This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'What are the types of cells present in coical collecting duct? \nSelect and explain. \nA. Both Principal (P) cells & Intercalated (I) cells., B. Only P cells, C. Only I cells, D. No cellular content', 'role': 'user'}, {'content': "Answer: A \nExplanation: Both Principal (P) cells & Intercalated (I) cells.Cells involved in reabsorption in coical collecting duct:Principal (P) cells.Intercalated (I) cells.FUNCTIONS OF 'P' CELLS:1. Sodium & water reabsorption:Reabsorbed from lumen.Occurs through Na2+ channels (ENaC channels). Approximately 3% Na reabsorption occurs.2. Potassium secretion:Secreted into lumen.K+ both secreted & reabsorbed.Note: Na2+ reabsorption & K+ secretion depends on,Na2+-K+-ATPase activity in basolateral membrane.Aldosterone.3. Water reabsorption:ADH Controlled.Stimulates water channel, aquaporin-2.FUNCTIONS OF 'I' CELLS:Reabsorb potassium ion.Secrete hydrogen ions into tubular lumen.", 'role': 'assistant'}]