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qn3 - satnaam
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06-03-2009, 03:58 AM
Which of the following substances is NOT reabsorbed primarily by simple diffusion in the proximal tubule?
(A) Urate (B) Potassium © Chloride (D) Urea (E) Water
06-03-2009, 11:36 AM
agree with A )uric acid mainly by active reabsorption..
but Urea reabsorbed by simple diffusion mainly in ascending limb of loop of henle& collecting duct..not in proximal tubule is nt it?? correct me if iam wrong??
06-03-2009, 12:11 PM
Urea Regulation:
A.Urea, an end product of nitrogen metabolism, is an example of a passively transported substance. B. It is freely filterable, and about 50% of the filtered load is reabsorbed in the proximal tubule. C. Although the distal tubule and collecting ducts are usually impermeable to urea, ADH increases the permeability of the medullary collecting ducts, thereby enhancing the osmolality of the medullary interstitium. D. Thus, in a water diuresis when ADH is low, the clearance of urea increases. E. About 40% of the osmolality in the medulla is due to the presence of urea. "USMLE Road Map: Physiology" |
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