Varicose Vein and
Veins return oxygen-poor blood back to the heart. When standing, the muscles of the legs work against gravity to pump the blood back to the heart. Veins have valves inside them which help keep the blood flowing in the correct direction. When the leg muscles contract, the valves in the veins open; when the leg relaxes, they close. A weakened vein wall and damaged valves can cause varicose veins and, in some cases, venous ulcers.