A
cough is a sudden and often repetitively occurring
reflex which helps to clear the large breathing passages from secretions, irritants, foreign particles and
microbes. The
cough reflex consists of three phases: an
inhalation, a forced
exhalation against a closed
glottis, and a violent release of air from the lungs following opening of the glottis, usually accompanied by a distinctive sound. Coughing is either voluntary or involuntary.