How are carbon dioxide and oxygen exchanged in the lungs? a. carbon dioxide and oxygen are exchanged in the aorta. b. large blood vessels constrict and enlarge near the lung tissue so that gases can be exchanged. c. the walls of the arteries thicken, harden, and lose their elasticity so that oxygen can pass through them. d. small blood vessels pass next to the air sacs of the lung, and gases are exchanged across a thin membrane.