Anatomy and function of leg veins
In the legs there are 2 systems of veins - the deep and superficial. The deep system is the main way blood leaves the leg and returns to the heart. This system is buried deep in the leg and cannot be seen from the outside. The superficial system is just under the skin and can be seen. Varicose veins affect this system. It is not essential for draining blood from the leg.
As you can see from the diagram deep veins start in the calf and join to form a single vein behind the knee (this is called the 'popliteal vein'). In the thigh the vein ('femoral vein') carries blood to the groin. There are essentially 2 superficial veins - the long and short 'saphenous' veins. The long saphenous vein runs from the inner ankle, along the inside of the leg and joins the deep veins in the groin (the 'sapheno-femoral junction'). The short saphenous vein starts at the outer ankle and runs along the back of the calf to join the popliteal vein behind the knee ('sapheno-popliteal junction'). In addition to these junctions the deep and superficial veins are connected by small veins called 'perforators'. They are so-named because they perforate through the tough covering of the muscles (fascia).
All of these veins have valves in them that allow blood to flow in one direction only - towards to heart.
