Cutaway illustration of the internal body mechanisms involved in coughing. Irritants like viral particles (spherical) are usually swept away by cilia in the throat (across bottom). Some make it past the outer defences though, and penetrate the throat’s cells, leading to inflammation and coughing. Coughing (tussis) involves inhalation, exhalation against a closed glottis, and a violent release of air from the lungs as the glottis opens. The details of what triggers coughing, however, are still largely unknown.