Which statement about venous drainage is correct?

• A. The cranial vena cava drains blood from the hind limbs.
• B. Veins carry oxygenated blood toward the heart.
• C. Veins have thicker walls than arteries.
• D. The cranial vena cava drains deoxygenated blood from the head and neck, while the caudal vena cava drains the remainder of the body.

Answer: (D)

The important idea is how blood is returned to the heart through the two main veins. Blood from the head and neck (and forelimbs) is collected by the cranial vena cava and carried to the right atrium, while blood from the abdomen, pelvis, hind limbs, and the rest of the body drains through the caudal vena cava. This makes the statement correct: it accurately assigns the cranial vena cava to deoxygenated blood from the head and neck and the caudal vena cava to the remainder of the body. The other ideas don’t fit: hind limbs drain via the caudal vena cava, not the cranial; veins generally carry deoxygenated blood toward the heart (with the pulmonary veins as an exception); and arteries have thicker, more muscular walls, whereas veins have thinner walls and valves to help return blood to the heart.