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Chapter 39

Chapter 39. Respiratory Physiology. Mechanisms of respiration. Pulmonary ventilation Inspiration Expiration Respiratory muscles Diaphragm External intercostal Others. Mechanisms of respiration. Steps of ventilation Contraction of diaphragm and external intercostal muscles

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Chapter 39

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  1. Chapter 39 Respiratory Physiology

  2. Mechanisms of respiration • Pulmonary ventilation • Inspiration • Expiration • Respiratory muscles • Diaphragm • External intercostal • Others

  3. Mechanisms of respiration • Steps of ventilation • Contraction of diaphragm and external intercostal muscles • Increase of thoracic volume • Expansion of the pleural cavities and lungs • Decrease of lung pressure below atmospheric pressure

  4. Mechanisms of respiration • Inspiration • Lung pressure becomes equal to atmospheric pressure • Air stops to flow inside • Relaxation of respiratory muscles • Recoiling of the lung tissue

  5. Mechanisms of respiration • Decrease of intrathoracic and intrapulmonary volumes • Increase of pulmonary pressure • Expiration

  6. Mechanisms of respiration • Pneumothorax it is the entry of air into the pleural cavity • It breaks the fluid bond between the visceral and parietal pleura • It will cause the lung to collapse – atelectasis

  7. Respiratory volumes and capacities • Spirometry • Tidal volume (TV) • It is the amount of air inspired or expired with each breath under resting conditions • 500 ml

  8. Respiratory volumes and capacities • Inspiratory reserve volume (IRV) • It is the amount of air that can be forcefully inspired after a normal tidal inspiration • 3100 ml

  9. Respiratory volumes and capacities • Expiratory reserve volume (ERV) • It is the amount of air that can be forcefully expired after a normal tidal expiration • 1200 ml • It is reduced in conditions in which the elasticity of the lungs is decreased

  10. Respiratory volumes and capacities • Vital capacity (VC) • It id the maximum amount of air that can be expired after a maximal inspiration • 4800 ml • VC = TV + IRV + ERV

  11. Respiratory volumes and capacities • Residual volume (RV) • It is the amount of air that remains in the lung after a ERV • 1200 ml

  12. Respiratory volumes and capacities • Functional residual capacity (FRC) • It is the amount of air that remains in the lung after a quiet respiratory cycle • 2400 ml • FRC = ERV+RV

  13. Respiratory volumes and capacities • Total lung capacity (TLC) • It is the total volume of the lungs • 6000 ml • TLC = VC+RV

  14. Respiratory volumes and capacities

  15. Respiratory volumes and capacities • Nonrecording spirometer • Handheld dry spirometer • Measures only expired air • Wet spirometer • Measures only expired air • Recording spirometer • Measures inspired and expired air

  16. Pulmonary disorders • Obstructive • Bronchitis • Asthma • Restrictive • Tuberculosis • Poliomyelitis

  17. Respiratory volumes and capacities • Forced vital capacity (FVC) • It is the amount of air expired after a deep inspiration and a forced and quick expiration • Reduced in restrictive pulmonary diseases

  18. Respiratory volumes and capacities • Forced expiratory volume measurement (FEV1%) • It is the percentage of vital capacity that is exhaled during specific intervals of time • It is reduced in obstructive diseases

  19. Respiratory rate and depth • Respiratory centers • Medulla oblongata • Pons • Keep the RR at 12-18 respirations/minute • Respiratory receptors • Stretch receptors in the lung • Change RR

  20. Respiratory rate and depth • Nerve vagus • Factors that changes the RR • Exercise • Coughing • Waking • Talking • Laughing, etc

  21. Respiratory rate and depth • O2 concentration in the blood • monitored by chemoreceptors in the aortic and carotid bodies • CO2 concentration in the blood • Directly stimulates the respiratory centers • Blood pH • Monitored by chemoreceptors in the aortic and carotid bodies

  22. Respiratory sounds • Bronchial sounds • Heard below the larynx • Vesicular sounds • Air filling the alveolar sacs • Heard over the chest • Crepitation (crackles) • Wheezing – a whistling sound

  23. Role of respiratory system in acid-base balance of blood • Blood pH • 7.35-7.45 • Carbonic acid-bicarbonate buffer • The main body buffer

  24. Acid-base imbalance • Alkalosis • Blood pH above 7.45 • Respiratory or metabolic • Acidosis • Blood pH bellow 7.35 • Respiratory or metabolic

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