Question

Blood flows from leg to heart against the gravity through the veins because

Answer 1

Answer:

The valves close when blood starts to flow in one direction, so that blood in the veins can only flow in the direction back to the heart, which is up the legs. ... So it is a combination of blood pressure from the heart's pumping action, the valves, and muscle movement that gets the blood up the legs against gravity

Answer 2

Explanation:

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. A closed valve working correctly prevents blood from flowing in reverse, back down your legs.