Topographic and anatomical characteristics of the bladder neck in early fetuses
Authors: Proniaiev D. , Kashperuk-Karpiuk I. , Proniaiev V. , Riabyi S. 
Published: December 2021

Aim. To determine macro-and microscopic anatomical characteristics and the dynamics in topographic and anatomical interactions of the bladder neck with adjacent organs and structures at the beginning of the fetal period. Material and methods. The study was carried out on 70 fetal specimens. The age of subjects included in the study was determined according to the tables of B.M. Patten, B.P. Khvatova, Yu.N. Shapovalov based on measurements of the parietal-calcaneal length (PCL), taking into account the Instructions for determining the perinatal period, live birth, and stillbirth criteria, approved by Order of the Ministry of Health of Ukraine No. 179 dated March 29, 2006. To achieve this goal, the following methods of anatomical research were used: anthropometry - to determine the age of the studied subjects; injection of arterial vessels with subsequent dissection under the control of a microscope – to study the peculiarities of the blood supply to the vesicoureteral segment; radiography - to determine the skeletotopy of the vesicoureteral segment; macro-microscopy – to explore the anatomical relationships of the components of the vesicoureteral segment, their structure, shape, position; histological – to study the structure of the wall of the vesicoureteral segment; morphometry – to determine the morphometric parameters of the vesicoureteral segment; 3-D reconstruction method – to study the spatial structure of the vesicoureteral segment; statistical – to analyze and establish the reliability of differences in organometric parameters.Results. Skeletopically, the projection of the vesicoureteral junction of early fetuses is located at the level of the upper third of the pubic symphysis. At the beginning of the perinatal period in female fetuses, the bladder neck (6.9 ± 2.6 mm) is longer than in male fetuses (6.4 ± 2.4 mm). Based on the analysis and generalization of the research results, it is substantiated that at the beginning of the fetal period, the internal urethral sphincter can be formed: a) by two loops of the outer longitudinal layer; b) the ring of the circular layer and the front bundles of the outer longitudinal layer; c) anterior bundles of the outer longitudinal layer and transverse bundles of the inner longitudinal layer within the trigone of urinary bladder; d) a ring of the circular layer, thickened in the anterolateral sections.Conclusions. Considering the topographic and anatomical characteristics of the angio- and myoarchitectonics of the vesicoureteral segment, we believe that its role as a physiological sphincter of the lower urinary tract is provided by the interaction of the vascular and muscle components. The vascular component of the sphincter apparatus of the vesicoureteral segment is provided by veins located in three layers: 1) cavernous-like veins of the submucosa; 2) veins of the muscular membrane; 3) veins of tunica adventitia. The second anatomical component of the sphincter function of the vesicoureteral segment is the muscular one, represented by the internal urethral sphincter.