IBBiology NotesforDigestion,Circulation&Respiration
A.DeJong/TFSS2009
TheinformationinthisdocumentismeanttocoverTopic6.1,6.2&6.4intheIBSyllabus.DigestionWhyisdigestionnecessary,anyway?Foodiscomposedofcarbohydrates,lipidsandproteins.Thesemacromoleculesmustbehydrolyzed(digested)beforecellscanabsorbthem.Chemicaldigestionoffoodbreaksdownmacromoleculesintotheirmonomers.
• Carbohydratesarebrokendownintosugars• Proteinsarebrokendownintoaminoacids• Fatsarebrokendownintofattyacidsandglycerol
Whyareenzymesneededfordigestion?Thehydrolysisofbiologicalmacromoleculesisaslowprocess.Enzymeslowertheactivationenergyofthesereactions,makingthemrunfaster.ExamplesofHumanDigestiveEnzymes:enzyme salivaryamylase pepsin phospholipaseA2source salivaryglands chiefcellsinstomach pancreassubstrate starch proteins phospholipidsproduct maltose polypeptide glycerol,phosphate&fattyacidsoptimumpH 7‐8 2‐3 8TheHumanDigestiveSystem
http://www.cudahychamber.com/images/digestive_system.gif
IBBiology NotesforDigestion,Circulation&Respiration
A.DeJong/TFSS2009
FunctionsofDigestiveOrgans
• Stomacho Primaryroleisstorageoffood(boluschyme)o Mechanical(physical)digestionoffoodaccomplishedbymusclecontractionand
actionofruggae;hydrochloricacidalsohasaneffecto Chemicaldigestionofproteinbegunbyactionofpepsino Carbohydrate(starch)digestioncontinues
• Smallintestineo Acidicchymeentersviathepyloricsphinctero Pancreaticjuice(bicarbonateion&enzymes)plusenzymessecretedbysmall
intestineneutralizechymeandcontinuechemicaldigestiono Aftercompletionofchemicaldigestion,foodmonomersareabsorbed
• Largeintestineo Primaryfunctionisreabsorptionofwater(enzymes,etc.addedtothelumenof
stomach&intestineinaqueoussolution)o Absorptionofmineralso Undigestedfoodmatter(feces)egested(defecated)viatherectum&anuso Regularintakeofdietaryfibre(cellulose,notdigested)assistsmovementoffeces
throughthelargeintestine(colon)
AbsorptionorAssimilation?Afterdigestion,foodmolecules(monosaccharides,aminoacids,glycerolandfattyacids)areabsorbedintothecirculatorysystem:monosaccharidesandaminoacidsareabsorbedintotheblood,whileglycerolandfattyacidsareabsorbedintothelymph.Thesenutrientsareassimilatedintothebodyoncetheyentercellsandareincorporatedintonew,largermoleculesagain.Thevillusisastructurefoundontheinnerwallofthesmallintestine.Villihelpincreasethesurfaceareaforabsorptionofnutrients:
Imagefromhttp://incostress1.files.wordpress.com/2007/10/villi.jpg
IBBiology NotesforDigestion,Circulation&Respiration
A.DeJong/TFSS2009
TheTransportSystemStructureoftheHumanHeart,andFlowofBlood:
Imagefromhttp://www.sirinet.net/~jgjohnso/heartstructure.html
**Note1:themitralvalveisalsocalledthebicuspidvalve.**Note2:theaorta&pulmonaryarterycontainsemi‐lunarvalves.ActionoftheHeartTheatria(sing.atrium)receivebloodfromtheveins.
• theleftatriumreceivesoxygenatedbloodfromthepulmonaryarteries• therightatriumreceivesdeoxygenatedbloodfromthevenacavae
Theventriclessendbloodoutoftheheartthrougharteries.• theleftventriclesendsoxygenatedbloodtobodytissuesviatheaorta• therightventriclesendsdeoxygenatedbloodtothelungsviathepulmonaryartery
IBBiology NotesforDigestion,Circulation&Respiration
A.DeJong/TFSS2009
Atrioventricular(AV)valvesconnecttheatriatotheventricles(thetricuspidontheright,andthebiscuspidontheleft),preventingbackflowofbloodintotheatriawhentheventriclescontract.Thesemi‐lunarvalvesintheaortaandpulmonarytrunkpreventbackflowofbloodintotheventriclesafterexitingtheheart.Theheartmuscleitselfreceivesoxygenandnutrientsviathecoronaryarteries.ControloftheHeartbeatHeartrate,measuredinbeatsperminute(b.p.m.)variesaccordingtofactorssuchasage,gender,fitness,activityandotherstimuli.Adultmale,atrest:75to80b.p.m.Adultfemale,atrest:85to90b.p.m.Nervousstimuli:fear,excitement,tensionPhysicalstimuli:exercise,temperatureChemicalstimuli:carbonmonoxide,oxygen,nicotine,caffeine,alcohol,hormonesUltimatecontroloftheheartrateisfromaregionofthebraincalledthemedullaoblongata.Twopairsofnervesrunfromthispartofthebraintotheheart.Onepairsendsstimulatorysignalstotheheart,andtheother,inhibitorysignals.Thesenervesconnectthebraintotheheart’scontrolcentre,thepacemaker.Theheartbeatitselfismyogenic–thismeansthatitisinitiatedwithintheheartmuscleitself,notthebrainoranotherpartofthebody.Thesinoatrial(SA)node(pacemaker)isaregionofspecializedhearttissuethatsendswavesofcontractionsthroughbothatria.Contractionoftheatriastimulatestheatrioventricular(AV)node,whichsendssignalsdownthebundleofHis,tothePurkinjefibres.Thiscausesventricularcontraction.Imagefromhttp://biology.about.com/library/organs/heart/blcardiacconduction.htm
IBBiology NotesforDigestion,Circulation&Respiration
A.DeJong/TFSS2009
Theventriclesmustcontractslightlyaftertheatria,toensureaproperflowofbloodthroughthesystem.Heartrateisapatternofaccelerationanddeceleration.Thevagusnervesendsinhibitorysignalstothepacemaker.Whenheartrateincreases,itisbecausetherearelessinhibitorysignalsfromthevagusnerve.Adrenalin,ahormoneproducedbytheadrenalgland,stimulatestheheartrateasapartofthebody’s“fightorflight”response.Ifthepacemakerfails,anartificialpacemakermaybeinsertedintotheheart.Thiswillhelpmaintainasteadyheartbeat,buttherecanbelittlevariationinheartrate.BloodVesselsTheflowofbloodthroughvesselsandtheheartisunidirectional.Thinkofarteries&veinsasone‐waystreets,justthesameaswiresincircuits.Arteriescarrybloodawayfromtheheart.Ingeneral,thisisoxygenatedbloodbeingbroughttothebody’stissues.Theexceptionisthepulmonaryartery,whichcarriesdeoxygenatedbloodtothelungs.RelatingStructuretoFunction:
• arterieshaveanarrowlumencomparedtotheirdiameter,whichhelpsmaintainhighbloodpressure&fastflowofblood
• arterieshaveamuscular,elasticwallwhichhelpspumpblood
• arterialwallshavecollagenfibreswhichhelppreventburstingduetohighbloodpressure
Arteriolesaresmallarteriesthateventuallyconnecttocapillaries.Veinscarrybloodtotheheart.Ingeneral,thisisdeoxygenatedbloodbeingbroughtbackfromthebody’stissues.Theexceptionisthepulmonaryvein,whichcarriesoxygenatedbloodfromthelungs.RelatingStructuretoFunction:
• veinshaveawidelumencomparedtotheirdiameter,whichallowsforslowbloodflowandlowbloodpressure
• veinshavethinnerwallswhichallowsurroundingskeletalmusclestopushbloodbacktowardstheheart
• veinscontainvalvestopreventback‐flowofblood,andpoolingofbloodinthelowerextremities
Venulesaresmallveinsthatcollectbloodfromcapillaries,andleadtolarger&largerveins.
IBBiology NotesforDigestion,Circulation&Respiration
A.DeJong/TFSS2009
Capillariesareextremelynarrowbloodvesselsthatconnectarteriolestovenules.Theyaretheonlysiteswithinthecirculatorysystemwherethereisamixofoxygenated&deoxygenatedblood.Exchangeofmaterials(gases,nutrients&wastes)occursinthecapillaries.RelatingStructuretoFunction:
• capillarywallsconsistofasinglelayerofflattenedcells,whichallowsfordiffusionofmaterialsbetweenthesurroundingtissuesandthebloodwithinthem
• capillarieshaveaveryfinediameter(oftensosmallthatredbloodcellsmustpassthrough“singlefile”),whichallowsthemtopenetratebetweencellsandtissues
• thecombinedsurfaceareaofcapillariesisgreat,whichincreasesthecapacityfordiffusionofmaterials
So,whydoweneedatransportsystem,anyway?Humansandmostothermulticellularorganismsaretoobigtosurvivewithoutatransportsystem.TheAmoeba,forexample,isaunicellularorganism,andusesdiffusionandcytoplasmicstreamingtotransportmaterialsthroughoutthecell.FunctionsoftheHumanTransportSystem:
1. TransportofNutrients:glucose,aminoacids,fattyacids&glycerol
2. TransportofRegulatoryChemicals:hormones,antibodies,enzymes
3. TransportofMetabolicWastes:urea(producedbytheliver),creatinine(producedbymuscles&releasedintoblood)
4. TransportofBloodProteins:albumins,globulins,fibrinogens
5. TransportofRespiratoryGases:oxygen,carbondioxide
6. MaintenanceofElectrolyte,pH,andosmoticbalancebetweentissuesandblood
7. ThermoregulationThreePathwaysforBlood
• Pulmonarysystemo Deoxygenatedbloodfromthebodyenterstherightatrium.o Itpassesthroughthetricuspidvalveintotherightventricle.o Fromhere,bloodgoesthroughthepulmonaryarterytothelungs.o Oxygenatedbloodreturnstotheheartviathepulmonaryvein.
• Coronarysystem(cardiacsystem)o Oxygenatedbloodenterstheleftatrium.o Itpassesthroughthebicuspidvalveintotheleftventricle.o Fromhere,bloodgoestotheaorta,thelargestarteryinourbody.o Thefirsttwoarteriesbranchingofftheaortaarethecoronaryarteries,which
supplytheheartmuscle.
IBBiology NotesforDigestion,Circulation&Respiration
A.DeJong/TFSS2009
• Systemic(Body)Systemo Bloodfromtheaortapassesintovariousmajorarteries,whichleadtoallpartsof
thebody.Bloodreturnstotheheartthroughveins&re‐entersthroughoneofthevenacavae.
Bloodiscomposedofthefollowing:
• Plasmao straw‐colouredliquido 90%watero contains:proteinsforclottingandinfections;dissolvednutrients;waste;
hormones;dissolvedgaseso 50%to60%ofbloodvolume
• RedBloodCellso a.k.a.erythrocyteso disk‐shaped;thinnerinthecentre(“biconcave”)o containhemoglobin
• WhiteBloodCellso a.k.a.leukocyteso <1%ofbloodo battleinfectionsandinvadersinourbodies
• Plateletso a.k.a.thrombocyteso responsibleforbloodclottingo formaplugatacut;alsoreleaseclottingfactorso producedasneeded(hormonalcontrol)
Imagefromhttp://content.answers.com/main/content/img/McGrawHill/Encyclopedia/images/CE087600FG0010.gif
IBBiology NotesforDigestion,Circulation&Respiration
A.DeJong/TFSS2009
Themainfunctionofbloodistocarryoxygenandcarbondioxidegases.Eachmoleculeofhemoglobinformsaweakbondwith4oxygenatoms.Thesebondsbreakinregionsoflowoxygen.Carbonmonoxidelovestotaketheplaceofoxygenonhemoglobin…hencethedangerofcarbonmonoxidepoisoning.GasExchangeVentilation,GasExchange&CellRespirationThesetermsareoftenallcalled“respiration”.Ventilation:muscularmovementrequiredinordertomaintainaconcentrationgradientsothatgaseousexchangecanoccur;breathingisventilationofthelungsGasExchange:themovementofoxygenfromtheairinthelungsintothebloodandcarbondioxideintheoppositedirectionCellRespiration:controlledreleaseofenergyintheformofATPfromorganiccompoundsincells
IBBiology NotesforDigestion,Circulation&Respiration
A.DeJong/TFSS2009
FunctionsoftheRespiratorySystem
1. Ventilation–providesoxygentothebloodstreamandremovescarbondioxide.2. Vocalization–productionofsounds;speech.3. Assistinginabdominalcompressionduring
a. Urinationb. Defecationc. Childbirthd. Liftingheavyobjects
Theabdominalmusclesbecomemoreeffectivewhenairisheldinthelungs&glottisisclosed.
Breathein…breatheout…VentilationofthelungsVentilationofthelungsisaccomplishedbybreathingin&out.Thisisnecessarybecausethelungsneedaconstantsupplyoffreshairtomaintaintheconcentrationgradientbetweenthealveoliandtheircapillaries.Sincethereisonlyoneconnectionbetweenthelungsandtheatmosphere,staleairmustbeexhaledbeforefreshairisinhaled.Breathein…Inspirationoccursbecausetheintercostalmuscles(betweentheribs)contract,movingtheribcageupward&outward;atthesametime,thediaphragmcontracts,movingitdownward.Theseactionscombinetoincreasethevolumeofthechestcavity.Whenthevolumeofthechestcavityincreases,theairpressureinsidethelungsdecreases,becominglessthantheatmosphericairpressure;thisbringsairintothelungs.Breatheout…Expirationoccursbecausetheintercostalmusclesanddiaphragmrelax,andtheyreturntotheiroriginalposition.Thisdecreasesthevolumeofthechestcavity.Whenthevolumeofthechestcavitydecreases,theairpressureinsidethelungsincreases,becominggreaterthantheatmosphericairpressure;thispushesairoutofthelungs.Imagefromhttp://www.fda.gov/fdac/graphics/1999graphics/breathing.gif
IBBiology NotesforDigestion,Circulation&Respiration
A.DeJong/TFSS2009
Howmuchairarewetalkingabout,here?Name Volume
(cm3)Description
TidalVolume(TV) 500 volumemovedinoroutofthelungsduringquietbreathing
InspiratoryReserve(IRV)
3000 volumethatcanbeinhaledduringforcedvolumebreathinginadditiontotidalvolume
ExpiratoryReserve(ERV)
1100 volumethatcanbeexhaledduringforcedvolumebreathinginadditiontotidalvolume
ResidualVolume(RV) 1200 volumethatremainsinthelungsatalltimesInspiratoryCapacity(IC)
3500 maximumvolumeofairthatcanbeinhaledfollowingexhalationoftidalvolumeIC=TV+IRV
FunctionalResidualCapacity(FRC)
2300 volumeofairthatremainsinthelungsfollowingexhalationoftidalvolumeFRC=ERV+RV
VitalCapacity(VC) 4600 maximumvolumeofairthatcanbeexhaledaftertakingthedeepestbreathpossibleVC=TV+IRV+ERV
TotalLungCapacity(TLC)
5800 totalvolumeofairthatthelungscanholdTLC+VC+RV
Non‐RespiratoryAirMovementsWhat? How? Why?coughing deepbreathistaken,glottisisclosed,andairis
forcedagainsttheclosure;suddenlytheglottisisopenedandablastofairpassesupward
clearslowerrespiratorypassages
sneezing sameascoughing,exceptairmovingupwardisdirectedintothenasalcavitybydepressingtheuvula
clearsupperrespiratorypassages
laughing deepbreathisreleasedinaseriesofshortexpirations
expressesemotionalhappiness
crying sameaslaughing expressesemotionalsadnesshiccupping diaphragmcontractsspasmodicallywhileglottis
isclosednousefulfunction
yawning deepbreathistaken ventilatesalargerproportionofthealveoliandaidsoxygenationoftheblood
speech airisforcedthroughthelarynx,causingvocalcordstovibrate
vocalcommunication;wordsareformedbylips,tongueandsoftpalate
IBBiology NotesforDigestion,Circulation&Respiration
A.DeJong/TFSS2009
IntroductiontoGasExchange
• Gasexchange(=respiration)istheuptakeofoxygenandthereleaseofcarbondioxideo O2isrequiredforcellularmetabolismo CO2isaby‐productofmetabolism
• O2isextractedfromairorwatero Diffusionacrossexternalsurfaceoverlayingacapillarybed.o CO2transportedacrosssamesurface(netflowinoppositedirection).
• Gasexchangeacrosslungs(=pulmonary)ornon‐pulmonary(i.e.inthetissues)routes.
Imagefromhttp://distance.stcc.edu/AandP/AP/imagesAP2/respiration/alvexch.jpg
Imagefromhttp://faculty.uca.edu/~johnc/CapillaryExchange.gif
IBBiology NotesforDigestion,Circulation&Respiration
A.DeJong/TFSS2009
RequirementsforGasExchangeFourthingsareneededforgasexchange:
1. aconcentrationgradient(fordiffusion)2. amoistmembrane(O2enterscellsdissolvedinwater)3. adequatesurfacearea(providedby1000’sofalveoli…ourlungsarenotemptyballoons)4. aninternaltransportsystem(networkofcapillariessurroundseachalveolus)
Howalveolimeettheneedsforgasexchange:
• largetotalsurfacearea• thinwallsconsistingofasinglelayerofflattenedcells• moistlining• densenetworkofcapillaries
PhasesofHumanRespiration
1. Breathing(ventilation)–movementofairinto&outofthelungs2. ExternalRespiration–exchangeofgasesbetweenair&blood(see,alveoliarereally
outsidethebody!)3. Circulation–movementofdissolvedgasestoandfromthecellsbyblood4. InternalRespiration–exchangeofgasesbetweenbloodandcells/tissues
ControlofBreathingBreathingisaninvoluntaryprocessthatcanbecontrolledvoluntarily.Breathingiscontrolledbytherespiratorycentreinthebrain(partofthemedullaoblongata),andbychemoreceptorsinlargearteries(e.g.aorta)thatmonitorlevelsofO2andCO2.CompositionofAtmospheric&ExhaledAir:Component AtmosphericAir(%) ExhaledAir(%)N2(plusinertgases) 78.62 74.9O2 20.85 15.3CO2 0.03 3.6H2O 0.5 6.2 100% 100%Notethatthelungsonlytakeupafractionoftheoxygeninhaled.ThisisexploitedwhenweperformArtificialRespirationduringCPR.Theoxygenlevelofexhaledairissufficienttosupplyoxygentothecellsofsomeonewhoisnotbreathing.