Blood is moved around your body using the cardiovascular system. It is made up of a central pump – the heart – and a series of channels through which the blood circulates – the arteries, veins and capillaries.
The cardiovascular system’s purpose is to maintain what’s called homeostasis in your body; in other words to keep your internal systems running smoothly at a constant speed and temperature. Your blood functions as a liquid transport system, using the cardiovascular system to move nutrients and oxygen to where they’re needed in the body, and to take away waste products and carbon dioxide. This transfer takes place through the walls of tiny, microscopic capillaries in what’s known as microcirculation.
The blood moves through your body in a double circuit. You have two systems of circulation – pulmonary circulation, which carries blood through the lungs, and systemic circulation, which carries blood through the rest of the body. The left side of your heart powers pulmonary circulation, while the right side powers systemic circulation.
Red and blue blood
In systemic circulation, oxygenated blood is pumped from the heart into the body tissue along arteries, which eventually branch out into microscopic capillaries. Once the blood has delivered oxygen to the body’s cells, it must return to the heart to be pumped on to the lungs. Deoxygenated blood returns to the heart via the veins. It is the oxygen in your blood which makes it red: once the oxygen has been taken out of your blood, it turns blue, which is why the veins you can see on the back of your wrist are blue. They are taking blood back to the heart, where it can then be pumped on to the lungs and turned red with oxygen once more.
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