Across
- 3. a movement from a low to a high concentration
- 6. a blood vessel that is really tiny
- 7. when you pull in oxygen
Down
- 1. a organ that is filled with oxygen when you breath
- 2. a huge, flat part that brings oxygen in and out
- 4. when take out air from your body
- 5. air sacs that can hold gases and can release it