Respiratory Respiratory physiology:physiology:

RespirationRespiration

VentilationVentilation: Movement of air into : Movement of air into and out of lungsand out of lungs

External respirationExternal respiration: Gas exchange : Gas exchange between air in lungs and bloodbetween air in lungs and blood

Transport of oxygen and carbon Transport of oxygen and carbon dioxide in the blooddioxide in the blood

Internal respirationInternal respiration: Gas exchange : Gas exchange between the blood and tissuesbetween the blood and tissues

Respiratory System Respiratory System Functions Functions

Gas exchangeGas exchange: Oxygen enters blood and : Oxygen enters blood and carbon dioxide leavescarbon dioxide leaves

Regulation of blood pHRegulation of blood pH: Altered by : Altered by changing blood carbon dioxide levelschanging blood carbon dioxide levels

Voice productionVoice production: Movement of air past : Movement of air past vocal folds makes sound and speechvocal folds makes sound and speech

OlfactionOlfaction: Smell occurs when airborne : Smell occurs when airborne molecules drawn into nasal cavitymolecules drawn into nasal cavity

ProtectionProtection: Against microorganisms by : Against microorganisms by preventing entry and removing thempreventing entry and removing them

Respiratory System Respiratory System DivisionsDivisions

Upper tractUpper tract Nose, pharynx Nose, pharynx

and associated and associated structuresstructures

Lower tractLower tract Larynx, Larynx,

trachea, trachea, bronchi, lungsbronchi, lungs

Nasal Cavity and Nasal Cavity and PharynxPharynx

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 Humidifies, warms

airair SmellSmell Along with paranasal Along with paranasal

sinuses are sinuses are resonating chambers resonating chambers for speechfor speech

PharynxPharynx Common opening Common opening

for digestive and for digestive and respiratory systemsrespiratory systems

Three regionsThree regions NasopharynxNasopharynx OropharynxOropharynx LaryngopharynxLaryngopharynx

LarynxLarynx

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

material from moving into larynxmaterial from moving into larynx Vocal folds are primary source of sound productionVocal folds are primary source of sound production

Vocal FoldsVocal Folds

TracheaTrachea

WindpipeWindpipe Divides Divides

to formto form Primary Primary

bronchibronchi CarinaCarina: :

Cough Cough reflexreflex

Tracheobronchial TreeTracheobronchial Tree

Conducting zoneConducting zone Trachea to terminal bronchioles Trachea to terminal bronchioles

which is ciliated for removal of debriswhich is ciliated 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

Fig. 4. Effects of Fig. 4. Effects of methacholine on depth of methacholine on depth of airwayairway

surface liquid. surface liquid. aa: control : control tissue not exposed to tissue not exposed to methacholine.methacholine.

bb: 2-min methacholine : 2-min methacholine exposure. Putativeexposure. Putative

sol and mucous gel are sol and mucous gel are clearly visible. clearly visible. cc: 30-min: 30-min

exposure. Tissues were exposure. Tissues were radiant etched for 20 s to radiant etched for 20 s to 11

min. Scale bar 5 20 μm.min. Scale bar 5 20 μm.

From From Am. J. Physiol. Am. J. Physiol. 274 274 ((Lung Cell. Mol. Physiol. Lung Cell. Mol. Physiol. 18): L388–L395, 1998.—18): L388–L395, 1998.—

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

Thoracic WallsThoracic WallsMuscles of RespirationMuscles of Respiration

Thoracic VolumeThoracic Volume

PleuraPleura

Pleural fluid produced by pleural Pleural fluid produced by pleural membranesmembranes Acts as lubricantActs as lubricant Helps hold parietal and visceral pleural Helps hold parietal and visceral pleural

membranes togethermembranes together

VentilationVentilation

Movement of air into and out of Movement of air into and out of lungslungs

Air moves from area of higher Air moves from area of higher pressure to area of lower pressurepressure to area of lower pressure

Pressure is inversely related to Pressure is inversely related to volumevolume

Alveolar Pressure Alveolar Pressure ChangesChanges

Changing Alveolar Changing Alveolar VolumeVolume

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 Surfactant: Reduces tendency of lungs to

collapsecollapse

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

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 The greater the compliance, the easier it

is for a change in pressure to cause is for a change in pressure to cause expansionexpansion

A lower-than-normal compliance means A lower-than-normal compliance means the lungs and thorax are harder to expandthe lungs and thorax are harder to expand Conditions that decrease complianceConditions that decrease compliance

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

Pulmonary VolumesPulmonary Volumes Tidal volumeTidal volume

Volume of air inspired or expired during a normal Volume of air inspired or expired during a normal inspiration or expirationinspiration or expiration

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

normal tidal volumenormal tidal volume

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

normal tidal volumenormal tidal volume

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

lungs after the most forceful expirationlungs after 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, Sum of inspiratory reserve volume, tidal volume,

and expiratory reserve volumeand expiratory reserve volume

Total lung capacityTotal lung capacity Sum of inspiratory and expiratory reserve volumes Sum of inspiratory and expiratory reserve volumes

plus the tidal volume and residual volumeplus the tidal 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 : Total amount of air moved into and out of respiratory system moved into and out of respiratory system per minuteper minute

Respiratory rate or frequencyRespiratory rate or frequency: Number of : Number of breaths taken per minutebreaths taken per minute

Anatomic dead spaceAnatomic dead space: Part of respiratory : Part of respiratory system where gas exchange does not take system where gas exchange does not take placeplace

Alveolar ventilationAlveolar ventilation: How much air per : How much air per minute enters the parts of the respiratory minute enters the parts of the respiratory system in which gas exchange takes placesystem in which gas exchange takes place

Physical Principles of Physical Principles of Gas ExchangeGas Exchange

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

a mixturea mixture 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 Concentration of a gas in a liquid is

determined by its partial pressure and its determined by its partial pressure and its solubility coefficientsolubility coefficient

Henry’s lawHenry’s law

Physical Principles of Physical Principles of Gas ExchangeGas Exchange

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

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

Relationship between ventilation Relationship between ventilation and pulmonary capillary flowand pulmonary capillary flow Increased ventilation or increased pulmonary Increased ventilation or increased pulmonary

capillary blood flow increases gas exchangecapillary blood flow increases gas exchange Physiologic shunt is deoxygenated blood Physiologic shunt is deoxygenated blood

returning from lungsreturning from lungs

Oxygen and Carbon Oxygen and Carbon Dioxide Dioxide

Diffusion GradientsDiffusion Gradients OxygenOxygen

Moves from alveoli Moves from alveoli into blood. Blood is into blood. Blood is almost completely almost completely saturated with oxygen saturated with oxygen when it leaves the when it leaves the capillarycapillary

P0P022 in blood decreases in blood decreases because of mixing because of mixing with deoxygenated with deoxygenated bloodblood

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

Carbon dioxideCarbon dioxide Moves from Moves from

tissues into tissue tissues into tissue capillariescapillaries

Moves from Moves from pulmonary pulmonary capillaries into capillaries into the alveolithe alveoli

Changes in Partial Changes in Partial PressuresPressures

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 that hemoglobin is almost completely saturated when P0saturated when P022 is 80 mm Hg or above. is 80 mm Hg or above. At lower partial pressures, the hemoglobin At lower partial pressures, the hemoglobin releases oxygen.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, increase in pH, a decrease in carbon dioxide, or a decrease in temperature results in an or a decrease in temperature results in an increase in the ability of hemoglobin to hold increase in the ability of hemoglobin to hold oxygenoxygen

Hemoglobin and Hemoglobin and Oxygen TransportOxygen Transport

A shift of the curve to the right because of A shift of the curve to the right because of a decrease in pH, an increase in carbon a decrease in pH, an increase in carbon dioxide, or an increase in temperature dioxide, or an increase in temperature results in a decrease in the ability of results in a decrease in the ability of hemoglobin to hold oxygenhemoglobin to hold oxygen

The substance 2.3-bisphosphoglycerate The substance 2.3-bisphosphoglycerate increases the ability of hemoglobin to increases the ability of hemoglobin to release oxygenrelease oxygen

Fetal hemoglobin has a higher affinity for Fetal hemoglobin has a higher affinity for oxygen than does maternaloxygen than does maternal

Oxygen-HemoglobinOxygen-HemoglobinDissociation Curve at Dissociation Curve at

RestRest

Bohr effect:Bohr effect:

Temperature effects:Temperature effects:

Shifting the CurveShifting the Curve

Transport of Carbon Transport of Carbon DioxideDioxide

Carbon dioxide is transported as Carbon dioxide is transported as bicarbonate ions (70%) in combination with bicarbonate ions (70%) in combination with blood proteins (23%) and in solution with blood proteins (23%) and in solution with plasma (7%)plasma (7%)

Hemoglobin that has released oxygen binds Hemoglobin that has released oxygen binds more readily to carbon dioxide than more readily to carbon dioxide than hemoglobin that has oxygen bound to it hemoglobin that has oxygen bound to it (Haldane effect)(Haldane effect)

In tissue capillaries, carbon dioxide In tissue capillaries, carbon dioxide combines with water inside RBCs to form combines with water inside RBCs to form carbonic acid which dissociates to form carbonic acid which dissociates to form bicarbonate ions and hydrogen ionsbicarbonate ions and hydrogen ions

Transport of Carbon Transport of Carbon DioxideDioxide

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 ions move out. Bicarbonate ions combine with hydrogen ions to form carbonic acid. with hydrogen ions to form carbonic acid. The carbonic acid is converted to carbon The carbonic acid is converted to carbon dioxide and water. The carbon dioxide dioxide and water. The carbon dioxide diffuses out of the RBCs.diffuses out of the RBCs.

Increased plasma carbon dioxide lowers Increased plasma carbon dioxide lowers blood pH. The respiratory system regulates blood pH. The respiratory system regulates blood pH by regulating plasma carbon blood pH by regulating plasma carbon dioxide levelsdioxide levels

COCO22 Transport and Cl Transport and Cl-- MovementMovement

Ventilation-perfusion Ventilation-perfusion coupling:coupling:

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 Ventral groups stimulate the intercostal

and abdominal musclesand abdominal muscles Pontine (pneumotaxic) respiratory Pontine (pneumotaxic) respiratory

groupgroup Involved with switching between Involved with switching between

inspiration and expirationinspiration and expiration

Respiratory Structures in Respiratory Structures in BrainstemBrainstem

Rhythmic VentilationRhythmic Ventilation Starting inspirationStarting inspiration

Medullary respiratory center neurons are continuously Medullary respiratory center neurons are continuously activeactive

Center receives stimulation from receptors and simulation Center receives stimulation from receptors and simulation from parts of brain concerned with voluntary respiratory from parts of brain concerned with voluntary respiratory movements and emotionmovements and emotion

Combined input from all sources causes action potentials Combined input from all sources causes action potentials to stimulate respiratory musclesto stimulate 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 Neurons stimulating also responsible for stopping

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

Modification of Modification of VentilationVentilation

Cerebral and Cerebral and limbic systemlimbic system Respiration can Respiration can

be voluntarily be voluntarily controlled and controlled and modified by modified by emotionsemotions

Chemical controlChemical control Carbon dioxide is Carbon dioxide is

major regulatormajor regulator Increase or decrease Increase or decrease

in pH can stimulate in pH can stimulate chemo- sensitive area, chemo- sensitive area, causing a greater rate causing a greater rate and depth of and depth of respirationrespiration

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

Modifying RespirationModifying Respiration

Regulation of Blood pH Regulation of Blood pH and Gasesand Gases

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

AdultsAdults Reflex important only when tidal volume Reflex important only when tidal volume

large as in exerciselarge as in exercise

Ventilation in ExerciseVentilation in Exercise Ventilation increases abruptlyVentilation increases abruptly

At onset of exerciseAt onset of exercise Movement of limbs has strong influenceMovement of limbs has strong influence Learned componentLearned component

Ventilation increases graduallyVentilation increases gradually After immediate increase, gradual increase After immediate increase, gradual increase

occurs (4-6 minutes)occurs (4-6 minutes) Anaerobic threshold is highest level of Anaerobic threshold is highest level of

exercise without causing significant exercise without causing significant change in blood pHchange in blood pH If exceeded, lactic acid produced by skeletal If exceeded, lactic acid produced by skeletal

musclesmuscles

Effects of AgingEffects of Aging

Vital capacity and maximum minute Vital capacity and maximum minute ventilation decreaseventilation decrease

Residual volume and dead space Residual volume and dead space increaseincrease

Ability to remove mucus from Ability to remove mucus from respiratory passageways decreasesrespiratory passageways decreases

Gas exchange across respiratory Gas exchange across respiratory membrane is reducedmembrane is reduced