VARICOSE VEINS

The leg veins contain valves, which open when calf muscle contraction forces blood towards the heart and close when the muscles relax, thus preventing backflow. If valves become incompetent (because of venous hypertension from, e.g., prolonged standing, occlusion by fetus, previous DVT), blood moves from deep to superficial vessels, resulting in prominent, bulging veins (varicosities).