What structures humidify and filter air in the nasal cavity?

• A. Cilia and mucus
• B. Sinuses
• C. Bronchi
• D. Alveoli

Answer: (A)

The structures that humidify and filter air in the nasal cavity are indeed cilia and mucus. Cilia are tiny hair-like structures that line the nasal passages. They play a crucial role in trapping dust, allergens, and other particles that may be inhaled. This mechanical filtration is complemented by mucus, which is produced by mucous membranes within the nasal cavity. Mucus not only traps particles and pathogens, but it also helps to humidify the incoming air, making it easier for the respiratory system to effectively manage the air before it reaches the lungs. Together, the cilia and mucus form an essential defense mechanism that maintains respiratory health by ensuring that the air is clean and moist when it enters the lower respiratory tract.

The other structures mentioned do not perform this specific function in the nasal cavity. Sinuses are air-filled spaces that can contribute to overall airflow but are not primarily responsible for humidifying or filtering air directly. Bronchi are larger air passages that branch from the trachea into the lungs, where further filtration occurs but not in the nasal cavity itself. Alveoli are tiny air sacs where gas exchange occurs in the lungs, but they are downstream of the nasal cavity and do not have a role in the initial humidification and filtration