The skin is the largest organ in the human body comprising two main layers; the thinner, outer layer, the epidermis and the inner, thicker layer, the dermis.

- Protection as a barrier between internal and external environments - Perception for stimuli - Body temperature - Excretion - Vitamin D synthesis - Disease immunity

One square inch of skin contains: - 65 hairs - 9,000,000 cells - 95 to 100 sebaceous glands - 17 metres of blood vessels - 70 metres of nerves - 650 sweat glands - 19,500 sensory cells at nerve fibre ends - 78 sensory apparatuses for heat - 1,300 nerve enedings that record pain - 13 sensory apparatuses for cold - 160 pressure apparatuses