How do arteries differ from veins in wall structure and blood flow direction relative to the heart?

• A. Arteries carry blood toward the heart under high pressure; veins carry blood away from the heart under lower pressure.
• B. Arteries have thicker walls and carry blood away from the heart under high pressure; veins have thinner walls, larger lumens, valves, and carry blood toward the heart under lower pressure.
• C. Arteries carry deoxygenated blood; veins carry oxygenated blood.
• D. Arteries and veins have identical wall structure but different colors.

Answer: (B)

Arteries are built to handle the high pressure generated when the heart contracts, so their walls are thicker and rich in smooth muscle and elastic fibers, with a relatively smaller lumen. This sturdy structure lets them push blood efficiently away from the heart and maintain pressure as the blood travels to tissues. Veins, by contrast, have thinner, more compliant walls, a larger lumen, and often valves to prevent backflow in the low-pressure system that returns blood to the heart. The direction of flow aligns with their roles: arteries carry blood away from the heart, while veins return blood toward the heart.