When most people discuss plasticity it's most often with respect to the brain. Neuroplasticity is the trait of the brain where it can change its functional structures to fit a new need by forming new neural connections. An example would be how after a brain injury during which damage was sustained to the parts of the brain which handle speech, the tasks of the damaged portions can be taken up by other regions of the brain. It is even possible that functionality will return to normal or at least improve. The kidney, unfortunately, does not behave the same way.
Kidney damage can rarely ever be reversed and the progression of chronic kidney disease can really only ever be slowed down, not stopped. In addition to this, at around the age of 40 the kidney begins to lose functional nephrons (they become obsolescent nephrons), renal plasma (due to the absorption of obsolescent nephrons), and have an overall decrease in the glomerular filtration rate (GFR). While the list of things that can harm or reduce its functionality is incredibly expansive the kidney does, however, have a mechanism for dealing managing those factors that is somewhat similar to plasticity in the brain.
The reason people can live normal lives past the age of 50 is because of compensatory hypertrophy. Hypertrophy is defined as the increase in the volume of an organ or tissue due to the enlargement of its component cells. With respect to the kidney, this means that nephrons in a sense swell up in order to be able to filter more more blood, thus compensating (for the most part) for nephron reduction due to old age. This process is seen to occur most strikingly in patients who have lost all (or nearly all) function in one of their kidneys.
Is the compensatory hypertrophy in an adult past 50 the same process that happens with a child that is born with only one kidney(I remember this from you 'facts' post)?
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