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Old 02-03-2013
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Default Difference between freely filtered and FF

Hello
Can anyone please explain to me the difference between freely filtered and FF. According to my understanding a substance is freely filtered when the conc in the filtrate is equal to conc in the plasma and FF is the fraction of substance that enters the kidney that is filtered.
But then it is said that the normal FF is 20% for a freely filtered substance. How can this be possible? If the conc in the filtrate and the plasma is the same for a freely filtered substance then how can the FF be 20% should'nt it be 100%
If anyone can explain to me I would appreciate it.
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Old 02-03-2013
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Originally Posted by abk@step1 View Post
Hello
Can anyone please explain to me the difference between freely filtered and FF. According to my understanding a substance is freely filtered when the conc in the filtrate is equal to conc in the plasma and FF is the fraction of substance that enters the kidney that is filtered.
But then it is said that the normal FF is 20% for a freely filtered substance. How can this be possible? If the conc in the filtrate and the plasma is the same for a freely filtered substance then how can the FF be 20% should'nt it be 100%
If anyone can explain to me I would appreciate it.
U are right that freely filtered substance is 100 % filtrable
But according to physiology from 600ml plasma flowing to kidneys only 120 ml is filtered through glomerulus which implies that whatever the concentration of substance in that 120ml plasma is completely filtered (20%) but remaining portion in 480ml (80%) returns back (if there are no additional tubular modifications)
According to this each time for freely filtered substance with normal kidney functions (gfr, rpf) and without further tubular modifications 20% is lost and 80% retained
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