What is the arrector pili muscle

Arrector pili muscle is a smooth muscle that extends from the superficial dermis of the skin to the dermal root sheath around the side of the hair follicle. Each hair follicle growing parallel to the skin attaches to the connective tissue of the basement membrane by the small band of arrector pili muscle. Arrector pili muscle develops independently of the hair follicle near the sebaceous gland and connects to the hair follicle at the hair follicle bulge. Hairs growing perpendicular to the skin, such as eyelash hairs, do not have associated arrector pili.

It In its normal position, hair emerges at a less than 90-degree angle to the surface of the skin. When their arrector pili is relaxed, most hairs lie flat because most follicles lie at an oblique angle to the skin surface. Under physiological or emotional stress, such as cold or fright, autonomic nerve endings stimulate the arrector pili muscles to contract, which pulls the hair shafts perpendicular to the skin surface. This action causes “goose bumps” or “gooseflesh” because the skin around the shaft forms slight elevations.

What is the function of the arrector pili?

The function of arrector pili muscles is to mediate thermoregulation by contracting and raising or relaxing and releasing the hair. Recent research indicates that elevating and lowering the hairs may also provide some support to the hair follicle’s integrity and stability, but the precise mechanism of this relationship is yet undiscovered.

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