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Hair is present across the entire surface of the human body, except for a few places like the palms of the hands or the soles of the feet. Each hair follicle is paired with a tiny muscle called the arrector pili muscle, which is responsible for involuntary contractions that cause the hair to stand on end, forming goose bumps. This response is often triggered by stress or cold temperatures, and it helps mammals retain heat by trapping air between the erect hairs. Beyond their role in goosebumps, these muscles also play a crucial role in hair regeneration and growth.
| Characteristics | Values |
|---|---|
| Do humans have hair? | Yes, humans have hair on their bodies. |
| Where is hair found on the human body? | Hair is found almost everywhere on the human body except the lips, palms, soles of feet, and sides of fingers and toes. |
| What is the function of hair? | Hair offers protection from the sun's rays, keeps dirt and sweat out of the eyes, and helps regulate body temperature. |
| What is the structure of hair? | Hair grows from hair follicles, which are tubular structures located in the dermis, the layer of skin below the epidermis. |
| What determines the shape of the hair? | The shape of the hair follicles determines whether hair will be straight, wavy, curly, or coiled. |
| Are there different types of hair? | Yes, there are two main types of hair: "vellus" hairs (short and thin) and "terminal" hairs (long and thick). |
| What is the growth cycle of hair? | The growth cycle includes a growth phase, a transitional phase (catagen phase), and a resting phase (telogen phase) before new hair growth begins. |
| Do hair follicles have muscles? | Yes, each hair follicle is paired with a tiny muscle called the arrector pili, which is involved in hair erection and regeneration. |
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What You'll Learn
The arrector pili muscle is attached to hair follicles
The arrector pili muscle, also known as the hair erector muscle, is a tiny muscle that attaches to the hair follicle. Each hair follicle is paired with an arrector pili muscle, which is composed of a bundle of smooth muscle fibres. The arrector pili muscle is innervated by the sympathetic division of the autonomic nervous system. It attaches to the follicular stem cell niche in the follicular bulge, with the muscle fibres splitting at their deep end to encircle the follicle.
The arrector pili muscle extends obliquely from the hair follicle to the papillary layer of the dermis. At the hair follicle, the arrector pili muscle is attached to a bulged region in the connective tissue sheath via elastin fibrils. A sebaceous gland sits at the angle between the muscle and the hair follicle.
The arrector pili muscle is absent from the hairs of the face, axilla, pubis, eyelashes, eyebrows, nostrils, and external auditory meatus. When the arrector pili muscle contracts, it pulls the hair into a vertical position, forming small hillocks known as goosebumps. The contraction of the muscle is involuntary and can be stimulated by stresses such as cold, fear, or the perception of a threat.
The contraction of the arrector pili muscle has a principal function in providing thermal insulation for mammals. The hair stands on end, trapping air between the erect hairs and helping the animal retain heat.
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Contraction of arrector pili muscles causes hair to stand up
The arrector pili muscle, also known as the hair erector muscle, is a tiny smooth muscle attached to hair follicles in mammals. Each hair follicle is paired with an arrector pili muscle. The arrector pili muscle is a bundle of smooth muscle fibres that attach to several hair follicles. The muscle attaches to the follicular stem cell niche in the follicular bulge, splitting at its deep end to encircle the follicle.
The contraction of the arrector pili muscle causes the hair to stand up, a phenomenon known colloquially as 'goosebumps' or piloerection. This contraction is involuntary and is caused by the stimulation of the sympathetic nervous system due to various stresses such as cold, fear, or the perception of a threat. The contraction of the arrector pili muscle has the principal function of providing thermal insulation in mammals. When the hairs stand up, air becomes trapped between them, helping the animal retain heat.
In addition, the contraction of the arrector pili muscle can aid in the expulsion of the sebaceous gland's contents. The sebaceous gland sits at the angle between the muscle and the hair follicle. The pressure exerted by the muscle may cause sebum to be forced along the hair follicle towards the surface, protecting the hair.
Recent studies have also suggested a possible role of the arrector pili muscle in maintaining the integrity and stability of the hair follicular unit, as well as in the hair cycle, wound healing, and the development of androgenetic alopecia, the most common cause of human hair loss.
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The arrector pili muscle is composed of smooth muscle fibres
The arrector pili muscle, also known as the hair erector muscle, is a tiny muscle that attaches to the hair follicle in mammals. Each hair follicle is paired with an arrector pili muscle. This muscle is composed of smooth muscle fibres.
The arrector pili muscle is a bundle of smooth muscle fibres that attach to several hair follicles, forming what is known as a follicular unit. The muscle attaches to the follicular stem cell niche in the follicular bulge, and at its deep end, it splits to encircle the hair follicle. The arrector pili muscle is innervated by the sympathetic division of the autonomic nervous system.
The arrector pili muscle is responsible for the contraction that causes hairs to stand on end, known as piloerection or goose bumps. This contraction is involuntary and can be triggered by various stimuli, such as cold temperatures or fear, which stimulate the sympathetic nervous system. The primary function of this contraction in most mammals is to provide thermal insulation. When the hairs stand on end, air becomes trapped between them, helping the animal retain heat.
In addition to its role in piloerection, the arrector pili muscle also stabilises the base of the hair follicle. Skin conditions, such as leprosy, can damage these muscles, impacting their ability to contract and potentially leading to hair shedding or traction alopecia.
The arrector pili muscle develops approximately 1–2 weeks after birth in the dorsal and ventral skin, but it eventually degenerates.
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The arrector pili muscle aids in forming goosebumps
The arrector pili muscle, also known as the hair erector muscle, is a tiny muscle attached to hair follicles in mammals. It is composed of a bundle of smooth muscle fibres that attach to several hair follicles. The arrector pili muscle is innervated by the sympathetic division of the autonomic nervous system, which means that it contracts involuntarily in response to certain stimuli.
When the arrector pili muscle contracts, it pulls the hair into a vertical position, forming small bumps on the skin known as goosebumps. This occurs when the muscle attaches to the follicular stem cell niche in the follicular bulge, splitting at its deep end to encircle the follicle. The contraction of the arrector pili muscle is associated with various stimuli, including cold temperatures, fear, euphoria, and sexual arousal.
The primary function of the arrector pili muscle in mammals is to provide thermal insulation. When the hairs stand on end, air becomes trapped between them, helping the body retain heat. This mechanism is particularly important for animals with thick fur, as it allows them to survive in cold environments. Additionally, the elevation of the hairs can aid in quicker drying by facilitating the evaporation of water clinging to the hair and moving it upward and away from the skin.
In addition to its role in thermoregulation, the arrector pili muscle may also play a role in wound healing and the development of androgenetic alopecia, the most common cause of human hair loss. Recent studies have suggested that the arrector pili muscle may contribute to maintaining the integrity and stability of the hair follicle. However, further research is needed to fully understand its role in hair loss disorders.
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The arrector pili muscle is essential for new hair growth
The arrector pili muscle, also known as the hair erector muscle, is a tiny smooth muscle attached to hair follicles in mammals. Each hair follicle is paired with an arrector pili muscle, which attaches to the base of the hair follicle on one end and to the upper layer of the dermis on the other. The arrector pili muscle is essential for new hair growth in several ways.
Firstly, the arrector pili muscle plays a role in the development and maintenance of the pilosebaceous unit, which includes the hair follicle, sebaceous gland, apocrine gland, and the arrector pili muscle itself. The pilosebaceous unit is responsible for producing and nourishing the hair, and the arrector pili muscle helps to stabilize the base of the hair follicle. This stability is crucial for the growth of new hair, as it provides a secure foundation for the hair to develop.
Secondly, the arrector pili muscle is involved in thermoregulation. When the body experiences cold temperatures, the arrector pili muscle contracts, pulling the hair into a vertical position and elevating the epidermis where the hair enters. This contraction creates small hillocks known as goosebumps. By elevating the epidermis, the arrector pili muscle may also aid in the expulsion of the sebaceous gland's contents, which can provide nourishment and protection for the hair. This function of the arrector pili muscle is important for new hair growth as it helps regulate the temperature and ensure the hair follicle receives the necessary nutrients.
Additionally, the arrector pili muscle may have a role in preventing hair loss. Recent studies have suggested that the arrector pili muscle could be involved in maintaining the integrity and stability of the follicular unit. This is significant because follicular miniaturization and muscle loss are associated with hair loss and baldness. By maintaining the stability of the follicular unit, the arrector pili muscle may help prevent hair shedding and promote new hair growth.
In summary, the arrector pili muscle is essential for new hair growth due to its role in stabilizing the hair follicle, regulating temperature, aiding in the expulsion of the sebaceous gland's contents, and potentially preventing hair loss. While the full extent of its involvement in hair growth may not be fully understood, the arrector pili muscle's functions undoubtedly contribute to the development and maintenance of healthy hair.
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Frequently asked questions
Yes, hair has tiny muscles called arrector pili muscles.
Arrector pili 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.
When the arrector pili muscle contracts, it pulls the hair into a vertical position, causing the hair to stand on end. This is known colloquially as goose bumps or piloerection.
Stresses such as cold, fear, etc. may stimulate the sympathetic nervous system, causing the arrector pili muscles to contract.
