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.
- Author:
Hiroshi MASUMOTO
1
;
Atsushi TAKENAKA
;
Jose Francisco RODRIGUEZ-VAZQUEZ
;
Gen MURAKAMI
;
Akio MATSUBARA
Author Information
- Publication Type:Original Article
- Keywords: Urethal rhabdosphincter; Genital tract; Urogenital sinus; Colliculus; Human fetus
- MeSH: Female; Fetus; Humans; Male; Muscle, Striated; Urethra; Vagina
- From:Anatomy & Cell Biology 2012;45(2):79-85
- CountryRepublic of Korea
- Language:English
- Abstract: To 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.
