Respiratory System Crossword

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Across
  1. 3. The muscle that controls breathing
  2. 5. The method of travel for oxygen molecules
  3. 8. Another term for breathing out
  4. 9. Another term for breathing in
Down
  1. 1. The first step after inhalation
  2. 2. The chemical used for flavoring popcorn and vapes
  3. 4. A lung condition caused by inhaling toxic chemicals
  4. 6. One chemical taken in during inhalation
  5. 7. Things that expand in order to allow inflation of the lungs