Respiratory System

1. Differentiate between ventilation, external respiration, and internal respiration.

• Ventilation: Movement of air into and out of the lungs (breathing).

• External respiration: Gas exchange between alveoli and pulmonary blood (O₂ enters blood, CO₂ leaves).

• Internal respiration: Gas exchange between systemic blood and body tissues (O₂ to tissues, CO₂ to blood).
  Connection with circulation: External respiration depends on pulmonary circulation; internal respiration relies on systemic circulation.

2. List major structures of the respiratory system and their functions.

• Nose: Filters, moistens, warms air; houses olfactory receptors.

• Pharynx: Pathway for food/air.

• Larynx: Routes food/air; voice production.

• Trachea: Conducts air; lined with cilia/mucus.

• Bronchi/branches: Distribute air to lungs.

• Lungs: Contain alveoli for gas exchange.

• Alveoli: Site of gas exchange.

3. What is the respiratory zone? How does it differ from the conducting zone?

• Respiratory zone: Site of gas exchange — includes respiratory bronchioles, alveolar ducts, and alveoli.

• Conducting zone: All other passages — only conduct air, no gas exchange.

• Transition: Terminal bronchioles mark the end of the conducting zone.

4. What is anatomical dead space? How is it different from alveolar dead space?

• Anatomical dead space: Air in conducting pathways (~150 mL) not involved in gas exchange.

• Alveolar dead space: Alveoli that do not exchange gases due to collapse or blockage.

5. How does cilia in the upper respiratory tract prevent infection?

• Cilia move mucus and trapped particles toward the throat for swallowing, keeping lungs sterile.

6. Why should inspired air be warmed? How is it accomplished?

• Warmer air increases diffusion efficiency and protects delicate alveoli.

• Warming occurs via blood vessels in the nasal mucosa.

• Contributes to lower PO₂ in lungs compared to atmosphere due to humidification and mixing.

7. What is the function of the sinuses?

• Lighten the skull, produce mucus, warm/moisten air.

• Connected to nasal cavity, assisting air conditioning.

8. Larynx: its role and Valsalva’s maneuver?

• Larynx routes food/air, houses vocal cords.

• Valsalva’s maneuver: Closure of glottis during straining — increases intra-abdominal pressure.

9. What is the pharyngotympanic (eustachian/auditory) tube?

• Connects middle ear to nasopharynx.

• Equalizes pressure between ear and throat.

10. Role of the epiglottis in respiration?

• Covers larynx during swallowing to prevent food from entering airway.

11. True vs. false vocal cords?

• True: Vocal folds — produce sound.

• False: Vestibular folds — no role in sound, help close glottis.

12. What determines pitch and loudness of voice?

• Pitch: Length and tension of vocal cords.

• Loudness: Force of air across cords.

13. What structures help amplify voice?

• Pharynx, oral/nasal/sinus cavities, lips, tongue, and soft palate.

14. What’s unique about the trachea anatomically?

• Reinforced with C-shaped hyaline cartilage rings, trachealis muscle posteriorly, mucosa with cilia.

15. How is coughing associated with the trachea?

• Triggered by irritants; glottis closes, pressure builds, air forcefully expelled to clear the airway.

16. Heimlich maneuver: what is it?

• Abdominal thrusts to expel a foreign object obstructing the trachea.

17. Which structures have more smooth muscle? Function?

• Bronchioles have more smooth muscle; control airway diameter and airflow resistance.

18. Where does gas exchange happen?

• In alveoli of the respiratory zone.

19. What is the respiratory membrane?

• Thin barrier for gas exchange: alveolar epithelium, fused basement membrane, capillary endothelium.

20. What cells make up alveolus and their function?

• Type I cells: gas exchange

• Type II cells: produce surfactant

• Macrophages: clean debris

21. Role of surfactant?

• Reduces surface tension to prevent alveolar collapse, especially during exhalation.

22. Connection between alveolus and capillary?

• Gas diffuses across the respiratory membrane — O₂ into blood, CO₂ into alveoli.

23. Are alveoli connected? Are lobes connected?

• Yes, via alveolar pores — equalize pressure. Lobes are not connected.

24. Describe visceral vs. parietal pleura.

• Visceral: covers lungs

• Parietal: lines thoracic cavity

• Important for lubrication and maintaining pressure gradients.

25. Describe parts of the lung.

• Apex, base, lobes, hilum, bronchopulmonary segments, lobules.

26. Blood supply: pulmonary vs. bronchial?

• Pulmonary: brings deoxygenated blood for oxygenation.

• Bronchial: provides oxygenated blood to lung tissue.

• Mixing explains lower PO₂ in pulmonary veins.

27. Atmospheric pressure?

• Pressure of air around the body (760 mm Hg at sea level).

28. Intrapulmonary pressure?

• Pressure in alveoli; equalizes with atmosphere during breathing.

29. Intrapleural pressure?

• Pressure in pleural cavity; always slightly negative (~756 mm Hg).

30. Transpulmonary pressure?

• Difference between intrapulmonary and intrapleural pressure; keeps lungs inflated.

31. Why does the lung collapse if air enters the pleural cavity?

• The vacuum (negative pressure) is lost, removing the force that keeps lungs expanded.

32. What prevents collapse in normal lungs?

• Negative intrapleural pressure and surface tension of pleural fluid.

33. Why is intrapleural pressure lower than intrapulmonary?

• Elastic recoil and surface tension pull lungs inward; chest wall pulls outward.

34. Do lungs have muscles for expiration?

• No. Expiration is passive due to lung recoil. Forced expiration uses abdominal muscles.

35. What promotes lung collapse?

• Elastic recoil of lungs and alveolar surface tension.

36. Boyle’s Law: How does volume affect pressure?

• Pressure and volume are inversely related.

• ↑ Volume = ↓ Pressure (air flows in); diaphragm and intercostals contract.

• ↓ Volume = ↑ Pressure (air flows out); diaphragm relaxes.

37. Factors hindering ventilation?

• Airway resistance

• Alveolar surface tension

• Lung compliance

38. What happens in an asthma attack? Why epinephrine?

• Bronchoconstriction; epinephrine dilates airways and reduces resistance.

39. What’s affected in premature babies?

• Surfactant production is low → alveolar collapse. Treated with surfactant replacement.

40. How does lung scarring affect ventilation?

• Reduces compliance — lungs become stiff, harder to inflate.

41. Fusion of sternocostal joints?

• Reduces thoracic expansion → reduced ventilation.

42. Obstructive vs. restrictive diseases?

• Obstructive: airflow limitation (↑ TLC, FRC, RV).

• Restrictive: reduced lung expansion (↓ TLC, FRC, RV).

43. What is partial pressure?

• The pressure each gas contributes to the total mixture. Drives gas diffusion.

44. How to calculate partial pressure?

• Multiply % of gas by total pressure (e.g., O₂ is 21% of 760 mm Hg = ~160 mm Hg).

45. What factors influence respiration?

• Partial pressure gradients, solubility, ventilation-perfusion coupling, membrane thickness.

46. Is O₂ as soluble as CO₂?

• No. CO₂ is 20x more soluble, allowing equal exchange despite a smaller gradient.

47. Why match ventilation and perfusion?

• To ensure efficient gas exchange; blood is directed to well-ventilated alveoli.

48. How does perfusion in lung differ?

• It is adjusted locally based on O₂ levels — unique to lungs.

49. What happens if respiratory membrane thickens?

• Gas exchange slows, less efficient — as in pneumonia or pulmonary edema.

50. Why PO₂ drop from atmosphere to alveoli (160 to 104)?

• Humidification and mixing with residual alveolar air.

51. Why PO₂ drops from alveoli to tissues (104 to 100)?

• Slight mixing with deoxygenated blood in pulmonary circulation.

52. Why PCO₂ is higher in tissues?

• Tissues produce CO₂ via metabolism.

53. What drives gas exchange?

• Partial pressure gradients of O₂ and CO₂.

54. Why do CO₂ and O₂ exchange in equal amounts despite smaller CO₂ gradient?

• CO₂ is much more soluble in blood.

55. What does the O₂ dissociation curve show?

• Relationship between PO₂ and hemoglobin saturation; shows cooperative binding.

56. Why is it sigmoidal?

• Binding of O₂ increases Hb’s affinity for more O₂ (cooperativity).

57. When 1 O₂ binds to Hb, what happens to affinity?

• It increases for the next O₂.

58. When CO₂ binds to Hb, what happens to O₂ affinity?

• It decreases (Bohr effect).

59. How does pH/temp affect Hb saturation?

• ↓ pH or ↑ temp = ↓ O₂ affinity = more O₂ delivered to tissues. (Important in exercise)

60. How does CO poisoning affect Hb?

• CO binds Hb 200x stronger than O₂, preventing O₂ transport → hypoxia.

61. What is cyanosis?

• Bluish skin color due to low O₂ saturation (hypoxia).

62. How is CO₂ transported?

• 70% as bicarbonate

• 20% bound to hemoglobin

• 7–10% dissolved in plasma

63. How is breathing controlled by nervous system?

• Medullary and pontine centers regulate rhythm; chemoreceptors monitor blood gases.

64. Main stimulant for respiration?

• Rising CO₂ levels (increased H+ in brain).

65. How does hyperventilation affect CO₂ levels?

• Decreases CO₂ → raises pH (alkalosis); breathing slows as compensation.

66. High altitude and blood viscosity?

• Low O₂ triggers erythropoietin → more RBCs → increased viscosity.

67. Why do athletes train at high altitudes?

• Stimulates RBC production for better O₂ delivery when back at sea level.