What happens to absorbed amino acids and glucose after crossing enterocytes into the portal blood?

• A. They enter lymphatic system.
• B. They enter portal blood and go to the liver for processing.
• C. They bypass liver and go directly to systemic circulation.
• D. They are stored in enterocytes.

Answer: (B)

A key fact is that water-soluble nutrients absorbed by enterocytes are delivered to the liver first. After crossing the cell, amino acids and glucose are released into the basolateral side and enter the hepatic portal vein, bringing them to the liver for processing. In the liver, glucose can be taken up for immediate use, stored as glycogen, or released to maintain blood sugar levels, while amino acids are directed toward protein synthesis or converted into other compounds as needed. This first-pass arrangement helps regulate nutrient levels before they reach the rest of the body.

Fats, in contrast, are packaged into chylomicrons and enter the lymphatic system, bypassing the liver initially—so they don’t follow the portal blood path. Since amino acids and glucose are water-soluble and go via the portal vein to the liver, they do not bypass the liver or get stored in enterocytes.