Respiratory zone pyright e The Mo GrawHill Companies, Inc, Permission required for reproduction or displa Region of Conducting zone Respiratory zone gas exchange between air Number of Trachea Terminal bronchiole and blood. branches/ Primary Includes bronchus respirator bronchioles (2) Respiratory and alveolar bronchioles Bronchial 500,000) sacs tree ALveolar sacs 8 million) Alveolus (60,000)Terminal bronchioles10 Respiratory Zone • Region of gas exchange between air and blood. • Includes respiratory bronchioles and alveolar sacs