The Venous System
How does our circulatory system work?
- intima (= inner layer)
- media (= middle layer) and
- adventitia (= outer layer)
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.
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.