The alveoli are tiny, fragile sacs that cluster in your lungs and are surrounded by small blood vessels. Oxygen passes from through the walls of the alveoli into these blood vessels while carbon dioxide passes out of your blood and into your lungs to be exhaled through a process called gas exchange. Your lungs have about 300 to 500 million alveoli, according to the Cleveland Clinic.
“If you take the all of the air sacs in the lungs and you spread them out flat, [someone without COPD] should have about a tennis court-sized surface area,” says Dr. Beuther.
Inhaled irritants like cigarette smoke and pollution trigger the production of inflammatory cells and enzymes that slowly damage the walls of the alveoli, says Dr. Mina. Over time, more and more of them stop functioning properly. They become less able expand to take in oxygen and contract to push out carbon dioxide. That leads to symptoms like shortness of breath and wheezing, Dr. Beuther says.
As he describes it, the alveoli walls become riddled with tiny holes and look increasingly moth-eaten as emphysema gets worse and the alveoli break down. “That tennis court-sized membrane gradually gets smaller and smaller, and the lung looks darker and darker as you lose more of these air sacs,” Dr. Beuther explains.
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