Gaseous exchange
David C. Dugdale (2012) defines gaseous exchange as the delivery of oxygen from the alveolar air space into the pulmonary capillaries and the elimination of carbon dioxide from the capillaries to the lungs. Both processes occur via diffusion. Capillaries are located in the walls of the alveoli.
reference
David C. Dugdale (2012) Gas exchange [internet],Department of Medicine, University of Washington School of Medicine, available from.[1] [Accessed 22/10/2015].