Arrector pili muscle

The Musculi arrectores pilorum (singular: arrector pili muscle ) ( Haaraufrichtemuskel, Haarbalgmuskel or Pilomotor ) are small, consisting of smooth muscle muscle that focus on the outer edge of the hair with the exception of the primary hair (top and coat hair). They derive from the superficial layer of the dermis and set below the sebaceous gland at the hair on. The innervation is done involuntarily by sympathetic nerve fibers.

The Musculi arrectores pilorum addressed to the hair in humans is called by the erection of the hair ( piloerection ) resulting skin texture also creeps. This can occur due to cold or psychological factors such as excitement and anger: "It hairs stand on end ," " the fur Bucks ".

The purpose of this erection of the hair is in an increased inclusion of air, which increases protection against the cold ( thermal insulation). In addition push the Haarbalgmuskel when rising on the sebaceous glands and empty it. As a protection against the cold arrives so increased sebum on the skin surface, which protects against further cooling by sweat evaporation. In humans, this mechanism has, however, due to the low density of hair little effect.