The hepatic portal vein is unusual because it
- A. carries oxygenated blood to the liver
- B. carries blood directly from the heart to the liver
- C. has thicker walls than any artery
- D. begins in the capillaries of the gut and ends in the capillaries of the liver
Explanation
A portal vessel runs between two capillary beds instead of returning blood to the heart, so absorbed glucose and amino acids reach the liver before entering the general circulation. This lets the liver regulate blood glucose and remove toxins straight after a meal. The blood it carries is deoxygenated, since it has already passed through the intestinal capillaries.