Which statement describes the absorption pathways for carbohydrates, proteins, and fats?

Which statement describes the absorption pathways for carbohydrates, proteins, and fats?

• A. Carbohydrates and fats are absorbed into the hepatic portal circulation; proteins go to lymphatics.
• B. Carbohydrates and proteins are absorbed into the hepatic portal circulation; fats are packaged as chylomicrons and enter lymphatics.
• C. Carbohydrates and proteins are absorbed into the hepatic portal circulation; fats enter the lymphatic system via chylomicrons.
• D. All macronutrients are absorbed into the hepatic portal circulation.

Answer: (C)

A key idea here is that the body uses two main routes to transport digested nutrients after they leave the small intestine, depending on their properties. Carbohydrates and proteins are digested into monosaccharides and amino acids, which are water-soluble and readily absorbed into the intestinal blood. These products then travel via the mesenteric veins into the hepatic portal vein and reach the liver for processing. Fats, on the other hand, are not water-soluble. In the intestinal cells, long-chain fatty acids and monoglycerides are reassembled into triglycerides and packaged into chylomicrons. These are large particles that can’t enter blood capillaries directly, so they enter the lymphatic system through the lacteals in the intestinal villi and travel via lymph before eventually draining into the bloodstream. Thus, the correct description is that carbohydrates and proteins enter the hepatic portal circulation, while fats are carried through the lymphatic system via chylomicrons. Note that short-chain fatty acids and glycerol can enter portal blood, but the typical route taught for dietary fats is through the lymphatics with chylomicrons.

A key idea here is that the body uses two main routes to transport digested nutrients after they leave the small intestine, depending on their properties. Carbohydrates and proteins are digested into monosaccharides and amino acids, which are water-soluble and readily absorbed into the intestinal blood. These products then travel via the mesenteric veins into the hepatic portal vein and reach the liver for processing.

Fats, on the other hand, are not water-soluble. In the intestinal cells, long-chain fatty acids and monoglycerides are reassembled into triglycerides and packaged into chylomicrons. These are large particles that can’t enter blood capillaries directly, so they enter the lymphatic system through the lacteals in the intestinal villi and travel via lymph before eventually draining into the bloodstream.

Thus, the correct description is that carbohydrates and proteins enter the hepatic portal circulation, while fats are carried through the lymphatic system via chylomicrons. Note that short-chain fatty acids and glycerol can enter portal blood, but the typical route taught for dietary fats is through the lymphatics with chylomicrons.