Electrolysis Practice Exam

What is the function of the arrector pili muscle?

1. To support hair structure

2. To control hair growth

3. To produce oil

4. To cause hair to stand on end

The correct answer is: To cause hair to stand on end

The arrector pili muscle is responsible for causing hair to stand on end, a phenomenon known as piloerection. This muscle is a small bundle of smooth muscle fibers that attach to the base of hair follicles. When the arrector pili muscles contract, they pull the hair follicles upright, which can create the appearance of goosebumps on the skin. This response often occurs in reaction to cold temperatures or emotional states, such as fear, as part of the body's fight-or-flight response. The contraction of these muscles can also serve to trap a layer of air for insulation or make the individual appear larger to potential threats, although this latter function is less relevant in modern humans. Supporting hair structure, controlling hair growth, and producing oil are functions associated with other structures in the skin, such as hair follicles, sebaceous glands, and the dermal layer, rather than the arrector pili muscle itself.