Question

Which blood vessel has the largest amount of urea
A. Renal vein
B. Hepatic vein
C. Hepatic portal vein
D. Dorsal aorta/renal artery

Answer 1

Hint: The largest amount of urea containing a vein must be the vein that emerges from the liver. When the liver breaks down amino acids and detoxifies the blood, the vein emerging from the liver will drain all the impurities i.e., the urea and pass the pure deoxygenated blood back to the heart. More specifically it passes the blood to the inferior vena cava where further reoxygenation takes place.

Complete answer:
Option A Renal vein: It is the blood vessel that receives deoxygenated blood from the kidney and returns it to the systemic circulation. Since this vein receives pure blood, it cannot contain urea. So, this option is wrong.
Option A is incorrect.
Option B Hepatic vein: The hepatic veins carry deoxygenated blood from the liver to the inferior vena cava. The hepatic vein is rich in urea. This is because urea is a by-product of amino acid catabolism, which occurs in the liver.
Option B is correct.
Option C Hepatic portal vein: Hepatic portal vein transports blood that is drained from the pancreas, small intestine, spleen and stomach to the liver. This blood contains nutrients and toxins that have been extracted from the digested contents.
Option C is incorrect.
Option D Dorsal aorta/renal artery: The renal artery transports oxygenated blood to the kidney. Inside the kidney it branches off into smaller arteries to supply blood to the interior parts of the organ. Since they carry pure blood, they do not contain any urea.
Option D is incorrect.

Therefore, Option B. Hepatic vein is the correct answer.

Note:
The hepatic veins originate from the core vein of the liver lobule. They do not have any valves. They can be classified into lower group and the upper group veins Any defects in the outflow of blood from the hepatic veins may result in a serious condition known as Budd-Chiari syndrome, which can cause liver damage.