呼吸（英文班和7年制最后稿）课件

Miao Bing (缪兵) Institute of Physiology Office: 6330 Tel: 83902 E-mail: ,An Overview of Key Steps in Respiration,Respiratory System Divisions,Upper tract nose, pharynx and associated structures Lower tract larynx, trachea, bronchi, lungs,Conducting Zone,All structures air passes through before reaching the respiratory zone. Cartilages that keep tube system open and smooth muscles that controls tube diameter Warms and humidifies inspired air. Filters and cleans.,Insert fig. 16.5,Respiratory Zone,Regions of gas exchange between air and blood. Including: respiratory bronchioles alveolar ducts, sacs and alveoli.,Airway branching,Bronchioles and Alveoli,Respiration is the process by which the body takes in and utilizes O2 and gets rid of CO2.,Respiration can be divided into four major functional events,Pulmonary ventilation: movement of air into and out of lungs. Gas exchange between air in lungs and blood. Transport of oxygen and carbon dioxide in blood. Internal respiration: gas exchange between blood and tissues.,Functions of Respiratory System,Gas Exchange: Oxygen enters blood and carbon dioxide leaves. Regulation of Blood pH: Alters pH by changing blood carbon dioxide levels. *Voice Production: Vibration of vocal cords induced by moving air makes sounds and speeches. *Sense of Smell (Olfaction): Smell occurs when airborne smell-inducing molecules move into nasal cavity. *Protection: Against microorganisms by preventing entry and removing them.,Outline,Section I: Pulmonary Ventilation Section II: Gas Exchange in Lungs and Tissues *Section III: Transport of O2 and CO2 in Blood. Section IV: Regulation of Respiration,Section 1: Pulmonary Ventilation Pulmonary Ventilation: the inflow and outflow of air between the atmosphere and the lung alveoli, which is determined by the activity of the airways, the alveoli and the thoracic cage. Air moves from area of higher pressure to area of lower pressure; Pressure is inversely related to volume.,Important Structures Associated with Pulmonary Ventilation,Airways,The pathway for air flow: nose-alveoli To protect the body: Protection Against microorganisms by preventing entry and removing them To warm and humidify the inspired air,Alveoli,Number: 300millions Diameter: 0.25mm Total area: 70m2 Two groups of cells I：small alveolar cells II：large alvoelar cells (DPPC).,Rrespiratory Membrane (RM),The membraneous structure that gas molecules must cross when gas exchange occurs between the alveoli and pulmonary capillaries. (also named alveolar membrane, alveolar-capillary membrane).,Composition of RM 1. Fluid and surfactant； 2. Epithelial cells of alveoli 3. Basement membrane of alveoli 4. cleft 5. Basement membrane of capillary 6. Endothelial cells of capillary,Thickened RM: pulmonary edema, fibrosis Decreased area of RM: fibrosis, emphysema,Surface Tension and Surface Active Substance (Surfactant),What is Surface Tension ?,Surface Tension in Alveoli,Exerted by fluid in alveoli to resist distension; Lungs secrete and absorb fluid, leaving a very thin film of fluid. This film of fluid causes surface tension. H2O molecules at the surface attract one other. Direction of surface tension: toward the center of alveoli; Raising pressure in alveoli.,Surface Tension in Alveoli,Law of Laplace: Pressure in alveoli is directly proportional to surface tension; and inversely proportional to radius of alveoli. Pressure in smaller alveoli would be greater than that in larger alveoli, if surface tension were the same in both.,Insert fig. 16.11,Effect of Surface Tension on Alveoli Size,Surfactant Prevents Alveolar Collapse,What is Surfactant? surface-tension-decreasing substances,Surfactant,Examples： Secretion Cells：type II alveolar cells Chemical： DPPC Importances: 1. Enhance the compliance of the lungs 2. Prevent pulmonary edema 3. Stabilize the alveoli,Thorax, Pleural Cavity and Intrapleural Pressure,Thorax,Thoracic Volume,Pleura,Pleural cavity： the airtight and potential cavity formed by the visceral and parietal pleura. It is filled with pleural fluid,Pleural fluid: produced by pleural membranes Acts as lubricant; Helps hold parietal and visceral pleural membranes together. pneumothorax,Intrapleural Pressure,Definition: the pressure in the pleural cavity. Normal value: 750mmHg The end of inspiration；-5 -10mmHg The end of expiration：-3 -5mmHg The lowest and highest value: -90mmHg- +110mmHg,*Calculation: intrapleural pressure = pressure of air in alveoli-contracting force Sources of contracting force: elastic force surface tension,Importances of Negative Intrapleural Pressure To hold the lungs and thorax together To promote the pulmonary and lymphatic circulation.,Changes in Pleural Pressure, Lung Volume and Alveolar Pressure,Principles of Pulmonary Ventilation,Driving forces: pressure difference between air in alveoli and atmosphere Resistences: 1) Elastic resistance（70%） 2) Inelastic resistance: airway resistance， pulmonary tissue resistance (viscosity, and inertia, 30% totally）,Definition of inspiration: inspiratory muscles-enlarged thorax-distended lungs-decreased pressure of air in alveoli-air flow into the lungs. Definition of expiration：omitted Definition of respiratory movement: the cyclic contraction and distension of the thorax induced by the movement of respiratory muscles.,Respiratory Muscles,Inspiratory muscles: diaphragm and external intercostal Expiratory muscles: abdominal recti and internal intercostal Associated muscles: scalenus, sternocleidomastoid muscle etc.,Muscles of Respiration,Occurs because the thoracic cavity changes its volume. Inspiration uses external intercostals and diaphragm. Expiration is passive at rest, but uses internal intercostals and abdominal recti during severe respiratory load. Breathing rate is 10-20 breaths/minute at rest, 40-45 at strenuous exercise in adults.,Breathing,Inspiratory Movement,The process by which the thorax is enlarged,Expiratory Movement,the process by which the volume of thorax is decreased,Supplements,Thoracic breathing Abdominal breathing Eupnea: 12-18 breath/min Forced respiration Dyspnea Artificial respiration,Intrapulmonary Pressure,The pressure of air in airways and alveoli normal range: -1mmHg +1mmHg 1cm H2O=500ml,Resistances to Ventilation,Elastic resistances: 70% In-elastic resistances: 30% airway resistance (friction) viscous resistance inertial resistance,Elastic Resistance,Definition: the contracting force of elastic tissue induced by being lengthened. Elasticity: Compliance: the reciprocal of the elasticity of elastic tissues (Inversely related to elastic resistance).,Compliance of the Lungs,Definition: the ratio of V of the lungs and P of the transpulmonary pressure Calculation: CL=V/P (L/cmH2O) Normal Value: 200ml/cm H2O,0,100,50,0,30,Lung Volume (%TLC),Transpulmonary Pressure (cmH2O),Static Lung Compliance,C = DV/DP,Inflation,Deflation,Normal Breathing,1. CL can be changed markedly with different distension of the lungs. 2. CL= the slope at different dots. 3. The higher slope, the higher CL, the smaller elastic resistance.,Elastic resistance of the lungs is always one of the resistance to inspiration and the driving force to expiration at the same time.,Elastic Resistance and Compliance of thorax,CT=V/P (L/cmH2O) Normal: 200ml/cmH2O,Calculation of total compliance: 1/Cs=1/CL+1/CT 1/Cs=1/0.2+1/0.2 Cs=0.1L/cmH2O.,Inelastic Resistances The inelastic resistances comprises the airway resistance (friction) and pulmonary tissue resistance (viscosity, and inertia). Airway resistance is by far the more important both in health and disease. It account for 80%-90% of the inelastic resistances.,Airway Resistance,Airway resistance is the resistance to flow of air in the airways and is due to frictional force: 1) intermolecular friction of gas 2) friction between gas molecules and the walls of the airways (trachea and primary bronchia).,Supplements,Inversely proportional to the cross-sectional area,Types of Flow,Laminar Flow,Laminar Flow: when concentric layers of gas flow parallel to the wall of the tube, the velocity profile obeys Poiseuilles Law.,Poiseuilles Law and Resistance,Airway Radius or Diameter is the KEY. radius by resistance by 16-fold; - think bronchodilator here!,Major sources of the airway resistances Nasal cavity and glottis: 75%。 Trachea and large bronchioles: 15% Small bronchioles: 10%,Airway-resistance-increasing Factors,Any factors that decreases airway diameter, or increases turbulence will increase airway resistance, eg: Rapid Breathing: because air velocity and hence turbulence increases; Narrowed Airways: asthma, parasympathetic stimulation, etc. Emphysema: which decreases small airway diameter during forced expiration.,Control of Airway Smooth Muscle,Smooth muscles of bronchi is controled by sympathetic, parasymthetic nerves and chemicals Neural Control: Adrenergic 2-Receptors: dilatation; Parasympathetic-muscarinic receptors: constriction;,Control of Airway Smooth Muscle,Local Factors: Histamine: H1 receptors-constriction; Histamine: H2 receptors-dilation; Slow reactive substance of anaphylaxsis-constriction-allergic response to pollen; Prostaglandins E series- dilation; Prostaglandins F series- constriction.,Control of Airway Smooth Muscle,Environmental Pollution: smoke, dust, sulfur dioxide, some acidic elements in smog; Elicit constriction of airways mediated by: parasympathetic reflex local constrictor responses,In some diseases, airway resistance can be changed markedly,Pulmonary Volumes and Pulmonary Capacities,Pulmonary Volumes,1) Tidal Volume (TV): Volume of air inspired or expired during a normal quiet inspiration or expiration (400500 ml). Ralatively constant. 2) Inspiratory Reserve Volume (IRV): maximum extra volume of air that can be inspired over and above the normal tidal volume (15002000 ml). Decreased in fibrosis, emphysema etc.,3) Expiratory Reserve Volume (ERV): maximum extra volume of air that can be expired by forceful expiration after the end of a normal tidal expiration (9001200 ml). Decreased in emphysema etc. 4) Residual Volume (RV): Volume of air remaining in respiratory passages and lungs after the most forceful expiration (1500 ml in male and 1000 ml in female). Increased in emphysema; Decreased in fibrosis.,Pulmonary Capacities,1) Inspiratory Capacity (IC): the amount of air a person can breathe in, beginning at the normal quiet expiratory level and distending lungs to the maximum amount. Tidal volume plus inspiratory reserve volume. Decreased in fibrosis and emphysema.,2) Functional Residual Capacity (FRC): amount of air that remains in lungs at the end of normal quiet expiration. Expiratory reserve volume plus the residual volume. Increased in emphysema; Decreased in fibrosis,3) Vital Capacity (VC): maximum amount of air a person can expel from lungs after first filling the lungs to their maximum extent and then expiring to the maximum extent. Sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume. Decreased in fibrosis, emphysema, COPD.,4) Total Lung Capacity (TLC): maximum volume to which the lungs can be expanded with the greatest possible effort. Sum of inspiratory and expiratory reserve volumes plus the tidal volume and residual volume. Decreased in fibrosis, emphysema, COPD.,5) Forced Vital Capacity (FVC),Inspire as much air as possible first (to the maximum extent), then expire the inspired air as forcefully, quickly and much as possible, the maximum volume of air that can be expired means FVC (slightly smaller than vital capacity). Represent the airway resistences and complience of the lungs better. Normal Values: 4L (decreases with aging).,Significantly decreased FVC suggests damages to lung parenchyma: Restrictive lung disease (fibrosis) Obstructive lung diseased (acute asthma/COPD) Constructive lung disease (emphysema) Loss of functional alveoli (atelectasis),6) Forced Expiratory Volume (FEV),Inspire as much air as possible first (to the maximum extent), then expire the inspired air as forcefully, quickly as possible, the maximum volumes of air that can be expired within 1s, 2s and 3s means FEV1, FEV2, FEV3 respectively. Should be normalized as ratios of FEV1/FVC, FEV2/FVC, FEV3/FVC. Represent the airway resistence and complience of the lungs best.,Normals for FEV1/FVC, FEV2/FVC, FEV3/FVC: FEV1/FVC = 0.83; FEV2/FVC = 0.96; FEV3/FVC = 0.99. Decreased ratios of FEV1/FVC, FEV2/FVC and FEV3/FVC (especially reduced FEV1/FVC) suggests obstructive damages to the airways: Acute obstruction: Asthma (reversible), can be treated with bronchodilators. Chronic obstruction: Chronic obstructive pulmonary disease (COPD, irreversible), can not be treated with bronchodilators.,Obstructive Lung Diseases,Diseases with reduced radius of the airways and markedly increased airway resistance (asthma / bronchitis) Resistance is inversely related to r4,FEV1 80% of FVC,Obstructive Lung Diseases,Restrictive Lung Diseases,Diseases that reduce the effective surface area available for gas exchange (fibrosis),Minute Ventilation Volume and Alveolar Ventilation volume,Minute ventilation volume: Total amount of air moved into and out of respiratory system per minute (TVRT, 6000-9000ml). Minute maximal respiratory volume: Inspire air as forcefully, quickly as possible, the maximum volumes of air that can be inspired into the lungs each minute (70-120L/min).,Respiratory rate (RR): times of breaths per minute. Dead space (DS): Part of respiratory system where gas exchange does not take place. Minute alveolar ventilation volume: total volume of fresh air entering the alveoli and adjacent gas exchange areas each minute. (TVDS)RR.,Dead Space,Definition: Area where gas exchange cannot occur. Includes most of airway volume Anatomical dead space (=150 ml) Airways Alveolar dead space(=0) Physiological dead space= anatomical + alveolar dead space,RR TV DS MVV AVV (times/min) (ml) (ml) (ml) (ml) 16 500 150 8000 5600 8 1000 150 8000 6800 32 250 150 8000 3200,Section 2 Respiratory Gases Exchange,Physical Principles of Gas Exchange,Partial pressure of gases The pressure exerted by each type of gas in a mixture. Diffusion of gases through liquids Concentration of a gas in a liquid is determined by its partial pressure and its solubility coefficient.,Partial Pressures of Gases,Basic Composition of Air 79% Nitrogen 21 % Oxygen,Pgas=PbFgas PN2=7600.79=600.4 mmHg P02=7600.21=159.6 mmHg,Partial Pressure of Gases in Fluids,Each gas has a specific solubility O2 Solubility Coefficient = 0.003 ml/100 ml Blood C02 = 0.06 ml/100 ml Blood ( 20 of 02),Gases dissolve in fluids by moving down a partial pressure gradient rather than a concentration gradient.,Partial Pressure of Gases in Fluids,At equilibrium, if the gas phase has a PO2 = 100 mm Hg, the liquid phase also has a PO2 = 100 mm Hg,The mechanism of gas exchange between the alveoli and pulmonary capillaries and eventually from the capillaries to the tissues-Diffusion; Gases diffuse from area of conc. (pp) to conc. (pp); Diffusion depends on perfusion and the partial pressure (pp) exerted by each gas;,Gas Exchange in the Lungs and the Tissues,PO2 and PCO2 in Blood,O2 and CO2 Diffusion Gradients,Oxygen The lungs: Moves from alveoli into blood. Blood is almost completely saturated with oxygen when it leaves the capillary. The tissues: Oxygen moves from tissue capillaries into the tissues.,Carbon Dioxide The tissues: Moves from tissues into tissue capillaries; The lungs: Moves from pulmonary capillaries into the alveoli.,Factors that affect gas exchange （1）Pressure difference（P） （2）Molecular weight（MW） （3）Solubility（S）； （4）Area（A） （5）Distance（d） （6）Temperature（T),P A T S Diffussion = d MW,Ventilation/perfusion ratio (VA/Q; V/Q) The ratio of alveolar ventilation per minute （VA） and alveolar blood flow per minute （Q）.,Both of ventilation and perfusion are better at the base of the lungs than that at the apex, but the changes in blood flow are more steep than that in ventilation. Therefore, V/Q ratio rises sharply from the base to the apex.,Normal: 0.84,Pulmonary diffusion capacity (DL) : The volume of a gas that cross the respiratory membrane and enters the blood per minute driven by the pressure difference of 1mmHg. DL=V/(PA-PC) V: ml/min PA: partial pressure in alveoli. PC: partial pressure in pulmonary capillaries Normal：DL(O2): 20ml/min/Kpa; DL(CO2): 400ml/min/Kpa.,Factors Affecting Gas Diffusion in Lungs,Properties of the Gas Molecular Weight. Diffusion rate is inversely proportional to the square root of the molecular weight; Temperature-kinetic motion of molecules; Solubility coefficient in water. Each gas has a specific solubility: O2 solubility coefficient = 0.003 ml 02/100 ml blood; CO2 = 0.06 ml/100 ml blood ( 20 of O2),2. Partial Pressure of the Gases Alveoli Ventilation; Blood Perfusion in Lung Capillary; Speed of the Chemical Reaction. slow chemical reaction HCO3- + H+ - H2CO3 -H2O + CO2 reduces the exchange of CO2 in the lungs. So, during the gas exchange in external respiration, the exchange of CO2 is a little lower than that of O2.,3. Properties of the Lung Area of the Respiratory Membrane (Definition: the membranous structure that gases must cross during gas exchange, six layers). Distance of the Diffusion (thickness of RM); Viscosity of the Medium (fluid).,Internal Respiration,All cells require O2 for metabolism; All cells require means to remove formed CO2; Gas exchanges also occur at cellular level.,Concept of Internal Respiration : Gas exchanges between the capillary and the tissues throughout the body. Mechanism: Simple Diffusion. Factors Affecting Internal Respiration: Distance between cells and capillary; Metabolic Rate; Speed of the Blood Flow in Capillary.,Section 3 Gas Transport in Blood,Two Forms of Ex