Respiratory membrane a Is the structure through which oXygen diffuse from the alveolus into the blood. and carbon dioxide in the opposite direction alveolus capillary endothelial cell surfactant epithelial cell red blood cell interstitial spaceRespiratory membrane surfactant epithelial cell interstitial space alveolus capillary red blood cell endothelial cell O2 CO2 ◼ Is the structure through which oxygen diffuse from the alveolus into the blood, and carbon dioxide in the opposite direction