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COPD Basics: How the Lungs Work

Your Lungs


  1. Your lungs are the central part of your respiratory system, which supplies your body’s cells with oxygen and expels carbon dioxide.
  2. Your lungs also act as filters by trapping harmful bacteria, viruses, pollutants, and other particles.
  3. If you have COPD, seasonal allergies, or asthma, mucus can build up in your lungs, making it harder to breathe.

Your lungs are the central part of your respiratory system. They take in oxygen, which enters your body each time you exhale. They also expel carbon dioxide, which is removed from your body each time you exhale.

Your lungs also perform other valuable functions, in addition to breathing and exchanging gases. They also act as secondary filters to reduce harmful materials in your body.

Your Respiratory System

Your respiratory system supplies your body’s cells with oxygen. It also expels the carbon dioxide gas that your cells produce as waste.

When you breathe, inhaled oxygen enters your windpipe or trachea. It travels through your trachea into both your left and right bronchi. Then, it travels into decreasingly smaller bronchioles that branch off on both sides of your chest in “V” shapes, like tree limbs. The smaller bronchioles continue dividing, each into more than 100,000 smaller tubes. Those tubes end in even smaller air sacs and clusters, which are called alveoli. This is where oxygen is exchanged for carbon dioxide.

Each alveolus, or singular alveoli, is surrounded by large numbers of tiny blood vessels, called capillaries. In those tiny alveoli, gas exchange happens. Oxygen is supplied to your body’s cells through your capillaries, and carbon dioxide gas is removed from them. The carbon dioxide makes the journey through your airways in reverse, where it’s eventually exhaled through your nose and mouth.

An Important Defense System

Your lungs also trap harmful particles, such as bacteria, viruses, and pollutants, to prevent them from reaching other parts of your body. Cilia help your bronchioles do this. Cilia are tiny hair-like extensions that help move material trapped in mucus secreted by your cells back up through your lungs.  

The mucus produced in your lungs helps to trap and expel certain harmful bacteria and viruses. Bacteria and other foreign particles are either sneezed or coughed out of your body. Or they’re swallowed, they enter your stomach, and they’re eventually released as waste.

Effects of COPD on Your Respiratory System

Producing mucus is normal. Everybody coughs and expresses sputum, which is a mixture of saliva and mucus. However, if your lungs are damaged because of chronic obstructive pulmonary disease (COPD), mucus can build up in them. This makes it harder to breathe. Your cilia are damaged or destroyed, which makes it increasingly difficult for you to cough up excess mucus.

Over time, people with COPD lose much of their lung function. Your airways become less elastic, and the walls between them become increasingly inflamed or are destroyed. Because your cilia are also damaged, fluid buildup further compromises your airways and makes it harder to breathe. Bacteria and viruses get trapped in your lungs and flourish, developing into infections.

Allergic reactions can also increase the amount of mucus in your lungs. This is often the case in people who have seasonal allergies or asthma. Sometimes, too much mucus buildup can compromise your ability to breathe. Usually, a short-acting bronchodilator can quickly reduce inflammation in your lungs and open up your airways enough to promote breathing.

The Takeaway

Even though your respiratory system has defenses to help protect your lungs and airways, it’s possible to damage your lungs so that these defenses can’t protect you anymore. COPD is one way for your lungs to be damaged. Talk to your doctor about strategies to help manage your COPD and to prevent it from getting worse.

You asked, we answered

  • How can I prevent any more damage to my lungs if I already have COPD? Will this help my condition?
  • In addition to stopping smoking and losing weight, attempt to avoid all allergens that trigger your symptoms. A pulmonary rehabilitation program can help you strengthen your lung capacity and improve your lung volume.

    - Mark Laflamme M.D.

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