Let's say the following task is set before you: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.
The liver is the largest gland ingastrointestinal tract, inherent in 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 towardsbile 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.
To compounds that help to break down complexmacromolecule of organic food components, refers to bile. It focuses on lipids, transferring them from the insoluble state to the appearance of the emulsion. Bile acids, chenodeoxycholic and cholate, found in bile 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 - lipase.
Knowing the structure of the structural elements of the liverlobules of the hepatocytes, as well as 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 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.
Having studied the chemical composition of the secret of the liver, 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 both enzymes that hydrolyze carbohydrates and proteins: amylase and trypsin, enhancing their catalytic properties. The enzyme 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.
Previously, we studied the properties of liver secretion,produced by the biliary parts of hepatocytes. And we also found 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 irritation of the interoreceptors of the walls of the mucous membranes of the oral cavity, stomach, small intestine.
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.
Для нормального протекания метаболических реакций In 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 are normal. They are determined by the method of multi-stage fractional duodenal sounding.
In the first phase of the study get the basalfraction. 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 (cystic bile) 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 betestify of pathological disorders in the liver, gallbladder or ducts. The most common type of pathology is the formation of stones in the bladder due to increased viscosity of the fluid, as well as the violation of its contractile function. As you can see, in this article we examined and studied the secret of the liver - bile, its value and functions in the processes of digestion.