Gas exchange can ONLY occur in which part of the lungs?

Gas exchange occurs specifically in the alveoli, which are tiny air sacs located at the end of the bronchial tree in the lungs. The structure of the alveoli, with their thin walls and extensive capillary networks, allows for the effective diffusion of oxygen into the bloodstream and the removal of carbon dioxide from the blood.

The alveoli are designed to maximize surface area, providing a large interface for gas exchange to occur efficiently. Unlike other parts of the respiratory system such as the bronchioles and trachea, which are primarily involved in conducting air to and from the lungs, the alveoli are the critical site where oxygen and carbon dioxide exchange happens.

Dead space refers to areas of the respiratory system where no gas exchange occurs, such as in parts of the trachea or bronchi, and is not involved in the actual exchange process. Thus, the alveoli are the only site where the physiological exchange of gases takes place, making it the correct answer.