Structural consequences of airway inflammation in asthma

Asthma represents a chronic inflammatory process of the airways followed by healing, the end-result of which is an altered structure referred to as a remodeling of the airways. Repair usually involves 2 distinct processes: re generation (which is the replacement of injured tissue by parenchymal cells of the same type) and replacement by connective tissue and its eventual ma turation into scar tissue. In many instances both processes contribute to t he healing response and inflammation. In asthma the processes of cell dedif ferentiation, migration, differentiation, and maturation and connective tis sue deposition can be followed either by complete or altered restitution of airway structure and function, the latter often seen as fibrosis and incre ase in smooth muscle and mucus gland mass. These features result in an incr eased resistance to airflow, particularly when there is bronchial contracti on and bronchial hyperresponsiveness. The effect on airflow is compounded b y the presence of increased mucous secretion and inflammatory exudate, whic h not only blocks the airway passages but also causes an increased surface tension that favors airway closure.