NAME GRADE & SECTION: 1. Smaller than bronchi and lie between the bronchi and the alveoli. 2. The primary airway used to breathe. 3. The main respiratory muscle that contracts and relaxes to allow air into the lungs. 4. Used as an alternative airway when the nasal pathway (nose) is blocked due to illness or trauma. 5. (Air sacs) millions of thin-walled sacs inside the lungs which are surrounded by microscopic blood vessels. 6. Serve as channel for airflow through the nose in which the air is warmed, cleaned, and moistened 7. Hollow tubes that branch off of the trachea into each lung. 8. It connects the pharynx and trachea. 9. The thin walls and significant amount of blood flow allow oxygen and carbon dioxide to be easil exchanged. 10. A hollow tube which passes air to the lower airways, it is the main airway to the lungs.​