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 part of the blood-air barrier.