[Morphological investigation of external sphincter muscle of the male posterior urethra].

For investigation of function of the male posterior urethra, morphological study was performed in terms of the muscle architecture including sphincter muscle of the posterior urethra. The muscle localization was demonstrated by microdissection in eight male cadavers. Histological examination was also employed with HE staining and immunohistochemical method to detect the nature of these muscles. At the dorsal side, the muscle fibers of the deep trigone were located from the inter-ureteral ridge beyond the bladder neck to the vermontanum surrounding the posterior urethra. They were regarded as the internal urethral sphincter muscles. At the ventral side, the muscle fibers were also found just outside the ventral prostate running from the base to the apex of the prostate. Then, they were circularly located around the membranous urethra. These saddle shaped muscles were proved to be striated muscle by the immunohistochemical examination using anti-Desmin and anti-Myoglobin antibody. Therefore, the external urethral sphincter muscle would consist of the pelvic floor muscles and the urethral sphincter muscles.