<prompt> Which of the following is true about Nephron function:Ascending thick limb is permeable to waterDescending thin limb is impermeable to waterOsmolality of intra-tubular content in DCT is more than surrounding interstitutionOsmolality of intratubular content in PCT is isotonic to surrounding interstiti um  <response>: D i.e. Osmolality of intratubular content in PCT is isotonic to surrounding interstitiumAt the end of proximal tubule 60-70 of filtered solute is reabsorbed also 60-70 of filtered water is reabsorbedQ. Thus in the proximal tubule, water moves passively out of the tubule, along osmotic gradients set up by active transpo of solutes and Isotonicity is maintainedQ.Intratubular content in DCT is HypotonicQ This is because of two factors:a The distal tubule, paicularly its first pa, is relatively impermeable to water.b The ascending limb of loop of Henle and the DCT have a strong active system of reabsorption of solutes. Active transpo of Nat, co- transpo of Kt C1 occurs out of thick ascending limb, thereby diluting the contents of DCT. Thus while most of the solutes are reabsorbed, water remains behind, causing dilution of tubular fluid.Permeability and transpo, in various segments of nephronSegmentsPermeabilityActive transpoof N aOsmolalityH20UreaNaC1 Proximal tubulePermeablePermeablePermeablePresentIsosmoticQ Loop of Henle - Thin descending limb4-0HypeonicQ- Thin ascending limb040Hypotonic- Thick ascending limb0--4Hypotonic Distal convoluted tubule---3HypotonicQ Collecting tubule - Coicle tubule30-2Isotonic- Outer medullary poion30-1 - Inner medullary poion33-1Hypeonic Indicates presence of vasopressinQ.The segments of nephron that are impermeable to water: Thin ascending limbQ - Thick ascending limbQ.- 1st pa of distal tubule DCTQ 