A clear understanding of the main stages of embryogenesis and the temporal dynamics of structural transformations of urinary system sources in the prenatal period of human ontogenesis will allow practicing doctors to clearly understand the features of the eriopathogenesis of malignant neoplasms of its organs and structures, to differentiate the remnants of embryonic tissues in the surgical material from tumors, to rationally apply the immunohistochemistry method in cancer diagnosis (Al-Harbi A. et al., 2016; MñBride J.M., 2016).
The aim of the study – to determine the peculiarities of the sources of the rudiments and the chronological sequence of topographical and anatomical transformations of the organs and structures of the human urinary system.
The material for the study was 14 series of consecutive histological sections of specimens of human embryos and prefetuses (4.0-66.0 mm parietal-coccygeal length (PCL)) aged from 4th to 11th weeks of intrauterine development (IUD). A complex of modern methods of morphological research (anthropometry, morphometry, microscopy, 3D computer reconstruction, statistical analysis) were applied.
The first signs of mesonephric duct diverticula formation are determined in human embryos of the 5th week of the IUD (embryos 7.0-7.5 mm PCL). It is represented by an ampoule-like blind expansion of the diverticulum – the primary lining of the renal pelvis, which is surrounded by a condensed mesenchyme, which is the source of the formation of the renal parenchyma – a nephrogenic blastema. Starting from the embryos of the middle of the 5th week of IUD, due to 3D computer reconstruction, the first topographical and anatomical features of the primordia of the structures of the definitive kidney are determined. The rudiments of the renal pelvises – paired ampoule-like blind expansions of the diverticulum of the mesonephric duct – are immersed in the metanephric blastema, which has the shape of a drop due to the upper narrowed end. Starting from the end of the 6th week of IUD, there is an evagination of the wall of the blind end of the diverticulum (the rudiment of the renal pelvis) in the cranial and caudal directions, i.e., the rudiments of major calyces appears. The rudiments of the minor cups is formed by the evagination of the wall of the major calices and appears in prefetuses at the beginning of the 7th week of IUD. Age-related topographical and anatomical changes of the kidneys were also traced.
Conclusions.
1. On the specimens of embryos 4.7-5.5 mm PCL (4th week of IUD), mesodermal sources of rudiments of structures and organs of the genitourinary system, which originate from the paired genitourinary crest, are determined. At the border of the dorsal and ventral parts of the mesoderm, in the intermediate mesoderm, the source of the urinary tubules is carried out, which form the nephrogenic cord – the only source of all three generations of the kidney. At the end of the 4th week of IUD, an evagination appears on both sides from the dorsal wall of the excretory duct of the mesonephros in its caudal part, which is the rudiment of the epithelial lining of the ureter and renal pelvis.
2. The rudiment of the renal pelvis is observed for the first time in the 5th week of IUD (embryos 7.0-7.5 mm PCL), major cups – at the end of the 6th week of VUR (embryos 12.0-13.5 mm TKD), small calices – at the beginning of the 7th week of IUD (prefetuses 14.0-15.0 mm PCL).
3. In the process of intrauterine development, the kidneys move from their original location in the pelvis, where the source of their blood supply is the common iliac artery, cranial to the primordia of the adrenal glands, giving their own vessels to the aorta, which become renal arteries.
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