Venous blood flow

How does the blood get up my legs against gravity?

Your leg veins contain one-way valves. Under normal conditions, these valves allow blood to flow only “upwards” (from the toes towards the heart) when your vein is squeezed by your muscles.
When you are in the upright position, the blood in your leg veins must work against gravity to return to your heart. When your leg muscles contract, the valves inside your veins open. When your legs relax, the valves close.

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A closed valve working correctly prevents blood from flowing in reverse, back down your legs. The entire mechanism of sending blood back to the heart is called the venous pump. Since superficial veins are not surrounded by muscles, they rely on gravity alone, so they drain best when your leg is elevated.