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.
Atherosclerosis (hardening of your blood vessels due to a buildup of plaques ... of heart attacks and strokes. This staging system is used for heart failure, which can get worse over time.