Across
- 1. White blood cells
- 3. Red blood cells
- 6. Middle, muscular layer of the heart, responsible for pumping action
- 10. Carries blood from the lungs to the left atrium
- 12. Outer fluid-filled sac that surrounds and protects the heart
- 14. Thin vessel where gas exchange occurs
- 15. Upper cavities of the heart
Down
- 2. smooth inner membrane that lines the chambers in the heart
- 4. Carries oxygen-rich blood to the body
- 5. Largest artery in the human body
- 7. Lower chambers of the heart
- 8. Platelets
- 9. Carries blood from the right ventricle to the lungs
- 11. A large vein that carries blood to the heart
- 13. Carries oxygen-poor blood to the heart