The Cardiovascular System

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Across
  1. 3. Inner lining of the heart
  2. 7. Thin-walled vessel that carries blood from tissues back to the heart
  3. 8. Muscular middle layer of the heart
  4. 10. Double-layered membrane surrounding the heart
  5. 11. Smallest type of blood vessel
  6. 13. Structure in veins or the heart that closes and opening
  7. 14. Relaxation phase of the heartbeat
  8. 15. Small vein
Down
  1. 1. Gas that enters the blood through the lungs
  2. 2. Beat of the heart felt through the walls of the arteries
  3. 4. The two lower chambers of the heart
  4. 5. Contraction phase of the heartbeat
  5. 6. Largest type of blood vessel
  6. 9. Small artery
  7. 12. Largest artery in the body