What is the role of cilia in the respiratory system?

• A. To filter dust and allergens from the air
• B. To help move mucus and trapped particles out
• C. To warm and humidify the air
• D. To assist in gas exchange

Answer: (B)

Cilia play a critical role in the respiratory system primarily by helping to move mucus and trapped particles out of the airways. These tiny, hair-like structures line the respiratory tract and are essential for maintaining respiratory health. They work in coordination with mucus-producing cells, which capture dust, allergens, and microbes that enter the airways during breathing.

As the cilia beat in a coordinated manner, they propel the mucus upward toward the throat, where it can be swallowed or expelled. This mechanism is often referred to as the mucus escalator, and it is vital for clearing out debris and preventing infections in the lungs. By efficiently transporting mucus loaded with trapped particles and pathogens, cilia contribute significantly to the body's first line of defense against respiratory infections and irritants.

Other functions mentioned, such as filtering, warming, and humidifying air or assisting in gas exchange, are performed by different structures and mechanisms within the respiratory system. For example, larger particles may be filtered by nasal hairs and turbinates, while the warming and humidification of air primarily occurs in the upper airways. Gas exchange happens in the alveoli, where the cilia are not directly involved.