How Veins Work
The cardiovascular system consists of the heart, arteries, and veins. Arteries circulate bright red oxygen-rich blood to the vital organs and tissues from the heart. Veins return the dark blue deoxygenated blood back to the heart from the vital organs and the tissues of our body.
The venous system of the legs is divided anatomically between the superficial veins, just beneath the skin, and the deep venous system, which lie within or beneath the muscles. The function of the superficial venous system is to direct blood to the deep venous system.
Arterial blood is pumped to the lower legs by the heart. Deoxygenated blood is pumped from the lower extremities by what is termed the “peripheral leg pump”. To get from the feet to the heart, in the upright position, blood must work against the force of gravity. The muscles of the calf and thigh contract, during walking, and squeeze the veins of the lower legs forcing blood upward toward the heart.
The veins in the lower legs have two functions. The first is to provide a conduit to return deoxygenated blood to the heart. The second is to prevent blood from pooling in the feet and lower legs when the muscle pump is off. A series of one-way valves (small flaps inside the veins) provides this function. When these valves become dysfunctional, blood flow is backward, a condition known as venous reflux. Over time the increased volume of the refluxing blood flow and pressure causes the walls of the veins to enlarge and dilate. As the vein walls enlarge, they become thinner and tend to buckle producing the characteristic “ropey-like” varicose veins.