This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System Pa 1, Subject name: Physiology
[{'content': 'The alveoli are normally kept dry by the:- \nSelect and explain. \nA. Macrophages, B. Surfactant, C. Negative intrapleural pressure, D. High pCO2 in the alveoli', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Surfactant is a mixture of dipalmitoyl phosphatidyl choline, other proteins & lipids. Role in keeping alveoli dry :- 1. The lipids in the alveolus 2. In the absence of surfactant, the unopposed surface tension in the alveoli would produce a force that greatly ors transudation of fluid from blood into alveoli. Note Factors increasing surfactant synthesis: Factors decreasing surfactant synthesis: Glucocoicoids Thyroxine Stretching of lungs in infancy Beta adrenergic agonist Calcium Smoking Long term inhalation of 100% oxygen Occlusion of main bronchus/pulmonary aery', 'role': 'assistant'}]