cough

A cough is a forceful, fast burst of air pushed out of the lungs to clear the airway. Think of it as the body's reset button for the breathing tubes: when mucus, a stray crumb, or an irritant is in the way, a cough blasts it loose and out, protecting the deeper lung.

Each cough has three phases. First a deep breath in; then the vocal cords snap shut while the chest and abdominal muscles squeeze, building up pressure behind the closed gate; then the cords burst open and air rushes out at very high speed, shearing secretions off the airway walls and carrying them upward. It can happen as an involuntary reflex or be done deliberately.

As a defense, cough is the lung's powerful clearance tool and a guard against material entering the airway. As a symptom, it is one of the most common reasons people seek care: short-lived coughs usually follow infections, while a cough lasting more than about eight weeks is called chronic and warrants looking for causes such as asthma, post-nasal drip, reflux, smoking, or medication side effects rather than just silencing it.