Across
- 3. Cava – Body’s largest vein
- 7. – Immune system soldier
- 9. – Muscular middle layer of the heart wall
- 12. – Red cell on a delivery mission
- 13. Artery – Carries oxygen-poor blood to lungs
- 15. – Vessel that returns blood to the heart
Down
- 1. – The body's biggest artery
- 2. – Protective sac around the heart
- 4. – Entry hall of the heart
- 5. Vein – Vessel bringing oxygen-rich blood to the heart
- 6. – Powerful heart chamber
- 8. – Cell that helps form clots
- 10. – Tiny bridge between arteries and veins
- 11. – Heart’s smooth inner lining
- 14. – Vessel that carries blood away from the heart