Your lungs are a pair of large organs in your chest. They are part of your respiratory system. Air enters your body through your nose or mouth. It passes through your windpipe (trachea) and through each bronchus, and goes into your lungs.

When you breathe in, your lungs expand with air. This is how your body gets oxygen.

When you breathe out, air goes out of your lungs. This is how your body gets rid of carbon dioxide.

Your right lung has three parts (lobes). Your left lung is smaller and has two lobes.

A thin tissue (the pleura) covers the lungs and lines the inside of the chest. Between the two layers of the pleura is a very small amount of fluid (pleural fluid). Normally, this fluid does not build up.

Educational information provided by The National Cancer Institute (NCI) Internet site.