Functional Anatomy of the foot venous system

The venous anatomy of the foot is quite different from that of other areas in the body, where veins are usually categorized as superficial, deep, and perforating. In the foot, however, the venous system is better understood as having two functional units-medial and lateral-each with its own network of superficial, deep, and perforating veins (PVs). This way of looking at it contrasts with the classification used for other parts of the lower limb, providing a unique insight into the foot's anatomy and function. The medial functional unit consists of the medial plantar veins, medial PVs, and the (superficial) marginal vein, while the lateral functional unit includes the lateral plantar veins along with the lateral and calcaneal PVs. The plantar veins are situated deep within the plantar pump. Certain dorsal perforating veins connect directly to the initial segments of the anterior tibial and fibular veins. Interestingly, some perforating veins in the foot are either valveless or possess valves in an "inverted" anatomical position, which allows blood to flow from deep to superficial veins under normal physiological conditions. These PVs act as the main outlet from the foot pump to the superficial venous system, promoting upward flow in both the great and small saphenous systems during the systolic phase of the foot's pump. Although the volume of blood pushed with each step is small, an effectively working foot pump is essential for aiding venous return from the limb.