SCANNING AND TRANSMISSION ELECTRON-MICROSCOPIC STUDY OF THE DEVELOPMENT OF THE PODOCYTE IN THE HUMAN FETUS

The metanephric kidneys of seven human fetuses at 11-17 weeks' gestati on were examined by scanning and transmission electron microscopy in o rder to evaluate differentiation of glomerular podocytes. When glomeru li were in the stage of S-shaped bodies, the surface of the visceral e pithelium of renal corpuscles was smooth, with indistinct cell borders . As the glomeruli developed, visceral epithelial cells of renal corpu scles became spherical and resembled clusters of grapes in dense aggre gation, In this stage, processes and foot processes were simultaneousl y formed at the base of epithelial cells. As glomeruli further differe ntiated, visceral epithelial cells of renal corpuscles began to separa te from one another and became flat with the development of vascular l oops. Processes and foot processes were exposed for the first time in Bowman's space. In this stage, the degree of differentiation of epithe lial cells varied widely among various sites of the glomerulus. As glo meruli developed further, projections became more complex and epitheli al cells began to show structures similar to those of adult epithelial cells. The adjacent foot processes arose from different cells through out the period of morphological differentiation.