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RESPIRATORY SYSTEM

RESPIRATORY SYSTEM. dr. Sri Lestari Sulistyo Rini, MSc. Respiratory System. Functions of the Respiratory System. Exchange O 2 Air to blood Blood to cells Exchange CO 2 Cells to blood Blood to air Regulate blood pH Vocalizations Protect alveoli. Function of the Nose.

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RESPIRATORY SYSTEM

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  1. RESPIRATORY SYSTEM dr. Sri Lestari Sulistyo Rini, MSc

  2. Respiratory System

  3. Functions of the Respiratory System • Exchange O2 • Air to blood • Blood to cells • Exchange CO2 • Cells to blood • Blood to air • Regulate blood pH • Vocalizations • Protect alveoli

  4. Function of the Nose • The only externally visible part of the respiratory system that functions by: • Providing an airway for respiration • Moistening and warming the entering air • Filtering inspired air and cleaning it of foreign matter • Serving as a resonating chamber for speech • Housing the olfactory receptors

  5. ConductingZone: Bronchi • The carina of the last tracheal cartilage marks the end of the trachea and the beginning of the right and left bronchi • Air reaching the bronchi is: • Warm and cleansed of impurities • Saturated with water vapor • Bronchi subdivide into secondary bronchi, each supplying a lobe of the lungs • Air passages undergo 23 orders of branching in the lungs

  6. Respiratory Zone • Defined by the presence of alveoli; begins as terminal bronchioles feed into respiratory bronchioles • Respiratory bronchioles lead to alveolar ducts, then to terminal clusters of alveolar sacs composed of alveoli • Approximately 300 million alveoli: • Account for most of the lungs’ volume • Provide tremendous surface area for gas exchange

  7. Four Respiration Processes • Breathing (ventilation): air in to and out of lungs • External respiration: gas exchange between air and blood • Internal respiration: gas exchange between blood and tissues • Cellular respiration: oxygen use to produce ATP, carbon dioxide as waste

  8. Lung Volumes: Spirometer Measurements

  9. PULMONARY VOLUMES, CAPACITIES, AND RATES maximum inspiration 6000 ml Volumes tidal volume (500 ml) 5000 ml IRV anatomical dead space (150 ml) alveolar ventilation (350 ml) physiological dead space VC TLC 4000 ml inspiratory reserve volume (3000 ml) expiratory reserve volume (1200 ml) residual volume (1300 ml) 3000 ml TV Capacities 2000 ml ERV total lung capacity (TV+IRV+ERV+RV) vital capacity (TV+IRV+ERV) (4700 ml) inspiratory capacity (TV+IRV) functional residual capacity (RV+ERV) 1000 ml RV maximum expiration SPIROGRAM Rates maximum voluntary ventilation = TV x breaths/minute alveolar ventilation rate = alveolar ventilation x breaths/minute

  10. Lung Volumes: Spirometer Measurements

  11. PHYSIOLOGY OF RESPIRATION Concepts related to pulmonary ventilation (breathing) - inspiration (inhalation) vs. expiration (exhalation) - atmospheric pressure - intrapulmonic pressure - pressure gradient

  12. Boyle’s Law • Boyle’s law – the relationship between the pressure and volume of gases P1V1 = P2V2 • P = pressure of a gas in mm Hg • V = volume of a gas in cubic millimeters • Subscripts 1 and 2 represent the initial and resulting conditions, respectively

  13. Pressure Relationships in the Thoracic Cavity • Respiratory pressure is always described relative to atmospheric pressure • Atmospheric pressure (Patm) • Pressure exerted by the air surrounding the body • Negative respiratory pressure is less than Patm • Positive respiratory pressure is greater than Patm

  14. Pressure Relationships in the Thoracic Cavity • Intrapulmonary pressure (Ppul) – pressure within the alveoli • Intrapleural pressure (Pip) – pressure within the pleural cavity

  15. Pressures • Atmospheric pressure – 760 mm Hg, 630 mm Hg here • Intrapleural pressure – 756 mm Hg – pressure between pleural layers • Intrapulmonary pressure – varies, pressure inside lungs

  16. Alveolar Pressure Changes

  17. Inspiration • Begins with the contraction of the diaphragm and the external intercostals • This causes thoracic volume to  • Which causes lung volume to  • Which causes lung pressure to  • Now Palv is <Patm so air will flow down its pressure gradient and enter the lungs. • Inspiration ends when Palv=Patm

  18. Inspiration • The diaphragm and external intercostal muscles (inspiratory muscles) contract and the rib cage rises • The lungs are stretched and intrapulmonary volume increases • Intrapulmonary pressure drops below atmospheric pressure (1 mm Hg) • Air flows into the lungs, down its pressure gradient, until intrapleural pressure = atmospheric pressure

  19. Pressure – Volume Relationships • As vol. , pressure  • As vol. , pressure  • This is given by Boyle’s Law which says: P1V1 = P2V2 • Why does this occur? • Remember, pressure equals force/area P = Force/Area So, in this equation as A gets larger P must get smaller

  20. INSPIRATION Active process Boyle’s Law decrease volume  increase pressure air molecule Inspiratory muscles Phrenic nerves (C3-5) Thoracic nerves (T1 – T11) increase volume  decrease pressure Process thoracic volume pleural volume intrapleural pressure lung volume intrapulmonic pressure air flow into the lungs sternocleidomastoid scalenes external intercostals (11 pairs) 760 mmHg 760 mmHg diaphragm 760 mmHg 758 mmHg RESTING INSPIRATION FORCED INSPIRATION BEFORE INSPIRATION DURING INSPIRATION

  21. Expiration • Inspiratory muscles relax and the rib cage descends due to gravity • Thoracic cavity volume decreases • Elastic lungs recoil passively and intrapulmonary volume decreases • Intrapulmonary pressure rises above atmospheric pressure (+1 mm Hg) • Gases flow out of the lungs down the pressure gradient until intrapulmonary pressure is 0

  22. Expiration • Quiet expiration is a passive process that is due to the elasticity of the lungs. • What pressure and volume changes occur during quiet expiration? • Forced expiration is an active process due to contraction of oblique and transverse abdominus muscles, internal intercostals, and the latissimus dorsi.

  23. EXPIRATION Passive process at rest elastic recoil surface tension internal intercostals (11 pairs) Process thoracic volume pleural volume intrapleural pressure lung volume intrapulmonic pressure air flow of the lungs external abdominal oblique internal abdominal oblique transversus abdominis rectus abdominis Forced expiration 760 mmHg internal intercostals (11 pairs) rectus abdominis abdominal obliques transversus abdominis 762 mmHg

  24. Factors that influence pulmonary air flow • F = P/R • Diameter of airways, esp. bronchioles • Sympathetic & Parasympathetic NS

  25. Factors Affecting Ventilation • Airway Resistance • Diameter • Mucous blockage • Bronchoconstriction • Bronchodilation • Alveolar compliance • Surfactants • Surface tension • Alveolar elasticity

  26. Airway Resistance • Due primarily to diameter of the conducting tubes. • How increased parasympathetic • affect tube diameter? How would it • affect airway resistance? • Histamine causes massive bronchoconstriction. • When might one experience massive histamine release? • Why treat it with epinephrine? • Local accumulations of mucus, infectious materials or solid tumors are also sources of airway resistance.

  27. DEAD SPACE Tidal volume NOT used in gas exchange Anatomical: conducting pathways (150mls) Alveolar: gas reach alveoli, not enough blood supply due to: - Pulmonary embolism - Non vascular air space Physiological dead space= anatomical + alveolar

  28. Types of Dead Space • Anatomic dead space • That contained in the conducting airways • Alveolar dead space • That contained in the respiratory portion of the lung • Physiologic dead space • The anatomic dead space plus alveolar dead space

  29. Efficiency of Breathing: Normal & High Demand • Total Pulmonary Ventilation (rate X tidal vol about 6 L/min) • Alveolar ventilation (– dead air space – 4.5 L/min) • Little variation [O2] & [CO2] • Exercise- High Demand •  Depth of breathing • Use inspiratory reserve

  30. Matching Ventilation with Alveolar Blood Flow (Perfusion) • Mostly local regulation • Low [O2] in alveoli  vasoconstriction of arteriole • Reduced blood flow at rest • (lung apex ) • saves energy • High blood [CO2]  bronchodilation

  31. VENTILATON-PERFUSION MATCHING V Alveolar gas Q Capillary flow

  32. Matching Ventilation and Perfusion • Required for exchange of gases between the air in the alveoli and the blood in pulmonary capillaries • Two factors interfere with the process: • Dead air space and shunt • The blood oxygen level reflects the mixing of blood from alveolar dead space and physiologic shunting areas as it moves into the pulmonary veins

  33. Efficiency of Breathing: Normal & High Demand Figure 17-2 g: Anatomy Summary

  34. FICK’S LAW • Rate of transfer of a gas through a sheet of tissue is proportional to • tissue area • difference in gas partial pressure • diffusion constant inversely proportional to tissue thickness

  35. Respiratory Membrane • This air-blood barrier is composed of: • Alveolar and capillary walls • Their fused basal laminas • Alveolar walls: • Are a single layer of type I epithelial cells • Permit gas exchange by simple diffusion • Secrete angiotensin converting enzyme (ACE) • Type II cells secrete surfactant

  36. Composition of the Alveolar Structures • Type I alveolar cells • Flat squamous epithelial cells across which gas exchange takes place • Type II alveolar cells • Produce surfactant, a lipoprotein substance that decreases the surface tension in the alveoli and allows for greater ease of lung inflation

  37. Respiratory Membrane

  38. Factors Affecting Alveolar-Capillary Gas Exchange • Surface area available for diffusion • Thickness of the alveolar-capacity membrane • Partial pressure of alveolar gases • Solubility and molecular weight of the gas

  39. Lung Compliance • The ease with which lungs can be expanded • Specifically, the measure of the change in lung volume that occurs with a given change in transpulmonary pressure • Determined by two main factors • Distensibility of the lung tissue and surrounding thoracic cage • Surface tension of the alveoli

  40. Lung Compliance • Lung compliance • (C) = (ΔV)/(ΔP) • The change in lung volume (ΔV) that can be accomplished with a given change in respiratory pressure (ΔP)

  41. COMPLIANCE Compliance is the ease with which the lungs and thoracic wall can be expanded during inspiration. Related to two factors: elasticity surface tension Compliance is decreased with any condition that: destroys lung tissue (emphysema) fills lungs with fluid (pneumonia) produces surfactant deficiency (premature birth, near-drowning) interferes with lung expansion (pneumothorax)

  42. Alveolar Surface Tension • Surface tension – the attraction of liquid molecules to one another at a liquid-gas interface • The liquid coating the alveolar surface is always acting to reduce the alveoli to the smallest possible size • Surfactant, a detergent-like complex, reduces surface tension and helps keep the alveoli from collapsing

  43. Factors That Diminish Lung Compliance • Scar tissue or fibrosis that reduces the natural resilience of the lungs • Blockage of the smaller respiratory passages with mucus or fluid • Reduced production of surfactant • Decreased flexibility of the thoracic cage or its decreased ability to expand

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