How do veins work?

A widely branching system of blood vessels transports our blood around our bodies. The blood vessels are divided into arteries and veins depending on the direction in which the blood is flowing. The heart pumps the blood through the arteries to every part of the body and supplies the cells with oxygen.

Anatomical classification of veins

The veins are divided into the individual parts of the body:

  • Head veins
  • Arm veins
  • Abdominal veins
  • Leg veins

The blood from abdominal organs initially passes through the portal vein into the liver, where it is filtered before being transported further to the heart. There are several systems in the leg veins. The major part of the return transport in the legs is undertaken by the deep veins of the leg that run through muscles. The rest of the blood flows back through the superficial veins of the leg that run from the ankles up to the hollow of the knee or the groin, where they connect up with the deep veins of the leg.

Legs have valve-like cusps that only allow the blood to pass in the direction of the heart like boats in a dock. If the blood flows up the leg as a result of the pressure exerted by the joint and muscle pumps, the valves open – if the blood wants to fall back into the leg under the effect of gravity, they close.

Non-return valves in the legs

Veins have crescent-shaped valves at intervals that divide vessels into segments. These valves open as soon as the blood is pressed upwards towards the center of the body against gravity and close in the instant that the blood comes to a “standstill” and would start to flow backwards.

Defective venous valves

Intact valves prevent the blood from pooling in the periphery (particularly when standing) and absorb the forces that act on the veins under stress (walking, jogging and jumping). The communicating veins also possess valves that prevent return flow from the deep to the superficial venous system.

Veins have crescent-shaped valves at longer intervals dividing long vessels into segments. These valves open as soon as the blood is pressed upwards towards the center of the body against gravity and close in the instant that the blood comes to a “standstill” and would start to flow backward.

Venous return – The function of the venous valves

The deoxygenated blood flows back to the heart via the circulatory venous system. The heart plays an important role here: it not only pumps the blood under high pressure through the arteries in the body, but it also sucks the blood back from the body into the right atrium. This is called venous return.

Non-return valves

The heart as a pump is not strong enough to guarantee continual venous return from parts of the body that are distant from the heart. To make it easier for the veins of the leg to transport the blood up to the heart against gravity, the veins in the trunk and the legs are equipped with valves. The venous valves are cusps that grow out of the inner vessel walls and lie flat against the vessel wall, i.e. open, to allow the blood to flow unimpeded in the direction of the heart. The venous return is stopped as soon as the pressure in the veins sinks. The closed venous valves then stop the blood flowing in the wrong direction. The venous valves work like non-return valves that only allow the blood to flow in a single direction.

How does a venous valve work: Calf muscle pump

Every time the muscles contract, they squeeze the deep veins in the legs together and transport the blood further. Here too, the venous valves determine the direction of flow and stop the blood flowing backwards.

The muscle pump only springs into action when we use our muscles, i.e. while walking or running. Long periods of standing or sitting still can lead to blood pooling in the legs. Water from the blood leaks through vessel walls into the surrounding tissues and leads to swollen legs and feet. Whenever the muscles of the feet and legs are working, the muscle pump works too and jump-starts venous return.

Do you think you have venous disease?