Michigan Esthetician State Board Practice Exam

What is the primary purpose of the arrector pili muscle?

1. To support hair growth

2. To assist in hair removal

3. To cause hair to stand on end

4. To protect hair follicles

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

The primary purpose of the arrector pili muscle is to cause hair to stand on end. This small, smooth muscle is attached to hair follicles and is responsible for the phenomenon known as "goosebumps." When the body experiences cold temperatures or emotional responses, such as fear or excitement, the arrector pili muscles contract. This contraction pulls the hair upright, creating the appearance of goosebumps and leading to a temporary increase in insulation by trapping a layer of air, which can help in thermal regulation. Additionally, this reaction can make an animal appear larger to threats and is a primitive response linked to our evolutionary past. Other options, such as supporting hair growth, assisting in hair removal, and protecting hair follicles, do not accurately describe the primary function of the arrector pili muscle. While hair follicles are supported by surrounding tissues, the specific role of the arrector pili is not related to hair growth or removal.