The arrector pili muscle (plural: Musculi arrectores pilorum) is a small, smooth muscle that is associated with each Hair follicles connected in the human body. The main function of this muscle is to raise the hair, which is commonly referred to as “goosebumps” or medically as piloerection. This reaction typically occurs in response to cold, fear, or various emotional states, and originally serves to increase the insulating power of fur in animals or to make them appear larger than they are to scare off predators.
Each arrector pili muscle is attached to the base of a hair follicle and extends to the superficial layer of the dermis (the middle layer of skin). When the muscle contracts, it pulls the hair follicle upwards, causing the hair to stand up and causing the visible goosebumps.
Although the arrectores pilorum muscles have no direct clinical significance, they are part of the studies of skin physiology and may be considered in dermatology when studying skin reactions and conditions. Their activity may also be relevant in cosmetic and therapeutic research, particularly related to skin texture and hair follicle function.
In modern human physiology, the function of the arrector pili muscle is largely vestigial, meaning that it has become less important over evolution because humans have less body hair than many of their animal relatives. Nevertheless, the goosebumps response remains a fascinating example of the complex interactions between the nervous system and the skin.
