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Similar to Chapter 22: Respiratory System (#2)
Chapter 22: Respiratory System (#2)
- 1. CHAPTER 22: RESPIRATORY SYSTEM (2):MECHANICS OF VENTILATION Human Anatomy and Physiology II – BIOL153
- 2. Processes of Respiration Pulmonary ventilation External respiration Transport Internal respiration Respiratory system Circulatory system
- 3. Goals/Objectives Explain thefunctional importance of the partial vacuum that exists in the intrapleural space Relate Boyle’s law to the events of inspiration and expiration Explain the relative roles of the respiratory muscles and lung elasticity in producing the volume changes that cause air to flow into and out of the lungs List several physical factors that influence pulmonary ventilation Explain and compare the various lung volumes and capacities Define dead space
- 4. Mechanics of Breathing Inspiration/InhalationExpiration/Exhalation
- 5. Pressure Relationships inthe Thoracic Cavity Atmospheric pressure (Patm) Pressure exerted by air surrounding body 760 mm Hg at sea level = 1 atmosphere Respiratory pressures described relative to Patm Intrapulmonary (intra-alveolar) pressure (Ppul) Pressure in alveoli Fluctuates with breathing Always eventually equalizes with Patm Intrapleural pressure (Pip) Pressure in pleural cavity Fluctuates with breathing Always a negative pressure (<Patm and <Ppul)
- 6. Pressure Relationships inthe Thoracic Cavity Atmospheric pressure (Patm) 0 mm Hg (760 mm Hg) Thoracic wall Parietal pleura Visceral pleura Pleural cavity Transpulmonary pressure 4 mm Hg (the difference between 0 mm Hg and −4 mm Hg) Intrapleural pressure (Pip) −4 mm Hg (756 mm Hg) Intrapulmonary pressure (Ppul) 0 mm Hg (760 mm Hg) Diaphragm Lung 0 – 4 If Pip = Ppul or Patm lungs collapse (Ppul – Pip) = transpulmonar y pressure Keeps airways open Greater transpulmonary pressure larger lungs
- 7.
- 8. Atelectasis (lung collapse) Plugged bronchioles collapse of alveoli Pneumothorax-air in pleural cavity From either wound in parietal or rupture of visceral pleura Treated by removing air with chest tubes; pleurae heal lung reinflates
- 9. Pulmonary Ventilation andBoyle's Law Volume changes pressure changes Pressure changes gases flow to equalize pressure Boyles Law: Pressure (P) varies inversely with volume (V): P1V1 = P2V2 OR P = 1/V Relationship between pressure and volume of a gas Gases fill container; if container size reduced increased pressure
- 10. Inspiration Sequence of events Changesin anterior-posterior and superior-inferior dimensions Changes in lateral dimensions (superior view) 1 Diaphragm moves inferiorly during contraction. Ribs are elevated and sternum flares as external intercostals contract. External intercostals contract. Inspiratory muscles contract (diaphragm descends; rib cage rises). Inspiration
- 11.
- 12. Inspiratory muscles contract (diaphragm descends;rib cage rises). Thoracic cavity volume increases. Inspiration Sequence of events Changes in anterior-posterior and superior-inferior dimensions Changes in lateral dimensions (superior view) 1 2 Diaphragm moves inferiorly during contraction. Ribs are elevated and sternum flares as external intercostals contract. External intercostals contract. Inspiration
- 13. Inspiratory muscles contract (diaphragm descends;rib cage rises). Thoracic cavity volume increases. Inspiration Sequence of events Changes in anterior-posterior and superior-inferior dimensions Changes in lateral dimensions (superior view) 1 2 3 Diaphragm moves inferiorly during contraction. Ribs are elevated and sternum flares as external intercostals contract. External intercostals contract. Lungs are stretched; intrapulmonary volume increases. Inspiration
- 14. Inspiratory muscles contract (diaphragm descends;rib cage rises). Thoracic cavity volume increases. Lungs are stretched; intrapulmonary volume increases. Inspiration Sequence of events Changes in anterior-posterior and superior-inferior dimensions Changes in lateral dimensions (superior view) 1 2 3 4 Diaphragm moves inferiorly during contraction. Ribs are elevated and sternum flares as external intercostals contract. External intercostals contract.Intrapulmonary pressure drops (to –1 mm Hg). Inspiration
- 15. Inspiratory muscles contract (diaphragm descends;rib cage rises). Thoracic cavity volume increases. Lungs are stretched; intrapulmonary volume increases. Intrapulmonary pressure drops (to –1 mm Hg). Air (gases) flows into lungs down its pressure gradient until intrapulmonary pressure is 0 (equal to atmospheric pressure). Inspiration Sequence of events Changes in anterior-posterior and superior-inferior dimensions Changes in lateral dimensions (superior view) 1 2 3 4 5 Diaphragm moves inferiorly during contraction. Ribs are elevated and sternum flares as external intercostals contract. External intercostals contract. Inspiration
- 16.
- 17. 1 Expiration Sequence of eventsChanges in anterior-posterior and superior-inferior dimensions Changes in lateral dimensions (superior view) Diaphragm moves superiorly as it relaxes. Ribs and sternum are depressed as external intercostals relax. External intercostals relax. Inspiratory muscles relax (diaphragm rises; rib cage descends due to recoil of costal cartilages). Expiration
- 18. 1 Expiration Sequence of eventsChanges in anterior-posterior and superior-inferior dimensions Changes in lateral dimensions (superior view) 2 Diaphragm moves superiorly as it relaxes. Ribs and sternum are depressed as external intercostals relax. External intercostals relax. Inspiratory muscles relax (diaphragm rises; rib cage descends due to recoil of costal cartilages). Thoracic cavity volume decreases. Expiration
- 19. 1 Expiration Sequence of eventsChanges in anterior-posterior and superior-inferior dimensions Changes in lateral dimensions (superior view) 2 3 Diaphragm moves superiorly as it relaxes. Ribs and sternum are depressed as external intercostals relax. External intercostals relax. Inspiratory muscles relax (diaphragm rises; rib cage descends due to recoil of costal cartilages). Thoracic cavity volume decreases. Elastic lungs recoil passively; intrapulmonary Volume decreases. Expiration
- 20. 1 Expiration Sequence of eventsChanges in anterior-posterior and superior-inferior dimensions Changes in lateral dimensions (superior view) 2 3 4 Diaphragm moves superiorly as it relaxes. Ribs and sternum are depressed as external intercostals relax. External intercostals relax. Inspiratory muscles relax (diaphragm rises; rib cage descends due to recoil of costal cartilages). Thoracic cavity volume decreases. Elastic lungs recoil passively; intrapulmonary Volume decreases. Intrapulmonary pressure rises (to +1 mm Hg). Expiration
- 21. 1 Expiration Sequence of eventsChanges in anterior-posterior and superior-inferior dimensions Changes in lateral dimensions (superior view) 2 3 4 5 Diaphragm moves superiorly as it relaxes. Ribs and sternum are depressed as external intercostals relax. External intercostals relax. Inspiratory muscles relax (diaphragm rises; rib cage descends due to recoil of costal cartilages). Thoracic cavity volume decreases. Elastic lungs recoil passively; intrapulmonary Volume decreases. Intrapulmonary pressure rises (to +1 mm Hg). Air (gases) flows out of lungs down its pressure gradient until intrapulmonary pressure is 0. Expiration
- 22.
- 24. Intrapulmonary pressure. Pressure insidelung decreases as lung volume increases during inspiration; pressure increases during expiration. Intrapleural pressure. Pleural cavity pressure becomes more negative as chest wall expands during inspiration. Returns to initial value as chest wall recoils. Volume of breath. During each breath, the pressure gradients move 0.5 liter of air into and out of the lungs. Pressurerelativeto atmosphericpressure(mmHg)Volume(L) Inspiration Expiration Intrapulmonary pressure Trans- pulmonary pressure Intrapleural pressure Volume of breath 5 seconds elapsed +2 0 –2 –4 –6 –8 0.5 0
- 25. Clicker Question The pressurein the pleural cavity is known as __________. a) intrapleural pressure b) intrapulmonary pressure c) transpulmonary pressure d) atmospheric pressure
- 26. Goals/Objectives Explain thefunctional importance of the partial vacuum that exists in the intrapleural space Relate Boyle’s law to the events of inspiration and expiration Explain the relative roles of the respiratory muscles and lung elasticity in producing the volume changes that cause air to flow into and out of the lungs List several physical factors that influence pulmonary ventilation Explain and compare the various lung volumes and capacities Define dead space
- 27. Physical Factors Influencing PulmonaryVentilation Three physical factors influence the ease of air passage and the amount of energy required for ventilation. Airway resistance Alveolar surface tension Lung compliance
- 28. Airway Resistance Relationshipbetween flow (F), pressure (P), and resistance (R) is: ∆P - pressure gradient between atmosphere and alveoli (2 mm Hg or less during normal quiet breathing) Gas flow changes inversely with resistance
- 29. Conducting zone Respiratory zone Medium-sized bronchi Resistance Terminal bronchioles 1 510 15 20 23 Airway generation (stage of branching) Airway Resistance Resistance usually insignificant Large airway diameters in first part of conducting zone Progressive branching of airways as get smaller, increasing total cross- sectional area Resistance greatest in medium-sized bronchi Resistance disappears at terminal bronchioles where diffusion drives gas movement
- 30. Alveolar Surface Tension Attracts liquid molecules to one another at gas-liquid interface Resists any force that tends to increase surface area of liquid Water–high surface tension; coats alveolar walls reduces them to smallest size
- 31. Lung Compliance Measureof change in lung volume that occurs with given change in transpulmonary pressure Higher lung compliance easier to expand lungs Normally high due to Distensibility of lung tissue Surfactant, which decreases alveolar surface tension Diminished by Nonelastic scar tissue replacing lung tissue (fibrosis)
- 32. Respiratory Volumes and Capacities Used to assess respiratory status Tidal volume (TV) Inspiratory reserve volume (IRV) Expiratory reserve volume (ERV) Residual volume (RV) Combinations of respiratory volumes Inspiratory capacity (IC) Functional residual capacity (FRC) Vital capacity (VC) Total lung capacity (TLC)
- 33. Measurement Adult male average value Adultfemale average value Description Respiratory volumes Respiratory capacities Summary of respiratory volumes and capacities for males and females Tidal volume (TV) Inspiratory reserve volume (IRV) Expiratory reserve volume (ERV) Residual volume (RV) 500 ml 500 ml 3100 ml 1200 ml 1200 ml 1900 ml 700 ml 1100 ml Amount of air inhaled or exhaled with each breath under resting conditions Amount of air that can be forcefully inhaled after a normal tidal volume inspiration Amount of air that can be forcefully exhaled after a normal tidal volume expiration Amount of air remaining in the lungs after a forced expiration Maximum amount of air contained in lungs after a maximum inspiratory effort: TLC = TV + IRV + ERV + RV Maximum amount of air that can be expired after a maximum inspiratory effort: VC = TV + IRV + ERV Maximum amount of air that can be inspired after a normal tidal volume expiration: IC = TV + IRV Volume of air remaining in the lungs after a normal tidal volume expiration: FRC = ERV + RV 6000 ml 4800 ml 3600 ml 2400 ml 4200 ml 3100 ml 2400 ml 1800 ml Total lung capacity (TLC) Vital capacity (VC) Inspiratory capacity (IC) Functional residual capacity (FRC) Respiratory Volumes and Capacities
- 34. 5000 4000 3000 2000 1000 0 Milliliters(ml) Spirographic record fora male 6000 Inspiratory reserve volume 3100 ml Expiratory reserve volume 1200 ml Residual volume 1200 ml Inspiratory capacity 3600 ml Functional residual capacity 2400 ml Vital capacity 4800 ml Total lung capacity 6000 ml Tidal volume 500 ml Respiratory Volumes and Capacities
- 35. Dead Space Anatomicaldead space No contribution to gas exchange Air remaining in passageways; ~150 ml Alveolar dead space–non-functional alveoli due to collapse or obstruction Total dead space-sum of anatomical and alveolar dead space
- 36. Pulmonary Function Tests Spirometer-instrument for measuring respiratory volumes and capacities
- 37. Clicker Question During pulmonarytests, a patient is asked to breath in normally and then inhale additionally as much as possible into the spirometer. The capacity being measured is the: a) Inspiratory capacity b) Functional residual capacity c) Vital capacity d) Total lung capacity
- 38. Pulmonary Function Tests To measure rate of gas movement Forced vital capacity (FVC)—gas forcibly expelled after taking deep breath Forced expiratory volume (FEV)—amount of gas expelled during specific time intervals of FVC