A blood vessel that carries blood away from the heart is an

• A. Artery
• B. Vein
• C. Capillary
• D. Lumen

Answer: (A)

In the circulatory system, whether a vessel is an artery or a vein is defined by the direction of blood flow relative to the heart. Vessels that carry blood away from the heart are arteries, while those that bring blood back toward the heart are veins. So a vessel that carries blood away from the heart is an artery. Think of the aorta—the main artery that leaves the heart to deliver blood to the body. Arteries typically have thicker, more muscular walls to handle the higher pressure of blood being pumped from the heart, and their lumens are relatively narrow compared to veins. Capillaries are the tiny vessels where exchange with tissues occurs, and the lumen is just the hollow interior of any vessel, not a separate vessel type. Even though pulmonary arteries carry blood to the lungs and are deoxygenated, they still carry blood away from the heart, which fits the same rule.