So if we examine our air passageways, we have trachea, we have the bronchi, we have these bronchioles, these are lined with our muscles. And these muscles can actually constrict. And when they constrict, they create a more narrow system of canals and that basically decreases the likelihood that our contaminant or harmful substance will pass into our body via our alveolar. So the air passageways of the lungs contain rings of muscle. When the passageways are irritated by, let's say, some type of allergen these muscles can constrict. Now, although this does make the airway more narrow and this decreases the likelihood that our pathogen will actually end up in our lungs and in our body, specifically in the alveoli of our lungs.