Microscopic hair-like extensions that line the respiratory tract and move in a synchronous motion to move secretions with entrapped inhaled dust, debris, and microbes forward into the pharynx to be expelled by the host through sneezing, coughing, or swallowing. For example, there are approximately 200 cilia per cell which beat at the rate of 1,000 to 1,500 times a minute propelling mucus, microorganisms and debris up and out of the airways. Influenza viruses often destroy cilia leaving gaps in the muco-cilliary conveyor belt hindering defense against further infections (e.g. secondary bacterial pneumonia). SEE mucocilliary escalator, oropharynx.