Across
- 4. branches into two bronchi, which connects to the lungs
- 7. branch into small bronchioles, each ending with a cluster of alveoli
- 8. the diaphragm relaxes, decreasing the volume of the thoracic cavity
- 9. is the exchange of gases between an organism and its environment
- 10. the respiratory pigment in the blood of vertebrates
Down
- 1. conducts air to the larynx
- 2. where gas exchange takes place in the lungs
- 3. cavities filter and adjust temperature and humidity of hair
- 5. the diaphragm contracts, increasing the volume of the thoracic cavity
- 6. have the most efficient respiratory system