[Morphological and functional characteristics of the urogenital diaphragm in women].

Macroscopical study of muscle layer of urogenital diaphragm in women has revealed two muscles situated between its superior and inferior fasciae--m. transversus perinei profundus (MTPP) and sphincter urethrae (SU),--which are separated by connective tissue. In females, SU is not ring-shaped, but is an arched structure situated in front of urethral lumen intertwining into urethral outer circular muscular layer. MTPP consists of three groups of bundles: anterior, medium and posterior. Anterior bundles of MTPP are periurethral and directly interlace with urethral muscular wall. Medium and posterior bundles of this muscle do not reach the urethral wall and act on the muscular wall of vagina. The study of histotopographic sections of urethral muscular wall made from the level of neck of the urinary bladder to the urogenital diaphragm, showed that the urethral outer circular muscular layer contains both bundles of smooth muscle cells and striated muscle fibers which ascend from urogenital diaphragm attaining an oblique-circular course. Major part of urethral striated muscle fibers, as well as SU and MTPP fibers belong to "red", slow-twitch, tonic fiber type.