last updated 24-06-2024

Normal bronchiolus

This is a schematic drawing of a small airway with the main tissue components: epithelium, smooth muscle, and some inflammatory cells. The airway is surrounded by alveoli, which are attached to the basement membrane. Blood vessels are also present in the sub-epithelial layer, but are not shown.

The ability to breathe in a patient with a respiratory illness such as asthma or chronic obstructive pulmonary disease can be reduced by a number of pathophysiological changes in the airways. These include inflammation, constriction, allergic response, mucus hypersecretion and alveolar damage. These topics are discussed in the following sections.


The total diameter of all bronchioles is much greater than the diameter of central airways. 


The bronchiolar resistance is greatly increased in obstructive lung disease.