<prompt> In which of the mentioned segments of a nephron, Na reabsorption primarily occurs by the Na-H exchange?PCTloop of HenleDCTCollecting duct  <response>: In the PCT, the apical membrane has NaH-antipoer, which couples H secretion with the Na movement across the apical membrane. In the TAL of loop of Henle:- The sympoer NKCC moves 1 Na, 1 K, 2 Cl- through the apical membrane into the cell. In DCT:- The sympoer is NCC. In the late distal tubule and collecting duct:- Nadiffuses across the apical membrane through the epithelial Na channel ENaC. 