Intergender differences in histological architecture of the fascia pelvis parietalis: a cadaveric study.

The fascia pelvis parietalis (FPP) or endopelvic fascia is a well-known structure, but few studies described the detailed histological architecture, including the composite fiber directions. We hypothesized a gender-specific fiber architecture corresponding to the functional demand. For the first step to examine this hypothesis, we investigated specimens from 27 adult cadavers (10 males and 17 females) and 11 midterm fetuses (five males and six females) using immunohistochemistry and aldehyde-fuchsin staining. The adult female FPP was a solid, thick monolayered structure that was reinforced by abundant elastic fibers running across the striated muscle fibers, but it contained little or no smooth muscles (SM). In contrast, the male FPP was multilayered with abundant SM. In midterm fetuses, SM originated from the inferior part of the bladder and extended inferiorly along the gender-specific courses. Thus, we found a clear intergender difference in FPP architecture. However, the functional significance remained unknown because the basic architecture was common between nulliparous and multiparous women. Rather than for meeting the likely mechanical demands of pregnancy and vaginal delivery, the intergender difference of the FPP seemed to result from differences in the amount and migration course of bladder-derived SM as well as in hormonal background.