ANATOMY

Detailed explanation-1: -Potassium secretion occurs mainly in the late distal collecting tubule (DCT) and the collecting duct (CD). The purpose of secretion is to control the serum potassium levels in the long term.

Detailed explanation-2: -As fluid travels down the DCT, the luminal potassium concentration increases, indicating that net K+ secretion occurs along the distal tubule.

Detailed explanation-3: -Potassium is secreted along the initial and cortical collection tubules. Net secretion can be replaced by net absorption in a state of potassium depletion. Also shown are the two cell types lining the distal tubule and cortical collecting duct.

Detailed explanation-4: -The distal convoluted tubule also contains intercalated (I) cells, responsible for the secretion of acid.

Detailed explanation-5: -K+ reabsorption in the proximal tubule primarily occurs through the paracellular pathway. Active Na+ reabsorption drives net fluid reabsorption across the proximal tubule, which in turn, drives K+ reabsorption through a solvent drag mechanism.