Which one of the following statements regarding water reabsorption in the tubules is true?
Maximum of filtered water (60-70%) is reabsorbed in the proximal tubule, with or without Vasopressin. This is independent of the fluid and electrolyte status of the body and is caused by the osmotic gradient created by Na+ reabsorption.
Obligatory water reabsorption- (Independent of ADH)- 85%
-        Proximal tubule- 60-70%
-        Descending limb of loop of Henle- 15%
Facultative water reabsorption- (ADH dependent)- 15%
This depends on fluid and electrolyte status of the body
-        Late distal tubule
-        Cortical collecting duct
Medullary collecting duct
The bulk of water reabsorption occurs secondary to Na+ reabsorption
Majority of facultative reabsorption occurs in proximal tubule
Obligatory reabsorption is ADH dependent
20% of water is always reabsorbed irrespective of water balance