understanding of the body

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Across
  1. 3. Muscular organ that pumps blood
  2. 4. Shin bone (largest of the lower leg bones)
  3. 9. dioxide The waste gas we breathe out
  4. 10. Kneecap
  5. 11. The main organs for breathing
  6. 12. To take air into your lungs
  7. 14. Flap of tissue that prevents backward blood flow
  8. 15. Thigh bone(largest bone in the human body)
Down
  1. 1. Lower chambers of the heart
  2. 2. Upper chambers of the heart
  3. 5. Measure of your heartbeat
  4. 6. The gas our body needs to live
  5. 7. To let air out of your lungs
  6. 8. Collar bone
  7. 13. Upper arm bone (funny bone)