A vein is a blood vessel that carries blood low in oxygen content from the body to the lungs and heart. It is a normal part of the circulatory system. Thousands of people every year consider getting treatment for varicose veins and spider veins.
Cause
The causes of varicose and spider veins are not entirely understood. In some instances, the absence or weakness of valves in the veins, which prevent the backward flow of blood away from the heart, may cause the poor circulation. In other cases, weaknesses in the vein walls may cause the pooling of the blood.