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How do valves in leg veins help blood move toward the heart?

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Silhouette diagram of the human body highlighting the heart and major blood vessels, with labeled arteries in red and veins in blue to show the structure of the cardiovascular system. — Circulatory system Human circulatory system.

Valves in the leg veins are essential for maintaining one-way blood flow toward the heart, particularly because blood must travel against the force of gravity.12

These valves function by preventing the backward flow of blood after it has been propelled upward. The movement of blood is primarily driven by the contraction of surrounding skeletal muscles, which squeeze the veins and push the blood toward the heart. Between these muscle contractions, the valves close to ensure that blood does not reverse its direction. Additionally, changes in pressure within the chest during breathing help draw blood upward from the legs, further assisting in efficient venous return.312

When these valves fail to function properly, blood can collect in the veins, potentially leading to conditions such as varicose veins.32