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Blood circulation


Blood is pumped at high pressure away from the heart in arteries. It travels through networks of thin capillaries, where it can exchange materials with the tissues. It's then collected up and returned to the heart at low pressure in veins.

How different blood vessels are adapted for their function - higher tier

Blood vesselFunctionAdaptions
Arterycarry blood away from heart at high pressurethick, elastic, muscular walls to withstand pressure and to exert force (pulse)
Capillaryallow exchange of materials between blood and tissuesthin permeable walls
Veinreturn low pressure blood to heartLarge diameter to offer least flow resistance. Valves to prevent back flow.

Cross-section of a vein

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