Difference between freely filtered and FF - USMLE Forums
 USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
 Home USMLE Articles USMLE News USMLE Polls USMLE Books USMLE Apps
 USMLE Forums Difference between freely filtered and FF
 Register FAQs Members List Search Today's Posts Mark Forums Read

 USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam

#1
02-03-2013
 USMLE Forums Newbie Steps History: --- Posts: 8 Threads: 7 Thanked 0 Times in 0 Posts Reputation: 10
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.

#2
02-03-2013
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 824 Threads: 66 Thanked 465 Times in 298 Posts Reputation: 475

Quote:
 Originally Posted by abk@step1 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
__________________
Everything is possible for him who believes (MARK 9:23)
245/247/passed on 1st attempt/223/2mos Obsie /3 US LORS/visa not needed/2008 grad

Message:
Options

## Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
User Name:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
 AMG IMG ---
USMLE Steps History
What steps finished! Example: 1+CK+CS+3 = Passed Step 1, Step 2 CK, Step 2 CS, and Step 3.

Choose "---" if you don't want to tell.

 Not yet Step 1 Only CK Only CS Only 1 + CK 1 + CS 1+CK+CS CK+CS 1+CK+CS+3 ---
Favorite USMLE Books
 What USMLE books you really think are useful. Leave blank if you don't want to tell.
Location
 Where you live. Leave blank if you don't want to tell.

## Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

 Similar Threads Thread Thread Starter Forum Replies Last Post bebix USMLE Step 1 Forum 33 03-09-2017 12:13 AM woodyjr. USMLE Step 1 Forum 14 07-30-2015 10:38 PM Evergreen USMLE Step 1 Forum 4 02-26-2012 01:19 PM jahn77 USMLE Step 1 Forum 12 07-20-2011 06:26 AM kemoo General Topics Forum 2 03-05-2011 11:57 AM

 Home - Contact Us - Forum Rules - Advertise - Mobile Site - Archive - Privacy Statement - Top
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.

USMLE® & other trade marks belong to their respective owners, read full disclaimer
USMLE Forums created under Creative Commons 3.0 License. (2009-2014)