Across
- 1. ... respiration which requires oxygen.
- 6. Exchange O2 and CO2 to produce energy.
- 7. Inhaling and exhaling of air into the lungs.
- 9. Hollow space within the nose and skull.
Down
- 1. The second stage in external respiration involves the exchange of gasses between the blood capillaries and ....
- 2. ... respiration known as fermentation.
- 3. Tiny hair in nasal cavity.
- 4. ... respiration occurs between the external environment and the cells of the body.
- 5. The first stage in external respiration involves...
- 8. The only part of respiratory system that is visible.