Additional images
Insertion of sebaceous glands into hair shaft
Cross-section of all skin layers
| Details | |
|---|---|
| Nerve | Sympathetic postganglionic nerve fibers |
| Identifiers | |
| TA98 | A16.0.00.024 |
| TA2 | 7051 |
| TH | H3.12.00.3.01041 |
| FMA | 67821 |
| Anatomical terms of muscle | |
The arrector pili muscles, also known as hair erector muscles, [1] are small muscles attached to hair follicles in mammals. Contraction of these muscles causes the hairs to stand on end, [2] known colloquially as goose bumps (piloerection). [3]
Each arrector pili is composed of a bundle of smooth muscle fibres which attach to several follicles (a follicular unit). [4] Each is innervated by the sympathetic division of the autonomic nervous system. [4] The muscle attaches to the follicular stem cell niche in the follicular bulge, [3] [4] [5] splitting at their deep end to encircle the follicle. [6]
The contraction of the muscle is involuntary. Stresses such as cold, fear etc. may stimulate the sympathetic nervous system, and thus cause muscle contraction. [4]
Contraction of arrector pili muscles have a principal function in the majority of mammals of providing thermal insulation. [4] Air becomes trapped between the erect hairs, helping the animal retain heat.
Many animals experience contraction of the arrector pili muscle in response to a perceived threat. This helps the animal seem larger and more intimidating as a result. [7]
Pressure exerted by the muscle may cause sebum to be forced along the hair follicle towards the surface, protecting the hair. [8]
Arrector pili muscles also stabilise the base of the hair follicle. [5] [6]
Skin conditions such as leprosy can damage arrector pili muscles, preventing their contraction. [9] Inducing contraction of the arrector pili muscles via an α1-adrenergic receptor agonist has been shown to reduce hair shedding as a result of traction alopecia [10]
The term "arrector pili" comes from Latin. It translates to "hair erector". [1]
