This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Introduction to Central Nervous System, Subject name: Physiology
[{'content': 'A 15-year-old girl is taken to see a physician because of a sore throat. An antibiotic is prescribed that can enter most tissues of the body but cannot penetrate the blood-brain barrier. The blood-brain barrier can be attributed primarily to which cell type? \nSelect and explain. \nA. Astrocyte, B. Endothelial cell, C. Glial cell, D. Macrophage', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The endothelial cells lining all blood vessels in the brain constitute the blood-brain barrier. Tight junctions between endothelial cells forms blood-brain barrier. The purpose of the blood-brain barrier is to protect the chemical environment of the brain from rapid changes in composition that occur normally in the rest of the body fluids.', 'role': 'assistant'}]