The blood-air barrier consists of all of the following Except: (A) Alveolar pores, (B) A layer of surfactant, (C) Type I alveolar cell cytoplasm, (D) Fused basal lamina of alveolar and endothelial cells
Answer is A. Alveolar pores connect neighboring alveoli and function in equalizing pressure in the alveoli and enable collateral circulation of air. They do not constitute pa of the blood-air barrier.