Hair

Hairs are formed from dead keratinized cells firmly cemented together, hard keratin. They protrude from the hair follicles, tubes of epidermis sunk obliquely in the dermis growing from the dilated end or bulb. A hair may last 2 or 3 years when it is replaced by a new hair growing from the summit of the papilla.

The arrector pili raises the hair erect by its contraction, smooth muscle, under control of sympathetic system and produces "goose-pimples" by depressing its superficial attachment and raising the skin round the opening of the hair follicle.