Think of your respiratory system as an upside-down tree. If we follow a breath of air, we'll start with your mouth and nose. When air enters your body, it'll go down your trachea. That's your trunk-the one airway at the beginning of the process. Then it'll quickly divide into two airways to feed into two lungs; those are your bronchial tubes.
Then, like tree branches, those airways break off into four, then eight, then hundreds of thousands of little airways in each lung. Those airways are your bronchi. At the end of each airway are tiny sacs, called alveoli. Think of them like leaves at the end of the branches. Healthy lungs have hundreds of millions of alveoli. Each alveolus is covered with a thin layer of fluid that helps you breathe by keeping the alveoli open so oxygen is absorbed and carbon dioxide is excreted.
Of course, your lungs also have other parts that are integral to the breathing process. Your bronchial tubes are responsible for cleaning out your lungs. Typically, they're like a 4-year-old's birthday cake-covered with mucous, which dirt and germs stick to.
Your lungs also have millions of tiny hairs called cilia. Cilia act like little brooms that sweep away all the stuff that's caught in your mucous. They're fast-action sweepers, like high-speed windshield wipers-constantly moving back and forth to clear your lungs of nasty stuff that makes it way in with every breath (that's why the city where you live can have a sizable effect on your aging process, because of the toxins and pollutants more prevalent in larger cities).
What's important to know here is cigarette smoke kills cilia, essentially destroying the very mechanism that's meant to protect your lungs from toxins.
The last part of your lungs that's especially important for healthy breathing is the musculature around them. Your diaphragm is a large muscle at the bottom of your chest cavity that pulls air down into your lungs. It's important to know that the movements of breathing are like other movements in your body. They're controlled by a muscle; imagine fireplace bellows that are sucked open and then passively eject air. By using the diaphragm, you can develop techniques to help you breathe more fully.
More Answers from Mehmet Oz, MD