This MedLibrary.org supplementary page on Arrectores pilorum is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
 |
This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (October 2008) |
Arrectores pilorum (singular Arrector pili) are tiny muscle fibers attached to each hair follicle, which contract to make the hairs stand on end, causing goose bumps. They exist in most mammals including humans.
Arrectores pilorum are smooth muscle, not skeletal muscle, which explains why humans cannot voluntarily give themselves goose bumps. In other animals with more hair than humans, they serve an important function — they raise the hairs so air gets trapped between them, providing a layer of insulation to keep the animal warm. Some animals also contract their Arrectores pilorum when they are cornered, in order to appear larger and more threatening. A prominent example of this function is the porcupine which uses Arrectores pilorum to raise its quills when threatened. Although humans' Arrectores pilorum also contract in response to cold or arousal, they are vestigial because humans do not have enough hair to make them effective.citation needed
The Arrectores pilorum are controlled by the sympathetic nervous system which is in general responsible for many fight-or-flight responses.
Additional images
 Pilosebaceous unit |
 Base of pilosebaceous unit |
 Insertion of sebaceous glands into hair shaft |
 Cross-section of all skin layers. |
|
||||||||||||||||||||||||||||||||||||||
Wikipedia content modification information:
- This page was last modified on 12 November 2008, at 15:54.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Arrectores pilorum".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.