The role of bile in digestion. Describe the function of bile in the digestion

Suppose, before you put the following task: describe the functions of bile in digestion. To do this, you first need to study its biochemical composition, properties and mechanisms of bile formation, necessary for normal splitting of organic substances that make up the food. This article will be devoted to the consideration of these questions.

Secretory function

The liver is the largest gland in the gastrointestinal tract of vertebrates and humans. It consists of parenchymal cells, called hepatocytes. A separately taken hepatic cell has one or more nuclei and consists of two parts, called biliary and vascular. The last side of the hepatocyte contacts the sinusoidal capillary, which receives blood from the hepatic vein. This part synthesizes glucose, proteins, vitamins and lipocomplexes.

The other side of the hepatocyte is directed towards the bile capillary. It is called biliary. It produces bile. It flows into the capillary, and from it into the ducts. Thus, in a healthy liver, the bile produced by the side of the hepatocyte does not enter the blood, since the biliary capillary is separated from the sinusoidal body of the hepatic cell.

It should be noted that hepatocytes are grouped, forming lobules, from which the bile ducts exit. They merge and form two main directions - left and right. They come out of the central parts of the liver. And then, merging, form a common duct, which departs from its gate and enters the gallbladder. Thus, the liver is the organ secreting the bile of a person. Anatomy of the bile, the structure of the gallbladder and its functions will be examined by us further.

Why is it necessary to extract bile?

Compounds that help to break down complex macromolecules of organic food components include bile. It focuses on the lipids, transferring them from the insoluble state to the appearance of the emulsion. Bile acids, which are bile acids - chenodeoxycholic and cholate - are surface-active substances. It is they who emulsify the food fats from the stomach into the duodenum, facilitating their cleavage by the enzyme of the pancreas - the lipase.

Biochemical composition of bile

Knowing the structure of the structural elements of the hepatic lobules, biliary parts of hepatocytes, and also the biochemical composition, you correctly describe the functions of bile in digestion. Gastroenterologists have found that the liver is a complex process of plastic and energy metabolism. The bile itself is a liquid of olive or light brown color. It contains 98% water, as well as pigments, cholesterol, cholic acids, lecithin, vitamins and enzymes.

Consider the structure and circulation of bile acids. They are formed from steroidal alcohol - cholesterol. It is also part of the cell membranes. In hepatocytes, cholesterol is oxidized and primary bile acids are formed. They can be modified, turning into secondary ones: methacholic and desoxycholic. Those, in turn, form complexes with monomers of proteins - taurine and glycine.

These complexes are the most chemically active and are contained in the liquid in the form of sodium or potassium salts. Yellow pigments are another biochemical component, the main one being bilirubin. It is formed as a result of the destruction of hemoglobin, which occurs in the liver macrophages - Kupffer cells, as well as in the spleen. Lecithin is a component of bile. It also forms in the liver and plays an important role in the metabolism of fatty acids and cholesterol, reducing its level. He also takes part in the emulsification of fats.

What are the properties of bile?

Having studied the chemical composition of liver secretion, it is possible to correctly represent its role in the cleavage of organic substances and to consider the basic functions of bile in digestion, which are diverse. For example, it contains acids and is a detergent that facilitates the splitting of large fat molecules into smaller ones. Bile also affects enzymes that hydrolyse carbohydrates, and proteins: amylase and trypsin, enhancing their catalytic properties. The enzyme of gastric juice - pepsin - it acts in the opposite way, that is, it inhibits its activity, which leads to a sharp increase in the pH of gastric contents, as its acidity decreases.

Bile secretion enhances the absorption of solutions, mineral salts, vitamins A and D, as well as amino acids. The secret of the liver regulates the motor and excretory functions of all parts of the small intestine. This is the role of bile in digestion.

Mechanisms of bile formation and bile secretion

Earlier we studied the properties of liver secretion, produced by the biliary parts of hepatocytes. And we also found out that the composition, the properties of bile and its importance in digestion are interrelated. These mechanisms are carried out by the human nervous system as well as by the humoral pathway. The formation of bile intensifies as a reflex response to stimuli of the interoceptors of the walls of the mucous membranes of the oral cavity, stomach, and small intestine.

The gallbladder: its structure and role in digestion

Being a muscular organ, it is located under the lower edge of the liver. Has neck, body and bottom. After you anatomically substantiate the mechanism of its work, then you can easily describe the functions of bile in digestion. It, constantly formed in the liver, is released into the duodenal gut only at the time of ingestion. Between meals, the secret is deposited in the gallbladder.

Diagnostic methods of biliary examination

For the normal course of metabolic reactions in the parts of the gastrointestinal tract, certain biochemical and physiological indices of liver secretion are needed. You are physiologically justified describe the functions of bile in digestion, if its clinical parameters are normal. They are determined by the method of multimodal fractional duodenal sounding.

The basal fraction is obtained in the first phase of the study. It should have a light yellow color and a pH greater than 7. In the second phase, with the sphincter of Oddi closed, the secret should not be released from the probe. In the third stage of the study, clinically normal parameters of bile are as follows: volume - from 3 to 5 ml, color - light brown. The fourth phase lasts about half an hour. The color of the liver secretion varies from olive (bubble bile) to yellow amber. Its pH is 6.5-7.5, and the density is about 1038. The last phase, the excretion of the liver bile, lasts up to 20 minutes. The density decreases to 1011, pH = 7.5-8.2.

Deviations from the above parameters will indicate pathological abnormalities in the functioning of the liver, gall bladder or ducts. The most common type of pathology is the formation of stones in the bladder due to an increase in the viscosity of the fluid, as well as a violation of its contractile function. As you can see, in this article we have examined and studied the secret of the liver - bile, meaning and its functions in the processes of digestion.