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#1
10-31-2011
 USMLE Forums Master Steps History: Not yet Posts: 674 Threads: 264 Thanked 963 Times in 394 Posts Reputation: 973
Calculate the net glomerular filtration pressure

At the afferent arteriolar end of a glomerular capillary, the glomerular capillary hydrostatic pressure is 50 mmHg. In Bowman’s space the hydrostatic pressure is 10 mmHg and the glomerular capillary oncotic pressure is 27 mmHg. Given these measurements, what is the value and direction of the net ultrafiltration pressure?

A. 33 mmHg positive filtration
B. 33 mmHg negative filtration
C. 43 mmHg negative filtration
D. 13 mmHg positive filtration
E. 13 mmHg negative filtration
 The above post was thanked by: N Nur (02-03-2012)

#2
10-31-2011
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13 positive filtration
#3
10-31-2011
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#4
10-31-2011
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D, 13mmHg positive filtration
#5
11-01-2011
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13 mmhg postive pressure
#6
11-01-2011
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The correct answer is D.
The driving force of glomerular filtration is the net ultrafiltration pressure across the glomerular capillaries. Using Starling’s equation:
Net pressure = [ (HPgc – HP bs) – (OPgc – OP bs)]
= 50-10 - 27
= 13.
Positive values favor filtration.
 The above post was thanked by: naush (11-01-2011)

 Tags Physiology-, Renal-, Step-1-Questions

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