PATHOLOGY

Detailed explanation-1: -Urea absorption in the inner medullary collecting duct provides a mechanism to elevate the concentration of urea in the papillary interstitial fluid and thereby permit the excretion of urea with as little water as possible. Urea reabsorption may have another important effect-to aid in the excretion of potassium (K).

Detailed explanation-2: -Tubular fluid passes through the collecting ducts to reach the calyces and renal pelvis. While traveling through the collecting ducts, the composition of tubular fluid undergoes alterations. These alterations pertain primarily to reabsorption and secretion of electrolytes, acid, and water.