The venous system in the lower limbs is made up of a number of complex anatomical structures, including principally:
The deep venous system, located in the central axis of the leg, follows the arteries and is surrounded by muscles and aponeurosis. (The veins have the same names as the arteries that they run alongside: iliac, femoral, popliteal, fibular, tibial veins, etc.).
The superficial venous system varies greatly from one person to another. This network of veins is located primarily in the subcutaneous adipose layer, between the wall of the skin and the aponeurosis encasing the muscles. The main two components of the superficial venous system are :
- the great saphenous (or greater saphenous) vein, which runs up the inner surface of the calf and thigh before joining the femoral vein,
- the small saphenous (or lesser saphenous) vein, located on the posterior surface of the calf and draining into the popliteal vein.
Perforating veins, which cross the aponeurosis to link deep and superficial veins
The superficial network formed of fine dermal and subcutaneous venules is also called the superficial plantar venous plexus and lines the entire sole of the foot. The deep system mainly consists of the medial and lateral plantar veins located between the muscle masses of the sole and draining blood into the posterior tibial veins, but also includes the pedal veins on the dorsal surface of the foot, and the dorsal veins of the foot forming the dorsal venous arch that is clearly visible beneath the skin.
This deep network is what forms the true venous pump of the foot and explains the impact of dorsi-flexion movements of the toes on acceleration of posterior tibial venous flow. Conversely, strong compression on the plantar zone is required to activate venous reflux.
The venous valves are mobile bicuspid structures with a tiered arrangement, made of fibrous, elastic tissue and coated with endothelium. The veins are dilated at the valves, creating a sinus space to facilitate opening and closing movements. These valves, which are arranged every 4 to 5 centimetres, ensure the blood flows in one direction only, preventing venous reflux.
