Across
- 2. tubes that carry air
- 4. outside protective layer
- 5. branch off of arteries to serve each cell
- 6. arched muscle in the respiratory system
- 9. vessel that carries oxygenated blood
- 10. group of cells working for a purpose
- 11. bottom sections of the heart
Down
- 1. air sacs on lungs
- 3. the heart is like a _______
- 5. the system that transports blood around the body
- 7. the heart has four ________, or sections
- 8. blood flows through _______ to every cell in the body