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 blood and remove carbon dioxide (a waste material) from the blood. When you breathe in, oxygen moves out of the air sacs (alveoli) of the lungs into the blood, where it is carried to every cell in your body. At the same time, carbon dioxide moves out of your blood and into the air sacs. You push the carbon dioxide out of your lungs when you breathe out. This process is called respiration.