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    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.

    1

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

    2

    The bronchiolar resistance is greatly increased in obstructive lung disease.

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