How are the portal vein and hepatic portal system related to digestion?

• A. They carry bile from liver to small intestine.
• B. They transport blood away from liver.
• C. They carry absorbed nutrients from gut to liver for processing before entering systemic circulation.
• D. They carry air from lungs to liver.

Answer: (C)

The key idea is that the portal vein and hepatic portal system deliver nutrients absorbed from the digestive tract to the liver for processing before they reach the rest of the body. After nutrients are absorbed in the small intestine, they travel via the hepatic portal vein to the liver, where they can be stored, converted, or detoxified. Once the liver has processed them, the blood returns to the general circulation, helping regulate nutrient levels and maintain metabolic balance.

Bile moving from the liver to the small intestine is done by the bile ducts, not the portal system. Blood that leaves the liver goes through hepatic veins to the inferior vena cava, not via the portal vein. And carrying air from the lungs to the liver isn’t a physiological role.