This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Functional Anatomy - Respiratory System, Subject name: Physiology
Ventilation perfusion ratio is maximum at - 
Select and explain. 
A. Apex of lung, B. Base of lung, C. Posterior lobe of lung, D. Middle of the lung
A: Apex of lung
Answer: A: Apex of lung 
Explanation: Ans. is 'a' i.e., Apex of lung o Due to gravity, the apical alveoli are both underventilated and underperfused while the basal alveoli are both overventilated and overperfused.o However, gravity affects perfusion much more than it affects ventilation.o Hence, apical alveoli are more underperfused than underventilated while the basal alveoli are more overperfused than overventilated.o Therefore, V/Q is maximun at apex (about 3.0) and least at base (about 0.6).