The scalp hair you see is physiologically speaking, 'dead'. It has no blood, muscles or nerves. Hair grows from a single follicle, an indentation in the skin, and each follicle has its own blood, nerve and muscle supply.

For a 'dead' fibre, scalp hair is remarkable. A healthy hair can stretch up to another 30% of its length, can absorb its weight in water and can swell up to 20% of its diameter. It has extraordinary insulating powers, rivalling that of asbestos. Its strength is greater than that of copper wire of the same diameter. A single scalp hair can support a weight of 100g and an average head of hair twisted together can support 23 tons.