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Across 3. A chemical gas, which is a biproduct of the Krebbs cycle. 6. A muscle-lined cage of bone, which aids the diapraghm in expelling air. 7. A cartilaginous tube connecting the larynx to the bronchus, bronchi; the windpipe 9. These force mucus to the throat, so that air can be moistened. 11. A cartilaginous organ in the throat, covering the glottis when swallowing to prevent food and liquid from entering the trachea; also a speech organ. 13. The small branches of a bronchus. 14. The tiny functional units of the lungs, which serve as the transfer point between the oxygen and the blood itself. 15. A chemical gas, which we need to survive; biproduct of trees. 16. An organ of the neck involved in breath control, protection of the trachea and sound production, housing the vocal cords, and that is situated at the point where the upper tract splits into the trachea and the esophagus.

Down 1. Tubes which are primary branches of the trachea, leading directly into the lungs. 2. This organ forces air in and out of the lungs; this organ is a muscle. 4. The process of inhaling and exhaling; Breathing. 5. The process by which the diaphragm expands, and forces the depleted air out of the lungs. 8. A pair of organs, whose main purpose is to extract oxygen from the air, and rid the body of carbon dioxide waste. 10. The process by which the Diapragm contracts, sucking in oxygen-rich air. 12. The part of the alimentary canal that extends from the mouth and nasal cavities to the larynx, where it becomes continuous with the esophagus.