Veins

What are veins and how do they work?

Veins are vessels through which the de-oxygenated blood flows from the organs and muscles to the heart. Most of the blood flow back from the legs is done by the deep veins, which lie within the muscles. Valve-like flaps in the veins allow the blood to overcome the difference in height of around one and a half metres from the legs to the heart. The venous valves allow the blood to flow only towards the heart.

Structure of the human venous system: The way that blood flows to the heart

Numerous small veins, so-called capillaries and venules, collect the used, oxygen-depleted blood from the muscles and organs. They work together to transport the blood through the veins and back to the heart. Roughly 7,000 litres of blood flow through our venous system every day.

The venous system is part of the body’s circulation system. A distinction is made between the superficial (subcutaneous) and the deep venous system. Both systems are connected by the perforating veins (connecting veins).

• The superficial leg veins run under the surface of the skin. The large and small saphenous veins can become visible as varicose veins on the leg.
• The deep veins run between the leg muscles. Pathological changes can also develop here, for example in the popliteal vein.

Video showing the circulation of blood

Venous return – the body’s mechanisms for returning blood to the heart

The return flow of blood in the veins is a passive process. It depends on the interaction of several factors. If only one of these factors is disturbed, venous flow may become impaired:

• Heart and breathing: The different pressure ratios in the two halves of the heart, as well as the processes of inhalation and exhalation, create a suction effect that supports the blood flow to the heart.
• The venous valves: The venous valves work like check valves that allow blood to flow only towards the heart: They are crucial for the blood to overcome the height from the leg veins to the heart.
• The calf muscle pump: When the foot and leg muscles are working, for example when running, the muscle pump is active and stimulates the venous return flow. This is where the term ‘calf muscle pump’ comes from.
• Vein tension: The vessel wall serves as a source of counter-pressure for the blood and ensures that venous pressure does not rise any further.

The venous valves: Check valves in the veins

Thanks to these venous valves, the blood in the veins flows in only one direction: back to the heart.

Injuries, inflammations or risk-related factors (for example, age, genes, gender, previous illnesses, occupation) can impair or destroy the function of the venous valves. Then, instead of being forced into the deep veins and towards the heart, the blood is forced in part into the superficial, subcutaneous veins by the work of the leg muscles. The result is an overload of the superficial venous system.

The calf muscle pump: Exercise is important for the veins

The deep venous system is embedded in the muscles. Every muscle contraction squeezes the veins together. Exercise to activate the calf muscle pump is also very important, therefore, to keep the venous valves functioning properly.

Video on the function of the venous valves

When veins dilate, compression can help

Only 10 per cent of people in Germany have healthy veins. In 90 per cent of people, the venous system is affected.¹ If the veins are weak, the blood pools in the leg veins. This can become noticeable through various indicators.

• Feeling of tightness
• Tired and heavy legs
• Swelling
• A tingling sensation
• Itching
• Spider veins
• Varicose veins

Medi compression stockings

Medical compression stockings from medi can support vein therapy. Find out more information about medi medical compression stockings.