Final answer:
Gas exchange occurs in the alveoli, which are located in the respiratory zone of the lungs.
Step-by-step explanation:
Gas exchange occurs in the alveoli, which are located in the respiratory zone of the lungs. The terminal bronchioles connect to the respiratory bronchioles and then to the alveolar ducts, which lead to the alveolar sacs. It is in the alveoli where gas exchange takes place between the lungs and the blood.