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How Veins Work

 

The legs are like any other part of body, in that they need a supply of blood to provide oxygen to the tissues and to remove carbon dioxide. The supply of oxygen rich blood to the legs and all around the body is via the arteries to a network of Capillaries. The capillaries disperse the blood through the tissues and then the deoxygenated blood returns to the heart via the veins.

The beating of the heart supplies the pressure needed to move blood through the arteries at high pressure. We can feel this in our pulse.

However, once the blood has passed through the capillary network in the tissues and on to the veins, this pressure is very much reduced and not sufficient to ensure the return of blood from the lower limbs, against the force of gravity

When you are lying down there is just enough pressure left in the blood for it to return to the heart. When you are sitting up or standing up this is a different story as the heart is above the level of your legs, which results in an increase in pressure at the ankles due to the column of blood above it. This is called “hydrostatic” or “gravitational” pressure.

The reduced blood flow out of the legs, can result in fainting in people who have been standing still for extensive periods.

Veins of the leg

The reason we do not all routinely faint when sitting or standing is because we actually have a functional ‘pump’ within the legs, that drives the blood back into the pelvis where breathing helps the blood back to the heart. This pump is called the muscle pump or a peripheral heart and it depends on 2 factors to get the blood out of the legs; movement and valves.

Movement of the leg muscles causes a compression on the veins and it is this compression of the veins that makes the blood flow. The valves prevent the blood from flowing in the wrong direction.

When the valves in the veins are functioning correctly, the veins are known as “competent”. When the valves do not work correctly, they are called “incompetent”.

With incompetent valves, the muscles compresses the veins and the blood is forced up the leg but when the pressure is eased the valves do not close completely to stop the blood from coming back down the leg, a process called reflux.

Venous reflux is the main cause of most venous related disorders and also is the only cause of varicose veins.

There are two systems of veins within the legs the deep veins and the superficial veins. The deep veins are responsible for doing the majority of the work within the leg and do not cause varicose veins. The superficial veins are the secondary system in the leg that helps drain blood from the superficial tissues and back into the deep veins for return the heart.

It is a problem with valves failing inside the superficial veins that causes varicose veins and related disorders.

 

 Contiune here to read about Varicose Veins