This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Physiology
Transpulmonary pressure is the difference between: 
Select and explain. 
A. The bronchus and atmospheric pressure, B. Pressure in alveoli and intrapleural pressure, C. Atmosphere and intrapleural pressure, D. Atmosphere and intraalveolar pressure
B: Pressure in alveoli and intrapleural pressure
Answer: B: Pressure in alveoli and intrapleural pressure 
Explanation: Transpulmonary pressure is the pressure difference between alveolar pressure and intrapleural pressure. Before the sta of inspiration or at the end of expiration it is about +5cm H2O. Positive transpulmonary pressure keeps the alveoli open. Intrapleural pressure is the pressure between two layers of pleura. It is about -5cm H2O before the sta of inspiration or at the end of expiration. Alveolar pressure is the pressure within the terminal air spaces. It is the sum of pleural pressure and elastic recoil pressure of the lung. It is atmospheric before the sta of inspiration or at the end of expiration. Transthoracic pressure is the pressure difference between alveolar pressure and pressure at the body surface. Ref: Guyton 12th Ed.