Final answer:
The exchange of gases in the lungs occurs in the alveoli, where oxygen is absorbed by the blood, and carbon dioxide is released, facilitated by a large surface area and numerous pulmonary capillaries.
Step-by-step explanation:
The exchange of gases in the lungs occurs at the level of the alveoli. Alveoli are tiny air sacs where oxygen from the inhaled air diffuses into the blood, and carbon dioxide from the blood diffuses into the alveoli to be exhaled. This process is facilitated by the large surface area provided by the numerous alveoli and the presence of pulmonary capillaries surrounding each alveolus. The respiratory membrane of the alveoli is highly permeable to gases, and the respiratory exchange occurs through a passive process called diffusion, which is driven by a concentration gradient without the need for energy.