Across
- 5. Process of oxygen entering bloodstream (11 letters)
- 6. Smallest air sacs where gas exchange occurs (7 letters)
- 7. Protective membrane surrounding lungs (6 letters)
Down
- 1. Windpipe that connects throat to lungs (7 letters)
- 2. Main breathing pathway in lungs (7 letters)
- 3. Primary muscle of respiration (9 letters)
- 4. Oxygen-carrying protein in red blood cells (10 letters)