The respiratory system is divided into upper and lower respiratory systems. The upper respiratory system includes the nose and nasal cavity; the paranasal sinuses; and the pharynx. The lower respiratory system includes the larynx, the trachea, the bronchi, the bronchioles, and the lungs which contain the alveoli.
The respiratory tract consists of the passageways that ...transport air to the tiny air sacs, or alveoli, of the lung where gas excange occurs and can be divided into the conducting portion and the respiratory portion. The conducting portion of the respiratory tract extends from the external nares to the terminal bronchioles. The respiratory portion includes the respiratory bronchioles and the alveoli where gas exchange occurs.