Asthma And The Lungs
By editor | July 3, 2007
Doctors and nurses refer to the swelling of the airways as inflammation and the squeezing of the airways as bronchospasm or bronchoconstriction of the muscles that encircle the airways. What is the cause? To answer that, here is a quick lesson in how the lungs work:
The lungs’ major job is to bring oxygen into the bloodstream and remove carbon dioxide from it. As you inhale through your nose and mouth, air enters your windpipe, or trachea. Picture your airways as an upside-down tree with the windpipe as the trunk. The windpipe goes down your throat and branches out at the top of your chest into two large tubes or bronchi, with one bronchus for each lung. Within each lung, the main bronchus divides to form several smaller tubes that branch again and again to form hundreds of thousands of even smaller tubes called bronchioles. The bronchioles split off into millions of pockets oftiny air sacs called alveoli. Your lungs have over 300 million alveoli. These air sacs resemble tiny clusters of grapes at the end of each bronchiole branch. Within the air sacs, life-giving oxygen from the air you inhale is exchanged for carbon dioxide, the waste product that leaves your body when you breathe out.
Inhaled air often contains harmful things like dust and bacteria. Your nose, windpipe, and bronchial tubes have several defenses to keep these nasty irritants from reaching your lungs. Airways are lined with membranes that produce mucus, the slippery, sticky substance that traps tiny particles and keeps them from getting inhaled any deeper into the lungs. Airways are also lined with tiny hairs that gently sweep the mucustrapped particles up and out. Coughing is another defense. When you cough, you force air and mucus out of your lungs along with any trapped particles.
Sometimes particles can sneak past the first line of defense and go deeper into the bronchial tubes. In an effort to get rid of them, the body reacts with inflammation. Cells in the airways lining release substances that make the lining swell, produce more mucus, and make the muscles around the bronchial tubes tighten and squeeze the tubes. Airway swelling and tightening happen to just about everybody at times. That’s what makes you cough when you have a bad cold or flu or when you breathe in smoke or other irritants.
Children with asthma have highly sensitive airways. They usually have a little swelling in their airways all the time. Your child can’t feel it, and you can’t see it happening in your child. This is sometimes called “silent asthma.” When a youngster with asthma inhales something that affects her breathing tubes, like pollen or cigarette smoke, her sensitive airways overreact. The tubes swell more and fill with mucus, the muscles tighten, and the child coughs and wheezes as she struggles to breathe. Doctors and nurses sometimes say that children with asthma have “twitchy,” “hyperreactive,” or “hyperresponsive” airways, because they react severely and for a long time to substances in the air that usually don’t bother other people.
Why does the asthmatic lung respond this way? To the best of our current knowledge, the immune system is the cause. When an irritant like pollen is inhaled, for example, chemicals in the pollen are released into the lung and cause swelling, muscle tightening, and overproduction of mucus. But this rarely occurs just once. With each new exposure to an infection or an irritant (or “trigger”) that causes even the mildest allergy flare, inflammatory cells increase the reaction, making it stronger and last longer.
When scientists look under the microscope, they see that the invading cells of inflammation are scattered throughout the airways. Imagine the lungs of a child who either keeps getting respiratory infections or breathes in allergy triggers over and over again. The airway inflammation builds up to higher and higher levels, and asthma flares become more difficult to control. Symptoms are more intense. They last longer and are harder to control with medicines.
Tagged under:air sacs alveoli Asthma bronchial tubes bronchioles bronchoconstriction bronchospasm bronchus carbon dioxide lungs oxygen windpipe
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