Fill in the Blanks

During normal inspiration, the (1) contracts and flattens, while the (2) intercostal muscles lift the ribs upward and outward. This increases (3) volume, causing intra-pulmonary pressure to fall (4) atmospheric pressure. Air then flows (5) the lungs along the pressure gradient.

Normal quiet expiration is (6) $\frac{active}{passive}$. The (7) recoil of the lungs drives air out. During forced expiration, the (8) intercostal muscles and (9) muscles actively contract to push air out.

The four basic lung volumes are: (10) Volume (TV = 500 mL), (11) Reserve Volume (IRV = 2500–3000 mL), (12) Reserve Volume (ERV = 1000–1100 mL), and (13) Volume (RV = 1100–1200 mL). Vital Capacity = (14) + (15) + (16), which equals approximately (17) mL.

Gas exchange occurs at the (18) by simple (19) along partial pressure gradients. The diffusion membrane has (20) layers. Oxygen diffuses from alveoli (pO2 = (21) mmHg) into blood (pO2 = (22) mmHg). Carbon dioxide diffuses from blood (pCO2 = (23) mmHg) into alveoli (pCO2 = (24) mmHg).

Oxygen is transported (25)% as oxyhaemoglobin. The O2–Hb dissociation curve is (26)-shaped due to (27) binding. The Bohr effect describes a (28) shift caused by increased CO2, decreased (29), elevated (30), and increased (31)-BPG.

Carbon dioxide is transported as: (32)% bicarbonate ions (formed by (33) in RBCs, with a (34) shift maintaining electrical neutrality), (35)% carbaminohaemoglobin, and (36)% dissolved in plasma.

Breathing rhythm is set by the (37) centre in the (38). The (39) centre in the pons limits inspiration. Peripheral (40) in aortic and carotid bodies detect changes in pO2, pCO2, and H+.

Answer Key

1. diaphragm | 2. external | 3. thoracic | 4. below | 5. into | 6. passive | 7. elastic | 8. internal | 9. abdominal | 10. Tidal | 11. Inspiratory | 12. Expiratory | 13. Residual | 14. TV | 15. IRV | 16. ERV | 17. 3500–4600 | 18. alveoli | 19. diffusion | 20. three | 21. 104 | 22. 40 | 23. 45 | 24. 40 | 25. 97 | 26. sigmoid | 27. cooperative | 28. right | 29. pH | 30. temperature | 31. 2,3- | 32. 70 | 33. carbonic anhydrase | 34. chloride | 35. 23 | 36. 7 | 37. respiratory rhythmicity | 38. medulla oblongata | 39. pneumotaxic | 40. chemoreceptors