A hair is a thin, flexible strand of dead, keratinised cells growing from a hair follicle. Each has a root within the follicle and a shaft above the skin, built of an inner medulla, a cortex holding the pigment, and a protective outer cuticle. Hair covers most of the body, ranging from fine vellus hairs to thick terminal hairs on the scalp, brows and, after puberty, the armpits and pubic area.
| Location | Over most of the skin surface except the palms, soles, lips, nipples and parts of the external genitals |
|---|---|
| Parts |
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Protects the skin and body openings, helps with touch sensation and temperature regulation, and contributes to appearance and social signalling.
Hair protects the scalp from sunlight, the eyes from debris (eyebrows, lashes) and the nose and ears from particles. Patterns of hair loss or excess hair can point to hormonal, nutritional or autoimmune disorders. Excess male-pattern hair growth in women (hirsutism) suggests high androgens, as in polycystic ovary syndrome.
Gradual, inherited thinning of scalp hair driven by androgens, in men and women.
Diffuse shedding of hair two to three months after a stressor such as illness, childbirth or crash dieting.
Excess coarse hair in a male pattern in women, usually from raised androgens.
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