A transport system is needed in the body to supply the needs of the body cells and remove the waste materials they produce.
Humans have a double circulation system. One carries blood from your heart to your lungs and back again and the other carries blood around the rest of your body and back again.
There are three main types of blood vessel: * The Artery * The Vein * The Capillary
Your heart is made up of two pumps (for double circulation) which beat together about 70 times each minute. The walls of the heart are entirely muscle, supplied with oxygen by the coronary blood vessels.
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Heart
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Artery
Your arteries carry blood away from your heart to the organs of your body.
This is usually oxygenated blood so it is bright red.
They stretch as the blood is forced through them and go back into shape afterwards.
You can feel this as a pulse where the arteries run close to the surface (like your wrist)
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Vein
The veins carry blood towards your heart
It is usually low in oxygen and so is a deep purply-red colour
They do not have a pulse, but they often have valves to prevent the backflow of blood as it moves from the various parts of the body back to the heart
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