Arrector pili
Arrector Pili
Arrector pili (pronounced: ah-REK-tor PYE-lee) are small muscles attached to hair follicles in mammals, including humans. The contraction of these muscles causes the hairs to stand on end, a phenomenon known as 'goosebumps' or 'piloerection'.
Etymology
The term 'arrector pili' comes from Latin, with 'arrector' meaning 'raiser' and 'pili' meaning 'of the hair'. This name is descriptive of the muscle's function.
Function
The primary function of the arrector pili is to cause piloerection, or 'goosebumps'. This is a reflex action in response to cold temperatures or emotional states such as fear or excitement. The standing up of the hairs traps an insulating layer of air around the body, helping to preserve heat.
Anatomy
The arrector pili are smooth, involuntary muscles. Each muscle is connected to a hair follicle. When the muscle contracts, it pulls the hair follicle upright, causing the hair to stand on end.
Related Terms
- Piloerection: The standing up of hairs in response to cold or fear, caused by the contraction of the arrector pili muscles.
- Hair Follicle: A part of the skin that grows hair by packing old cells together. Attached to it are sebaceous glands, arrector pili muscles, and a hair shaft.
- Sebaceous Gland: Small oil-producing gland present in the skin of mammals. They are usually attached to hair follicles and release a fatty substance, sebum, into the follicular duct and thence to the surface of the skin.
External links
- Medical encyclopedia article on Arrector pili
- Wikipedia's article - Arrector pili
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