What happens to fatty acids after absorption by enterocytes?

• A. They are oxidized for energy in the enterocyte.
• B. They are converted to glycogen in the enterocyte.
• C. They enter the portal circulation directly to the liver.
• D. They are remade into triglycerides and enter the lymphatic system.

Answer: (D)

Fatty acids that are absorbed by enterocytes are reassembled into triglycerides and packaged for transport. Inside the enterocyte, long-chain fatty acids are re-esterified with glycerol-3-phosphate to form triglycerides, which then combine with cholesterol esters, phospholipids, and apolipoprotein B-48 to make chylomicrons. These chylomicrons are too large to enter blood capillaries directly, so they enter the lymphatic system via lacteals and travel through the lymphatic vessels to the thoracic duct, eventually reaching the bloodstream. This pathway allows dietary fats to reach tissues via the lymphatic system, rather than directly through the portal vein to the liver. Short- and medium-chain fatty acids, in contrast, can be absorbed directly into the portal circulation and go to the liver, and enterocytes do not store fats as glycogen.