You first breathe in air through your mouth (oral cavity) or nose (nasal cavity). The air then travels through the pharynx (the cavity behind both the nose and mouth) and the trachea (windpipe) before reaching the primary, secondary, and tertiary bronchi (airway passages). Next, the air goes through even tinier passages, called the bronchioles, before finally reaching the alveoli (air bags) in the lungs.