Which of the following is true about Nephron function:
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 a+OsmolalityH20UreaNaC1* Proximal tubulePermeablePermeablePermeablePresentIsosmoticQ* Loop of Henle - Thin descending limb4+++-0HypeonicQ- Thin ascending limb0+4+0Hypotonic- Thick ascending limb0+-+-4+Hypotonic* Distal convoluted tubule+-+-+-3+HypotonicQ* Collecting tubule - Coicle tubule3+*0+-2+Isotonic- Outer medullary poion3+*0+-1+ - Inner medullary poion3+*3++-1+Hypeonic* Indicates presence of vasopressinQ.The segments of nephron that are impermeable to water: Thin ascending limbQ - Thick ascending limbQ.- 1st pa of distal tubule (DCT)Q
Ascending thick limb is permeable to water
Descending thin limb is impermeable to water
Osmolality of intra-tubular content in DCT is more than surrounding interstitution
Osmolality of intratubular content in PCT is isotonic to surrounding interstiti um