AP BIOLOGY

Detailed explanation-1: -The main harmful substances in the blood are urea and bicarbonate ions. Urea is the product of excess amino acids. It is transported into blood plasma by the liver and removed by the kidney.

Detailed explanation-2: -Hepatic vein is the correct answer.

Detailed explanation-3: -The hepatic vein is connected to the liver. It transports the deoxygenated blood with urea away from the liver to the inferior vena cava. That’s why the hepatic vein contains the highest concentration of urea.

Detailed explanation-4: -The hepatic vein carries the largest amount of urea in mammals. It leads from the small intestine to the liver. Since the liver is the primary site for urea production the hepatic vein carries it in great concentration. It carries blood from the liver to the vena cava, which in turn, takes it to the heart.

Detailed explanation-5: -Urea is a nitrogenous waste produced as a by-product of the metabolism of proteins. This process takes place in the liver. It does not occur in the kidney.