Caption

Artwork of a cross-section through a healthy (at left) and asthmatic lung airway (bronchus). The healthy airway has a wide lumen (core) through which breathing can occur normally. The inflamed asthmatic airway has a narrowed lumen following contraction of the outer muscle layer (red) and swelling of the mucous lining, leading to congestion and impaired breathing. Asthma may be due to an allergy.