What veins do
Veins form a network throughout the body. They carry used blood from the tissues to the heart and on to the lungs.
Deep and superficial veins
Most of the blood in the legs flows in deep veins that run between the muscles and are supported by the muscle sheath. Superficial veins under the skin carry a smaller share. They lack the wall support of deep veins, so increased pressure from long periods of standing or sitting can affect the vein wall and valves more easily.
Saphenous veins and valves
There are two large superficial veins in the leg. The great saphenous vein runs along the inner leg from ankle to groin, where it joins the deep system. The small saphenous vein starts behind the outer ankle, runs up the back of the calf and joins the deep system behind the knee.
Valves where these veins join the deep system stop blood flowing backwards when standing. Failure of these valves plays a key role in varicose veins.
The calf muscle pump
When walking, the calf muscles squeeze the veins and help push blood up towards the heart. Inactivity weakens this pump, which is why regular walking is recommended for vein health.
Related pages
Frequently asked questions
What is valve failure?
Venous valves no longer close fully, so blood flows backwards; it is the most common cause of varicose veins.
Why is walking recommended?
The calf muscles working during walking help blood return to the heart.
