Which of the following is NOT a function of the upper respiratory tract?

The upper respiratory tract is primarily responsible for several key functions, but gas exchange is not one of them. The upper respiratory tract includes structures such as the nasal cavity, pharynx, and larynx, which play crucial roles in preparing the air we breathe.

Filtering particles helps remove dust, allergens, and pathogens from the air before it reaches the lungs. Humidifying air ensures that the air is moist, which protects the delicate tissues of the lower respiratory tract. Sensing smell is facilitated by olfactory receptors located in the nasal cavity, allowing us to detect different odors.

Gas exchange, however, occurs in the lower respiratory tract, specifically in the alveoli of the lungs, where oxygen and carbon dioxide are exchanged between the air and the bloodstream. Therefore, since gas exchange is not a function associated with the upper respiratory tract, it is accurately identified as the correct answer.