Which doctor should I contact?

Treatment against the background of impaired bile secretion functions belongs to the specialization of a gastroenterologist. A referral to a specialist is issued by a local physician. Ultrasound specialists are involved in diagnostic activities. If the solution to the problem is impossible without surgery, treatment is carried out by a surgeon.

Diagnostic methods

To make the correct diagnosis, laboratory and instrumental research methods are used, taking into account the patient’s complaints. Along with urine and feces, the qualitative composition of liver secretion is also examined. The method of fractional duodenal intubation is used, when digestive juice is collected from different parts of the digestive system.

If there is a suspicion of a reliable result, an ultrasound will show it.

Treatment highlights

Therapeutic tactics for diseases associated with bile secretion function depend on the diagnostic results. May be appointed. They are divided into the following groups:

Grinevich, V. B. Monitoring bile pH and impedance monitoring in the diagnosis of GERD / V. A. Grinevich // Clinical and experimental gastroenterology. – 2004. – No. 5.
Depokina, O. V. Motor dysfunctions of the biliary tract and features of the biochemical composition of bile during biliary sludge, methods for their correction: Dissertation for the degree of candidate of biological sciences / Research Institute of Gastroenterology of the Department of Health. Moscow, 2007.
Kozlov, D.V. Features of lipid metabolism of tissues of the enterohepatic system in conditions of altered outflow of bile and its correction: Dissertation for the academic degree of Candidate of Biological Sciences / Nizhny Novgorod Gastroenterological Institute of Pediatric Gastroenterology. Nizhny Novgorod, 2003.
Korotko G. F. Physiology of the digestive system / G. F. Korotko. – Krasnodar: Group B, 2009. – 608 p.
Maev, I. V. Functions of bile in the body and gastroenterological pathologies / I. V. Maev, A. A. Samsonov. – M.: MEDpress-inform, 2005. – 510 p.
Sablin O. A. Functional diagnostics in gastroenterology / O. A. Sablin, V. B. Grinevich, Yu. P. Uspensky, V. A. Ratnikov. – St. Petersburg: VMedA, 2002.

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Northern State Medical University

Department of Biomedical Chemistry and Toxicology

Abstract on the topic:

Bile: physical properties, chemical composition, biological role.

Arkhangelsk, 2010

1. Bile and its physical properties

2. Chemical composition

3. Biological role

4. Bile formation and bile excretion

References

Bile and its physical properties

Bile (bilis) is a biological fluid produced by the liver, yellow-brown or green in color, alkaline. Its color is determined by concentration. If it is concentrated, then it is dark brown in color (vesical bile). If it is liquid, then it is much lighter (to golden yellow). In herbivores it is green, in carnivores it is yellow-brown. bile hepatic digestion cholekinesis

Normally, 500-1400 ml of bile is secreted per day (about 15 ml per 1 kg of body weight). It is transparent, slightly viscous (due to the admixture of the mucous secretion of the biliary tract epithelium) consistency. Its consistency is very different: from quite liquid with 1.5% content of dense substances and to relatively thick with 12-15% of dense substances (vesicle bile).

The specific gravity of bile is 1.01, that is, its density is very slightly higher than the density of water. It ranges in different portions from 1007 to 1034. Bile has a bitter taste due to the presence of bile salts in it.

The pH of bile secreted by the liver is 7.5-8.0 (that is, it has a slightly alkaline reaction). The pH of bile, which has been in the gallbladder for some time, is 6.0-7.0 (that is, it acquires a slightly acidic reaction due to the formation of bile salts and the absorption of bicarbonates). During inflammatory processes in the gallbladder, the pH of bile decreases to 4.0-4.5.

Normal bile levels are as follows:

Basal bile (phases I and III, portion A) should be transparent, have a light straw color, density 1007-1015, and be slightly alkaline.

Cystic bile (phase IV, portion B) should be transparent, have a dark olive color, density 1016-1035, acidity - 6.5-7.5 pH.

Liver bile (phase V, portion C) should be transparent, golden in color, density 1007-1011, acidity - 7.5-8.2.

Chemical composition of bile

Bile is an aqueous solution of various ingredients that has the properties of a colloidal solution. In general, the formation of bile occurs through active and passive transport of substances from the blood through cells and intercellular contacts (water, glucose, creatinine, electrolytes, vitamins, hormones, etc.), active secretion of bile components (bile acids) by hepatocytes and reabsorption of water and a number of substances from bile capillaries, ducts and gallbladder. The leading role in the formation of bile belongs to secretion.

The main components of bile are

Bile acids (cholic and in small quantities deoxycholic)

· phospholipids

Bile pigments (bilirubin and biliverdin)

cholesterol

fatty acids

electrolytes (bicarbonates, sodium, potassium, calcium, chlorine, magnesium, iodine, trace amounts of manganese)

· vitamins

· hormones

· urea

· uric acid

· a number of enzymes

· lecithin

In addition to endogenous substances, bile may also contain exogenous substances. With bile, many drugs, toxins and excess of certain substances (copper, zinc, mercury, etc.) are removed from the body.

The process of bile formation - bile secretion (choleresis) - occurs continuously, and the flow of bile into the duodenum - bile secretion (cholekinesis) - periodically, mainly in connection with food intake. On an empty stomach, almost no bile enters the intestine; it is sent to the gallbladder, where, when deposited, it concentrates and slightly changes its composition, so it is customary to talk about two types of bile - hepatic and bladder (Table 1).

In gallbladder bile, the concentration of many components is 5-10 times higher than in liver bile. Thus, the concentration of cholesterol is so high that it is only due to the presence of bile acids that it does not precipitate. However, the concentration of a number of components, for example sodium, chlorine, bicarbonates, due to their absorption in the gallbladder, is much lower; Albumin, present in hepatic bile, is not detected at all in cystic bile.

Components	Liver bile	Bile bile

Dense residue, %
Organic substances,	Bile salts
	Bile pigments and mucin
	Cholesterol
	Fatty acids and other lipids

Inorganic substances,

The main component of bile - bile acids - are synthesized in hepatocytes. About 85-90% of the bile acids released into the intestine as part of bile are absorbed into the blood from the small intestine. Absorbed bile acids are transported in the blood through the portal vein to the liver and are included in the composition of bile. The remaining 10-15% of bile acids are excreted from the body mainly in feces. This loss of bile acids is replenished by their synthesis in hepatocytes.

The main amount of bile acids and their salts is contained in bile in the form of compounds with glycocol and taurine. Human bile contains about 80% glycocholic acids and about 20% taurocholic acids. Eating foods rich in carbohydrates increases the content of glycocholic acids; if protein predominates in the diet, the content of taurocholic acids increases. Bile acids and their salts determine the basic properties of bile as a digestive secretion.

Bile acids are formed in the liver from cholesterol (a lipid, or fat). In humans, this process is not very effective; part of the cholesterol is not converted into bile acids and is released into bile in its pure form. It is this cholesterol that can then become the main source of gallstones. The problem is that cholesterol at a temperature of 37 degrees (body temperature) does not dissolve in water at all, and in its pure form immediately begins to form crystals (that is, actually the smallest stones). In order to keep cholesterol from crystallizing, bile contains another component - lecithin. Lecithin by itself or together with bile acids forms special molecular structures that allow cholesterol to be transported from the liver to the intestines, preventing it from falling out in the form of crystals. Such transport forms are called micelles and vesicles.

Bile consists of three fractions. Two of them are formed by hepatocytes, the third by epithelial cells of the bile ducts. Of the total volume of bile in humans, the first two fractions account for 75%, the third - 25%. The formation of the first fraction is associated, but the second is not directly related to the formation of bile acids. The formation of the third fraction of bile is determined by the ability of the epithelial cells of the ducts to secrete fluid with a sufficiently high content of bicarbonates and chlorine, to reabsorb water and electrolytes from the tubular bile.

Bile pigments are products of the breakdown of hemoglobin and other porphyrin derivatives excreted by the liver. The main bile pigment in humans is bilirubin, a red-yellow pigment that gives liver bile its characteristic color. Another pigment - biliverdin (green) - is found in trace amounts in human bile, and its appearance in the intestines is due to the oxidation of bilirubin.

There are three enzyme substances identified: an enzyme acting on starch, an enzyme acting on protein, and an enzyme acting on fats. These enzyme substances are available in relatively small quantities.

Bile contains a complex lipoprotein compound, which includes phospholipids, bile acids, cholesterol, protein and bilirubin. This compound plays an important role in the transport of lipids into the intestine and takes part in the hepatic-intestinal circulation and general metabolism of the body.

Biological role

The biological role of bile is associated mainly with the digestive process.

By reducing the acidity of the gastric contents entering the intestine, bile stops the action of pepsins and creates an environment for the activity of pancreatic juice enzymes.

Due to bile salts, fats are emulsified, large drops of which disintegrate into small droplets, sharply increasing the area of contact with pancreatic juice lipase and the efficiency of fat hydrolysis. About 7 - 20% of bile acids are excreted from the body with feces, most of them are absorbed in the ileum into the blood of the portal vein, from where hepatocytes re-extract bile acids.

What are bile acids needed for? It is known that the human and animal body consists of 95% water. Water is the basis of life, its main environment. To be absorbed by the body, any substance must go into an aqueous solution. On the other hand, the fat we eat does not dissolve in water. To assimilate fats that are valuable to us, the liver produces bile, which enters the intestines through the bile duct system, where food is digested and absorbed. So, bile acids are natural detergents, that is, detergents (an example of detergents artificially created by people are soap and washing powder). Bile acids of bile, mixing with the eaten fat, erode its emulsion state, while the fat turns into tiny droplets that float in an aqueous environment. After this, the fat emulsion is treated with enzymes (biological catalysts), which break down large fat molecules into small structural elements. Only such small structural elements of fat can be absorbed in the intestines.

Foreign substances are also excreted with bile, for example, some drugs (alkaloids, salicylates, sulfonamides, etc.). The excretion of iodide compounds with bile is used in the X-ray diagnosis of diseases of the gallbladder and biliary tract.

Bile also plays a regulatory role, being a stimulator of bile formation, bile excretion, motor and secretory activity of the small intestine, proliferation and desquamation of epithelial cells (enterocytes). Bile can increase the activity of pancreatic and intestinal enzymes, especially lipase.

Bile is able to stop the action of gastric juice, not only by reducing the acidity of gastric contents entering the duodenum, but also by inactivating pepsin. Bile has bacteriostatic properties. Its role in the absorption of fat-soluble vitamins (D, E, K), cholesterol, amino acids and calcium salts from the intestine is important. Bile also inhibits the development of intestinal microflora and prevents putrefactive processes in the large intestine.

When bile is excluded from digestion, the process of digestion and absorption of fats and other lipid substances is disrupted. Bile enhances the hydrolysis and absorption of proteins and carbohydrates.

Bile formation and bile secretion

The formation of bile begins with the secretion of water, bilirubin, bile acids, cholesterol, phospholipids, electrolytes and other components by hepatocytes. The secreting apparatus of the hepatocyte is represented by lysosomes, lamellar complex, microvilli and bile canaliculi. Secretion occurs in the microvilli zone. Bilirubin, bile acids, cholesterol and phospholipids, mainly lecithin, are secreted in the form of a specific macromolecular complex - bile micelle. The ratio of these four main components, which is fairly constant under normal conditions, ensures the solubility of the complex. In addition, the low solubility of cholesterol increases significantly in the presence of bile salts and lecithin. Violation of a certain ratio of the main components of bile, necessary for their sufficient solubility, can cause a pathological process in the gallbladder and bile ducts; Cholesterol, precipitating, contributes to the formation of stones.

In the mechanism of bile formation, the phenomena of diffusion are important (when the so-called primary bile formed in the hepatocyte passes through the bile ducts, an equilibrium of electrolytes is established between it and the blood plasma), as well as active and passive transport from the blood of glucose, electrolytes, creatinine, vitamins, hormones, etc. and reabsorption of water and some substances into the blood from the bile ducts and gallbladder. The energy required for bile secretion is generated by tissue respiration of liver cells and associated oxidative phosphorylation.

Despite the fact that bile production occurs continuously, the intensity of bile formation fluctuates throughout the day. Increased bile formation is facilitated by certain types of food (for example, fats), hydrochloric acid of gastric juice, gastrin, secretin, cholecystokinin-pancreozymin, as well as stimulation of the vagus nerve. Weakening of bile formation is observed during fasting, overheating or hypothermia of the body. The regulator of bile secretion is also the hepatic-intestinal circulation of its components. The more bile acids enter the blood of the portal vein from the small intestine, the less they are synthesized by hepatocytes, and, conversely, with a decrease in the flow of bile acids into the blood, their synthesis in the liver increases.

The flow of bile into the duodenum occurs periodically. The movement of bile is caused by unequal pressure in different parts of the biliary system and the duodenum. The level of pressure in the bile ducts depends on the degree of their filling with bile, contraction of the smooth muscles of the bile ducts and gallbladder, as well as on the tone of the sphincter muscles - the physiological sphincter corresponding to the area of \u200b\u200bthe confluence of the cystic and common bile ducts, the sphincter located in the neck of the gallbladder and the sphincter the terminal section of the common bile duct (sphincter of Oddi). Muscle contraction is regulated by nervous and humoral mechanisms. The pressure in the common bile duct and in the gallbladder outside of digestion is equal to -1-300 mm of water, respectively. Art. and 6--185 mm water. Art., the flow of bile into the duodenum outside of digestion is limited. During digestion, due to contraction of the gallbladder, the pressure rises to 200-300 mm of water. Art., ensuring the release of bile. The first to enter the duodenum is bile, which is located in the common bile duct, then cystic bile, then bile from the hepatic ducts and liver. The entry of bile into the intestine occurs during peristaltic movements of the smooth muscles of the bile ducts, contraction of the gallbladder, and relaxation of the sphincter of Oddi.

Muscle tone and peristalsis of the biliary tract and gallbladder are regulated by the vagus and sympathetic nerves. Bile secretion is also carried out thanks to conditioned and unconditioned reflexes with the participation of numerous reflexogenic zones, including receptors of the oral cavity, stomach and duodenum. Egg yolks, milk, meat, fats, and some medications have a strong stimulating effect on bile secretion. Regulation of bile secretion is also carried out by the humoral route. Thus, gastrin, in addition to its main function - stimulating the release of hydrochloric acid in the stomach, reduces the tone of the sphincter of Oddi muscles; cholecystokinin pancreozymin causes contraction of the gallbladder; secretin enhances its contraction.

Changes in the chemical composition of bile, disturbances in bile formation or bile excretion may be associated with various pathological processes. In case of infectious and toxic damage to the liver, the processes of binding bilirubin with glucuronic acid and releasing it into bile are disrupted, which leads to the development of jaundice. With cholestasis, even in the case of unimpaired liver cell function, bilirubin glucuronide cannot be excreted into the intestine, which also leads to its release from bile into the blood and the development of jaundice. The secretion of bile and the formation of bile micelle can be disrupted as a result of a violation of the hormonal regulation of cholesterol and phospholipidogenesis, which is observed during pregnancy, menopause, taking certain hormonal drugs, etc. With the inflammatory process in the gallbladder and changes in pH, the protective properties of colloidal structures decrease and change physicochemical properties of bile (the so-called pre-stone state), which subsequently leads to the formation of primary centers of crystallization and the formation of stones.

A significant increase in the amount of bile secreted is observed with hypomotor dyskinesia of the biliary tract and atony of the gallbladder. A decrease in the secretion of bile up to its complete cessation is characteristic of blockage of the biliary tract; a decrease in the amount of gallbladder bile is observed with hypermotor dyskinesia of the biliary tract

References:

1. Podymova S. D. “Liver diseases” Medicine 1998

2. Severin E. S. “Biochemistry” GEOTAR - Media 2005

3. Tkachenko B. I. “Normal human physiology”

4. Filimonov V.I. “Guide to general and clinical physiology” LLC “MIA” 2002

5. http://gallbladder.surgery.ru/bile/bile_chemistry/

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Indicators, mEq/l	Cystic bile		Liver bile
Indicators, mEq/l	5–10 years	11–15 years	5–10 years	11–15 years
Lipids	1583 ± 569	1182 ± 284	594 ± 188	366 ± 144