Development of the definitive kidney in albino rat

The current understanding of the kidney development in the pelvis and then a subsequent migration to the lumbar region is disputed. A total of 96 embryos were examined after they were obtained from 24 pregnant rats. A group of 4 pregnant rats were sacrificed at each day over the period from 12 to 17 successive days of pregnancy. An almost equal number of embryos were histologically investigated at each day using the paraffin technique. This was fulfilled by taking serial sections throughout the entire length of the trunk. The 13 days old embryo presented the appearance of the definitive kidney as indicated by the microscopical display of the ureteric bud invading the nephrogenic cord. This microscopic event took place at the lower lumbar region of all examined embryos. Therefore, the present work gives a microscopic evidence that the definitive kidney develops in the lumbar region.