Cilia in the trachea are an important protective mechanism of the body and work to trap inhaled foreign particles, preventing them from becoming lodged in the lungs, explains Encyclopædia Britannica. When a particle is inhaled, the cilia of the trachea stop and move the object away from the lungs with a coordinated sweeping action.
Cilia project from the moist mucous-membrane lining of the trachea, extending into the open channel known as the lumen. They have the appearance of small hair-like projections and are part of the ciliated cells that predominate the trachea. Each ciliated cell contains approximately 250 cilia, and these cells extend the full length of the trachea, notes Michael H. Ross in "Histology: A Text and Atlas."
In the event a foreign object is inhaled toward the lungs, the cilia attempt to grab the object. Then, working in a coordinated movement, the cilia move the particle upward toward the pharynx so it is swallowed and digested in the gastrointestinal tract. If the cilia fail to function, foreign bodies grow bacteria that remain in the airway. Bacteria built up in the trachea cause breathing problems, infections and other disorders. In rare instances, a person genetically inherits primary ciliary dyskinesia, a condition that affects cilia growth and function in the trachea, according to the National Heart, Lung, and Blood Institute. The cilia may be the wrong size, move in the wrong way or be missing altogether.