Across
- 2. Contraction phase of the heartbeat.
- 3. Record of the electrical activity of the heart.
- 6. Gas that enters the blood through the lungs.
- 10. Relaxation phase of the heartbeat.
- 11. Muscular middle layer of the heart.
- 12. Largest artery in the body.
- 14. Valve between the left atrium and the left ventricle.
- 15. Innermost lining of the blood vessels.
Down
- 1. Double layered membrane surrounding the heart.
- 4. One of the two upper chambers of the heart.
- 5. Blood vessels that branch from the aorta and carry oxygen-rich blood to the heart muscle.
- 7. Inner lining of the heart.
- 8. Specialized nervous tissue in the right atrium that begins the heartbeat.
- 9. Gas (waste)released by the body cells.
- 13. Smallest type of blood vessel.