Lipid Absorption

In the duodenum, dietary triglycerides in chyme are mixed with bile salts.

This process breaks down large fat droplets into smaller ones.

Once emulsified, the pancreatic lipases hydrolyze the triglycerides into fatty acids and monoglycerides.

These breakdown products bind the bile salts and lecithin to form micelles, which easily pass between microvilli to come in close contact with the apical enterocyte membrane.

At the membrane, fatty acids and monoglycerides leave the micelles to enter the enterocytes via simple diffusion, where they undergo re-esterification back into triglycerides.

The newly formed triglycerides combine with proteins and phospholipids within the enterocytes to create chylomicrons, large lipoprotein particles.

Chylomicrons exit the enterocytes by exocytosis to enter lacteals, specialized lymphatic vessels in the intestinal villi.

They travel through the lymphatic system and enter the bloodstream via the thoracic duct.

In the blood, triglycerides in the chylomicrons are hydrolyzed by lipoprotein lipase associated with the capillary endothelium into free fatty acids and glycerol, which are used for energy production or stored as fat.