Arrector pili muscle connects with hair follicle
The arrector pili muscles, also known as hair erector muscles, are small muscles attached to hair follicles in mammals. Contraction of these muscles causes the hairs to stand on end, known colloquially as goose bumps (piloerection).Structure
Each arrector pili is composed of a bundle of smooth muscle fibres which attach to several follicles (a follicular unit). Each is innervated by the sympathetic division of the autonomic nervous system. The muscle attaches to the follicular stem cell niche in the follicular bulge, splitting at their deep end to encircle the follicle.Function
The contraction of the muscle is involuntary. Stresses such as cold, fear etc. may stimulate the sympathetic nervous system, and thus cause muscle contraction.Thermal insulation
Contraction of arrector pili muscles have a principal function in the majority of mammals of providing thermal insulation. Air becomes trapped between the erect hairs, helping the animal retain heat.