The human respiratory system consists of the nose, pharynx, larynx, trachea, bronchi, lungs, and alveoli. The nose and nasal cavity warm and filter incoming air. The pharynx and larynx are passageways that lead to the trachea, which divides into the left and right bronchi and further branches into bronchioles and alveoli within the lungs. Gas exchange occurs in the alveoli, where oxygen passes into the bloodstream and carbon dioxide passes out.