What feature of the trachea and bronchi helps in trapping pathogens?

The feature of the trachea and bronchi that plays a crucial role in trapping pathogens is the mucus secretion. Mucus is produced by goblet cells in the lining of the respiratory tract, and it acts as a sticky barrier that captures dust, pathogens, and other particles inhaled with air. This sticky mucus helps prevent harmful microorganisms from reaching the lungs and facilitates their removal from the airways.

When pathogens are trapped in the mucus, cilia—tiny hair-like structures on the surface of respiratory epithelial cells—move the mucus upwards toward the throat. This process, often referred to as the mucociliary escalator, allows for the expulsion of the trapped pathogens, usually through coughing or swallowing.

The other features mentioned, such as hairs, blood flow, and sound waves, do not directly contribute to the trapping of pathogens. Hairs in the nose can filter larger particles, blood flow is related to immune response rather than physical trapping, and sound waves pertain to vocalization, which is unrelated to pathogen defense mechanisms.