The Human Body

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Across
  1. 2. the lungs are filled with these
  2. 4. prevents blood from flowing backwards
  3. 6. carries air to each lung
  4. 8. A system that involves the lungs
  5. 9. this is a trapdoor at the bottom of the pharynx
Down
  1. 1. makes up 55% of blood
  2. 3. takes blood away from the heart
  3. 5. a chamber of the heart
  4. 7. Allows nutrients and gases to be delivered to cells