The Blood Flow System of the Legs
A healthy blood flow within the legs is dependent on a number of factors all working together. It requires the surface veins, the deep veins, the bicuspid valves and the calf muscles all to be operating well and in cooperation with each other. In some cases, however, due to injury, illness or simple aging, that doesn't always happen.
Normally, the surface veins generally carry a smaller amount of blood at lower pressure than the deep veins. The blood from these surface veins normally drains through the vascular system into the larger, deep veins in the leg. It is these deeps veins, situated within the major leg muscles, that carry the majority of the blood back up the leg. They carry a large volume of blood at high pressure as they help it on its journey back to the heart.
It is the movement of the calf muscle as we walk that provides the energy necessary to drive the blood back up our legs. That muscle contracts and relaxes as we move, forcing the blood upward out of the vein. As a portion of the vein empties, the backflow of that blood is prevented by the bicuspid valves, thus allowing the vein to fill with additional blood from the leg. The cycle of pumping the blood back up the leg is then repeated.