Arrector pili muscle
The arrectores pilorum muscles (singular: arrector pili muscle ) (hair erectile muscle, hair follicle muscle or pilomotor ) are small muscles made of smooth muscles that attach to the outer edge of the hair with the exception of the primary hair (top and fur hair). They arise from the superficial layer of the dermis and attach to the hair below the sebum gland . The innervation occurs involuntarily through sympathetic nerve fibers .
The arrectores pilorum muscles straighten the hair; in humans, the skin structure created by straightening the hair ( piloerection ) is also known as goose bumps . This can occur through cold or psychological influences such as excitement and anger: "The hair stands on end", "the fur stands on end".
The purpose of this straightening of the hair consists in an increased inclusion of air, which increases the protection against cold ( thermal insulation ). Furthermore, the hair follicle muscles press on the sebum glands when straightening up and empty them. As a protection against the cold, sebum increasingly reaches the skin surface, which protects against further cooling through sweat evaporation. In humans, however, this mechanism has hardly any effect due to the low hair density.
literature
- Hans Geyer: hair. In: Franz-Viktor Salomon, Hans Geyer, Uwe Gille (Ed.): Anatomy for veterinary medicine. 2nd, revised and expanded edition. Enke, Stuttgart 2008, ISBN 978-3-8304-1075-1 , pp. 637-640.
