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.

The aim: To study the forms of anatomical variability of the external structure of the upper and lower parathyroid glands in the fetal period of human ontogenesis. Materials and methods: The study involved 48 specimens of human fetuses with 81,0-375,0 mm of crown-rump length (CRL). The study was conducted by means of macromicroscopic preparation, morphometry and variation statistics method. Results: The age and individual anatomical variability, complex way of development and formation of synotopic embryotropographic correlations of the upper and lower parathyroid glands in the prenatal period of human ontogenesis create numerous prerequisites for the emergence of variants of their external structure and topography in the fetuses of both different and the same age groups. Conclusions: There is a significant anatomical variability of the upper and lower parathyroid glands in 4-10-month-old fetuses, which is manifested by varieties of their shape and topical location. Aplasia of the upper parathyroid glands, which was found in two human fetuses aged 7 months, was due to the fetures of their organogenesis and the formation of syntopy in the embryonic and prefetal periods of their development. Parathyroid glands are mainly supplied with blood by the branches of the inferior thyroid artery. The branches of the upper thyroid artery and the arteries of adjacent organs: larynx, trachea and esophagus are involved in the blood supply. The right and left inferior thyroid veins are tributaries of the corresponding brachiocephalic vein, paired (right and left) superior and middle thyroid veins are those for the internal jugular vein.

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