What is the main function of the nasal cavity?

The main function of the nasal cavity is to filter and humidify the air before it enters the lungs. The nasal cavity contains mucous membranes and fine hairs called cilia that trap dust, allergens, and other particles, preventing them from reaching the delicate tissues of the lower respiratory system. Additionally, the mucous membranes add moisture to the inhaled air, ensuring that it is adequately humidified, which is essential for maintaining respiratory health. This process helps to protect the lungs from irritation and infection, as well as aids in proper gas exchange once the air reaches the alveoli.

While the nasal cavity does play a role in protection from pathogens and can assist with functions related to speech, its primary and most critical roles are the filtration and humidification of the air. Therefore, filtering and humidifying air accurately captures the essence of the nasal cavity's main function.