The superficial veins lie under the skin and in the subcutaneous fatty tissue. Superficial veins are not fully surrounded by muscles and not capable of generating the force necessary to return blood to the heart in the upright position. The superficial veins are under the influence of the nervous system and function primarily to maintain body temperature by dilating to allow increased heat loss or contracting to prevent heat loss. When the valves in the superficial veins become incompetent the veins may enlarge and appear raised above the level of this skin and look like twisted bulging chords. The largest superficial vein is the Great Saphenous vein which runs from the inner part of the ankle all the way up to the inner thigh and empties at the groin level into the Femoral Vein through the Saphenofemoral Junction (SFJ). The Small Saphenous Vein runs along the outer part of the ankle and empties into the Popliteal Vein through the Saphenopopliteal junction which is located behind the knee. Other important superficial veins are the Anterior Accessory Saphenous Veins which run along the course of the thigh and empty into the Great Saphenous Vein just below the level of the SFJ. The Lateral Subdermic Complex runs along the outer surface of the calf and thigh and connects with the deep veins in the pelvis and upper thigh.