Heart and circulation

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Across
  1. 4. blood with very little oxygen in it
  2. 6. the number of chambers in the heart
  3. 7. these vessels carry blood away from the heart
  4. 9. carries blood away from the heart to the lungs
  5. 10. liquid carried in the circulatory system
  6. 13. the bottom chambers of the heart
  7. 14. the largest artery in the body
  8. 16. these blood vessels carry blood into the heart
Down
  1. 1. the side of the heart with a thicker muscle wall
  2. 2. carry oxygen in the blood
  3. 3. another name for cardiac arrest
  4. 5. the job of the heart
  5. 8. the smallest blood vessels
  6. 11. this bad habit can lead to heart disease
  7. 12. the main vein of the body
  8. 13. ensure that blood travels in one direction only
  9. 15. a gas carried by red blood cells