Structure of the perineal membrane in females: gross and microscopic anatomy.

OBJECTIVE: To re-examine the anatomy of the perineal membrane and its anatomical relationships in whole-pelvis and histologic serial section as well as gross anatomical dissection.

METHODS: Serial trichrome-stained histologic sections of five female pelvic specimens (0-37 years old) were examined. Specimens included the urethra, perineal membrane, vagina, and surrounding structures. Macroscopic whole-pelvis sections of three adults, 28-56 years of age, in axial, sagittal, and coronal sections were also studied. Dissections of six female cadavers, 48-90 years of age, were also performed.

RESULTS: The perineal membrane is composed of two regions, one dorsal and one ventral. The dorsal portion consists of bilateral transverse fibrous sheets that attach the lateral wall of the vagina and perineal body to the ischiopubic ramus. This portion is devoid of striated muscle. The ventral portion is part of a solid three-dimensional tissue mass in which several structures are embedded. It is intimately associated with the compressor urethrae and the urethrovaginal sphincter muscle of the distal urethra with the urethra and its surrounding connective. In this region the perineal membrane is continuous with the insertion of the arcus tendineus fascia pelvis. The levator ani muscles are connected with the cranial surface of the perineal membrane. The vestibular bulb and clitoral crus are fused with the membrane's caudal surface.

CONCLUSION: The structure of the perineal membrane is a complex three-dimensional structure with two distinctly different dorsal and ventral regions; not a simple trilaminar sheet with perforating viscera.