Arrector pili muscle
Template:Short description Script error: No such module "Infobox".Template:Template otherTemplate:Main otherScript error: No such module "Check for unknown parameters". 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]
Structure
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]
Function
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]
Thermal insulation
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.
Self defence
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]
Sebum excretion
Pressure exerted by the muscle may cause sebum to be forced along the hair follicle towards the surface, protecting the hair.[8]
Hair follicle stability
Arrector pili muscles also stabilise the base of the hair follicle.[5][6]
Clinical significance
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]
History
The term "arrector pili" comes from Latin. It translates to "hair erector".[1]
Additional images
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Insertion of sebaceous glands into hair shaft
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Cross-section of all skin layers
Notes
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- ↑ Journal of the American Academy of Dermatology Volume 51, Issue 2, August 2004, Pages 217-222 The contribution of the arrector pili muscle and sebaceous glands to the follicular unit structure☆ Enrique Poblet, Francisco Ortega. https://doi.org/10.1016/j.jaad.2004.01.054
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References
- Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2006. The Animal Diversity Web; https://web.archive.org/web/20110903154915/http://animaldiversity.ummz.umich.edu/site/topics/mammal_anatomy/hair.html
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Template:Skin layers and appendages Template:Authority control