This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cailage,cell junction,lymphoid and integumentary system, Subject name: Anatomy
[{'content': 'Which of the following statements concerning Hassall corpuscles is true? \nSelect and explain. \nA. They are located in the thymic coex of young individuals., B. They are located in the thymic coex of old individuals., C. They are derived from mesoderm., D. They are located in the thymic medulla', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Hassall corpuscles are epithelial reticular cells (derived from endoderm) found only in the medulla of the thymus.', 'role': 'assistant'}]