Venous system transports blood from the body back to the heart. The superficial subcutaneous division in the legs contains the long and short saphenous veins, which transports blood from the surface to the deep veins. The deep venous division includes iliac, femoral, popliteal, and deep femoral veins. Deep veins are parallel to corresponding arteries. These two divisions are further connected by perforating veins (communicating). Vein walls are thinner and less elastic than that of the arteries and consist of three layers: intima (inner), media (middle), and adventitia (outer). Veins have valves that open when blood is pressed upwards towards the center of the body against gravity. They close to prevent blood from flowing backwards.