What is the primary function of the sinuses in relation to the nasal cavity?

• A. Heating air
• B. Filtering dust
• C. Reducing weight of the skull
• D. Regulating humidification

Answer: (C)

The primary function of the sinuses in relation to the nasal cavity is to reduce the weight of the skull. The sinuses are air-filled spaces located within the bones of the face and skull, particularly around the nasal cavity. By being filled with air rather than solid bone, these cavities help lighten the overall weight of the skull, making it easier for the head to be supported and moved without requiring excessive muscular effort.

Additionally, while the sinuses do play roles in other functions—such as contributing to the resonance of the voice, providing a buffer against facial trauma, and contributing to the regulation of temperature and humidity of inhaled air—these features are secondary to their structural purpose of reducing skull weight. Each of the other options touches on a functional aspect of the nasal cavity or the respiratory system but does not address the primary anatomical function that the sinuses serve.