Chapter 13 - Respiration PDF

Chapter 13 Respiration Alveolar = A arterial = a Blank Arterial Venous PO2 95 mm Hg (85–100) 40 mm Hg PCO2 40 mm Hg (35–45) 46 mm...

Chapter 13 Respiration Alveolar = A arterial = a Blank Arterial Venous PO2 95 mm Hg (85–100) 40 mm Hg PCO2 40 mm Hg (35–45) 46 mm Hg pH 7.4 (7.38–7.42) 7.37 -muscles, pressure gradient, active vs passive, gases, diffusion, signals to breathe  Objectives Basic Values Role of anatomy in function- zones, cells Role of Physics- pressures, partial pressures Role of breathing – gas exchange 02/C02 Respiration Stressors/Diseases The body needs oxygen and removes carbon dioxide Hypoxia – too little oxygen Hypercapnia – increased concentrations of carbon dioxide Pulmonary gas exchange and transport External Systemic respiration/ The respiratory system Internal Cells Cellular respiration Figure 13.1 Organization of the Figure 13.2 Airway Respiratory System Branching 4 Figure 13.3 Relationships between Blood Vessels and Airways 5 Figure 13.4 Cross Section Through an Area of the Respiratory Zone 6  Figure 13.6 The Steps of Respiration 1. Ventilation: Exchange of air between atmosphere and alveoli by bulk flow 2. Exchange of O2 and CO2 between alveolar air and blood in lung capillaries by diffusion 3. Transport of O2 and CO2 through pulmonary and systemic circulation by bulk flow 4. Exchange of O2 and CO2 between blood in tissue capillaries and cells in tissues by diffusion 5. Cellular utilization of O2 and production of CO2 Movement of gases/molecules occurs from areas of HIGH pressure to LOW pressure 7 Figure 13.14a and b Muscles of Normal and Maximal Inspiration (a) Normal (b) Maximal inspiration) inspiration) 8 Breathing  Figure 13.14c and d Muscles of Normal and Maximal Expiration Elastic recoil Forced recoil (c) Normal, resting (d) Maximal expiration) expiration) 10 Figure 13.12-13 Sequence of Events During Inspiration and Expiration Intrapleural (Pip) Alveolar (Palv) 11 Figure 13.5 Relationship of Lungs, Pleura, and Thoracic Wall, Shown as Analogous to Pushing a Fist Into a Fluid- Filled Balloon 12  Figure 13.7 Relationships Required for Ventilation Volume Pressure Atmospheric pressure Relationship (Patm ) Pressure and Movement (flow) Volume are Palv − Patm from HIGH pressure inversely related F= to LOW pressure R 13  “We live submerged at the bottom of an ocean of the element air“ Torricelli mmHg = Torr -air is compressible - a given volume at sea level (SL) contains more molecules than at ALT-conversely at ALT a given volume contains less molecules that at sea level Figure 13.8 Boyle’s Law: The Pressure Exerted by a Constant Number of Gas Molecules (at a Constant Temperature) Is Inversely Proportional to the Volume of the Container P1V1 = P2V2 15  Air = 79.04% N2,.03% CO2 and 20.93% O2 so 79.04% +.03% + 20.93% =100%, -same at any altitude or.7904 +.0003 +.2093 =1 Together (as air) these gases at Sea Level exert a pressure of 760 mmHg of mercury (Hg) or Torr Any place on earth - the concentration of gases does not change but the content per unit volume decreases with altitude  Partial Pressures (Pgas) of Atmospheric Gases at 760 mm Hg In humid air, water vapor “dilutes” the contribution of other gases to the total pressure. Gas and its percentage in Pgas in 25 °C air, 100% Pgas in 37 °C air, 100% Pgas in dry 25 °C air air humidity humidity O2 21% 160 mm Hg 155 mm Hg 150 mm Hg CO2 0.03% 0.25 mm Hg 0.24 mm Hg 0.235 mm Hg Water vapour 0 mm Hg 24 mm Hg 47 mm Hg To calculate the partial pressure of a gas in humid air, you must first subtract the water vapor pressure from the total pressure. At 100% humidity and 25 °C, water vapor pressure (PH O ) is 24 mm Hg. STPD vs BTPD 2 Pgas inhumid air =(Patm − PH2O )  %of gas Dry vs Saturated 𝐏𝐎𝟐 = (𝟕𝟔𝟎 − 𝟐𝟒) × 𝟐𝟏% = 𝟏𝟓𝟓𝐦𝐦𝐇𝐠 At 37C 𝐏𝐎𝟐 = (𝟕𝟔𝟎 − 𝟒𝟕) × 𝟐𝟏% = 𝟏𝟓𝟎𝐦𝐦𝐇𝐠  Figure 13.10 Alveolar (Palv), Intrapleural Figure 13.9 Pressure (Pip), Transpulmonary (Ptp), and Trans- Differences Involved in Chest-Wall (Pcw) Pressures (millimeters Hg) at the End of an Unforced Ventilation Expiration—That Is, Between Breaths When There Is No Airflow 18  Figure 13.13 Summary of Alveolar(Palv), Intrapleural (Pip), and Transpulmonary (Ptp) Pressure Changes and Airflow During a Typical Respiratory Cycle Your text IN EX Transpulmonary (Ptp) Alveolar (Palv) Intrapleural (Pip) 19 Alveolar (Palv) Intrapleural (Pip) Volume Figure 13.16 A Graphic Representation of Lung Compliance Lung volume V Compliance = = (Palv − Pip ) Ptp The greater the lung compliance, the easier it is to expand the lungs at any given change in transpulmonary pressure. Compliance can be considered the inverse of stiffness. There are two major determinants of lung compliance: The stretchability of the lung tissues The surface tension at the air-water interfaces within the alveoli 21  Figure 13.17 Stabilizing Effect of Surfactant No surfactant With surfactant 2T If Ta = Tb P= r If Tb  Ta (due to unique property of surfactant) then Pa  Pb then Pa = Pb ra  rb and air flows from b to and there is no flow from b to a; b collapses into a a; smaller alveoli do not collapse into bigger alveoli 22 Figure 13.18 Lung Volumes and Capacities Recorded on a Spirometer 1 Respiratory Volumes and Capacities for an Average Young Adult Male 23  Rate vs. Depth Both rate and depth of breathing can be increased. 1 Pulmonary Ventilation Minute ventilation is the volume of air breathed in and out in 1 minute – Pulmonary ventilation (mL/min) = tidal volume (ml/breath) × respiratory frequency (breaths/min) Examples Rest: Exercise: Maximal: 500 ml/breath X 3000 ml/breath 4000 ml/breath 12 breaths/min X 50 breaths/min X 70 breaths/min = 6 L/min = 150 L/min = 280 L/min 6 Alveolar Ventilation More important than pulmonary ventilation – Volume of air exchanged between the atmosphere and the alveoli per minute – Less than pulmonary ventilation due to anatomic dead space Volume of air in conducting airways that is useless for exchange Averages about 150 mL in adults Alveolar ventilation = (tidal volume – dead space) × respiratory rate Figure 13.19 Effects of Anatomical Dead Space on Alveolar Ventilation 27  TV f VE = TV x f No change in dead Space VA= (TV– DS) × f Factors Affecting Gas Exchange in the Alveoli Pulmonary gas exchange and transport OUTSIDE Blood CV INSIDE Cells Figure 13.20 Summary of Typical Oxygen and Carbon Dioxide Exchanges Between Atmosphere, Lungs, Blood, and Tissues During One Minute in a Resting Individual 31  Figure 13.21 Partial Pressures of Carbon Dioxide and Oxygen in Inspired Air at Sea Level and in Various Places in the Body 32 Figure 13.22 Effects of Increasing or Decreasing Alveolar Ventilation on Alveolar Partial Pressures 33 Figure 13.24 Local Control of Ventilation-Perfusion Matching 34  02 Figure 13.25 Heme in Two Dimensions 1 02 2/3 02 2/3 02 Most oxygen is transported in the blood bound to hemoglobin. 35 Gas Transport in the Blood Gas entering into the capillaries first dissolve in the plasma – Dissolved gas accounts for