Revision

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Across
  1. 2. the scientific word for a muscle tensing
  2. 3. the tube that connects the mouth to the lungs
  3. 5. something made of two or more different elements chemically bonded
  4. 7. the bones that protect your lungs and heart
  5. 9. the organ where gas exchange happens
Down
  1. 1. the branches inside the lungs
  2. 4. depressant that contains ethanol
  3. 6. sheet of muscle that helps to push air in and out of lungs
  4. 8. the part of your lungs where oxygen enters the blood