Explanation

The lungs are two spongy organs in your chest where oxygen enters your blood and carbon dioxide leaves. Tiny air sacs called alveoli in the lungs provide a huge surface area for gas exchange. Oxygen passes from air into blood while carbon dioxide passes from blood into air.

Each lung contains millions of alveoli surrounded by tiny blood vessels called capillaries. This close contact allows gases to move quickly between air and blood. You breathe in oxygen your body needs and breathe out carbon dioxide waste.

The trachea is the windpipe that carries air to the lungs but does not exchange gases. The diaphragm is a muscle that helps you breathe by moving up and down. Bronchi are tubes that branch from the trachea into each lung.