Question: How Do the Lungs Work?
If you look at a slice of normal, healthy lung, it looks like a pink sponge filled with tiny bubbles or holes. Around each bubble is a fine network of tiny blood vessels. These bubbles, surrounded by blood vessels, give the lungs a large surface to exchange oxygen (into the blood where it is carried throughout the body) and carbon dioxide (out of the blood). This process is called gas exchange. Healthy lungs do this very well.
Answer: How The Lungs Work
Air is breathed in through the nose and mouth. The air travels down through the trachea then through large and small tubes in your lungs called bronchial tubes. The airways (various tubes or passages) to your lungs look something like an upside-down tree with many branches.
At the ends of the small bronchial tubes, there are groups of tiny air sacs called alveoli. The alveoli have very thin walls, and small blood vessels called capillaries run in the walls. Oxygen passes from the alveoli into the blood in these small blood vessels. At the same time, carbon dioxide passes from the blood into the alveoli. Carbon dioxide, a normal byproduct of the body's metabolism, must be removed.
The airways and alveoli in the lung are normally elastic - that is, they try to spring back to their original shape after being stretched or filled with air. This elastic quality helps retain the normal structure of the lung and helps to move the air in and out quickly.
In COPD, much of the elastic quality is gone, and the airways and alveoli no longer bounce back to their original shape. This means that the airways collapse, and the air sacs tend to stay inflated. The floppy airways obstruct the airflow out of the lungs, leading to an abnormal increase in the lungs' size. In addition, the airways may become inflamed and thickened and mucus-producing cells produce more mucus, further contributing to the difficulty of getting air out of the lungs.
In emphysema, the walls between the alveoli are destroyed, leading to a few large alveoli, instead of many tiny ones. Then, the lung looks like a sponge with large bubbles or holes in it instead of a sponge with very even tiny holes. These few large air sacs have less surface area than the many tiny ones for the exchange of oxygen and carbon dioxide. (See a photo of Emphysema)
Source: National Heart, Lung, and Blood Institute
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