Gas Exchange

6. Found in insects and some arthropods, air enters through openings called ___ and moves to cells directly through tracheae
8. The volume of the thoracic cavity is decreased by the upward movement of the diaphragm
9. How many small aquatic animals perform gas exchange
13. Branches into two bronchi, which connects to the lungs
15. In bony fishes, a ___ exchange system increases the efficiency of gills
16. Where gas exchange takes place at the end of each bronchiole
17. How carbon dioxide is transported in body
18. ___ flow is air being breathed in and out
20. The bronchi branch into small ___
21. These organisms have the most efficient respiratory systems

1. Closes the larynx when food is swallowed
2. A respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide
3. Conducts air to the larynx
4. The exchange of gases between and organism and its environment
5. Breathing is an involuntary process regulated by respiratory centers in the ___ (two words)
7. Inversely proportional to volume
10. The volume of the thoracic cavity is increased by the downward movement of the diaphragm
11. The circulatory system carries ___ from alveoli to body cells
12. Sensitive to changes in pH and stimulate respiratory centers
14. ___ cavities filter and adjust temperature and humidity in air
19. Where air enters in mammals