Dominic Stone
The arrector pili muscles, also known as hair erector muscles, are the muscles attached to hair follicles that cause goose bumps. When these muscles contract, they pull the hair follicle upright, causing the hair to stand on end and creating a bumpy appearance on the skin. This phenomenon is called piloerection or pilomotor reflex.
| Characteristics | Values |
|---|---|
| Name | Arrector pili muscles |
| Alternative Names | Hair erector muscles, arrector folliculi, arrector integument, levator folliculi |
| Composition | Bundle of smooth muscle fibres |
| Attachment | Follicular stem cell niche in the follicular bulge |
| Function | Causes hair to stand on end (goose bumps or piloerection) |
| Controlled By | Sympathetic division of the autonomic nervous system |
| Contraction | Involuntary; stimulated by cold, fear, etc. |
| Principal Function in Mammals | Providing thermal insulation |
| Other Functions | Stabilise the base of the hair follicle, may play a role in wound healing |
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What You'll Learn
Arrector pili muscles
The arrector pili muscles, also known as hair erector muscles, are small muscles attached to hair follicles in mammals. The arrector pili muscle is a bundle of smooth muscle fibres that attach to several hair follicles (a follicular unit). The muscle attaches to the follicular stem cell niche in the follicular bulge, splitting at its deep end to encircle the follicle.
Contraction of the arrector pili muscles causes the hairs to stand up, which is known colloquially as "goosebumps" or piloerection. This phenomenon is also called the pilomotor reflex. The contraction of the muscle is involuntary and is stimulated by the sympathetic nervous system. Stresses such as cold, fear, or the perception of threat may stimulate the sympathetic nervous system, thus causing muscle contraction.
The contraction of arrector pili muscles serves a principal function in the majority of mammals: providing thermal insulation. Air becomes trapped between the erect hairs, helping the animal retain heat. In addition, the pressure exerted by the muscle may cause sebum to be forced along the hair follicle towards the surface, protecting the hair.
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Arrector folliculi muscles
The arrector pili muscles, also known as hair erector muscles, are small muscles attached to hair follicles in mammals. They are composed of a bundle of smooth muscle fibres which attach to several follicles (a follicular unit). The arrector pili muscles are innervated by the sympathetic division of the autonomic nervous system.
When the arrector pili muscle contracts, it pulls the hair into a vertical position, causing the hair to stand on end, known colloquially as goose bumps (piloerection). This phenomenon is also called the pilomotor reflex. The contraction of the muscle is involuntary. Stresses such as cold, fear, etc. may stimulate the sympathetic nervous system, thus causing muscle contraction.
The arrector pili muscles also stabilise the base of the hair follicle. Skin conditions such as leprosy can damage these muscles, preventing their contraction. 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.
The arrector pili muscles are absent from the hairs of the face, axilla, pubis, eyelashes, eyebrows, nostrils, and external auditory meatus.
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Levator folliculi muscles
Goose bumps, or piloerection, are caused by the contraction of small muscles attached to hair follicles. These muscles are called arrector pili muscles, and they are composed of smooth muscle fibres that attach to several follicles. The arrector pili muscles are innervated by the sympathetic division of the autonomic nervous system, and their contraction is involuntary.
While the arrector pili muscles are the primary cause of goose bumps, other factors may also contribute. These include secretions from the sudoriferous glands, stimulation of the hair root plexus, contraction of dermal papillae, and secretions from the sebaceous gland.
In conclusion, the muscles primarily responsible for causing goose bumps by contracting and pulling on the hair follicles are the arrector pili muscles. These muscles have a crucial function in providing thermal insulation for mammals, as the erect hairs trap air and help retain body heat.
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Arrector integument muscles
The arrector pili muscles, also known as hair erector muscles, are tiny muscles attached to hair follicles in mammals. They are composed of a bundle of smooth muscle fibres which attach to several follicles (a follicular unit). The arrector pili muscles are innervated by the sympathetic division of the autonomic nervous system. They attach to the follicular stem cell niche in the follicular bulge, splitting at their deep end to encircle the follicle.
The contraction of the arrector pili muscle is involuntary. When contracted, the muscle pulls the hair into a vertical position, causing the hair to stand on end, which is known colloquially as "goosebumps" or piloerection. This phenomenon is also called the pilomotor reflex. Stresses such as cold, fear, etc. may stimulate the sympathetic nervous system, causing the arrector pili muscles to contract.
The arrector pili muscles have a principal function in the majority of mammals of providing thermal insulation. Air becomes trapped between the erect hairs, helping the animal retain heat. In addition, because of the relationship between the arrector pili muscle and the sebaceous gland at the hair follicle, its contraction aids the expulsion of the gland's contents.
Skin conditions such as leprosy can damage arrector pili muscles, preventing their contraction. 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.
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Contraction of arrector pili muscles
The arrector pili muscles, also known as hair erector muscles, are tiny muscles attached to hair follicles in mammals. Each arrector pili muscle is composed of a bundle of smooth muscle fibres that attach to several follicles, forming a follicular unit. The arrector pili muscle attaches to the follicular stem cell niche in the follicular bulge, splitting at its deep end to encircle the follicle.
The arrector pili muscle contracts involuntarily in response to various stimuli, such as cold temperatures or fear. This contraction pulls the hair into a vertical position, causing the hair to stand on end and creating a bumpy appearance on the skin. This phenomenon is known colloquially as "goosebumps" or, in medical terminology, piloerection.
The contraction of the arrector pili muscle serves a critical function in the majority of mammals, providing them with thermal insulation. When the hairs stand erect, air becomes trapped between them, helping the animal retain heat. Additionally, the contraction of these muscles may aid in the expulsion of the sebaceous gland's contents, protecting the hair.
In certain skin conditions, such as leprosy, the arrector pili muscles can become damaged, impairing their ability to contract. However, inducing contraction through the use of an α1-adrenergic receptor agonist has been shown to reduce hair shedding in cases of traction alopecia.
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Frequently asked questions
The arrector pili muscles, also known as hair erector muscles, are small muscles attached to hair follicles in mammals. Contraction of these muscles causes the hairs to stand on end, resulting in goose bumps.
Stresses such as cold, fear, and other emotional stimuli can cause the arrector pili muscles to contract, resulting in goose bumps.
While goose bumps may have served a purpose in our evolutionary past by helping to retain warmth, they do not provide significant thermal insulation for humans today. However, research suggests that goose bumps may play a role in triggering hair growth.
Skin conditions such as leprosy can damage the arrector pili muscles, preventing their contraction and resulting in hair shedding or alopecia.
