Little sacs for oxygen Show
Alveoli are tiny air sacs in your lungs that take up the oxygen you breathe in and keep your body going. Although they’re microscopic, alveoli are the workhorses of your respiratory system. You have about 480 million alveoli, located at the end of bronchial tubes. When you breathe in, the alveoli expand to take in oxygen. When you breathe out, the alveoli shrink to expel carbon dioxide. There are three overall processes involved in your breathing:
Although tiny, the alveoli are the center of your respiratory system’s gas exchange. The alveoli pick up the incoming energy (oxygen) you breathe in and release the outgoing waste product (carbon dioxide) you exhale. As it moves through blood vessels (capillaries) in the alveoli walls, your blood takes the oxygen from the alveoli and gives off carbon dioxide to the alveoli. These tiny alveoli structures taken all together form a very large surface area to do the work of your breathing, both when you’re at rest and when you are exercising. The alveoli cover a surface that measures more than 1,076.4 square feet (100 square meters). This large surface area is necessary to process the huge amounts of air involved in breathing and getting oxygen to your lungs. Your lungs take in about 1.3 to 2.1 gallons (5 to 8 liters) of air per minute. When you’re at rest, the alveoli send 10.1 ounces (0.3 liters) of oxygen to your blood per minute. To push the air in and out, your diaphragm and other muscles help create pressure inside your chest. When you breathe in, your muscles create a negative pressure — less than the atmospheric pressure that helps suck air in. When you breathe out, the lungs recoil and return to their normal size. Picture your lungs as two well-branched tree limbs, one on each side of your chest. The right lung has three sections (lobes), and the left lung has two sections (above the heart). The larger branches in each lobe are called bronchi. The bronchi divide into smaller branches called bronchioles. And at the end of each bronchiole is a small duct (alveolar duct) that connects to a cluster of thousands of microscopic bubble-like structures, the alveoli. The word alveolus comes from the Latin word for “little cavity.”  Alveoli in cross-section The alveoli are organized into bunches, each bunch grouped is what’s called the alveolar sac. The alveoli touch each other, like grapes in a tight bunch. The number of alveoli and alveolar sacs are what give your lungs a spongy consistency. Each alveolus (singular of alveoli) is about 0.2 millimeters in diameter (about 0.008 inches). Each alveolus is cup-shaped with very thin walls. It’s surrounded by networks of blood vessels called capillaries that also have thin walls. The oxygen you breathe in diffuses through the alveoli and the capillaries into the blood. The carbon dioxide you breathe out is diffused from the capillaries to the alveoli, up the bronchial tree and out your mouth. The alveoli are just one cell in thickness, which allows the gas exchange of respiration to take place rapidly. The wall of an alveolus and the wall of a capillary are each about 0.00004 inches (0.0001 centimeters). About alveoli cellsThe outside layer of alveoli, the epithelium, is composed of two types of cells: type 1 and type 2. Type 1 alveoli cells cover 95 percent of the alveolar surface and constitute the air-blood barrier. Type 2 alveoli cells are smaller and responsible for producing the surfactant that coats the inside surface of the alveolus and helps reduce surface tension. The surfactant helps keep the shape of each alveolus when you breathe in and out. The type 2 alveoli cells can also turn into stem cells. If necessary for repair of injured alveoli, alveoli stem cells can become new alveoli cells. This seemingly perfect machine for breathing can break down or become less efficient because of:
SmokingAccording to the U.S. Centers for Disease Control, tobacco smoke injures your lungs and leads to lung diseases like chronic obstructive pulmonary disease (COPD), emphysema, and chronic bronchitis. Tobacco smoke irritates your bronchioles and alveoli and damages the lining of your lungs. Tobacco damage is cumulative. Years of exposure to cigarette smoke can scar your lung tissue so that your lungs can’t efficiently process oxygen and carbon dioxide. The damage from smoking isn’t reversible. PollutionIndoor pollution from secondhand smoke, mold, dust, household chemicals, radon, or asbestos can damage your lungs and worsen existing lung disease. Outdoor pollution, such as car or industrial emissions, is also harmful to your lungs. DiseaseChronic smoking is a known cause of lung disease. Other causes include genetics, infections, or compromised immune systems. Chemotherapy and radiation treatments for cancer can also contribute to lung disease. Sometimes the cause of lung disease is unknown. Lung disease has many types, all of which affect your breathing. Here are some common lung diseases:
AgingThe normal aging process can slow down your respiratory system. You may notice that your lung capacity is lessened, or that your chest muscles are weaker. Older people also tend to be more at risk for pneumonia, both bacterial and viral. Read more about growing older and your lung health. Limit your exposure to pollutantsUse an air cleaner or purifier at work or at home to reduce indoor dust and fumes. You can also wear a mask, if you’re exposing yourself to extra dust, mold, or allergens. Be aware of days when outdoor air pollution is high. You can find forecasts online for
On days when the air quality index (AQI) is at an unhealthy range, keep your exposure minimal by keeping doors and windows closed and circulating air inside. Decrease how often you smokeNumber one on the list for keeping your lungs healthy is to not smoke. If you’re interested in ways to quit, there are new methods to try, such as nicotine replacement therapy. You can also check out blogs for people trying to quit. Or join a support group, such as Quit Now: Freedom From Smoking, sponsored by the American Lung Association. Take care of your health
The respiratory system with its millions of alveoli is a complex machine. But most of the time we don’t even think about it. We just breathe in and out in the normal course of our day. As you learn more about your lungs, or if you have a problem with your lungs, you may want to do some “maintenance” work to help your lungs function well. Breathing exercises to increase lung capacity may be a good place to start. What is the term used to describe the maximum amount of air that can be exchanged in one breath?Capacities are measurements of two or more volumes. The vital capacity (VC) measures the maximum amount of air that can be inhaled or exhaled during a respiratory cycle. It is the sum of the expiratory reserve volume, tidal volume, and inspiratory reserve volume.
What is the term for the amount of air one can take into the lungs over and above the tidal volume?The inspiratory reserve volume, IRV, is the additional volume of air that can be inspired at the end of a normal or tidal inspiration.
What name is given to the term that describes the maximum volume of air that an individual can expire in one second?FVC (forced vital capacity) – the maximal volume of air that a subject can expel in one maximal expiration from a point of maximal inspiration. FEV1 (forced expiratory volume in one second) – the maximal volume of air that a subject can expel in one second from a point of maximal inspiration.
What term is used to describe the amount of air that can be brought into the lungs and is measured using a spirometer?Key spirometry measurements include the following: Forced vital capacity (FVC). This is the largest amount of air that you can forcefully exhale after breathing in as deeply as you can.
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