sturge_weber
Forum Guru
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q. a normal 26 yr old medical student has a urine flow rate of 1ml/min. uosm is 800 mosmol/kg. in this subject the lowest osmoloarity would be found in which of the following locations?
a. beginning of pct
B. end of cortical collecting tybule or duct
C. end of papillary collecting tubule or duct
D. macula densa
E. tip of loop of henle
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| mildus
Forum Guru
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It must be D. This pt has hyperosmotic urine, which means that ADH is present in the kidneys.
In PCT osmolarity is 300 mOsmol/L (isoosmotic reabsorption of water and solutes),
the descending part of loop of Henle is obligatory concentrating segment (very permeable for water and not for solutes) ,
the ascending part of the loop of Henle is obligatory dilutional segment (permeable for solutes but not for water),
DCT is facultative concentrating segment (on its beginning near macula densa osmolarity is 100 mosm/L, and near its end osmolarity increases if there is much ADH)
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| dharjma
Forum Senior
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i agree.because macula densa (where all solutes reabsorbed, osmolarity is lowest here) is the first structure encountered after Asc loop of henle. so osmolarity there would be low low low.
almost picked tip of loop of henle till i realised solutes are only collected at the ASCending part of loop.
Edited by dharjma on 10/30/05 - 10:06 AM. Reason: correction. sentence didnt make sense initially :)
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| sturge_weber
Forum Guru
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yes guys thanks, u re right
thanks for explaining it so well mildus
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