lungs .
Microbes and foreign matter that have entered the airways cause inflammation of the bronchi and stimulate excess secretion of mucus. Symptoms include a productive cough and a sensation of chest congestion. Long-term repetitive injury, as from smoking, may lead to chronic bronchitis, in which severe, irreversible damage leaves the lungs open to infection and fibrosis. Smoking-related chronic bronchitis often occurs in association with {{link=emphysema">emphysema (together called chronic obstructive pulmonary disease). Treatment includes drugs to dilate the bronchi and promote coughing, antibiotics, and lifestyle adaptations (e.g., quitting smoking).