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Chronic obstructive pulmonary disease (COPD) is a term that is used for two respiratory system diseases: chronic bronchitis and emphysema. COPD is sometimes called chronic obstructive lung disease.
Chronic bronchitis is a condition of excessive airway mucus secretion that leads to a persistent, productive cough. In chronic bronchitis, there also may be narrowing of the large and small airways making it more difficult to move air in and out of the lungs.
In emphysema there is permanent destruction of the alveoli, the tiny elastic air sacs of the lung, because of irreversible destruction of a protein in the lung called elastin that is important for maintaining the strength of the alveolar walls. The loss of elastin also causes collapse or narrowing of the smallest air passages, called bronchioles, which in turn limits airflow out of the lung.
Cigarette smoking is the most important risk factor for COPD. Other risk factors include age, heredity, exposure to air pollution at work and in the environment, and a history of childhood respiratory infections.
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