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.

This is a picture of the lungs and nearby tissues.

Glossary Terms

A large airway that leads from the trachea (windpipe) to a lung. The plural of bronchus is bronchi.

A colorless, odorless gas. It is a waste product made by the body. Carbon dioxide travels in the blood from the body’s tissues to the lungs. Breathing out clears carbon dioxide from the lungs.

A portion of an organ, such as the liver, lung, breast, thyroid, or brain.

A colorless, odorless gas. It is needed for animal and plant life. Oxygen that is breathed in enters the blood from the lungs and travels to the tissues.

A thin layer of tissue that covers the lungs and lines the interior wall of the chest cavity. It protects and cushions the lungs. This tissue secretes a small amount of fluid that acts as a lubricant, allowing the lungs to move smoothly in the chest cavity while breathing.

The organs that are involved in breathing. These include the nose, throat, larynx, trachea, bronchi, and lungs. Also called respiratory tract.

The airway that leads from the larynx (voice box) to the bronchi (large airways that lead to the lungs). Also called windpipe.