Anatomy and Function of the Lungs: Pulmonary Structure for Gas Exchange

1. Chapter 12 Pulmonary Structure and Function McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

2. Anatomy of Ventilation • Pulmonary ventilation • Process of air moving in and out of lungs • Anatomy • Trachea • Bronchi • Bronchioles • Alveoli McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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4. The Lungs • Provide a large surface area (50 − 100 m2) • Highly vascularized to allow for gas exchange McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

5. The Alveoli • The lungs contain 600 million membranous sacs called alveoli. • Characteristics of alveoli • Elastic • Thin walled • Very small blood–gas barrier McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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7. The Alveoli • Pores of Kohn allow for even dispersion of surfactant. • Surfactant decreases surface tension. • Pores also allow for gas interchange between alveoli. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

8. Mechanics of Ventilation • Conducting zone (anatomic dead space) • Trachea • Bronchioles • Respiratory zone • Respiratory bronchioles • Alveolar ducts • Alveoli McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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10. Fick’s Law • Explains gas exchange through the alveolar membranes • Gas diffuses through a tissue at a rate proportional to surface area and inversely proportional to its thickness. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

11. Inspiration • During inspiration • Diaphragm contracts and flattens • Chest cavity elongates and enlarges and air expands in lungs • Intrapulmonic pressure decreases • Air is sucked in through nose and mouth McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

12. Expiration • During rest and light exercise, expiration is predominantly passive. • Stretched lung tissue recoils • Inspiratory muscles relax • Air moves to atmosphere • During strenuous exercise • Internal intercostals and abdominal muscles assist McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

13. Surfactant • Resistance to expansion of the lungs increases during inspiration due to surface tension on alveoli. • Surfactant _ a lipoprotein mix of phospholipids, proteins, and Ca2+ produced by alveolar epithelial cells _ mixes with fluid around alveoli. • Surfactant disrupts and lowers surface tension. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

14. Lung Volumes & Capacities • Are measured using a spirometer • Lung volumes vary with • Age • Size (mainly stature) • Gender McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

15. Static Lung Volumes • TV: Tidal volume: 0.4 − 1.0 L air/breath • IRV: Inspiratory reserve volume: 2.5 − 3.5 L • ERV: Expiratory reserve volume: 1.0 − 1.5 L • IRV and ERV decrease during exercise as TV increases • FVC: Forced vital capacity: 3 − 5 L McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

16. Residual Lung Volume • RLV averages 0.8 − 1.4 L • RLV increases with age as lung elasticity decreases. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

17. Total Lung Capacity RLV + FVC = TLC McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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19. Dynamic Lung Volumes • Dynamic ventilation depends upon • Maximal FVC of lungs • Velocity of flow • Velocity of flow is influenced by lung compliance. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

20. FEV-to-FVC Ratio • FEV1/FVC indicates pulmonary airflow capacity. • Healthy people average ~ 85% of FVC in 1 second. • Obstructive diseases result in significant lower FEV1/FVC. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

21. Maximum Voluntary Ventilation • MVV evaluates ventilatory capacity with rapid and deep breathing for 15 seconds. • MVV = 15 second volume × 4 • MVV in healthy individuals averages 25% > ventilation than occurs during max exercise. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

22. Exercise Implications • Gender Differences in Static and Dynamic Lung Functional Measures • Women have smaller lung function measures than men. • Highly fit women must work harder to maintain adequate alveolar-to-arterial O2 exchange. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

23. Lung Function, Aerobic Fitness, and Exercise Performance • Little relationship exists among diverse lung volumes and capacities and exercise performance. • Maximum exercise is not limited by ventilation. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

24. Pulmonary Ventilation • Volume of air moved into or out of total respiratory tract each minute • Air volume that ventilates only alveolar chambers each minute McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

25. Minute Ventilation • Minute ventilation • Volume of air breathed each minute VE • Minute ventilation increases dramatically during exercise. • Values up to 200 L · min-1 have been reported. • Average person ~ 100 L · min-1 • Despite huge VE, TVs rarely exceed 60% VC. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

26. Alveolar Ventilation • Anatomic dead space • Averages 150 − 200 mL • Only ~ 350 mL of the 500 mL TV enters alveoli. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

27. Dead Space vs. Tidal Volume • Anatomic dead space increases as TV increases. • Despite the increase in dead space, increases in TV result in more effective alveolar ventilation. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

28. Ventilation−Perfusion Ratio • Ratio of alveolar ventilation to pulmonary blood flow • V/Q during light exercise ~ 0.8 • V/Q during strenuous exercise may increase up to 5.0. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

29. Physiologic Dead Space • Occurs when there is either 1. Inadequate ventilation 2. Inadequate blood flow McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

30. Rate vs. Depth • During exercise, both rate and depth of breathing increase. • Initially, larger increases in depth occur. • Followed by increases in rate and depth McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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32. Hyperventilation • An increase in pulmonary ventilation that exceeds O2 needs of metabolism • Hyperventilation decreases PCO2. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

33. Dyspnea • Subjective distress in breathing • During exercise, respiratory muscles may fatigue, resulting in shallow, ineffective breathing and increased dyspnea. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

34. Valsalva Maneuver • Closing the glottis following a full inspiration while maximally activating the expiratory muscles • Causes increase in intrathoracic pressure • Helps stabilize chest during lifting McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

35. Physiologic Consequences of Valsalva Maneuver • An acute drop in BP may result from a prolonged Valsalva maneuver. • Decreased venous return • Decreased flow to brain • Dizziness or fainting result McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

36. Respiratory Tract During Cold-Weather Exercise • Cold ambient air is warmed as it passes through the conducting zone. • Moisture is lost if the air is cold and dry. • Contributes to • Dehydration • Dry mouth • Irritation of respiratory passages McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

37. Postexercise Coughing • Related to water loss and the drying of the throat McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition