The Arrector Pili Muscle and the Follicular Unit of the Scalp

In a study examining the microscopic anatomy of the arrector pili muscles and their relationship with follicular units in the scalp, researchers analyzed horizontal sections of skin from 20 adult cadavers. They discovered that hair follicles within follicular units are located above the insertion points of the arrector pili muscles. These muscles appeared to converge at the isthmus level, forming a single structure that connects to the superior attachment zone, indicating that each follicular unit shares a common arrector pili muscle. The findings led to the proposal of an anatomical model that could enhance the understanding of hair follicle physiology and the broader role of the arrector pili muscle beyond hair elevation.