What is the function of the arrector pilli muscle found in the hair root?

The arrector pilli muscle is a small muscle connected to hair follicles that plays a key role in facilitating the phenomenon known as piloerection, which is when hair stands up on the skin, commonly referred to as "goosebumps." When the body is cold or experiences strong emotions like fear, the arrector pilli muscles contract, causing the hair to rise and the skin to form small bumps. This reaction is a remnant of our evolutionary past, potentially serving to make our ancestors appear larger in response to threats or to trap air and provide insulation for warmth.

While nourishment of the hair is primarily the function of the blood vessels surrounding the hair follicles, moisture provision is typically handled by sebaceous glands. Support of the follicle structure is maintained by other connective tissues and do not directly involve the arrector pilli muscle. Thus, the primary and distinct function of the arrector pilli is its ability to contract and raise the hair, making that the correct understanding of this muscle's role.