What is the role of cilia in the respiratory system?

Cilia in the respiratory system play a vital role in maintaining the cleanliness and functionality of the airways. Their primary function is to filter and move mucus, which captures dust, pathogens, and other particles that enter the respiratory tract. These tiny hair-like structures are located on the surface of epithelial cells lining the airways. As they beat in a coordinated manner, they help push the mucus upwards towards the throat, where it can be either swallowed or expelled. This process is crucial for keeping the respiratory system free from obstructions and preventing infections.

The importance of cilia extends beyond merely moving mucus; they contribute significantly to the respiratory system's defense mechanisms. By clearing out debris and pathogens, cilia help to ensure that the air reaching the lungs is as clean as possible.

In contrast, the other options highlight functions that do not pertain to cilia. Producing sound is primarily the role of the vocal cords located in the larynx. Trapping food particles is associated with structures in the digestive system, while facilitating gas exchange occurs in the alveoli of the lungs, not through the action of cilia. Therefore, option B correctly reflects the essential function of cilia in respiratory health and efficiency.