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Across 1. the two branches of the trachea 3. the opening between the vocal folds 5. carries food to the stomach 7. a thick substance that coats much of the opens into the esophagus and "windpipe" 9. the microscopic sacs in which the exchange of gases takes place in the lungs 11. bands of tissue that vibrate to produce sound 12. the thin, flexible flap that covers the larynx when swallowing 14. The waste product of aerobic cellular respiration is 16. Oxygen enters your blood and carbon dioxide leaves by the process of 21. Trachea is to lungs as esophagus is to 22. "voice box"

Down 1. one of the many tiny divisions of the bronchi 2. A lung ____ when the alveoli lose most of their air. 4. __ is the body's most common source of energy. 6. What system provide the new materials needed for matabolism? 8. the total of all the body's process 10. the organ of the respiratory system responsible for the exchanges of gases 13. the muscle responsible for inhaling 15. ___ percent of the people who die of lung cancer are smokers. 17. Trachea is to air as esophagus is to 18. "windpipe" 19. the chest cavity 20. When your diaphragm contracts, you