Hair follicle (magnified skin block)

Folliculus pili

Integumentary (skin)SkinLeg

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What it is

A tubular pocket of epidermis sunk obliquely into the dermis; its swollen base, the hair bulb, wraps a dermal papilla of capillaries that feeds the dividing matrix cells which build the hair.

Function

Produces the hair shaft; its bulge region holds stem cells that regenerate the follicle and help re-surface wounds.

Size

Terminal scalp follicles ~3–4 mm deep, bulb ~0.3 mm wide (magnified here)

Clinical note

Follicles cycle through growth (anagen), regression (catagen) and rest (telogen); chemotherapy attacks the rapidly dividing matrix cells, causing hair loss.