Peculiarities of prenatal vagina morphogenesis

Introduction: The rapid development of perinatal gynecology requires from the anatomists comprehensive studies of the patterns of prenatal morphogenesis and the development of topographic and anatomical relationships of female reproductive organs in the human fetuses of different age groups. The aim: To study the development and formation of the vaginal topography in the prenatal period of human ontogenesis.

Materials and methods: The study has been conducted based on 23 series of histological and topographic-anatomical sections of human prefetuses aged 9-12 weeks with 31.0-80.0 mm of crown-rump length (CRL) and 83 specimens of female human fetuses aged 4-9 months with 81.0-345.0 mm of CRL by means of a complex of adequate morphological methods of investigation.

Results and conclusions: Vaginal formation occurs during the 9th week of embryogenesis (prefetuses of 31.0-41.0 mm of CRL) due to the fusion of two different embryonic structures: mesodermal paramesonephral ducts and endodermal urogenital sinus. In this case, the caudal regions of the paramesonephral ducts are transformed into the uterus and the superior two thirds of the vagina, and the inferior third of the vagina develops from the urogenital sinus. Common uterovaginal canal, divided into right and left cavities by mesenchymal septum, is formed in the female prefetuses of 38.0-43.0 mm of CRL due to the fusion of the caudal regions of the paramesonephral ducts in the area of the posterior wall of the urogenital sinus. Complete dissolving of the septum of the uterovaginal canal occurs in prefetuses of 55.0-58.0 mm of CRL. The anterior and posterior vaginal vaults of the same depth are formed in 5-month-old fetuses. Canalization of vagina in the caudo-cranial direction is observed in the fetuses of 170.0-185.0 mm of CRL, with no clear boundary between the uterovaginal canal and the urogenital sinus. The vaginal epithelium in the upper third part originates from the uterovaginal canal, and in the lower two thirds of the vagina - from the urogenital sinus. In the 6-month-old fetuses there was detected the variability of the shape of the superior, middle and inferior third of the vagina, namely: oval (5 cases), elongated-oval (2 cases), stellate (1 case); in the lower third, the H-shaped form was predominantly found (6 fetuses). The proliferation of the hymen membrane occurs in fetuses of 220.0-245.0 mm of CRL. The absence of timely proliferation of the hymen membrane can lead to its atresia, and its premature proliferation causes the appearance of transverse vaginal septa.