Blood return from the legs is propelled by the leg muscles. When in motion (walking, exercising), our muscles contract, squeezing the veins. Blood gets pushed up towards the heart. In healthy veins, the blood does not reflux back (back down towards the foot) upon muscle relaxation. Vein valves play a major role in the process.
Many veins, particularly those in the legs, have one-way valves. Each valve consists of two flaps with edges that meet. Blood, as it moves toward the heart, pushes the cusps open like a pair of one-way swinging doors. If the blood tries to pull backward, the cusps close, stopping backward flow. Valves help the return of blood to the heart—by opening when the blood flows toward the heart and closing when blood might flow backward because of gravity.
What happens when valves stop working, lose their function?
Leaky valves, what we call them, promote development of varicose veins.
The blood flow is not directed towards the heart anymore. Valves do not close and the backward stream of returning blood moves down towards the foot. Legs vein pressure increases. Veins become larger and larger, trying to accommodate the surplus of retained blood. Blood finds its way to smaller, subsequently enlarging superficial veins. Varicose veins form in a perpetuated manner.
©Peter Brukasz MD