Structural and functional development of outer versus inner cortical proximal tubules.

The concept of centrifugal renal development is based on renal embryogenesis. It implies a relationship between nephron age and nephron position along a cortical to medullary axis. In common usage, however, it often also implies a relationship between nephron age or position and nephron maturity. We consider here whether the ideas of centrifugal development and centrifugal maturation should in fact be considered as separate and distinct concepts. That is, we consider the possibility that nephron maturity does not necessarily correlate with nephron age. Unfortunately, pertinent reported data give no clear answer. We conclude only that further study will be required before definitive conclusions about renal developmental stages can be stated with certainty.