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The arrector pili muscle, also known as the hair erector muscle, is a tiny muscle attached to hair follicles in mammals. When the muscle contracts, it pulls the hair into a vertical position, forming small hillocks known as goosebumps. The arrector pili muscle is also believed to play a role in hair loss and stabilising the base of the hair follicle.
| Characteristics | Values |
|---|---|
| Type of muscle | Smooth muscle |
| Size | Tiny |
| Location | Skin |
| Origin | Papillary layer of dermis |
| Insertion | Hair follicle |
| Innervation | Sympathetic |
| Action | Elevate hair on the skin |
| Formation | Bundles of closely packed smooth muscle cells |
| Attachment | Hair follicle, connective tissue sheath, follicular stem cell niche |
| Function | Contraction, elevation of epidermis, formation of goosebumps, expulsion of sebaceous gland contents, thermal insulation |
| Contraction causes | Cold, fear, threat |
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What You'll Learn
The arrector pili muscle is a tiny smooth muscle
The arrector pili muscle is innervated by the sympathetic division of the autonomic nervous system. When the muscle contracts, it pulls the hair into a vertical position, forming small hillocks known as goosebumps. This involuntary contraction may be stimulated by stress, such as cold or fear, which activates the sympathetic nervous system. The principal function of the arrector pili muscle in mammals is to provide thermal insulation. When the hairs stand erect, air becomes trapped between them, helping the animal retain heat.
In addition to its role in thermoregulation, the contraction of the arrector pili muscle can aid in the expulsion of the sebaceous gland's contents. The pressure exerted by the muscle may force sebum along the hair follicle towards the surface, protecting the hair. The arrector pili muscle also stabilises the base of the hair follicle.
The arrector pili muscle has been implicated in hair loss, or alopecia. Fat infiltration and degeneration of the arrector pili muscle have been observed in patients with androgenic alopecia, suggesting a potential role for the muscle in hair shedding. Inducing contraction of the arrector pili muscle has been shown to reduce hair shedding due to traction alopecia.
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It contracts to make hair stand up
The arrector pili muscle, also known as the hair erector muscle, is a tiny muscle attached to hair follicles in mammals. When it contracts, it pulls the hair into a vertical position, making it stand up. This process is known as piloerection and results in the formation of "goosebumps" on the skin.
The arrector pili muscle is composed of a bundle of smooth muscle fibres that attach to several hair follicles, forming a follicular unit. The muscle originates from the papillary layer of the dermis and extends obliquely, attaching to the hair follicle. At the hair follicle, the arrector pili muscle connects to a bulged region in the connective tissue sheath via elastin fibrils.
When the arrector pili muscle contracts, it exerts pressure on the hair follicle, causing the hair to stand erect. This contraction also elevates the epidermis where the hair enters and depresses the epidermis where the muscle attaches, forming small bumps on the skin. The arrector pili muscle is innervated by the sympathetic division of the autonomic nervous system, and its contraction is involuntary.
Various factors, such as cold temperatures, fear, or the perception of a threat, can stimulate the sympathetic nervous system, triggering the contraction of the arrector pili muscle. This response may serve a protective function, making the animal seem larger and more intimidating when faced with a potential danger. Additionally, the contraction of these muscles can aid in thermal insulation, as air becomes trapped between the erect hairs, helping the animal retain heat.
In summary, the arrector pili muscle's contraction leads to the elevation of the hair and the formation of goosebumps. This response is involuntary and can be triggered by various stimuli, serving protective and thermal functions for mammals.
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This is known as piloerection or getting goosebumps
The arrector pili muscle, also known as the hair erector muscle, is a small muscle attached to hair follicles in mammals. When it contracts, it pulls the hair into a vertical position, causing the hair to stand erect. This process is known as piloerection or getting goosebumps. The arrector pili muscle is composed of a bundle of smooth muscle fibres that attach to several hair follicles. The muscle originates from the papillary layer of the dermis and extends obliquely, attaching to the hair follicle. At the hair follicle, the arrector pili muscle is attached to a bulged region in the connective tissue sheath via elastin fibrils.
The contraction of the arrector pili muscle is involuntary and can be stimulated by various factors such as cold, fear, or the perception of a threat. When an animal perceives a threat, the contraction of these muscles can make the animal seem larger and more intimidating. In addition, the contraction of the arrector pili muscle aids in the expulsion of the sebaceous gland's contents, which can protect the hair.
In humans, the arrector pili muscles form well-defined anatomic structures known as follicular units, which are composed of terminal and vellus hairs, associated sebaceous glands, and arrector pili muscles. At the isthmus level, above their follicular attachments, the arrector pili muscles that originate from their respective follicles join together to form a single muscular structure. This single muscular structure then extends upward to its superior attachment zone.
The arrector pili muscle plays a crucial role in providing thermal insulation for mammals. When the hairs stand erect, air becomes trapped between them, helping the animal retain heat. This function is particularly important for survival in cold environments.
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Contraction aids the expulsion of the sebaceous gland's contents
The arrector pili muscle, also known as the hair erector muscle, is a tiny muscle connected to each hair follicle and the skin. When it contracts, it pulls the hair into a vertical position, forming small hillocks known as "goosebumps" or "goose flesh".
The arrector pili muscle is closely associated with the sebaceous gland at the hair follicle. The sebaceous gland sits at the angle between the muscle and the hair follicle. The muscle attaches to the follicular stem cell niche in the follicular bulge, splitting at its deep end to encircle the follicle. At a lower level, the muscle divides and encircles the sebaceous gland, penetrating between the sebaceous lobules towards the follicular attachment zone.
The contraction of the arrector pili muscle aids in the expulsion of the sebaceous gland's contents. This process is known as piloerection or constriction of the sebaceous glands, which helps release sebum onto the skin surface. Sebum is a natural oil that protects the hair and skin. When the arrector pili muscle contracts, it can cause sebum to be forced along the hair follicle towards the surface.
Piloerection is an involuntary response to various stimuli, such as cold, fear, or emotional disturbance. It is believed to provide thermal insulation, as air becomes trapped between the erect hairs, helping the body retain heat. Additionally, piloerection can make an animal seem larger and more intimidating in response to a perceived threat.
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The arrector pili muscle may play a role in hair loss
The arrector pili muscle, also known as the hair erector muscle, is a tiny muscle attached to hair follicles in mammals. Its contraction pulls the hair into a vertical position, forming small hillocks known as goosebumps. The arrector pili muscle also has a relationship with the sebaceous gland at the hair follicle, aiding in the expulsion of its contents.
In AGA, there is evidence of significant decreases in arrector pili muscle volume and extensive fat infiltration around the residual muscle of hair follicles. This fat infiltration and muscle degeneration are thought to contribute to irreversible hair loss. However, the exact relationship between APM degeneration, fat infiltration, and follicle miniaturization leading to hair loss remains unclear and is a subject of ongoing research.
Additionally, the arrector pili muscle's role in hair loss may be related to its function in stabilizing the base of the hair follicle. Inducing contraction of the arrector pili muscle has been shown to reduce hair shedding due to traction alopecia. This suggests that the muscle's contraction can help prevent hair loss by securing the hair follicle.
Furthermore, skin conditions such as leprosy can damage arrector pili muscles, preventing their contraction and potentially contributing to hair loss. While the exact mechanisms remain to be fully elucidated, the arrector pili muscle's involvement in hair loss is an active area of investigation, with studies employing advanced imaging techniques to understand its role beyond its well-known function in goosebumps.
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Frequently asked questions
The arrector pili muscle is a small, fan-shaped smooth muscle associated with the base of each hair follicle.
When the arrector pili muscle contracts, it pulls the hair into a vertical position, causing the hair to stand erect and creating "goosebumps" on the skin.
Arrector pili muscles are located in the dermis layer of the skin and attach to the hair follicle at the bulge region of the connective tissue sheath.
No, arrector pili muscles are absent from the hairs of the face, axilla, pubis, eyelashes, eyebrows, nostrils, and external auditory meatus.
Yes, due to their relationship with the sebaceous gland at the hair follicle, the contraction of arrector pili muscles aids in the expulsion of the gland's contents. Additionally, there is research suggesting that arrector pili muscles may play a role in hair loss and wound healing.
