The most important secret involved in digestion is bile..

It is a product of the activity of liver cells - hepatocytes, has a complex composition and helps to neutralize acidic gastric contents entering the duodenum, emulsifies fats, dissolves their hydrolysis products, activates pancreatic lipase.

Bile stimulates bile formation, bile secretion, motor and secretory activity of the small intestine, has bacteriostatic properties, promotes the absorption of fat-soluble vitamins, cholesterol, amino acids and other substances from the intestine..

A person produces up to 2 liters of bile per day. The formation of bile occurs through the active secretion of its components (bile acids) by hepatocytes, active and passive transport of certain substances from the blood (water, glucose, creatinine, electrolytes, vitamins, hormones, etc.).. ) and reabsorption of water and a number of substances from the bile capillaries, ducts and gallbladder.

The process of bile formation.

The process of bile formation - bile secretion (choleresis) - is continuous, and the flow of bile into the duodenum - bile secretion (cholekinesis) - periodically, mainly in connection with food intake. On an empty stomach, bile hardly enters the intestine, it goes to the gallbladder, the capacity of which is only 50-60 ml, where it concentrates and somewhat changes its composition.. Therefore, it is customary to talk about two types of bile - hepatic and cystic..

Bile is not only a secret, but also an excretion, since various endogenous and exogenous substances are excreted in its composition.. This largely determines the complexity and differences in the composition of hepatic and gallbladder bile (Table.

The qualitative originality of bile is determined by the bile acids, pigments and cholesterol contained in it.. In the human liver, cholic and chenodeoxycholic acids (primary) are formed, which in the intestine under the influence of enzymes are converted into several secondary bile acids..

The main amount of bile acids and their salts is found in bile in the form of compounds with glycocol and taurine.. In humans, glycocholic acids are about 80% and taurocholic acids are about 20%. This ratio changes under the influence of a number of factors.. So, when eating a meal rich in carbohydrates, the content of glycocholic acids increases, with a high-protein diet - taurocholic acids..

About 85-90% of bile acids (glycocholic and taurocholic) released into the intestine as part of bile are absorbed into the blood from the small intestine.. Then they are brought to the liver and included in the composition of bile.. The remaining 10-15% of bile acids are excreted from the body mainly in the feces (a significant amount of them is associated with undigested food fibers). This loss of bile acids is replenished by their synthesis in the liver..

Although bile formation is continuous, its intensity changes in some processes due to regulatory influences.. Thus, the act of eating increases bile formation, various types of food taken, t. bile formation changes somewhat with irritation of the interoreceptors of the gastrointestinal tract (GIT), other internal organs and with conditioned reflex effects.

Bile itself is one of the humoral stimulants of bile formation.. The more bile acids enter from the small intestine into the blood of the portal vein, the more they are excreted in the bile and the less is synthesized by hepatocytes..

If less bile acids enter the bloodstream, then the deficiency is compensated by increased synthesis of bile acids in liver cells.. Secretin increases the secretion of bile (that is, the release of water and electrolytes in its composition). Glucagon, gastrin and cholecystokinin-pancreozymin stimulate bile formation less.

The movement of bile in the biliary apparatus is due to the pressure difference in its parts and in the duodenum, as well as the state of the sphincters of the extrahepatic biliary tract. There are three sphincters (Fig.. 6): at the confluence of the cystic and common bile ducts (sphincter of Mirizzi), at the neck of the gallbladder (sphincter of Lutkens) and at the terminal section of the common bile duct (sphincter of Oddi). The muscle tone of these sphincters is important for the direction of bile flow..

A small amount of bile passes through the sphincter of Oddi into the duodenum.. This period of the primary reaction of the biliary apparatus lasts 7-10 minutes. This is followed by a period of emptying of the gallbladder, during which contractions of the bladder alternate with relaxation, and through the open sphincter of Oddi passes into the duodenum, first mainly gallbladder bile, and later - hepatic. The duration of the latent and evacuation periods, the amount of secreted bile are different and depend on the type of food taken..

Strong causative agents of bile secretion are egg yolks, milk, meat and fats.. After 3-6 hours after eating, a decrease in bile secretion is observed, the attenuation of the contractile activity of the gallbladder, in which hepatic bile begins to be deposited again.

Insufficient flow of bile into the intestines is called hypocholia, a complete cessation of its flow is called acholia.. These phenomena are possible with blockage or compression of the common bile duct, with a violation of the bile-forming function of the liver. With acholia, the digestion and absorption of fat suffers sharply, since pancreatic lipase in the absence of bile is inactive, and fats are not emulsified and their contact with the lipolytic enzyme is difficult..

With a lack of bile, the absorption of fatty acids, cholesterol, fat-soluble vitamins suffers.. Due to insufficient digestion and absorption of fat, steatorrhea develops - excess fat in the stool.

With feces, up to 70-80% of fat is excreted.. In the intestine, unsplit fat envelops the food masses and makes it difficult for pancreatic proteolytic enzymes and a-amylase to act on them.. The hydrolytic activity of enzymes decreases with a lack of bile, since bile takes part in the neutralization of acidic gastric contents and helps to maintain an alkaline environment in the duodenum, which is optimal for duodenal juice enzymes..

Finally, bile acids stimulate the sorption properties of the intestinal epithelium, therefore, when they are deficient, the adsorption of enzymes from the chyme by the intestinal cells decreases and membrane digestion is disturbed.. Thus, with hypo- and acholia, the initial and intermediate stages of digestion of proteins and carbohydrates in the small intestine are also disturbed..

Along with undigested fats, fat-soluble vitamins are also excreted from the intestines.. Hypovitaminosis develops, in particular, blood clotting often decreases due to vitamin K deficiency..

With hypo- and acholia, intestinal peristalsis is weakened, which, combined with the loss of the bactericidal action of bile, leads to an increase in the processes of fermentation and putrefaction in the intestine, to flatulence - intestinal dysbacteriosis develops. The result is intoxication of the body..

Reflex influences on the biliary apparatus are carried out conditionally and unconditionally reflexively with the participation of numerous reflexogenic zones, including receptors in the oral cavity, stomach and duodenum.

The role of humoral regulation of bile secretion is great. Cholecystokinin plays an important role as a humoral stimulant of bile secretion, causing contraction of the gallbladder.. The contractions of the gallbladder, although weak, also cause gastrin, secretin, bombesin. Inhibits gallbladder contractions glucagon, calcitonin, anticholecystokinin.

Baranovsky.

medbe. en.