Suppose you have 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 the normal splitting of organic substances that make up the food. Consideration of these issues and will be devoted to this article.
Secretory function
Печень является самой крупной железой в gastrointestinal tract inherent in vertebrate animals and humans. It consists of parenchymal cells called hepatocytes. A single hepatic cell has one or several nuclei and consists of two parts, called biliary and vascular. The last side of the hepatocyte is in contact with a sinusoidal capillary that receives blood from the hepatic vein. This part synthesizes glucose, proteins, vitamins and lipocomplexes.
The other side of the hepatocyte is directed towardsgall 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 from the central lobes of the liver. And then, merging, form a common duct, which departs from its gate and falls into the gallbladder. Thus, the liver is the organ secreting human bile. The anatomy of bile, the structure of the gallbladder and its functions will be discussed below.
What is bile excretion necessary for?
To compounds that help break down complexmacromolecules of organic components of food, applies bile. It acts on lipids, transferring them from an insoluble state to an emulsion. Cholic acid bile acids — chenodeoxycholic and cholic acids — are surfactants. It is they who emulsify the food fats that have entered from the stomach into the duodenum, facilitating their breakdown by the pancreatic enzyme - lipase.
Biochemical composition of bile
Knowing the structure of the structural elements of the liverslices, biliary parts of hepatocytes, as well as the biochemical composition, you correctly describe the function of bile in digestion. Gastroenterologists have found that complex processes of plastic and energy metabolism take place in the liver. Bile itself is an olive or light brown liquid. It contains 98% of water, as well as pigments, cholesterol, cholic acids, lecithin, vitamins and enzymes.
Consider the structure and circulation of bile acids.They are formed from steroid alcohol - cholesterol. It is also part of the cell membrane. In hepatocytes, cholesterol is oxidized and primary bile acids are formed. They can be transformed into secondary ones: metacholic and deoxycholic. Those, in turn, form complexes with protein monomers taurine and glycine.
These complexes are the most chemicallyactive and contained in the liquid in the form of sodium or potassium salts. Bile pigments are another biochemical component, the main of which is bilirubin. It is formed as a result of the destruction of hemoglobin, which occurs in the macrophages of the liver - Kupffer's cells, as well as in the spleen. Lecithin is a component of bile. It is also formed in the liver and plays an important role in the metabolism of fatty acids and cholesterol, reducing its level. It also participates in the emulsification of fats.
What properties does bile have?
Having studied the chemical composition of liver secretion, you cancorrectly represent its role in the breakdown of organic substances and consider the main functions of bile in digestion, which are diverse. For example, it contains acids and is a detergent that promotes the breakdown of large fat molecules into smaller ones. Bile affects also the enzymes hydrolyzing carbohydrates, and proteins: amylase and trypsin, enhancing their catalytic properties. On the enzyme of gastric juice - pepsin - it acts in the opposite way, that is, inhibits its activity, which leads to a sharp increase in the pH of the gastric contents, as its acidity decreases.
The secretion of bile enhances the absorption of solutionsmineral 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 the liverproduced by the biliary parts of hepatocytes. And we also found out that the composition, properties of bile and its value in digestion are interrelated. These mechanisms are carried out both by the human nervous system and by the humoral path. The formation of bile is enhanced as a reflex response to stimuli of the interoreceptors of the walls of the mucous membranes of the oral cavity, stomach, small intestine.
Gallbladder: its structure and role in digestion
Being a muscular organ, it is located underlower edge of the liver. It has a 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 is constantly formed in the liver, is excreted into the duodenum only at the time of intake of food. Between meals, the secret is deposited in the gallbladder.
Diagnostic methods for the study of bile
For the normal course of metabolic reactionsIn the sections of the gastrointestinal tract, certain biochemical and physiological parameters of the liver secretion are necessary. You physiologically sound describe the function of bile in the digestion, if its clinical parameters will be normal. They are determined by the method of multi-stage fractional duodenal sounding.
В первую фазу исследования получают базальную fraction. It should have a light yellow color and a pH greater than 7. In the second phase, with the Oddi sphincter closed, the secret should not be separated from the probe. In the third stage of the study, the clinically normal indicators of bile are as follows: the volume is from 3 to 5 ml, the color is light brown. The fourth phase lasts about half an hour. The color of the liver secretion varies from olive (gallbladder) to yellow-amber. Its pH is 6.5–7.5, and its density is approximately 1038. The last phase, the release of hepatic bile, lasts up to 20 minutes. The density decreases to 1011, pH = 7.5–8.2.
Deviations from the above parameters will beto testify about pathological disorders in the liver, gallbladder or ducts. The most common type of pathology is the formation of stones in the bladder due to the increase in fluid viscosity, as well as the violation of its contractile function. As you can see, in this article we reviewed and studied the secret of the liver - bile, its value and functions in the processes of digestion.
