لخّصلي

Every day a person needs to consume 80-100 grams of lipids. Food sources are products of animal and vegetable origin: oils, fat, dairy products, nuts. It must be said that polyunsaturated fatty acids (such as linoleic, linolenic, arachidonic acids) are not synthesized in the human body, these are essential acids, so they should come with food: oils, arachidonic acid is present in pork fat and dairy products.

The digestion of lipids begins in the small intestine. The whole process is divided into 5 stages:

1. 
   

   Fat emulsification.

   
   


2. 
   

   Hydrolysis by digestive enzymes

   
   


3. 
   

   Formation of micelles from decay products.

   
   


4. 
   

   Absorption of micelles into the intestinal epithelium.

   
   


5. 
   

   Resynthesis of triacylglycerols, phospholipids and cholesterol esters in enterocytes. Let's take a closer look at each stage.

   
   

For the first stage, the necessary condition is the emulsification of fats and the activation of lipases. Both states are achieved by the action of bile acids.

Bile acids are formed in the liver from cholesterol, deposited in the gallbladder and are released through the duct into the lumen of the small intestine as part of bile. Bile acids break up a large fat drop into many small ones and keep them in this state for a while, that is, they emulsify fat. At the same time, paired bile acids have the best detergent properties. Bile acids activate lipolysis enzymes (in particular, lipase and phospholipase) and are involved in the absorption of lipolysis products. Therefore, part of the bile acids is absorbed back, making a cycle. Emulsification is also facilitated by intestinal peristalsis and carbon dioxide released during the interaction of chyme and bicarbonates, which also contributes to the mixing of food gruel The second stage is hydrolysis by digestive enzymes. Depending on the class of lipids, some features of their digestion are formed (look at the scheme).

Absorption. Water-soluble lipid hydrolysis products are absorbed in the small intestine without the participation of micelles. Choline and ethanolamine are absorbed in the form of their active forms, that is, phosphorylated alcohols. Phosphoric acid is absorbed in the form of potassum and sodium salts, glycerol is absorbed in free form.

Fatty acids with a short and medium chain (up to 8-10 carbon atoms) are absorbed without the participation of micelles mainly in the small intestine.

Hydrophobic lipid hydrolysis products are absorbed in the small intestine with the participation of micelles. The micelles approach the brush border of enterocytes, and the lipid components of the micelles (betha-MAG. fatty acids, cholesterol, lysolecitin, phospholipids, etc.) diffuse through the membranes into the

cells. Regulation of lipid digestion is carried out with the help of cholecystokinin (or

pancreosimin), which causes the release of bile from the gallbladder and pancreatic juice from the pancreas into the lumen of the duodenum. Acidic chyme stimulates the secretion of the hormone secretin from the cells of the mucous membrane of the small intestine into the blood, stimulating the secretion of bicarbonates into the juice of the pancreas.