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Arrangement of FSUs
renal tubuli
functional subunit
[FSU]*
* FSU = largest unit of cells
that can be regenerated from a
single surviving stem cell
(Withers 1988)
parallel organization
functional damage:
if critical number of FSU is inactivated
volume effect:
weak !
total dose more important
than „hot spots“ !
serial organization
FSU
FSU
FSU
FSU
FSU
© Pearson Education, Inc. 2004
inactivation of one FSU can
lead to loss of organ function
risk of complication strongly
influenced by „hot spots“ !
Spinal cord
Intestine
Esophagus
Lung
Liver
Kidney
volume eff c :
high !
Normal tissues