The lungs are the organs in the chest involved in breathing. The lungs are surrounded and protected by the rib cage. The lung on the left side of the body is a little smaller than the lung on the right.

The lungs transfer oxygen from the air to the bloodstream and remove carbon dioxide (a waste material) from the blood. When you breathe in, oxygen moves out of the air sacs of the lungs into the blood vessels. At the same time, carbon dioxide moves out of your blood and into the air sacs. You remove the carbon dioxide from your lungs when you breathe out. This process is called respiration.