Which one of the following statements regarding water reabsorption in the tubules?
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
A i.e. The bulk of water reabsorption occurs secondary to Na+ reabsorptionProximal convoluted tubule reabsorbs approximately 50-60% of water (bulk of water), which is secondary (obligatory) to Na+ reabsorptionQReabsorption of waterObligatory reabsorption Absorption of water in proximal tubules secondary to Na+ reabsorptionQ - Absorption of water in renal tubules independent of plasma osmolality (irrespective of water balance) - Filtered water is reabsorbed isoosmotically & is independent of ADH levels. Facultative reabsorptionAbsorption of water in distal tubules and collecting duct in presence of ADHQ- Absorption of water depends on variation in plasma osmolalityNormally DCT and collecting ducts are not permeable to water but in presence of ADH, these segments become permeable.* Thick ascending limb of Henle & early distal tubule are both impermeable to waterQ & no reabsorption occurs irrespective of water balance.