Why Do Veins Have Valves and Arteries Do Not?
Veins have valves to prevent blood from flowing backwards and pooling, whereas arteries pump blood at higher pressures, which naturally prevents backflow. Veins need valves to keep blood flowing in one direction because the flow is less constant; the flow in arteries is constant and requires artery walls to be more flexible and strong enough to accommodate the high pressures.
The valves in veins allow blood flow in one direction while blocking any counter-flow. These valves assist the body in sending blood in the correct direction; for example, blood flow must work against gravity to move blood from your legs back toward your heart. The valves ensure success, as they keep blood moving forward in the veins.
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