The Perineal Membrane: Its Composite Fibers and Nerve Content, and Relationship to the Levator Ani and Deep Transverse Perineal Muscles

The perineal membrane (PM) is a thick, elastic fiber-rich, smooth muscle-poor membrane ex-tending along the vestibule and lower vaginal wall and embedding the urethrovaginal sphincter and compressor urethrae muscles. To provide a better understanding of the topographical rela-tionship between the PM and the levator ani muscle, we examined histological sections from 15 female cadavers. The composite fibers of the PM were usually continuous with that of a fascia cov-ering the inferior or lateral surface of the levator ani (fascia diaphragmatis pelvis inferior) rather than the endopelvic fascia covering the superior or medial surface of the latter muscle. However, this fascial connection was sometimes interrupted by a venous plexus. The deep transverse peri-neal muscle was consistently adjacent to the posterolateral aspect of the PM, but whether it ex-tended superficially or deeply to the PM depended on size of the muscle. In contrast to the endo