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 Normal Airways
The picture at the right shows normal airways. Ideally, air enters through the mouth and nose and flows down into the lungs via these airways. The airways start to branch and become narrower and smaller the further down you go. Eventually you reach the smallest part of the lung, the alveoli. These alveoli are air sacs that are one cell wall thick. This is where the oxygen molecules go into the blood.
Muscles surround the airways and help somewhat to push air out when a person breathes out (exhales) normally.
The inside of the airways is smooth.
Triggers and Reactions
A trigger can be airborne allergens - dust mites, pollen, and mold. It can also come from an infection - cold virus. It may also be from an irritant - smoke, fumes, and particulate matter.
When the lungs of an individual with asthma are irritated by a trigger(s), three things happen to the airways that make it harder to breathe:
1. They become red and swollen, i.e., inflamed
2. They become hyperactive
3. They have an increase in mucus production.
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