The blood-air barrier consists of all of the following Except
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.
Alveolar pores
A layer of surfactant
Type I alveolar cell cytoplasm
Fused basal lamina of alveolar and endothelial cells
Respiratory system