A new perspective on the anatomic relationships of the perineum, vagina, urethra, and urethral vesical junction part 1

Anatomic dissections were carried out to better determine the perineal muscular structures that contribute to the support of the vagina, urethra, and urethral vesical junction beneath the symphysis pubis, Perineal and abdominal dissections were performed on 12 cadavers after removal of the inferior extremities and subsequently the symphysis pubis, The muscular component of the urogenital diaphragm could not be identified as a separate entity from the levator ani muscle(s). The thin perineal muscles add little if any structural support to the vagina, urethra, or urethral vesical junction. A major component of urethral support was identified as an anterior band of muscle attached to the upper (proximal) third of the urethra arising from the right and left levator ani muscles. The subpubic urethra is surrounded by vascular structures, including the bulb of the vestibule and respective clitoral crus, The lateral vagina as well as the lateral urethra received muscular support (insertion) from the levator ani muscles throughout their length. The anatomic description of a separate muscular entity, the urogenital diaphragm, is in reality part of the levator ani muscle complex. An anterior muscle mass derived from the levator ani muscles provides significant voluntary support at the urethral vesical junction. The intimate relationship of the perineal cavernous vascular structures to the proximal urethra suggests a role for these structures in the continence mechanism and in normal voiding.