Scalp hair

Capilli

Integumentary (skin)SkinHead

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What it is

Short scalp hair covering the vault of the skull from the frontal hairline and temples to the nape. Each hair is a dead keratin shaft growing from a living follicle in the dermis.

Function

Insulates the head against heat loss and sunlight, cushions minor blows and has social and sensory roles (hair follicles are wrapped by touch receptors).

Size

~100 000 follicles; each hair 50–100 µm thick, growing ~1 cm per month for 2–7 years (anagen) before shedding

Clinical note

Losing 50–100 scalp hairs a day is normal. Male-pattern baldness is driven by dihydrotestosterone shrinking follicles at the temples and crown.