This set of medical illustrations depicts chronic obstructive pulmonary disease (COPD), also known as chronic obstructive airway disease (COAD). COPD is a general term for airway obstruction associated with lung disorders such as emphysema and chronic bronchitis, both of which are depicted here. Chronic bronchitis is characterized by a chronic productive cough, accompanied by a narrowed airway and decreased gas exchange. Emphysema is characterized by decreased gas exchange and the abnormal permanent enlargement of the alveoli, along with destruction of their walls and without obvious fibrosis (emphysematous alveoli). Labeled structures include respiratory bronchiole, pulmonary artery, pulmonary vein, alveolus (air sac), intra-alveolar septum, terminal bronchiole, mucous membrane and alveolar capillary network. more