Like the arteries, the veins are tube-like vessels in graduated sizes, but unlike the arteries, the veins have tiny valves on their inner walls to prevent the blood from flowing backward, toward the arteries. If the valves do not work properly, circulation is impaired and blood accumulates in the veins, stretching them. The result is varicose veins. Proper health and nutrition can help support proper functioning of venous valves and maintain elasticity of the veins.