M Veins

The veins from the arms, together with those from the upper trunk and the head and neck, drain into the superior vena cava and on into the right atrium. Veins from the legs and the lower trunk drain upward into the inferior vena cava. Because the leg veins are especially susceptible to dysfunction, they warrant special attention.

The deep veins of the legs carry about 90% of the venous return from the lower extremities. They are well supported by surrounding tissues.

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In contrast, the superficial veins are located subcutaneously, and are supported relatively poorly. The superficial veins include (1) the great saphenous vein, which originates on the dorsum of the foot, passes just in front of the medial malleolus, and then continues up the medial aspect of the leg to join the deep venous system (the femoral vein) below the inguinal ligament; and (2) the small saphenous vein, which begins at the side of the foot and passes upward along the back of the leg to join the deep system in the popliteal space. Anastomotic veins connect the two saphenous veins superficially and, when dilated, are readily visible. In addition, communicating (or perforating) veins connect the saphenous system with the deep venous system.

Deep, superficial, and communicating veins all have one-way valves. These allow venous blood to flow from the superficial to the deep system and toward the heart, but not in the opposite directions. Muscular activity contributes importantly to venous blood flow. As calf muscles contract in walking, for example, blood is squeezed upward against gravity, and competent valves keep it from falling back again.

Femoral vein

Great saphenous vein

Femoral vein

Great saphenous

Small saphenous vein t t

Communicating vein

Small saphenous vein

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