<prompt> The blood-air barrier consists of all of the following except:Alveolar poresA layer of surfactantType I alveolar cell cytoplasmFused basal lamina of alveolar and endothelial cells  <response>: 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. 