Answer
There are four pairs of paranasal sinuses, maxillary, frontal, sphenoid and the ethmoid. These cavities are lined with mucous membrane ; the mucous secretion produced drains into the lateral walls of the nasal cavities
Work Step by Step
Inspired air is moistened and cleansed by the mucous secretions of the paranasal sinuses. These hollow chambers also serve to reduce the weight of the skull. But probably the most important function of the paranasal sinuses is that they serve as echo chambers that affect the quality of vocalizations--speech and song.
