Lipid metabolism: the main stages of fat metabolism

Lipid metabolism is the metabolism of fats and fat - like substances. The exchange of lipids consists of four stages: splitting, absorption, intermediate and final exchanges.

Lipid exchange: cleavage. Most lipids that make up the food are absorbed by the body only after preliminary digestion. Under the influence of digestive juices they are hydrolyzed (broken down) to simple compounds (glycerol, higher fatty acids, sterols, phosphoric acid, nitrogenous bases, higher alcohols, etc.), which are absorbed by the mucosa of the digestive canal.

In the oral cavity, food containing lipids, mechanically crushed, mixed, moistened with saliva and transformed into a food coma. Shredded food masses through the esophagus enter the stomach. Here they are mixed and seeped with gastric juice. Gastric juice contains a lipolytic enzyme - lipase, which can break down emulsified fats. From the stomach food masses enter small amounts in the duodenum, then into the skinny and iliac. Here the process of lipid cleavage is completed and the products of their hydrolysis are absorbed. Bile, pancreatic juice and intestinal juice are involved in lipid digestion.

Bile is a secret that is synthesized by hepatocytes. Bile acids include bile acids and pigments, hemoglobin decomposition products, mucin, cholesterol, lecithin, fats, certain enzymes, hormones, and the like. Bile takes part in the emulsification of lipids, their splitting and absorption; Promotes normal intestinal peristalsis; Has a bactericidal effect on the intestinal microflora. Bile acids are synthesized from cholesterol. Fatty acids reduce the surface tension of fat drops, emulsifying them, stimulate the release of pancreatic juice, and also activate the action of many enzymes. In the small intestine, food masses leak from pancreatic juice, which includes sodium hydrogencarbonate and lipolytic enzymes: lipase, cholinesterase, phospholipase, phosphatase, etc.

Lipid exchange: absorption. Most of the lipids are absorbed in the lower part of the duodenum and in the upper part of the jejunum. Products of food lipid digestion are absorbed by the villous epithelium. The suction surface of the epithelial cell is enlarged due to microvilli. The final products of lipid hydrolysis consist of fine fat particles, di- and monoglycerides, higher fatty acids, glycerol, glycerophosphates, nitrogenous bases, cholesterol, higher alcohols and phosphoric acid. In the thick section of the intestine, lipolytic enzymes are absent. Mucus of the large intestine contains a small amount of phospholipids. Cholesterol, which is not absorbed, is reduced to cola koprostelin.

Lipid metabolism: intermediate metabolism. In lipids, it has some peculiarities, which consist in the resynthesis of lipids inherent in a person in the small intestine immediately after absorption of the cleavage products.

Lipid exchange: final exchange. The main end products of lipid metabolism are carbon dioxide and water. The latter is excreted in the composition of urine and sweat, partly feces, exhaled air. Carbon dioxide is predominantly light. The final exchange for individual groups of lipids has its own peculiarities.

Disorders of lipid metabolism. Lipid metabolism is disrupted in many infectious, invasive and non-contagious diseases. The pathology of lipid metabolism is observed in the violation of neurohumoral regulation of the processes of cleavage, absorption, biosynthesis and lipolysis. Among the violation of lipid metabolism, obesity is most often recorded.

Obesity is a predisposition of the body to excessive weight gain due to excess fat deposition in the subcutaneous tissue and other body tissues and intercellular space. Fats are deposited inside the fat cells in the form of triglycerides. The number of lipocytes does not increase, but only their volume increases. It is this hypertrophy of lipocytes that is the main factor of obesity.