We have looked for electron microscopy aspects tissue fragments of human nephrons harvested from fetuses of 7,5-19 weeks to show ultrastructure aspects of the nephron during development.
Material and methods: We have used 9 fragments from human embryos; Four cases were aged of 7,5, 8, 12 and 17 weeks. The other 5 cases were between 18 and 19 weeks. Tissue fragments were fixed in glutaraldehyde at 4 degrees C and processed by the classic technique.
Results: The electron microscopy study shows the evolutive steps of the human nephron (stages I-IV), stages met for the 12-19 weeks embryo. For the cases under this age the meta-nephrogenic blastema was dominant. In the IVth development stage, the cells in the proximal tubule show a higher development degree than the distal segments.
Conclusion: These observations indicate that during early development the proximal segment is better developed and probably more functional than the distal segments.