Each 2.54 square centimetre (a square inch) of human skin has six metres (20ft) of blood vessels. Veins hold about 65 per cent of the body's blood and have one-way valves tohelp blood move.

Temperature control Your skin's blood vessels, sweat glands and hairs play a crucial role in regulating your body temperature. When you need to cool down Your blood vessels widen and allow heat to ...