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': 'Which pa of the renal system produces and secretes renin? \nSelect and explain. \nA. JG cells, B. Macula densa, C. Tubular cells, D. All of the above', 'role': 'user'}, {'content': "Answer: A \nExplanation: The renin is produced by the juxtaglomerular cells (JG cells). These epitheloid cells are located in the media of the afferent aerioles as they enter the glomeruli. Renin is also found in agranular lacis cells that are located in the junction between the afferent and efferent aerioles. This enzyme acts in conce with angiotensin-conveing enzyme (ACE) to form angiotensin II. Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 38. Regulation of Extracellular Fluid Composition & Volume. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.", 'role': 'assistant'}]