Coughing is a sudden expulsion of air from the lungs through the epiglottis at an amazingly fast speed (estimated at 100 miles per hour). With such a strong force of air, coughing is the body's mechanism for clearing the breathing passageways of unwanted irritants.
In order for a cough to occur, several events need to take place in sequence. First, the vocal cords open widely, allowing additional air to pass through into the lungs. Then the epiglottis closes off the windpipe (larynx), and simultaneously, the abdominal and rib muscles contract, increasing the pressure behind the epiglottis. With the increased pressure, the air is forcefully expelled, and creates a rushing sound as it moves very quickly past the vocal cords. The rushing air dislodges the irritant, making it possible to breathe comfortably again.
Denis Hadjiliadis, MD, MHS, Associate Professor of Medicine, Pulmonary, Allergy, and Critical Care, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
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