Which vessels are equipped with valves to direct blood flow?

• A. Arteries
• B. Veins
• C. Capillaries
• D. Lymphatic vessels

Answer: (B)

Valves are essential in vessels whose flow can be slowed or reversed by gravity, helping push blood back toward the heart. Veins carry blood back to the heart at low pressure and use one-way valves to prevent backflow, especially in the limbs where muscle movement helps pump blood upward. Arteries transport blood away from the heart under high pressure and typically do not have valves along their length, since the pressure keeps the blood moving forward. Capillaries are tiny exchange vessels without valves, because their role is diffusion and rapid transit. Lymphatic vessels have valves too, but they carry lymph, not blood, so they aren’t blood vessels. Thus, the vessels equipped with valves to direct blood flow are the veins.