This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
JG cells (juxta glomerular apparatus) are 
Select and explain. 
A. Macula densa, B. Smooth muscullar cells of afferent aeriole, C. Smooth muscullar cells of efferent aeriole, D. Islets of epithelial cells
B: Smooth muscullar cells of afferent aeriole
Answer: B: Smooth muscullar cells of afferent aeriole 
Explanation: INDERBIR SINGH&;S TEXTBOOK OF HUMAN HISTOLOGY-PAGE NO:313Juxtaglomerular cells the muscle cells in the wall of the afferent aerioles are modified.they are large and rounded(epithelium)and have spherical nuclei. their cytoplasm contains granules that can be stained with special methods. these are called juxtaglomerular cells