What term describes the air that fills the conducting division of the airway but cannot exchange gases?

The correct term that describes the air occupying the conducting division of the airway, which is unable to participate in gas exchange, is anatomical dead space. This refers specifically to the regions of the respiratory tract, such as the trachea and bronchi, where air fills the spaces but there are no alveoli present to facilitate the exchange of oxygen and carbon dioxide.

In contrast, physiological dead space includes both anatomical dead space and any alveolar dead space, which occurs when some alveoli are ventilated but not perfused with blood, making them unavailable for effective gas exchange. Alveolar dead space focuses solely on those alveoli that are ventilated but not participating in gas exchange due to issues with blood flow. Functional residual capacity pertains to the volume of air remaining in the lungs after a normal expiration but does not specifically relate to areas that cannot exchange gases.

Thus, anatomical dead space is the most accurate description of the air present in the conducting zones that cannot partake in gas exchange, as it strictly encompasses regions without respiratory surfaces.