What happens to air as it is drawn through the nasal cavities?
Drawn into the respiratory system through the nostrils or external nares, air enters the nasal cavities, where it is warmed and moistened and where dust particles are filtered out. While the bony ridges in the cavities cause the incoming air to swirl, insuring that all the air is exposed to these processes, the mucous lining and the cilia of the cavities' epithelial cells increase the efficiency of these processes.
