Respiratory PhysiologyRespiratory Physiology

Dr.Swanny, MSc.Dr.Swanny, MSc.Integrative Teaching Bloc 12Integrative Teaching Bloc 12

General learning objectivesGeneral learning objectives

After studying this section, you will be able to:After studying this section, you will be able to:1.1. Understand and describe the basic process Understand and describe the basic process

that responsible for respiratory tract to be that responsible for respiratory tract to be functioning well.functioning well.

2.2. Understand the pathogenesis of respiratory Understand the pathogenesis of respiratory insufficiency.insufficiency.

3.3. Use and apply the basic physiology knowledge Use and apply the basic physiology knowledge to recognize and diagnose and treat the to recognize and diagnose and treat the respiratory disorders. respiratory disorders.

An Illustrative caseAn Illustrative case

Mr. A, a 65-year old man, is diagnosed Mr. A, a 65-year old man, is diagnosed having EMPHYSEMA by his doctor. He is having EMPHYSEMA by his doctor. He is a heavy smoker for nearly 45 years.a heavy smoker for nearly 45 years.

Explanation of the caseExplanation of the case

EmphysemaEmphysema..Literally means excess air in the lungs.Literally means excess air in the lungs.Is a name given to disease in which AIR Is a name given to disease in which AIR

EXCHANGE is impaired by narrowing of EXCHANGE is impaired by narrowing of the airways.the airways.

Is an example of respiratory insufficiency Is an example of respiratory insufficiency Structure and Function disturbances.Structure and Function disturbances.

Structure impairedStructure impaired

Can be detected in:Can be detected in:

RadiographRadiograph Lung tomographyLung tomography Post mortem Post mortem

POST MORTEM of Smoker lungPOST MORTEM of Smoker lung

RespirationRespiration

VentilationVentilation: Movement of air into and : Movement of air into and out of lungsout of lungsExternal respirationExternal respiration: Gas exchange : Gas exchange between air in lungs and bloodbetween air in lungs and bloodTransport of oxygen and carbon dioxide Transport of oxygen and carbon dioxide in the bloodin the bloodInternal respirationInternal respiration: Gas exchange : Gas exchange between the blood and tissuesbetween the blood and tissues

Respiratory System Functions Respiratory System Functions Gas exchangeGas exchange: Oxygen enters blood and : Oxygen enters blood and carbon dioxide leavescarbon dioxide leavesRegulation of blood pHRegulation of blood pH: Altered by changing : Altered by changing blood carbon dioxide levelsblood carbon dioxide levelsVoice productionVoice production: Movement of air past vocal : Movement of air past vocal folds makes sound and speechfolds makes sound and speechOlfactionOlfaction: Smell occurs when airborne : Smell occurs when airborne molecules drawn into nasal cavitymolecules drawn into nasal cavityProtectionProtection: Against microorganisms by : Against microorganisms by preventing entry and removing thempreventing entry and removing them

Respiratory System DivisionsRespiratory System Divisions

Upper tractUpper tract– Nose, pharynx Nose, pharynx

and associated and associated structuresstructures

Lower tractLower tract– Larynx, trachea, Larynx, trachea,

bronchi, lungsbronchi, lungs

Nasal Cavity and PharynxNasal Cavity and Pharynx

Nose and PharynxNose and Pharynx

NoseNose– External noseExternal nose– Nasal cavityNasal cavity

FunctionsFunctions– Passageway for airPassageway for air– Cleans the airCleans the air– Humidifies, warms airHumidifies, warms air– SmellSmell– Along with paranasal Along with paranasal

sinuses are sinuses are resonating chambers resonating chambers for speechfor speech

PharynxPharynx– Common opening for Common opening for

digestive and digestive and respiratory systemsrespiratory systems

– Three regionsThree regionsNasopharynxNasopharynxOropharynxOropharynxLaryngopharynxLaryngopharynx

LarynxLarynx

FunctionsFunctions– Maintain an open passageway for air movementMaintain an open passageway for air movement– Epiglottis and vestibular folds prevent swallowed material Epiglottis and vestibular folds prevent swallowed material

from moving into larynxfrom moving into larynx– Vocal folds are primary source of sound productionVocal folds are primary source of sound production

Vocal FoldsVocal Folds

TracheaTrachea

WindpipeWindpipeDivides to Divides to formform– Primary Primary

bronchibronchi– CarinaCarina: :

Cough Cough reflexreflex

Tracheobronchial TreeTracheobronchial Tree

Conducting zoneConducting zone– Trachea to terminal bronchioles which is Trachea to terminal bronchioles which is

ciliated for removal of debrisciliated for removal of debris– Passageway for air movementPassageway for air movement– Cartilage holds tube system open and Cartilage holds tube system open and

smooth muscle controls tube diametersmooth muscle controls tube diameter

Respiratory zoneRespiratory zone– Respiratory bronchioles to alveoliRespiratory bronchioles to alveoli– Site for gas exchangeSite for gas exchange

Tracheobronchial TreeTracheobronchial Tree

Bronchioles and AlveoliBronchioles and Alveoli

Alveolus and Respiratory Alveolus and Respiratory MembraneMembrane

Structure of Respiratory SystemStructure of Respiratory System

The structure can be imagined as:The structure can be imagined as:Covering the surface of a racquetball court Covering the surface of a racquetball court

(about 75 m2) with thin plastic wrap, and (about 75 m2) with thin plastic wrap, and stuffing it into a 3- liter soft drink bottle.stuffing it into a 3- liter soft drink bottle.

Structure and function relationshipStructure and function relationship

The structure serves a good relationship The structure serves a good relationship with the function.with the function.

The tremendous large surface area for gas The tremendous large surface area for gas exchange is needed to supply the trillions exchange is needed to supply the trillions of cells in the body with adequate amounts of cells in the body with adequate amounts of oxygen.of oxygen.

LungsLungs

Two lungsTwo lungs: Principal organs of respiration: Principal organs of respiration– Right lungRight lung: Three lobes: Three lobes– Left lungLeft lung: Two lobes: Two lobes

DivisionsDivisions– Lobes, bronchopulmonary segments, lobulesLobes, bronchopulmonary segments, lobules

Processes in respiratory systemProcesses in respiratory system

1. VENTILATION1. VENTILATION

2. DIFFUSION2. DIFFUSION

3. TRANSPORT3. TRANSPORT

VentilationVentilation

Movement of air into and out of lungsMovement of air into and out of lungsAir moves from area of higher pressure to Air moves from area of higher pressure to area of lower pressurearea of lower pressurePressure is inversely related to volumePressure is inversely related to volume

VENTILATIONVENTILATION

During ventilation During ventilation AIRFLOW because of AIRFLOW because of Pressure Gradients.Pressure Gradients.

FLOW = FLOW = ΔΔP / RP / R1.1. Air flow in response to a pressure Air flow in response to a pressure

gradient.gradient.2.2. Flow decreases as resistance increasesFlow decreases as resistance increases

InspirationInspiration

During inspiration, the thoracic volume During inspiration, the thoracic volume increases when skeletal muscles of the rib increases when skeletal muscles of the rib cage and diaphragm contract cage and diaphragm contract pressure pressure inside lung become lower than the inside lung become lower than the pressure of atmosphere pressure of atmosphere pressure pressure gradient gradient air flow into lung. air flow into lung.

Thoracic WallsThoracic WallsMuscles of RespirationMuscles of Respiration

Thoracic VolumeThoracic Volume

Alveolar Pressure ChangesAlveolar Pressure Changes

Changing Alveolar VolumeChanging Alveolar Volume

Lung recoilLung recoil– Causes alveoli to collapse resulting from Causes alveoli to collapse resulting from

Elastic recoil and surface tensionElastic recoil and surface tension– Surfactant: Reduces tendency of lungs to collapseSurfactant: Reduces tendency of lungs to collapse

Pleural pressurePleural pressure– Negative pressure can cause alveoli to Negative pressure can cause alveoli to

expandexpand– Pneumothorax is an opening between Pneumothorax is an opening between

pleural cavity and air that causes a loss of pleural cavity and air that causes a loss of pleural pressurepleural pressure

Alveolar PressureAlveolar Pressure

This is the pressure, measured in cm H20, This is the pressure, measured in cm H20, within the alveoli, the smallest gas within the alveoli, the smallest gas exchange units of the lung. Alveolar exchange units of the lung. Alveolar pressure is given with respect to pressure is given with respect to atmospheric pressure, which is always set atmospheric pressure, which is always set to zero. Thus, when alveolar pressure to zero. Thus, when alveolar pressure exceeds atmospheric pressure, it is exceeds atmospheric pressure, it is positive; when alveolar pressure is below positive; when alveolar pressure is below atmospheric pressure it is negative. atmospheric pressure it is negative.

Normal Breathing CycleNormal Breathing Cycle

ComplianceCompliance

Measure of the ease with which lungs Measure of the ease with which lungs and thorax expandand thorax expand– The greater the compliance, the easier it is The greater the compliance, the easier it is

for a change in pressure to cause expansionfor a change in pressure to cause expansion– A lower-than-normal compliance means the A lower-than-normal compliance means the

lungs and thorax are harder to expandlungs and thorax are harder to expandConditions that decrease complianceConditions that decrease compliance

– Pulmonary fibrosisPulmonary fibrosis– Pulmonary edemaPulmonary edema– Respiratory distress syndrome Respiratory distress syndrome

SURFACTANTSURFACTANT

Surfactant decreases the surface tension Surfactant decreases the surface tension created by the thin fluid layer between created by the thin fluid layer between alveolar cells and the air.alveolar cells and the air.

Surfactant Surfactant decrease WORK of decrease WORK of BREATHING.BREATHING.

Airway resistanceAirway resistance

Parameters that contribute to resistance is:Parameters that contribute to resistance is:1.1. The length of the system ( L ).The length of the system ( L ).2.2. The viscosity of substance flowing The viscosity of substance flowing

through the system (through the system (ηη))3.3. The radius in the system ( r )The radius in the system ( r )

R = LR = Lηη / r4 / r4

Airway resistance decreases as Airway resistance decreases as lung volume increases.lung volume increases.

Pulmonary VolumesPulmonary VolumesTidal volumeTidal volume– Volume of air inspired or expired during a normal inspiration Volume of air inspired or expired during a normal inspiration

or expirationor expiration

Inspiratory reserve volumeInspiratory reserve volume– Amount of air inspired forcefully after inspiration of normal Amount of air inspired forcefully after inspiration of normal

tidal volumetidal volume

Expiratory reserve volumeExpiratory reserve volume– Amount of air forcefully expired after expiration of normal Amount of air forcefully expired after expiration of normal

tidal volumetidal volume

Residual volumeResidual volume– Volume of air remaining in respiratory passages and lungs Volume of air remaining in respiratory passages and lungs

after the most forceful expirationafter the most forceful expiration

Pulmonary CapacitiesPulmonary Capacities

Inspiratory capacityInspiratory capacity– Tidal volume plus inspiratory reserve volumeTidal volume plus inspiratory reserve volume

Functional residual capacityFunctional residual capacity– Expiratory reserve volume plus the residual volumeExpiratory reserve volume plus the residual volume

Vital capacityVital capacity– Sum of inspiratory reserve volume, tidal volume, and Sum of inspiratory reserve volume, tidal volume, and

expiratory reserve volumeexpiratory reserve volume

Total lung capacityTotal lung capacity– Sum of inspiratory and expiratory reserve volumes plus the Sum of inspiratory and expiratory reserve volumes plus the

tidal volume and residual volumetidal volume and residual volume

Spirometer and Lung Spirometer and Lung Volumes/CapacitiesVolumes/Capacities

Minute and Alveolar Minute and Alveolar VentilationVentilation

Minute ventilationMinute ventilation: Total amount of air moved : Total amount of air moved into and out of respiratory system per minuteinto and out of respiratory system per minuteRespiratory rate or frequencyRespiratory rate or frequency: Number of : Number of breaths taken per minutebreaths taken per minuteAnatomic dead spaceAnatomic dead space: Part of respiratory : Part of respiratory system where gas exchange does not take system where gas exchange does not take placeplaceAlveolar ventilationAlveolar ventilation: How much air per minute : How much air per minute enters the parts of the respiratory system in enters the parts of the respiratory system in which gas exchange takes placewhich gas exchange takes place

Ventilation perfusion relationshipVentilation perfusion relationship

Ventilation-perfusion coupling:Ventilation-perfusion coupling:

WORK of BREATHINGWORK of BREATHING

DIFFUSIONDIFFUSIONFICK law of diffusion:FICK law of diffusion: V = A/T x D ( P1 – P2 ). V = A/T x D ( P1 – P2 ). D=Sol / √MWD=Sol / √MWV= rate of diffusionV= rate of diffusionA=areaA=areaT=thicknessT=thicknessD=diffusion constantD=diffusion constantSol=solubilitySol=solubilityMW= molecular weightMW= molecular weight

Physical Principles of Gas Physical Principles of Gas ExchangeExchange

Partial pressurePartial pressure– The pressure exerted by each type of gas in a The pressure exerted by each type of gas in a

mixturemixture– Dalton’s lawDalton’s law– Water vapor pressureWater vapor pressure

Diffusion of gases through liquidsDiffusion of gases through liquids– Concentration of a gas in a liquid is determined by Concentration of a gas in a liquid is determined by

its partial pressure and its solubility coefficientits partial pressure and its solubility coefficient– Henry’s lawHenry’s law

Physical Principles of Gas Physical Principles of Gas ExchangeExchange

Diffusion of gases through the Diffusion of gases through the respiratory membranerespiratory membrane– Depends on membrane’s thickness, the diffusion Depends on membrane’s thickness, the diffusion

coefficient of gas, surface areas of membrane, partial coefficient of gas, surface areas of membrane, partial pressure of gases in alveoli and bloodpressure of gases in alveoli and blood

Relationship between ventilation and Relationship between ventilation and pulmonary capillary flowpulmonary capillary flow– Increased ventilation or increased pulmonary capillary Increased ventilation or increased pulmonary capillary

blood flow increases gas exchangeblood flow increases gas exchange– Physiologic shunt is deoxygenated blood returning Physiologic shunt is deoxygenated blood returning

from lungsfrom lungs

Oxygen and Carbon Dioxide Oxygen and Carbon Dioxide Diffusion GradientsDiffusion Gradients

OxygenOxygen– Moves from alveoli into Moves from alveoli into

blood. Blood is almost blood. Blood is almost completely saturated completely saturated with oxygen when it with oxygen when it leaves the capillaryleaves the capillary

– P0P022 in blood decreases in blood decreases because of mixing with because of mixing with deoxygenated blooddeoxygenated blood

– Oxygen moves from Oxygen moves from tissue capillaries into tissue capillaries into the tissuesthe tissues

Carbon dioxideCarbon dioxide– Moves from tissues Moves from tissues

into tissue capillariesinto tissue capillaries– Moves from Moves from

pulmonary capillaries pulmonary capillaries into the alveoliinto the alveoli

Changes in Partial PressuresChanges in Partial Pressures

TRANSPORT OF GASTRANSPORT OF GAS

Gas transport to blood is important for Gas transport to blood is important for survival of life.survival of life.

The Law of MASS ACTION plays an The Law of MASS ACTION plays an important role in this process.important role in this process.

Changes in O2 or CO2 concentration Changes in O2 or CO2 concentration disturbs the equilibrium of reactions, disturbs the equilibrium of reactions, shifting the balance between substrate shifting the balance between substrate and products.and products.

Hemoglobin and Oxygen Hemoglobin and Oxygen TransportTransport

Oxygen is transported by hemoglobin (98.5%) Oxygen is transported by hemoglobin (98.5%) and is dissolved in plasma (1.5%)and is dissolved in plasma (1.5%)Oxygen-hemoglobin dissociation curve shows Oxygen-hemoglobin dissociation curve shows that hemoglobin is almost completely saturated that hemoglobin is almost completely saturated when P0when P022 is 80 mm Hg or above. At lower partial is 80 mm Hg or above. At lower partial pressures, the hemoglobin releases oxygen.pressures, the hemoglobin releases oxygen.A shift of the curve to the left because of an A shift of the curve to the left because of an increase in pH, a decrease in carbon dioxide, or a increase in pH, a decrease in carbon dioxide, or a decrease in temperature results in an increase in decrease in temperature results in an increase in the ability of hemoglobin to hold oxygenthe ability of hemoglobin to hold oxygen

Hemoglobin and Oxygen Hemoglobin and Oxygen TransportTransport

A shift of the curve to the right because of a A shift of the curve to the right because of a decrease in pH, an increase in carbon dioxide, decrease in pH, an increase in carbon dioxide, or an increase in temperature results in a or an increase in temperature results in a decrease in the ability of hemoglobin to hold decrease in the ability of hemoglobin to hold oxygenoxygenThe substance 2.3-bisphosphoglycerate The substance 2.3-bisphosphoglycerate increases the ability of hemoglobin to release increases the ability of hemoglobin to release oxygenoxygenFetal hemoglobin has a higher affinity for oxygen Fetal hemoglobin has a higher affinity for oxygen than does maternalthan does maternal

Oxygen-HemoglobinOxygen-HemoglobinDissociation Curve at RestDissociation Curve at Rest

Bohr effect:Bohr effect:

Temperature effects:Temperature effects:

Shifting the CurveShifting the Curve

Transport of Carbon DioxideTransport of Carbon Dioxide

Carbon dioxide is transported as bicarbonate Carbon dioxide is transported as bicarbonate ions (70%) in combination with blood proteins ions (70%) in combination with blood proteins (23%) and in solution with plasma (7%)(23%) and in solution with plasma (7%)Hemoglobin that has released oxygen binds Hemoglobin that has released oxygen binds more readily to carbon dioxide than hemoglobin more readily to carbon dioxide than hemoglobin that has oxygen bound to it (Haldane effect)that has oxygen bound to it (Haldane effect)In tissue capillaries, carbon dioxide combines In tissue capillaries, carbon dioxide combines with water inside RBCs to form carbonic acid with water inside RBCs to form carbonic acid which dissociates to form bicarbonate ions and which dissociates to form bicarbonate ions and hydrogen ionshydrogen ions

Transport of Carbon DioxideTransport of Carbon Dioxide

In lung capillaries, bicarbonate ions and In lung capillaries, bicarbonate ions and hydrogen ions move into RBCs and chloride hydrogen ions move into RBCs and chloride ions move out. Bicarbonate ions combine with ions move out. Bicarbonate ions combine with hydrogen ions to form carbonic acid. The hydrogen ions to form carbonic acid. The carbonic acid is converted to carbon dioxide carbonic acid is converted to carbon dioxide and water. The carbon dioxide diffuses out of and water. The carbon dioxide diffuses out of the RBCs.the RBCs.Increased plasma carbon dioxide lowers blood Increased plasma carbon dioxide lowers blood pH. The respiratory system regulates blood pH. The respiratory system regulates blood pH by regulating plasma carbon dioxide levelspH by regulating plasma carbon dioxide levels

COCO22 Transport and Cl Transport and Cl-- Movement Movement

Respiratory Areas in Respiratory Areas in BrainstemBrainstem

Medullary respiratory centerMedullary respiratory center– Dorsal groups stimulate the diaphragmDorsal groups stimulate the diaphragm– Ventral groups stimulate the intercostal and Ventral groups stimulate the intercostal and

abdominal musclesabdominal muscles

Pontine (pneumotaxic) respiratory groupPontine (pneumotaxic) respiratory group– Involved with switching between inspiration Involved with switching between inspiration

and expirationand expiration

Respiratory Structures in BrainstemRespiratory Structures in Brainstem

Rhythmic VentilationRhythmic VentilationStarting inspirationStarting inspiration– Medullary respiratory center neurons are continuously activeMedullary respiratory center neurons are continuously active– Center receives stimulation from receptors and simulation from Center receives stimulation from receptors and simulation from

parts of brain concerned with voluntary respiratory movements and parts of brain concerned with voluntary respiratory movements and emotionemotion

– Combined input from all sources causes action potentials to Combined input from all sources causes action potentials to stimulate respiratory musclesstimulate respiratory muscles

Increasing inspirationIncreasing inspiration– More and more neurons are activatedMore and more neurons are activated

Stopping inspirationStopping inspiration– Neurons stimulating also responsible for stopping inspiration and Neurons stimulating also responsible for stopping inspiration and

receive input from pontine group and stretch receptors in lungs. receive input from pontine group and stretch receptors in lungs. Inhibitory neurons activated and relaxation of respiratory muscles Inhibitory neurons activated and relaxation of respiratory muscles results in expiration.results in expiration.

Modification of VentilationModification of Ventilation

Cerebral and limbic Cerebral and limbic systemsystem– Respiration can be Respiration can be

voluntarily controlled voluntarily controlled and modified by and modified by emotionsemotions

Chemical controlChemical control– Carbon dioxide is Carbon dioxide is

major regulatormajor regulatorIncrease or decrease in Increase or decrease in pH can stimulate pH can stimulate chemo- sensitive area, chemo- sensitive area, causing a greater rate causing a greater rate and depth of respirationand depth of respiration

– Oxygen levels in blood Oxygen levels in blood affect respiration when affect respiration when a a 50%50% or greater or greater decrease from normal decrease from normal levels existslevels exists

Modifying RespirationModifying Respiration

Regulation of Blood pH and Regulation of Blood pH and GasesGases

Herring-Breuer ReflexHerring-Breuer Reflex

Limits the degree of inspiration and Limits the degree of inspiration and prevents overinflation of the lungsprevents overinflation of the lungs– InfantsInfants

Reflex plays a role in regulating basic rhythm of Reflex plays a role in regulating basic rhythm of breathing and preventing overinflation of lungsbreathing and preventing overinflation of lungs

– AdultsAdultsReflex important only when tidal volume large as in Reflex important only when tidal volume large as in exerciseexercise

Effects of AgingEffects of Aging

Vital capacity and maximum minute Vital capacity and maximum minute ventilation decreaseventilation decreaseResidual volume and dead space increaseResidual volume and dead space increaseAbility to remove mucus from respiratory Ability to remove mucus from respiratory passageways decreasespassageways decreasesGas exchange across respiratory Gas exchange across respiratory membrane is reducedmembrane is reduced

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