Masumoto, HiroshiTakenaka, AtsushiRodríguez Vázquez, José FranciscoMurakami, GenMatsubara, Akio2024-11-222024-11-222012Masumoto, Hiroshi, et al. «Reappraisal of Intergender Differences in the Urethral Striated Sphincter Explains Why a Completely Circular Arrangement Is Difficult in Females: A Histological Study Using Human Fetuses». Anatomy & Cell Biology, vol. 45, n.o 2, 2012, p. 79. DOI.org (Crossref), https://doi.org/10.5115/acb.2012.45.2.79.2093-366510.5115/acb.2012.45.2.79https://hdl.handle.net/20.500.14352/110947To investigate why the development of a completely circular striated sphincter is so rare, we examined histological sections of 11 female and 11 male mid-term human fetuses. In male fetuses, the striated muscle initially extended in the frontal, rather than in the horizontal plane. However, a knee-like portion was absent in the female fetal urethra because, on the inferior side of the vaginal end, a wide groove for the future vestibule opened inferiorly. Accordingly, it was difficult for the developing striated muscle to surround the groove, even though there was not a great difference in width or thickness between the female vestibule and the male urethra. The development of a completely circular striated sphincter seems to be impossible in females because of interruption of the frontal plane by the groove-like vestibule. However, we cannot rule out the possibility that before descent of the vagina, the urethral striated muscle extends posteriorly.engAttribution-NonCommercial 4.0 Internationalhttp://creativecommons.org/licenses/by-nc/4.0/journal article2093-3673https://doi.org/10.5115/acb.2012.45.2.7922822461https://acbjournal.org/journal/view.html?doi=10.5115/acb.2012.45.2.79https://pubmed.ncbi.nlm.nih.gov/22822461/open access611Urethal rhabdosphincterGenital tractUrogenital sinusColliculusHuman fetusAnatomía2410.02 Anatomía Humana2410.06 Embriología Humana