Respiratory System - Physiology

Respiratory System - Physiology

1. PHYSIOLOGY OF
RESPIRATORY SYSTEM

2. Respiratory System Functions
1.Supplies the body with oxygen and
disposes of carbon dioxide
2.Filters inspired air
3.Produces sound
4.Clears the body from excess water and
heat
5.Control blood pH

3. •Primaryfunctionistoobtainoxygenforuse
bybody'scells&eliminatecarbondioxide
thatcellsproduce

4. Breathing
•Breathing (pulmonary ventilation). consists
of two cyclic phases:
•Inhalation, also called inspiration -draws gases
into the lungs.
•Exhalation,also called expiration -forces gases
out of the lungs.

5. Respiratory events
•Pulmonaryventilation=exchangeofgases
betweenlungsandatmosphere
•Externalrespiration=exchangeofgases
betweenalveoliandpulmonarycapillaries
•Internalrespiration=exchangeofgases
betweensystemiccapillariesandtissuecells

7. Phases of pulmonary ventilation
•Inspiration,orinhalation-Averyactiveprocess
thatrequiresinputofenergy.Thediaphragm
contracts,movingdownwardandflattening.
•Expiration,orexhalation-Apassiveprocessthat
takesadvantageoftherecoilpropertiesofelastic
fiber.Thediaphragmrelaxes.Theelasticityofthe
lungsandthethoraciccageallowsthemtoreturn
totheirnormalsizeandshape.
•Thistwoprocessesarehappenswhenphrenic
nervesStimulates.

8. LUNG VOLUMES
•Minuteventilation(MV):MV12breaths/min500mL
/breath=6liters/min.totallungcapacity.
•TIDALVOLUME(TV):Volumeinspiredorexpiredwitheach
normal/breath.=500ml
•INSPIRATORYRESERVEVOLUME(IRV):Maximumvolumethat
canbeinspiredovertheinspirationofatidalvolume/normal
breath.Usedduringexercise/exertion.=Male3100ml/Female
1900ml
•EXPIRATRYRESERVEVOLUME(ERV):Maximalvolumethat
canbeexpiredaftertheexpirationofatidalvolume/normal
breath.=Male1200ml/Female700ml
•RESIDUALVOLUME(RV):Volumethatremainsinthelungs
afteramaximalexpiration.Male1200ml/Female1100ml

9. •Inspiratorycapacityisthesumoftidalvolumeand
inspiratoryreservevolume,IRV+TV(500ml3100ml
3600mlinmalesand500ml1900ml2400mlin
females).
•Functionalresidualcapacityisthesumofresidual
volumeandexpiratoryreservevolume,ERV+RV(1200ml
1200ml2400mlinmalesand1100ml700ml1800mlin
females).
•Vitalcapacityisthesumofinspiratoryreservevolume,
tidalvolume,andexpiratoryreservevolume,IRV+TV+
ERV=IC+ERV(4800mlinmalesand3100mlinfemales).
•Totallungcapacityisthesumofvitalcapacityand
residualvolumeIRV+TV+ERV+RV=IC+FRC(4800ml
1200ml6000mlinmalesand3100ml1100ml4200ml
infemales).

11. Physiology of respiration
The process of gas exchange in the body, called respiration, it has three
basic steps:
1.Pulmonaryventilationorbreathing
–Itistheinhalation(inflow)andexhalation(outflow)ofairand
involvestheexchangeofairbetweentheatmosphereandthealveoli
ofthelungs.
2.External(pulmonary)respiration
–Itistheexchangeofgasesbetweenthealveoliofthelungsandthe
bloodinpulmonarycapillariesacrosstherespiratorymembrane.
–Inthisprocess,pulmonarycapillarybloodgainsO
2andlosesCO
2.
3.Internal(tissue)respiration
–Itistheexchangeofgasesbetweenbloodinsystemiccapillaries
andtissuecells.InthisstepthebloodlosesO
2andgainsCO
2.Within
cells,themetabolicreactionsthatconsumeO
2andgiveoffCO
2
duringtheproductionofATParetermedcellularrespiration

12. Inhalation
•Breathinginiscalledinhalation(inspiration)
•Eachinhalation,theairpressureinsidethelungsisequal
totheairpressureoftheatmosphere,whichisabout760
mmHg.
•Airtoflowintothelungs,thepressureinsidethealveoli
mustbecomelowerthantheatmosphericpressure.
•Thisconditionisachievedbyincreasingthesizeofthe
lungs.

13. Exhalation
Breathingoutorexhalationstartswhentheinspiratorymusclesrelax.As
thediaphragmrelaxes,itsdomemovessuperiorlyowingtoitselasticity.
Astheexternalintercostalsrelax,theribsaredepressed.
•Thepressureinthelungsisgreaterthanthepressureofthe
atmosphere.Normalexhalationduringquietbreathing
•Itisapassiveprocessbecausenomuscularcontractionsareinvolved.
Instead,exhalationresultsfromelasticrecoilofthechestwalland
lungs,bothofwhichhaveanaturaltendencytospringbackafterthey
havebeenstretched.
•Twoinwardlydirectedforcescontributetoelasticrecoil:
a.Therecoilofelasticfibersthatwerestretchedduringinhalation
b.Theinwardpullofsurfacetensionduetothefilmofalveolarfluid.

15. External respiration or pulmonary
gas exchange
•ItisthediffusionofO
2fromairinthealveoliofthelungstobloodin
pulmonarycapillariesandthediffusionofCO
2intheopposite
direction.
•Externalrespirationinthelungsconvertsdeoxygenatedblood
(depletedofsomeO
2)comingfromtherightsideoftheheartinto
oxygenatedblood(saturatedwithO
2)thatreturnstotheleftsideof
theheart.
•Asbloodflowsthroughthepulmonarycapillaries,itpicksupO
2from
alveolarairandunloadsCO
2intoalveolarair,thisprocessiscalledan
“exchange”ofgases,thisprocessiscarriedbydiffusion.

16. Internal respiration
Theleftventriclepumpsoxygenatedblood
intotheaortaandthroughthesystemic
arteriestosystemiccapillaries.Theexchange
ofO
2andCO
2betweensystemiccapillaries
andtissuecellsiscalledinternalrespiration
orsystemicgasexchange

17. Oxygen Transport
•Oxygendoesnotdissolveeasilyinwater,soonlyabout
1.5%ofinhaledO
2isdissolvedinbloodplasma,whichis
mostlywater.About98.5%ofbloodO
2isboundto
hemoglobininredbloodCells.Each100mLofoxygenated
bloodcontainstheequivalentof20mLofgaseousO
2.
•Thehemeportionofhemoglobincontainsfouratomsof
iron,eachcapableofbindingtoamoleculeofO
2.The
98.5%oftheO
2thatisboundtohemoglobin.Oxygenand
hemoglobinbindinaneasilyreversiblereactiontoform
oxyhemoglobin.O
2+Hgb=4HgbO
2
•Asbloodflowsthroughtissuecapillaries,theiron–oxygen
reactionreverses.Hemoglobinreleasesoxygen,which
diffusesfirstintotheinterstitialfluidandthenintocells.

18. Factors Affecting the Affinity of
Hemoglobin for Oxygen
•AlthoughPO
2isthemostimportantfactor
thatdeterminesthepercentO
2saturationof
hemoglobin.Thefollowingfourfactors
affecttheaffinityofhemoglobinforO
2:
1.Acidity (pH).
2.Partial pressure of carbon dioxide
3.Temperature.
4.2,3-bisphosphoglycerate(BPG)

19. Acidity
•Asacidityincreases(pHdecreases),the
affinityofhemoglobinforO
2decreases,and
O
2dissociatesmorereadilyfrom
hemoglobin.
•WhenH
+
ionsbindtoaminoacidsin
hemoglobin,theyalteritsstructureslightly,
decreasingitsoxygen-carryingcapacity.
Thus,loweredpHdrivesO
2offhemoglobin,
makingmoreO
2availablefortissuecells.

20. Oxygen–hemoglobin dissociation curves
showing the relationship of pH

21. Partial pressure of carbon dioxide
•CO
2enterstheblooditistemporarily
convertedtocarbonicacid(H
2CO
3).
•Itdissociatesandformhydrogenionsand
bicarbonateions.Soinredbloodcellsthe
H+concentrationincreases,pHdecreases.
Thus,anincreasedPCO
2producesamore
acidicenvironment,whichhelpsreleaseO
2
fromhemoglobin.

22. Oxygen–hemoglobin dissociation curves
showing the relationship of PCO
2

23. Temperature
•Heatisaby-productofthemetabolic
reactionsofallcells,andtheheatreleased
bycontractingmusclefiberstendstoraise
bodytemperature.Metabolicallyactivecells
requiremoreO
2andliberatemoreacidsand
heat.

24. Oxygen–hemoglobin dissociation curves
showing the effect of temperature changes.

25. 2,3-bisphosphoglycerate (BPG)
(Diphosphoglycerate)
•BPGisformedinredbloodcellswhenthey
breakdownglucosetoproduceATPina
processcalledglycolysis.WhenBPG
combineswithhemoglobin,itunloadsor
decreasesthebondingwithoxygen.

26. CO
2 Transportation
•Normalrestingconditions,each100mLof
deoxygenatedbloodcontainstheequivalent
of53mLofgaseousCO
2,whichis
transportedinthebloodinthreemain
forms
1.DissolvedCO
2.Thesmallestpercentage—
about7%—isdissolvedinbloodplasma.On
reachingthelungs,itdiffusesintoalveolarair
andisexhaled.

27. 2.Carbaminocompounds:-About23%of
CO
2,combineswiththeaminogroupsof
aminoacidsandproteinsinbloodtoform
carbaminocompounds.ThemainCO
2
bindingsitesaretheterminalaminoacids
inthetwoalphaandtwobetaglobin
chains.HemoglobinthathasboundCO
2is
termedcarbaminohemoglobin(Hb—CO
2):

28. 3.Bicarbonateions.Thegreatestpercentage
ofCO
2about70%—istransportedinblood
plasmaasbicarbonateions(HCO
3
-
).
•CO
2diffusesintosystemiccapillariesand
entersredbloodcells,itreactswithwaterin
thepresenceoftheenzymecarbonic
anhydrase(CA)toformcarbonicacid,which
dissociatesintoH
+
andHCO
3
-
.

29. CO
2Dissociation Curve
The arterial point (a) and the venous point (v)

31. Regulation of respiration
•Regulationofrespirationcontrolistherateand
depthofrespirationasperthephysiologic
demand.Controlofrespirationprimarily
involvesneuronsinthereticularformationof
themedullaandpons.Becausethemedullasets
therespiratoryrhythm.Thepurposeof
Regulationofrespirationare
1.TomaintainaconstantO
2andCO
2levelinblood
2.ItadjusttheO
2supplyasperthemetabolic
demandofthebody.
3.IthelpstoregulateacidbasebalanceorpH.

32. •Thesizeofthethoraxisalteredbytheactionofthe
respiratorymuscles,whichcontractasaresultofnerve
impulsestransmittedtothemfromcentersinthebrainand
relaxintheabsenceofnerveimpulses.Thisimpulsestravels
alongthephrenicandintercostalnervestoexcitethe
diaphragmandexternalintercostalmuscles
•Thesenerveimpulsesaresentfromclustersofneurons
locatedbilaterallyinthemedullaoblongataandponsofthe
brainstem.
•Thiswidelydispersedgroupofneurons,collectivelycalled
therespiratorycenter.

33. Mechanism of Regulation of
respiration
•There are two major mechanisms
1.Nervous regulation of respiration
2.Chemical regulation of respiration

34. 1. Nervous regulation of respiration
RespiratoryCenter
Therespiratorycentersaredividedintofour
majorgroups,twogroupsinthemedullaandtwo
inthepons.
Thetwogroupsinthemedullaare
a.Thedorsalrespiratorygroup
b.Theventralrespiratorygroup.
Thetwogroupsintheponsarethepneumotaxic
centerandtheapneusticcenteralsoknownas
thepontinerespiratorygroup.

36. •Respiratory centers can be divided into
three areas on the basis of their functions:
1.The medullary rhythmicity area in the medulla
oblongata
2.The pneumotaxicarea in the pons
3.The apneusticarea, also in the pons

38. Medullary Rhythmicity Area
•Thefunctionofthemedullary
rhythmicityareaistocontrolthe
basicrhythmofrespiration.Itincludes
twoareas
a.Inspiratorymedullaryrhythmicityareaor
inspiratorycentre
b.Expiratorymedullaryrhythmicityareaor
expiratorycentre

39. a.Inspiratorycentre:
Itestablishthebasicrhythmofbreathing.When
itsinspiratoryneuronsfire,aburstof
impulsestravelsalongthephrenicand
intercostalnervestoexcitethediaphragm
andexternalintercostalmuscles.
b.Expiratorycentre:
Impulsesfromtheexpiratoryareacause
contractionoftheinternalintercostaland
abdominalmuscles,whichdecreasesthesizeof
thethoraciccavityandcausesforceful
exhalation.

40. PneumotaxicArea
•Ittransmitsinhibitoryimpulsestothe
inspiratoryarea.Themajoreffectofthese
nerveimpulsesistohelpturnoffthe
inspiratoryareabeforethelungsbecome
toofullofair.

41. Apneusticarea
•Thisareasendsstimulatoryimpulsestothe
inspiratoryareathatactivateitandprolong
inhalation.Theresultisalong,deep
inhalation.

42. 2. Chemical regulation of respiration
•Therearethreeimportantchemicalfactors
controllingrespiration
1.ConcentrationofCO
2inblood
2.ConcentrationofH+ionsorpH
3.ConcentrationofoxygenInblood

43. Concentration of CO
2 in blood
•When CO
2concentration in blood increases,
it stimulates the chemoreceptors. There are
two group of chemoreceptors
1.Peripheral chemoreceptors –situated at the
carotid body and aortic body
2.Central chemoreceptors –situated at the
medulla oblongata

44. When CO
2concentration in blood increases
Stimulates the chemoreceptors
Transmission of sensory impulses to respiratory centers
Activation of respiratory centers
Increases the activities of respiration (rate and Depth)
Increase alveolar ventilation
Expulsion of CO
2and decreases the level of CO
2in blood

45. Concentration of H+ ions or pH
WhenConcentrationofH+ionsincreases,it
stimulatestheperipheralchemoreceptors.
H+ionsdiffuseswithCO
2andformcarbonicacid,to
crossthebloodbrainbarrierthendissociatesinto
H+andHCO
3.TherebyH+ionsstimulatesthe
centralchemoreceptorsthentherespiratorycenters,
resultingareductioninthelevelofCO
2inblood.This
willinturndecreaseconcentrationofH+inbloodor
increasethepHintonormal.

46. Concentration of oxygen In blood
When O
2concentration in blood decreases
Stimulates the peripheral chemoreceptors
Transmission of impulses to respiratory centers
Activation of respiratory centers
Increases the activities of respiration (rate and Depth)
Increase alveolar ventilation
Increases the uptake of O
2
Thereby increases the level of O
2in blood

47. Respiratory System Terminologies
•Apnea:temporarycessationofbreathing
•Tachypnea:abnormallyrapidrespirations
•Bradypnea:abnormallyslowrespiration
•Dyspnea:laboredbreathingorshortnessofbreath
•Hypoxemia:decreaseinarterialoxygentensionintheblood
•Hypoxia:decreaseinoxygensupplytothetissuesandcells
•Hypercapnia:anincreaseinthepartialpressureofcarbon
dioxideintheblood.
•Hypocapnia:adecreasedamountofcarbondioxideintheblood.
•Physiologicdeadspace:portionofthetracheobronchialtreethat
doesnotparticipateingasexchange.
•Centralcyanosis:bluishdiscolorationoftheskinormucous
membranesduetohemoglobincarryingreducedamountsof
oxygen.
•Intrapleural(intrathoracic)pressure:pressurebetweenthe
twopleurallayersinthepleuralcavity.

48. •Alveolar(intrapulmonic)pressure:Thepressurewithinthe
tinygas-exchangingstructuresofthelungs.
•Diffusion:exchangeofgasmoleculesfromareasofhigh
concentrationtoareasoflowconcentration.
•Osmosis:Thepassageofsolventthroughasemipermeable
membranethatseparatessolutionsofdifferentconcentrations.
•Dalton’slaw:(JohnDalton,Brit.chemist,1766–1844)Alaw
thatstatesthat,inamixtureofgases,thetotalpressureisequal
tothesumofthepartialpressuresofeachgas.
•Henry’slaw:(WilliamHenry,Brit.chemist,1774–1836)The
weightofagasdissolvedbyagivenvolumeofliquidata
constanttemperatureisdirectlyproportionaltothepressure.
•Boyle’slaw:(RobertBoyle,Brit.physicist,1627–1691)Alaw
statingthat,ataconstanttemperature,thevolumeofagas
variesinverselywiththepressure.

49. Normal Values
•Normal respiration: 12 –16 breaths/min
•Normal Arterial blood gas values
–pH: 7.35 –7.45
–PaO
2 : (80 to 100 mm Hg) and SaO
2(95% to
98%)
–P CO
2 : 35 –45 mm Hg
–HCO
3: 22 –27 mEq/L