What does the arrector pili muscle do in conjunction with hair follicles?

The arrector pili muscle plays a significant role in the physiology of hair follicles by causing hair to stand erect. This smooth muscle is attached to the base of hair follicles and is responsible for the phenomenon commonly referred to as "goosebumps." When the muscle contracts, typically in response to cold or emotional stimuli, it pulls the hair follicle upwards. This response can make the hair stand on end, which has evolutionary significance; in animals, it can increase insulation or make them appear larger in the face of danger.

In terms of its function, the contraction of the arrector pili muscle also compresses the sebaceous glands associated with hair follicles, resulting in the secretion of sebum that helps to lubricate the hair and skin. However, the primary and most direct effect of the arrector pili muscle is its role in making hair erect, which is reflected in the correct answer. The other choices do not accurately represent the primary function of the arrector pili muscle in relation to hair follicles.