THE RESPIRATORY SYSTEM

5. Rigid ring-shaped structures that keep the trachea open to prevent it from collapsing.
7. Smaller sub-branches of airways located inside the lung tissue.
8. Cavity protected by the ribs where the lungs are located.
13. Mechanical phase where the breathing muscle relaxes, chest space decreases, and air containing carbon dioxide leaves the body.
14. Waste gas produced by cells that crosses into the alveoli to be expelled from the body.
15. Mechanical phase in which oxygen-rich air enters the body and chest volume increases.

1. Components in the blood that act as vehicles transporting oxygen and carbon dioxide throughout the body.
2. Extremely thin blood vessels surrounding the alveoli that allow gas exchange.
3. Essential gas that crosses from the alveoli into the blood for cells to produce energy.
4. Characteristic of the respiratory process indicating that it occurs continuously without having to think about it.
6. Main organs of the respiratory system that house the bronchioles and millions of alveoli.
9. Tiny spherical structures at the end of each bronchiole where gas exchange occurs.
10. Main windpipe descending through the neck that connects the upper airway to the bronchi.
11. Vital product generated by cells when they receive a continuous supply of oxygen.
12. Microscopic hair-like structures in the tracheal lining that move in a continuous sweeping motion to clear impurities.