When you breathe, the airway (respiratory) system supplies oxygen to your blood. Then your blood takes oxygen to all parts of the body.

The nose, mouth, throat (pharynx and larynx), and hollow spaces in the cheeks and around the eyes (sinuses) make up the upper respiratory tract. The windpipe (trachea), breathing tubes (bronchial tubes and bronchioles), and structures inside the lungs make up the lower respiratory tract.