The venous system within the cardiovascular system
The venous system is an integral part of the cardiovascular system designed to circulate blood to enable gas and metabolic exchanges within the billions of cells making up the body.
The cardiovascular system is a closed circulatory system in which blood circulates in one direction only. It is organised around a central organ – the heart pump – and is made up of three different types of blood vessels (arteries, veins and capillaries).
A hollow muscle and powerful pump, the heart rhythmically propels blood into the arteries. The arteries (which have walls that are much more elastic than the walls of veins) thus carry blood at high pressure , regulated by the rhythm of the heart beats (creating a constant residual pressure that oscillates between two values: the systolic pressure and the diastolic pressure).
In the venous network, the blood flow does not have any direct impulsion equivalent to that of the heart pump in the arterial system. The venous system is therefore a low-pressure system . The blood therefore flows back towards the heart thanks to a combination of several mechanisms (both intrinsic and extrinsic to the venous system). (see the chapter on physiology to find out more)
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The arteries and veins are linked by microscopic capillaries, where oxygen, carbon dioxide and metabolite exchanges occur.
see full size image | Blood travels on two different routes through the circulatory system : - the general circulation, originating from the left heart, which carries oxygenated blood, nutrients, hormone and immune system messengers, etc. towards the organs and extremities, and then carries oxygen-depleted blood and waste back to the heart through the veins.
- the pulmonary circulation, originating from the right heart, which takes oxygen-depleted blood towards the pulmonary capillaries, where gas exchanges with the air contained inside the pulmonary alveoli occur, before the now oxygenated blood returns to the heart via the pulmonary veins.
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