How are fats broken down and absorbed in the small intestine?

• A. Digested by pancreatic amylase; absorbed into portal blood.
• B. Emulsified by saliva; absorbed by capillaries directly.
• C. Broken down into fatty acids and glycerol by lactase; absorbed into lymph.
• D. Emulsified by bile produced by the liver; organized into chylomicrons and diffused into the lymphatic capillaries (since they are too big to be absorbed by the blood capillaries) and end up in the veins.

Answer: (D)

Fats are processed by first being emulsified in the small intestine by bile, which comes from the liver. This increases the surface area for enzymes to act. Pancreatic lipase then digests the triglycerides into fatty acids and monoglycerides. Inside the enterocytes, these products are rebuilt into triglycerides and packaged with cholesterol and apolipoproteins into chylomicrons. Because these particles are too large to enter blood capillaries, they enter the lymphatic system via the lacteals in the intestinal villi. The lymphatic vessels carry them to the thoracic duct and then into the veins, so fats ultimately reach the bloodstream through the venous system. This sequence—bile emulsification, lipase digestion, chylomicron formation, lymphatic transport, and eventual venous return—is why fats are absorbed via the lymph rather than directly into portal blood.