Deep Venous System and the Musculovenous Pump
Venous blood from the legs has to be actively pumped by the leg muscles so that it will be able to return the blood up to the level of the heart. The largest veins in the legs are the deep veins which are completely surrounded by the muscle compartments in the calf and thigh. The deep vein at the top of the calf is called the Popliteal Vein and it drains all the venous blood from the calf muscles. This vein continues up through the thigh where it drains all of venous blood from the thigh muscles and is called the Femoral Vein. When we walk, or simply cross our legs, or even make minor unconscious changes in the position of our feet, the respective muscles in the calf and thigh exert pressure on the deep veins forcing the venous blood upwards to the heart. These deep veins are the “heart” of the musculovenous pump system. Above the groin area the Femoral Vein courses into the pelvis to form the Iliac Vein. The right and left Iliac Veins join to form the Inferior Vena Cava which returns venous blood into the heart through the Right Atrium. There are no muscles surrounding the deep veins in the pelvis and abdomen to aid in pumping the blood up to the chest. The diaphragm muscle used for breathing creates negative pressure in the chest and this helps to pull the blood up to the level of the heart.