Lipid absorption - end products & transport mechanism

• The end products, fatty acids and monoglycerides, depend on bile salts for absorption. • Bile salts form micelles (tiny spheres), which ferry fatty acids and monoglycerides to epithelial cells. • Free fatty acids, monoglycerides, and some phospholipids and cholesterol molecules, diffuse freely into epithelial cells. • Micelles diffuse back into the chyme and continue transporting end products. • Monoglycerides are commonly digested further by lipase, producing glycerol and fatty acids. • Glycerol and fatty acids then recombine to form triglycerides. • Triglycerides then aggregate with phospholipids and cholesterol to form chylomicrons. • Chylomicrons are then coated with proteins and leave the epithelial cell via exocytosis. • Chylomicrons are too bulky to enter blood capillaries directly. • They enter lacteals, travel through lymphatic vessels and enter the bloodstream at the left subclavian vein. • Chylomicrons are quickly removed from the blood and broken down by lipoprotein lipase in capillary endothelial cells in the liver and adipose tissue.

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