Cardiovascular system

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Across
  1. 4. relaxation phase of the heartbeat
  2. 8. specialized nervous tissue in the right atrium that begins the heartbeat
  3. 9. small artery
  4. 12. double layered membrane surround the heart
  5. 13. small vein
  6. 15. gas that enters the blood through the lungs
Down
  1. 1. muscular middle layer of the heart
  2. 2. abnormal swishing sound caused by improper closure of the heart valves
  3. 3. smallest type of blood vessel
  4. 5. larger artery in the body
  5. 6. beat of the heart as felt through the walls of the artery
  6. 7. innermost lining of blood vessels
  7. 10. inner lining of the heart
  8. 11. larger type of blood vessel
  9. 14. record of the electrical activities of the heart