Three-Dimensional Ultrastructural Analysis of Human Skin with the Arrector Pili Muscle Interacting with the Hair Follicle Epithelium

This study utilized a three-dimensional ultrastructural analysis application with serial block-face scanning electron microscopy (SBF-SEM) to examine human skin tissues containing the arrector pili muscle. The analysis revealed dense nerve fiber networks branching from nearby bundles and running among muscle fibers, but these networks rarely penetrated the connective tissues between smooth muscle fibers and epithelial cells. Additionally, no adhesion structures were formed between individual smooth muscle fibers and the epithelial cells of the hair follicle. The findings demonstrate the effectiveness of this method for analyzing structural changes in skin tissues, particularly the arrector pili muscle and nerve fibers with hair follicular epithelium, in aging and diseased conditions.