Arrector pili muscle (magnified skin block)

Musculus arrector pili

Integumentary (skin)SkinLeg

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What it is
A tiny band of smooth muscle running from the follicle bulge region to the papillary dermis on the obtuse-angle side of the hair.
Function
Contracts under sympathetic control to stand the hair upright ("goose bumps") and squeeze sebum from the gland.
Size
~0.5–1 mm long, a few cells thick
Clinical note
Goose bumps are a vestige of fur-fluffing for warmth and display seen in other mammals.

Nearby integumentary (skin) structures Dermal capillaries (magnified skin block), Dermis (magnified skin block), Eccrine sweat gland (magnified skin block), Epidermis (magnified skin block), Hair follicle (magnified skin block), Hair shaft (magnified skin block), Hypodermis (magnified skin block), Leg skin, Sebaceous gland (magnified skin block), Sensory nerve endings (magnified skin block)