Key Points

• Your lungs are organs in your chest that allow your body to take in oxygen from the air. They also help remove carbon dioxide (a waste gas that can be toxic) from your body.
• The respiratory system is a group of organs and tissues that help you breathe. The main parts of this system are the airways, the lungs and linked blood vessels, and the muscles that enable breathing.
  • The airways are pipes that carry oxygen-rich air to your lungs and remove carbon dioxide from your lungs.
  • Your lungs and linked blood vessels deliver oxygen to your body and remove carbon dioxide.
  • Muscles near the lungs expand and contract (tighten) to allow breathing. These muscles include the diaphragm, intercostal muscles, abdominal muscles, and muscles in the neck and collarbone area.
• When you breathe in, your diaphragm and intercostal muscles contract to increase the space in your chest cavity, into which your lungs expand. As your lungs expand, air is sucked in through your nose or mouth. The air travels down your windpipe and into your lungs' air sacs.
• In the air sacs, oxygen moves from the air into the blood in the lungs. At the same time, carbon dioxide moves from the blood in the lungs into the air in the air sacs. Surrounding blood vessels carry the oxygen-rich air to the rest of the body.
• When you breathe out, your diaphragm and intercostal muscles relax to make the size of the chest cavity smaller. As the chest cavity gets smaller, air rich in carbon dioxide is forced out of your lungs and windpipe, and then out of your nose or mouth.
• Your breathing is controlled by the base of your brain and sensors located in the brain, blood vessels, muscles, and lungs. These sensors adjust your breathing to changing needs.
• Many steps are involved in breathing. If injury, disease, or other factors affect any of the steps, you may have trouble breathing.