Lipid Digestion and Absorption

Digestion

-consist mainly of triacylglycerols, with the remainder comprised of cholesterol, cholesteryl esters, phospholipids and free fatty acids. -lipids are transported to the small intestine essentially intact, up on entry into the duodenum, emulsification occurs which is aided by bile. Finally, the pancreas secretes pancreatic lipase, colipase and cholesterol esterase into the small intestine, these enzymes hydrolyze the lipid components to 2-monoacylglycerol, free fatty acids and cholesterol.

Absorption

1. Micelles diffuse to the brush border of the intestinal mucosal cells where they are absorbed. 2. The digested lipids pass through the brush border, where they are absorbed into the mucosa and re-esterifed to form triacylglycerols and cholesteryl esters and packaged, along with certain apoproteins, fat-soluble vitamins and other lipids into chylomicrons. 3. Chylomicrons leave the intestine via lacteals and re-enter the bloodstream via the thoracic duct.

Micelles formation

Are formed from free fatty acids, cholesterol, 2-monoacylglycerol and bile salts which cluster amphipathic lipids that are soluble in the aqueous environment of the intestinal lumen

emulsification

The mixing of two normally immiscible liquids; increases the surface area of the liquid,which permits greater enzymatic interaction and processing.

bile

a substance secreted by the liver and stored in the gallbladder; contains bile salts, pigments and cholesterol.

Chylomicrons

the class of lipoproteins that transport lipids from the intestinal cells to the rest of the body

lacetals

vessels of the lymphatic system