B3.1

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Across
  1. 2. The term for muscles that work in pairs, such as the internal and external intercostals.
  2. 4. The dome-shaped muscle that contracts to increase thoracic volume during inspiration.
  3. 5. The process of breathing in air.
  4. 6. Gas exchange occurs due to a ________ gradient between the air and blood.
  5. 8. The specific type of cell that makes up the wall of an alveolus.
  6. 12. The diffusion of oxygen and carbon dioxide between the alveoli and the blood.
  7. 14. The two main branches of the trachea that enter the lungs.
  8. 15. Smaller branching tubes that lead from the bronchi to the alveoli.
  9. 16. Ventilation occurs because movements of the thorax change the air ________ inside the lungs.
  10. 17. The muscles located between the ribs that assist in breathing.
Down
  1. 1. The physical process of pumping fresh air into the alveoli and removing stale air.
  2. 3. Small air sacs in the lungs where gas exchange takes place.
  3. 7. The process of breathing out air.
  4. 9. The tiny blood vessel that surrounds each alveolus.
  5. 10. The main airway (windpipe) that leads from the throat to the lungs.
  6. 11. The state of the alveolar surface required for gases to dissolve and diffuse.
  7. 13. A substance secreted by Type II pneumocytes to prevent the alveoli from collapsing.
  8. 16. Gas exchange is a ________ process because it relies entirely on diffusion.