Circulatory/Respiratory System Crossword Puzzle

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Across
  1. 4. A long tube where air moves freely
  2. 7. A dome shaped muscle under lungs, contracts and relaxes when yo inhale and exhale
  3. 10. At the end of Bronchioles and where O2 and CO2 exchange is the __________
  4. 11. Guards the entrance to the lungs
  5. 12. Smaller tubes that branch from the Bronchi
Down
  1. 1. Delivers oxygen and nutrients
  2. 2. The lower chambers of the heart
  3. 3. Two tubes that branch from the Trachea
  4. 5. The top chambers in the heart
  5. 6. Open and close to stop backflow
  6. 8. The __________ are a single-cell-thick blood vessel
  7. 9. The main artery