Across
- 1. These blood vessels carry blood back toward the heart.
- 4. These blood vessels carry blood away from the heart.
- 9. The process of breathing in.
- 10. The large artery that carries oxygen-rich blood away from the heart.
- 11. This gas is transported by red blood cells.
- 12. The main organ of the respiratory system.
- 13. The liquid part of blood.
Down
- 2. The process of breathing out.
- 3. The organ responsible for pumping blood throughout the body.
- 5. The muscle that contracts and relaxes to help you breathe.
- 6. These are tiny blood vessels that connect arteries to veins.
- 7. The small sacs in the lungs where gas exchange occurs.
- 8. These structures in the heart prevent the backflow of blood.