In your veins there are one-way valves that are placed about one inch apart that keep blood flowing in the right direction. When your leg muscles relax, the valves inside your veins close preventing the backward flow of blood back down the legs.
Why do veins have valves?
Most veins contain valves (known as the valvula venosa in the TA) to prevent backflow, i.e. ensuring that blood flow is always towards the heart 1.
How many valves do veins have?
Many veins, particularly those in the arms and legs, have one-way valves. Each valve consists of two flaps (cusps or leaflets) with edges that meet.
