This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urinary System: Functional Anatomy and Urine Formation, Subject name: Physiology
Collecting duct has which cells - 
Select and explain. 
A. Principle and intercalated, B. Parietal and oxyntic, C. Lac is cells, D. Podocytes
A: Principle and intercalated
Answer: A: Principle and intercalated 
Explanation: Ans. is 'a' i.e.. Principle and intercalatedo Collecting duct is 20 mm long and pass through the renal cortex and medulla to empty- into the pelvis of the kidney at the apex of the medullary pyramids. The epithelium of the collecting ducts is made up of two types of cell: -Principal cells (P cells), which are involved in Na+ reabsorption and ADH stimulated water reabsorption.Intercalated cells (I cells) which are concerned with acid (H+) secretion and HCO3 transport.