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The Asthma Corner
: What causes asthma?
Our bodies need oxygen from the air we breath in order for our
cells to do their work. When we breath in, air, containing oxygen,
enters through the mouth or nose, and descends through the windpipe,
to tubes called the bronchi. The bronchi branch out into each
lung where oxygen is picked up by passing blood. The blood then
carries the oxygen throughout the body.
For a variety of reasons, what happens during an asthma episode
is that the bronchial tubes become narrow, or even blocked. As
a result, air can't get in or out of the lungs easily, and the
child begins to breathe heavily, wheeze or cough.
There are two reasons the bronchi narrow: Either because they
are squeezed by muscles from the outside or because they are blocked
by mucus and swelling inside the bronchial tubes.
Bronchoconstriction
The condition when bronchi are narrowed by squeezing, is called
"Bronchoconstriction." This occurs when muscles, wrapped
around the bronchi like a series of elastic bands, tighten and
restrict the passage of air. It's normal for these muscles to
occasionally close the airway. But in asthmatics these muscles
sometimes overreact, become twitchy and constrict or block the
bronchi.
Inflammation
For many years, bronchoconstriction was thought to be the main
cause of asthma. More recently, we've become aware of another
problem: Bronchial Inflammation. This occurs when the walls of
the bronchi swell up and produce mucus, in reaction to some sort
of irritation.
It's normal for the bronchi to produce mucus in order to trap
breathed-in irritants, and protect the lungs. But some asthmatics
can produce an overabundance of mucus, and the bronchi can become
chronically inflamed, resulting in blocked airways and asthmatic
symptoms.
So there are two possible conditions associated with an asthmatic's
airways, bronchoconstriction and bronchial inflammation. In fact
it is widely believed that the more an airway is inflamed, the
more likely it is that the bronchial muscles will constrict.
Other Asthma Corner
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