Veins are blood vessels that return blood to the heart and lungs so it can be re-oxygenated. This means that blood in the veins should move up and out of the legs towards the heart. There are two mechanisms which counteract gravity and promote blood flow up the veins: the calf muscles and one way valves. Each time the calf muscles contract with activities such as walking, it squeezes the veins in the legs forcing blood to move in an upwards direction (towards the heart). Once blood is squeezed up the legs, the one way valves close preventing blood from flowing backwards in the veins (towards the feet).
There are two systems of veins at work in the legs: the deep system and the superficial system. The deep system veins are of a large diameter and are situated close to the bone, surrounded by muscle. The superficial system veins are located in the fat tissue under the skin, and at times are visible. These two systems meet at two junctions, one at the groin and the other behind the knee, and also through a series of connecting veins called perforators.
Click one of the links below to learn more about the different types of vein disease.