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Respiratory System
Differences b/w Breathing & Respiration
S. No. Breathing( Ventilation) Respiration
1. It isthe firstste...
havingcellsmore distantthan0.5 mm from the respiratorysurface require circulatory
systemtotransport the gasesb/w the respi...
of oxygenatthe lungsurface enablesthe cytochrome P450 to oxidize foreignmaterials.
Thus,like the liver,lungstooare detoxif...
 Theyopenintothe nasal chambers.
2. Nasal Chambers :-
 The nasal chambersare a pairof passagesinthe headabove the palate...
 Gobletcellsintheirliningepitheliumproducemucusthatdrainsintothe nasal chambers.
3. InternalNares ( Choanae ) :-
 The na...
 The epiglottis projectsintothe pharynx opposite the uvula.
 Duringswallowing,the larynx movesupwardtomeetthe epiglottis...
Respiratory Organs
 The respiratoryorgansprovide the surface forthe exchange of gases.
 In humanbeings,the respiratoryor...
Mechanics of Pulmonary Respiration
( Breathing Mechanism )
 Lungs have little musculature &cannotexpandorcontract of thei...
(a) Diaphragm:-
 The diaphragmis convex upward&has a peripheral muscle attachedtothe ribs& vertebral
column.
 Thismuscle...
 Withthe expansionof the thoraciccavity&the lungs,additionalbloodisdrawnintothe
bloodvesselsof the lungs&the thorax.
2. C...
 The progressof the corpusclesisalsoslow,thusincreasingthe time availableforgaseous
exchange tooccur.
 Whenthe bloodleav...
 Much air stays inthe alveoli afterexpiration.This airkeepsthe wallsof the alveoli from
stickingtogether&collapsing.
 Th...
4. Vital Capacity( VC ) of Lungs:- It is the amountof air whichone can inhale with
maximumeffort&alsoexhale withmaximumeff...
Composition of Inspired, Expired & Alveolar Airs
 Duringnormal breathing,apart of the inspiredairisleftinthe respiratoryt...
(a) Uptake of OxygenbyBlood:-
 The Po₂ ( partial pressure of oxygen ) of the alveolarairishigherthanthe Po₂ of bloodin
al...
2. Tissues :-
 In the tissues,exchangeof gasesoccursb/w the blood& the tissue cells.Thisexchange
occurs viatissue fluidth...
 Beingslightlysolubleinwater,asmall amountof oxygen( about 3% ) travelsas itssolution
inthe plasma.
(ii) Oxyhaemoglobin :...
 From the figure,itisclearthat as Po₂ increases,there isprogressiveincreaseinthe
percentage of the haemoglobinthatisbound...
2. Carbondioxide tension.
3. Temperature.
4. Erythrocyte concentrationof 2,3 diphosphoglycerate( DPG).
Increase inthese fa...
Significance
 The Bohr effectallowsforenhancedunloadingof oxygeninmetabolicallyactiveperipheral
tissuessuchas exercisings...
(ii) Bicarbonate Ions:-
 About70% of carbon dioxide releasedbyrespiringtissuecellsdiffusesintothe plasma&
thencarriedinto...
 It isa processwhichoccursin a cardiovascularsystem&referstothe exchange of
bicarbonate ( HNO₃¯) & chloride ( Cl¯) across...
 The opposite processoccursinthe pulmonarycapillariesof the lungswhenthe pO₂rises&
pCO₂falls,& the Haldane effect occurs(...
HHb H⁺ + Hb
Release of Carbon Dioxide :-
 The venousbloodloadedwithcarbondioxide inthe tissuesreturnstothe lungsviaheart....
(i) Artificial Hypoxia:- Itresultsfromthe shortage of oxygeninthe air as at high( over
2400 m ) altitudes.Itcausesmountain...
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Respiratory system by RAHUL GAUTAM

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Respiratory system by RAHUL GAUTAM

  1. 1. Respiratory System Differences b/w Breathing & Respiration S. No. Breathing( Ventilation) Respiration 1. It isthe firststepof respiration&isa physical process. It isa biochemical process&catabolic process. 2. It involvesinspirationof freshair( O₂ ) to the respiratoryorgans& expirationof foul air fromthe respiratoryorgans( CO₂ ). It involvesexchange of gases( i.e.,O₂&CO₂ ) & step-wise oxidationof food withthe incomingoxygen;&eliminationof carbon dioxide producedinthe cellsduring oxidation. 3. It doesnotrelease anyenergy. It releasesenergythatisstoredinATP during oxidationof food. 4. It isan extracellularprocess. It isan intracellularprocess. 5. It doesnotinvolve enzymeaction. It involvesanumberof enzymesinoxidation. 6. Breathingmechanismvariesindifferent animals. Respiratorymechanismissimilarinall animals. 7. It isconfinedtocertainorgansonly. It occurs in all cellsof the body Respiratory Surface  The surface at whichexchange of gases( CO₂& O₂ ) occurs is termed respiratorysurface.  Thissurface must have enoughareaforgas exchange tomeetthe metabolicneedsof the organism. Respiratory Medium  Most of the earth’soxygenoccursinthe air, but some isdissolvedinwater.Thus,airor watermay serve asthe source of oxygenforthe animals.  The source of oxygeniscalled respiratorymedium.  The respiratorymediumsuppliesoxygentothe bodyat the body’srespiratorysurface.  The body’srespiratorysurface maybe the general bodysurface or some specializedarea such as lungor gill.  Most of the animal’scellslie somedistance fromthe respiratorysurface ,& obtainoxygen fromthe tissue fluid,whichbathesall the cells.Bloodbringsoxygenfromthe respiratory surface to the tissue fluid&carriesCO₂from the tissue fluidinthe reverse direction.  Exchange of gasesacross a respiratorymembrane occursbydiffusion,&diffusioncan distribute substancesoverashortdistance only,about0.5 mm. Therefore,the animals
  2. 2. havingcellsmore distantthan0.5 mm from the respiratorysurface require circulatory systemtotransport the gasesb/w the respiratorysurface & the tissue fluidpresentaround the cells. Differences b/w Anaerobic & Aerobic Respiration S. No. AnaerobicRespiration( Fermentation) AerobicRespiration 1. It doesnotuse molecularO₂. It usesmolecularO₂. 2. It may or may notrelease CO₂ It alwaysreleasesCO₂. 3. It doesnotproduce H₂O. It producesH₂O. 4. It provideslessenergy( only5% of that is available inglucose ). It providesmuchmore energy( whole of that isavailable inglucose ). 5. It consistsof 2 steps:- glycolysis& incomplete breakdownof pyruvate. It consists of 5 steps:- glycolysis,pyruvate oxidation,TCA cycle,ETS& chemiosmotic ATP synthesis. 6. It yieldsorganicendproductwithorwithout an inorganicone. It yieldsinorganicendproductsonly. 7. It occurs inthe cytoplasmonly. It occurs partlyin the cytoplasm&partly in the mitochondria. 8. It isfoundina feworganismssuchasyeasts, some bacteria& parasiticworms. It isfoundinthe majorityof animals& plants.  The organismswhichcarry on aerobicrespirationare termed aerobes whereasthose which carry on anaerobicrespirationare termed anaerobes.  Certaincells,suchasmammalianredbloodcorpuscles,lackmitochondriaforaerobic respiration&mustdependonanaerobicrespiration.  Anaerobicrespirationisalsooccursincertaintissues suchas skeletal musclesduring vigorousmovements,byproducinglacticacidfromglucose. Functions of Respiration 1. MetabolicRole ( EnergyProduction) :- RespirationprovidesO₂foraerobicmetabolism to release energyforcreatingATPmoleculesthatlaterpowerthe bodyactivities. 2. Excretion:- It excretesCO₂& volatile substancessuchasammonia,ketone bodies, alcohol,watervapour,etc. 3. Maintenance of Acid-Base Balance :- Thisisdone byadjustingthe amountof CO₂ elimination. 4. Maintenance of Temperature :- Large amountof heatislostin expiredair. 5. Returnof Blood& Lymph:- Duringinspiration,the intrathoracicpressure falls&the intraabdominal pressure rises.Thisfacilitatesthe returnof blood&lymph. 6. Detoxification:- Atthe respiratorysurface of the lungs,the toxicsubstancesare oxidized to lessharmful materials. 7. Cytochrome P450 :- This cytochrome isusedas a carrier proteininfacilitateddiffusion. It alsooxidizesthe toxicsubstancestomake themlessharmful tothe body.Availability
  3. 3. of oxygenatthe lungsurface enablesthe cytochrome P450 to oxidize foreignmaterials. Thus,like the liver,lungstooare detoxifyingorgans. Human Respiratory System  The human respiratorysystemmaybe dividedintotwomajorcomponents:- respiratory tract ( conductingportion) & respiratoryorgans. Respiratory Tract  Respiratorytractservesas a passagewayforthe freshairto flow fromoutside tothe lungs& for the foul airto returnfrom the lungsto the exterior.  Gas exchange doesnotoccurin the respiratorytract.  The respiratorytract consistsof external nares,nasal chambers,internal nares,pharynx, larynx,trachea,bronchi & bronchioles.Of these,some bronchi &all bronchiolesliewithin the lungs,otherparts lie outside the lungs. 1. External Nares ( Nostrils ) :-  The external naresare a pair of slitsat the lowerendof the nose.
  4. 4.  Theyopenintothe nasal chambers. 2. Nasal Chambers :-  The nasal chambersare a pairof passagesinthe headabove the palate.  The two chambersare separatedfromeachotherbya medianpartition,the nasal septum.  Each chamber showsthree regions:- lowervestibular,middle respiratory&upperolfactory. (a) VestibularRegion:-  It liesjustwithinthe external naris.  It isvery short & linedwithskin.  It bearshair,& containssome sweat&oil glands.  The hair act as a sieve tocheckthe entryof large dustparticles. (b) RespiratoryRegion:-  It isthe middle regionof the nasal chamber.  It islinedwith respiratoryepithelium.Thisisaciliated,pseudostratifiedcolumnarepithelium rich inglandcells.The glandcellsinclude mucous&serouscells.  The mucous cellssecrete aviscidfluidcalled mucus.  The serouscellsproduce a wateryfluid.  The respiratoryepitheliumishighlyvascular&appearspinkor reddish.  The respiratoryregionactsas an air-conditioning&filteringunitinbreathing. (c) OlfactoryRegion:-  It isthe upperregionof the nasal chamber.  It islinedwith olfactoryepithelium.Thisepitheliumisconfinedto the upperpartof the nasal chamber& the superiornasal concha.  It looksyellowish-brown.  The olfactoryregionacts as an organ of smell.Itdetectsthe odourof the inspiredair.If the odouris offensive orpungent,the airisnotallowedtopassin.Thus,the organof smell helps inselectingthe airforinspiration. Nasal Conchae:-  Arisingfromthe wall of eachnasal chamber are 3 shallow bonyridgescalled nasal conchae. These are individuallynamed superior, middle &inferiornasal conchae accordingtotheir position.  The conchae are coveredwithmucousmembrane.  Theygreatlyincrease the surface areaof the nasal chambers. Paranasal Sinuses:-  These are cavitiesinthe frontal,maxillary,ethmoid&sphenoidbones.
  5. 5.  Gobletcellsintheirliningepitheliumproducemucusthatdrainsintothe nasal chambers. 3. InternalNares ( Choanae ) :-  The nasal chambersopenbehindintothe nasopharynxbyinternal nares. 4. Pharynx:-  The pharynx isa short,vertical,about12 cm longtube behindthe buccal cavity. The food& air passagescrosshere.  Its upperpart iscalled nasopharynx.The internal naresopenintoit.  The middle partiscalled oropharynx.The oropharynx receivesthe buccal cavity.  The lowerpart iscalled laryngopharynx.Itleadsintotwotubes:- the one at the frontisthe windpipe ortrachea& the one at the back isthe foodpipe or oesophagus.  The pharynx islinedwithnonkeratinizedstratifiedsquamousepitheliumwhichisciliatedin the nasopharynx.  Mouth servesasan alternate route forair whennasal chambersare blocked.Itleadsinto the oropharynx throughthe buccal cavity. Differences b/w Pharynx & Larynx S. No. Pharynx Larynx 1. Locatedin the headat the back of the buccal cavity. Locatedin the upperpart of the neck. 2. Linedwithnonkeratinized,stratified squamousepithelium. Linedwithpseudostratified,ciliated columnarepithelium. 3. Wall not supportedbycartilages. Wall supportedbycartilagesheldtogether by fibroelasticconnective tissue. 4. Buccal cavity,internal nares,glottis& eustachiantubesopenintothe pharynx. Pharynx opensintoitviaglottis& ititself leadsintothe trachea. 5. Both food& air passthroughit. Onlyair passesthroughit. 6. It isneverclosed. It isclosedby epiglottisduringdeglutition. 7. It doesnotact as a soundbox. It acts as a soundbox. 8. Pharynx isabout12 cm long. Larynx is muchshorter. 9. Showsno enlargementafterpuberty. Afterpuberty,itgrows& become more prominentinmales. 5. Larynx :-  The larynx isoftencalledthe Adam’sapple,&ismore prominentinmenthaninwomen.  Before puberty,the larynx isinconspicuous&similarinbothsexes.  The larynx isthe upperpart of the trachea.  It isa short,tubularchambersupportedbya cartilaginousframework.  It opensintothe laryngopharynx byaslit-like aperture,the glottis.The glottisalways remainsopenexceptduringswallowing.  The glottisbearsa leaf-like cartilaginousflap,the epiglottis,atitsanteriormargin.
  6. 6.  The epiglottis projectsintothe pharynx opposite the uvula.  Duringswallowing,the larynx movesupwardtomeetthe epiglottis.Thisclosesthe glottisto preventthe entryof foodintoit.  Besidesformingapartof the respiratorytract,it alsoservesasthe voice box.  It islinedwithciliatedepithelium, the ciliaof whichbeattowardthe pharynx.  The larynx allowsnothingbutairto passintothe lungs.  A laryngeal spasm( an involuntarymuscularcontraction),inthe formof a cough,resultsif any substance enters the larynx.  Entry of foodintothe respiratorytractcan be fatal.  The larynx isfollowedbytrachea. 6. Trachea :-  The trachea is a thin-walledtube,about11 cm long& 2.5 cm wide.  It isalso called windpipe.  It extendsdownwardthroughthe neck. 7. Primary Bronchi:-  In the middle of the thorax,tracheadividesintotwotubes,the majororprimarybronchi.  One majorbronchusentersthe rightlung,& the otherentersthe leftlung.  The right primarybronchusfurtherdividesintothree lobarorsecondarybronchii which extendseparatelyintothe three lobesof the rightlung.  The leftprimarybronchusdividesintotwo lobarorsecondarybronchii thatlikewisepass intothe two lobesof the leftlung.  The secondarybronchi subdivideintosmaller tertiarybronchi whichdivideintostillsmaller bronchioles.  The small terminal bronchioles giveoff respiratorybronchioles whichdivide into alveolar ducts.The alveolarductsenterthe alveolarsacs.  The respiratorypassagewayswithinthe lungsare referredtoasthe bronchial tree.  Wall of trachea,bronchi & bronchiolesiscomposedof fibromusculartissue &islinedby pseudostratifiedciliatedcolumnarepitheliumrichinmucus-secretingcells.  The mucus holdsthe dust& bacteria,whichare sweptbyciliatowardthe pharynx from where theyare thrownout or swallowed.Thisensuresclean&bacteria-freeairtothe lungs.  Terminal bronchiolesare linedwithsimple ciliatedcolumnarepitheliumwithoutmucous cells.The mucus,if present,mayblockthese narrow tubules.  A shortdistance downthe respiratorybronchioles,epitheliumchangestolow nonciliated cuboidal type.  The alveolarductsalsohave thin,nonciliatedcuboidal epithelium.  Cartilaginousrings,incomplete behind,supportthe wallsof the trachea&the bronchi to preventtheircollapsing.Thus,the trachea&bronchi remainpermanentlyopenevenduring negative pressure createdbyexhalation.Thisnormallyallowseasypassage forair.  The rings graduallybecome thinner,&finallydisappearoverthe bronchioles.  The bronchioleshave smoothmuscle controlledbyautonomicnervoussystemsothatair- flowisadjustedtosuitmetabolicneeds.
  7. 7. Respiratory Organs  The respiratoryorgansprovide the surface forthe exchange of gases.  In humanbeings,the respiratoryorgansare a pairof lungs.
  8. 8. Mechanics of Pulmonary Respiration ( Breathing Mechanism )  Lungs have little musculature &cannotexpandorcontract of theirown.  Breathingisbroughtaboutby alternate expansion&contractionof the thoracic cavity whereinthe lungslie.Thisleadstointake of freshair calledinspiration( inhalation, breathingin) & eliminationof foul aircalledexpiration( exhalation,breathingout) respectively.  Inspiration&expirationare togetherreferredtoas respiratorymovements.  Lungs can be expandedorcontractedintwo ways :- 1. By downward& upwardmovementof the diaphragmtoexpandorcontract the chest cavity. 2. By raisingor loweringof the ribstoincrease ordecrease the diameterof the chest cavity. 1. Inspiration :-  Inspirationisanactive process.  It isbroughtabout by diaphragmmuscles&external intercostal muscles.Therefore,these musclesare called inspiratorymuscles.  The abdominal musclesplayapassive role inthisprocess.
  9. 9. (a) Diaphragm:-  The diaphragmis convex upward&has a peripheral muscle attachedtothe ribs& vertebral column.  Thismuscle contracts & lowersthe diaphragm, makingitflat.Thispushesthe abdominal visceradownward &enlargesthe thoraciccavityvertically. (b) External Intercostal Muscles:-  These musclesslantforward&downwardb/w the ribs.  Theircontractionpullsthe ribs& sternumupward& downward.Thisenlargesthe thoracic cavityfromfront- to- back as well asfromside- to- side. (c) Abdominal Muscles:-  These musclesrelax &allow compressionof abdominalorgansbythe diaphragm. Movementof FreshAirintothe Lungs :-  As the lungsare heldtightlyagainstthoracicwall,enlargementof the thoraciccavityresults inexpansionof the lungs.Thisreducesthe pressure of airinthe lungsbelow atmospheric pressure bya few( -2 to -6 ) mmHg. In otherwords,lungscome to have a negative pressure.  Airalwaysmovesfroma place of higherpressure toaplace of lowerpressure.Hence,the freshairfrom outside,where pressure ishigher, rushesintothe lungsthroughthe respiratorypassage till the pressure of airinthe lungsbecomesequal tothe atmospheric pressure.  On reachingthe lungs,the freshairisdistributedbythe bronchi,bronchioles&alveolar ducts to the alveoli.  The freshair followsthe followingroute :- External Nares Nasal Chambers Internal Nares Pharynx Glottis Larynx Trachea Bronchi Bronchioles AlveolarDucts Alveoli.
  10. 10.  Withthe expansionof the thoraciccavity&the lungs,additionalbloodisdrawnintothe bloodvesselsof the lungs&the thorax. 2. Conditioning & Filteration of Air :-  The air passingthroughthe nasal chambersis subjectedtofourimportantprocesses:- (i) Warming:- Bloodvesselsof the conchae radiate heatlike hotwaterpipes, &warmthe air passingoverthemtothe bodytemperature.Verycoldwinterair,if inhaledassuch, may freeze the lungtissues. (ii) Moistening:- Fluidsecretedbynasal mucousmembrane isslowlyevaporated&the vapoursare addedtothe passingair,whichgetsalmostsaturatedwithmoisture.Dryair wouldkill the lungcells. (iii) Sterilization:-Mucusissticky& antiseptic.Ithold& killsthe bacteriaof the air. (iv) Cleaning:- Hairinthe vestibularregionentrapthe coarse dustparticlesfromthe ingoing air. A large inhaleddustparticle stimulatesasensorycell inthe nasal chamber.Thiscell signalsthe brainto cause a sneeze thatforcefullythrowsoutthe particle.Mucusalso holdsdustparticlesof the passingair.The ciliaof the nasal chambersbytheirceaseless beating‘‘sweep’’the dust&germstrappedinthe mucus to the exterior viaexternal nares. Advantagesof Nasal Breathing:-  The above processesoccurringinthe nasal chambersprove the advantagesof nasal breathingoverthe mouthbreathing.The vital functionsof the nose are disrupted by cigarette smoking.  The cilialiningthe trachea& bronchi alsocleanthe air by sweepingthe tinyforeignparticles heldinmucustoward the pharynx,where theyare disposedof byswallowingorthrowing out. 3. Exchange of Gases in Alveoli :-  Exchange of gasestakesplace in the alveoli.  Oxygeninthe alveoli hasahigherpartial pressure orconcentrationthanthatinthe blood. Hence,oxygendiffusesfromthe alveoli intothe bloodthroughthe alveolarepithelium& capillaryendothelium.  Oxygenpassesfirstintothe bloodplasma&thencombineswiththe haemoglobininthe red bloodcorpusclestoformoxyhaemoglobin.  Carbondioxide inthe lungcapillarieshasahigher partial pressure orconcentrationthanthat inthe alveoli.Therefore,carbondioxidediffusesfromthe bloodintothe alveoli.Thus,the air of the alveoli becomesfoul&needsrenewal.  The alveolarcapillariesare narrowerthanthe redbloodcorpusclessothat the RBCs are squeezedthroughthe capillariesbybloodpressure.Thisexposesmore of theirsurface area to the gaseousexchange surface of the alveolus,allowinggreateruptake of oxygen.
  11. 11.  The progressof the corpusclesisalsoslow,thusincreasingthe time availableforgaseous exchange tooccur.  Whenthe bloodleaves the alveolus,ithasalmostthe same partial pressure of O₂& CO₂ as the alveolarair. 4. Expiration :-  Expirationisnormallyapassive processasitsimplyinvolvesrelaxationof the inspiratory muscles,i.e.,peripheral muscleof diaphragm&external intercostal muscles. (a) Diaphragm:-  The peripheral muscle of the diaphragmrelaxes.Withthis,the abdominal viscera, compressedduringinspiration,pushthe diaphragmupward,makingitconvex. (b) External Intercostal Muscles:-  These musclesalsorelax.Thisbringsthe ribs&the sternumto theiroriginal position.Thisis aidedbythe elasticrecoil ( contraction) of the lungs& thoracic wall whichare stretched duringinspiration.  Withthe above twoevents,the thoraciccavitybecomessmaller. (c) Abdominal &Internal Intercostal Muscles:-  In forcedbreathing,asduringexercise,abdominal muscles&internal intercostal muscles come intoaction,makingexpirationalsoanactive,energy-consumingprocess.  These musclescontract& decrease the thoraciccavity further.  The contractionof abdominal musclespressesthe abdominal visceraagainstthe diaphragm, bulgingitfurtherupward.Thisshortensthe thoraciccavityvertically.  The abdominal musclesare practicallyinactiveduringnormal breathing,butbecome active duringcoughing& sneezing.  Contractionof internal intercostal musclesmovesthe ribsdownward&inward.Thisreduces the thoracic cavityfromfront- to- back& alsofromside- to- side.  The abdominal & internal intercostal musclesare called expiratorymuscles. Movementof Foul Airoutof the Lungs:-  All rounddecrease inthe thoraciccavity,reducesthe lungs& raisesthe pressure of airinthe lungsabove atmosphericpressureby+3 to +4 mm Hg. Thispositive pressureinthe lungs pushes outthe foul air fromthe lungsuntil the airpressure inthe lungsfallstothat of the atmosphere.  On itsreturnjourney,the airagainpassesthroughthe respiratorypassage.
  12. 12.  Much air stays inthe alveoli afterexpiration.This airkeepsthe wallsof the alveoli from stickingtogether&collapsing.  The foul air followsthe followingroute :- Alveoli AlveolarDucts Bronchioles Bronchi Trachea Larynx Glottis Pharynx Internal Nares Nasal Chambers External Nares Atmosphere Respiratory Rate :-  Each respirationconsistsof one inspiration&one expiration.  At rest,breathingoccursabout14 – 18 timesperminute ina normal humanbeings.  Alternate inspiration&expirationare due tothe rhythmicarrival & suspensionof nerve impulsesfromthe braintothe inspiratorymuscles. Advantage of Negative PressureBreathing :-  Mammalshave negative pressure breathing,i.e.,the lungsdraw airdue toreductionin pressure withinthem.Thisallowsthemtoeat& breathe atthe same time.  If air were to be forcedintothe lungs,itmightcarry foodparticlesintothe trachea& block it.  Negative pressurebreathinggentlymovesairwhichislesslikelytocarryfoodparticlesinto the windpipe. Pulmonary Air Volumes & Capacities  The quantitiesof airthe lungscan receive,holdorexpel underdifferentconditionsare calledpulmonary orlungvolumes.  Pulmonarycapacityreferstoa combinationof two or more pulmonaryvolumes. 1. Tidal Volume ( TV ) :- It is the volume of airnormallyinspiredorexpiredinone breath withoutanyeffort.Itisabout 500 ml foran average adulthumanmale.Actually,only about350 ml of air entersthe lungalveoli forthe exchangeof gases,the remaining150 ml fillsthe respiratorypassage.The respiratorypassage isoftencalled deadairspace because noexchange of gasestakesplace here.Thus,the tidal volume consistsof about 350 ml of alveolarair& some 150 ml of deadspace volume.Duringexcitement & activity,the tidal volume increases4to10 times. 2. InspiratoryReserve Volume( IRV ) :- It isthe extraamount of air whichcan be inhaled forciblyafteranormal inspiration.Itisabout2000 to 2500 ml. 3. ExpiratoryReserve Volume ( ERV ) :- It isthe extraamountof air whichcan be exhaled forciblyafteranormal expiration.Itisabout1000 to 1500 ml.
  13. 13. 4. Vital Capacity( VC ) of Lungs:- It is the amountof air whichone can inhale with maximumeffort&alsoexhale withmaximumeffort.Itisabout3.5 – 4.5 litresina normal adultperson.Itis equal tothe sum of the tidal,inspiratoryreserve &expiratory reserve volumesof air( 500 + 2000 + 1500 = 4000 ml ).Vital capacityrepresents the maximumamountof airone can renew inthe respiratorysysteminasingle respiration. The vital capacity ishigherinathletes&sportsmenthaninothers,inmountaindwellers than inplainsdwellers,inmalesthaninfemales,&inthe youngthanin the oldpersons. Smokingreducesthe vital capacityof the lungs& decreasesthe capacityforstrenuous muscularactivity. 5. Residual Volume ( RV ) :- Some air alwaysremainsinthe lungsevenafterforcible expiration. Thisamountof airiscalled residual volume.Itisabout1500 ml.The residual air enablesthe lungstocontinue exchange of gasesevenaftermaximum exhalationor on holdingthe breath.Inotherwords,exchange of gasesgoesoninthe lungs uninterruptedduringinspirationaswellasexpiration. 6. InspiratoryCapacity( IC ) :- It is the total volume of airwhichcan be inhaledaftera normal expiration.Itisequal tothe tidal volume plusthe inspiratoryreserve volume ( IC = TV + IRV ).It is about2500 to 3000 ml. 7. Functional ResidualCapacity ( FRC) :- It is the sum of residual volume &the expiratory reserve volume ( FRC= RV + ERV ).It is about2500 to 3000 ml. 8. Total LungCapacity( TLC ) :- It isthe sumof vital capacity& the residual volume ( 3500 – 4500 + 1500 = 5000 – 6000 ml ).It isabout 5000 – 6000 ml. RespiratoryQuotient ( RQ) :- The ratioof the volume of CO₂producedto the volume of O₂usedina unittime iscalled respiratoryquotient( RQ). Itvarieswithdifferentfoodsutilizedinrespiration.For glucose,RQis 1 ( RQ = 6CO₂/6O₂ = 1 ), forfats about0.7, & for proteinsabout0.85. The RQ indicates the type of foodoxidizedinthe animal bodyduringrespiration.
  14. 14. Composition of Inspired, Expired & Alveolar Airs  Duringnormal breathing,apart of the inspiredairisleftinthe respiratorytract,the so called ‘‘deadspace’’,where nogaseousexchange occurs.This ‘‘deadspace’’ airisexpelledatthe nextexpiration.  Thus,the expired aircontainsfreshairfromthe ‘‘deadspace’’&foul airfrom the lungs. Therefore,the alveolarairhaslessoxygen&more carbon dioxide thanthe expiredair.  A part of the expiredairisalsoleftinthe deadspace.Thisairentersthe lungsat the next inspiration.  Some air isalsoleftinthe lungsafterexpirationasresidual air.  The freshinspiredairismixedupinthe lungswiththe foul airfromthe ‘‘deadspace’’& the stale residual air.Therefore,the alveolarairhaslessO₂& more CO₂ than the inspiredair also.  The inspiredairhasthe compositionof the atmosphericair. Exchange of Gases  Exchange of gasesoccurs in the lungs& the bodytissuespartlyby diffusion &partlyby facilitateddiffusion.  The facilitateddiffusionusesacarrierprotein,acytochrome,whichspeedsupdiffusion, allowingthe bloodtotake upoxygenfaster.The kineticmotionof the moleculesprovides the energyrequiredforthisdiffusionof gaseousmolecules.  Diffusionisthe netflowof asubstance froma regionof higherconcentrationtoa regionof lowerconcentration.  The diffusionisdirectlyproportional to:- (i) Partial pressure gradient( difference ) of gasesonthe twosidesof a membrane b/w them. (ii) Thinnessof the membrane. (iii) Surface area of the membrane. (iv) Permeabilityof the membrane.  Moisture isalsonecessarybecause bothO₂& CO₂ are more easilyexchangedincellswhenin a liquidmedium. Partial Pressure :-  Partial pressure of a gas isthe pressure itexertsin a mixture of gases,&is equal tothe total pressure of the mixture dividedbypercentageof thatgas inthe mixture.  In otherwords,the partial pressure of a gas isproportional toitsconcentrationinthe mixture. 1. Lungs :-  In the lungs,exchange of gasestakesplace b/w the airinthe alveoli &the bloodinthe capillariesaroundthe alveoli.Inthisexchange,the bloodtakesupO₂fromthe alveolarair& releasesCO₂tothe alveolarair.
  15. 15. (a) Uptake of OxygenbyBlood:-  The Po₂ ( partial pressure of oxygen ) of the alveolarairishigherthanthe Po₂ of bloodin alveolarcapillaries.  Due to a Po₂difference b/w air&blood,oxygendiffusesrapidlyfromthe alveolarairinto the bloodof alveolarcapillaries.  Gasesalwaysdiffuse fromaregionof higherpartial pressure ( concentration) toa regionof lowerpartial pressure ( concentration). (b) Release of CarbonDioxidebyBlood:-  The Pco₂ ( partial pressure of carbondioxide ) of bloodreachingthe alveolarcapillariesis higherthanthe Pco₂ of alveolarair.Therefore,carbondioxide diffusesfromthe bloodof alveolarcapillariesintothe alveolarair.  The exchange of gasesinthe alveoli thatraisesthe Po₂of blood&lowersitsPco₂ isthe external respiration.The bloodoxygenatedbythisrespirationisreturnedfromthe lungsby pulmonaryveinstothe leftside of the heart.The heartsuppliesthe oxygenatedbloodtothe bodytissues.
  16. 16. 2. Tissues :-  In the tissues,exchangeof gasesoccursb/w the blood& the tissue cells.Thisexchange occurs viatissue fluidthatbathesthe tissue cells.  The bloodreachingthe tissue capillarieshasPo₂ higherthanthatin the tissue cells&Pco₂ lowerthanthat inthe tissue cells.  The tissue cellsconstantlyuse oxygeninoxidationthatproducescarbondioxide.Therefore, theyalwayshave lowerPo₂& higherPco₂than the bloodcomingtothem.  Because of Po₂ & Pco₂ differencesb/w blood&tissue cells,oxygenseparatesfrom oxyhaemoglobin&diffusesfromthe bloodintothe tissue fluid&thence intothe tissue cells; & carbon dioxide diffusesfromthe tissue cellsintothe tissuefluid&thence intothe bloodin the tissue capillaries.  Gasesmostlydiffuse throughthe tissuefluidassuch,onlysmall amountsdissolve init.  Exchange of gasesin the tissuesthatlowersthe Po₂ of the blood& raisesitsPco₂ iscalled internal respiration.The blooddeoxygenatedbythisrespirationreturnstothe rightside of the heart that sendsitto the lungsforreoxygenation. Transport of Gases in Blood  Bloodcarriesoxygenfromthe respiratoryorganstothe tissue cellsforoxidation,&carbon dioxide fromthe tissue cellstothe respiratorysurface forelimination. Transport of Oxygen :-  Oxygeniscarriedbythe bloodintwo forms:- solution&oxyhaemoglobin. (i) Solution :-
  17. 17.  Beingslightlysolubleinwater,asmall amountof oxygen( about 3% ) travelsas itssolution inthe plasma. (ii) Oxyhaemoglobin :-  Bulkof oxygen( about97% ) diffusesfromthe plasmaintothe redbloodcorpuscles.  Here it looselyjoinswiththe Fe²⁺ionsof haemoglobin( Hb) to formbrightred oxyhaemoglobin ( HbO).The processiscalledoxygenation.  Haemoglobinmolecule hasfourFe²⁺ions,eachof whichcan combine withone oxygen molecule.Thus,anoxyhaemoglobinmoleculemaycarry 1 to 4 oxygenmolecules,depending on itsdegree of saturationwithoxygen. Hb₄ + 4O₂ Hb₄O₈  Onlyabout0.3 ml of O₂ can dissolve in100 ml of plasma,about20 ml of O₂ is carriedby haemoglobinin100 ml of blood. Special Feature/Role of Haemoglobin :-  Haemoglobinisawonderful pigment.  It readilycombineswithoxygenwhenexposedtohighPo₂inthe respiratoryorgans,& releasesoxygenequallyreadilywhenexposedtolow Po₂inthe tissues.  The affinityof haemoglobinforoxygenincreaseswith afall inthe Pco₂of the bloodresulting fromthe diffusionof CO₂fromthe bloodintothe alveoli of the lungs.  Simultaneousexposure of haemoglobintohighPo₂& low Pco₂in the lungalveoli enablesit to take up a large amountof oxygen.  Because of its role of carryingoxygen,haemoglobiniscalled respiratorypigment. Release of Oxygen :-  In the tissue capillaries,low Po₂&highPco₂favourdissociationof oxyhaemoglobintodarker purplishreddeoxygenatedhaemoglobin( reducedhaemoglobin) & molecularoxygen.  Oxygendiffusesfromthe bloodintothe tissuefluid&thenintothe cellswhere itisusedin oxidation.  Haemoglobinisreturnedtothe lungsforreuse inoxygentransport. Oxygen Dissociation Curveof Haemoglobin :-  A more active tissue hasmuchlowerPo₂& muchhigherPco₂than a lessactive tissue. Therefore,muchmore oxygenisreleasedfromoxyhaemoglobininamore active tissue than ina lessactive tissue.  The relationshipb/wthe percentage saturationof the haemoglobininthe blood&the oxygentensionPo₂of the blooddepicts oxygendissociationcurve of haemoglobin.  The curve issigmoid.
  18. 18.  From the figure,itisclearthat as Po₂ increases,there isprogressiveincreaseinthe percentage of the haemoglobinthatisboundwithoxygen.  Infact,haemoglobinis97%saturatedwithoxygen( atPo₂ ≈ 100 mm Hg ) as it leavesthe pulmonarycapillaries.  On the otherhand,the bloodwhichhas returnedfromperipheral tissuestothe lungs& entersthe pulmonarycapillaries hasPo₂of only40 mm Hg withhaemoglobinonly70% saturatedwithoxygen.  Whenfullysaturated,eachgramof haemoglobincombineswithnearly1.34 ml of oxygen. Taking14.5 g/dl of bloodas the concentrationof haemoglobin,the total amountof oxygen that can be transportedas oxyhaemoglobinwouldbe 14.5X 1.34 = 19.43 ml/dl of blood. The sigmoidal patternof oxygendissociationcurve of haemoglobinisthe resultof twoproperties whichplaysignificantrole inthe transportof oxygen.Thesetwoproperties are :- 1. Minimal lossof oxygenfromhaemoglobinoccursabove Po₂70-80 mmHg despite significant changesintensionof oxygenbeyondthis.Thisisdepictedbyrelativelyflatportionof the curve. 2. Significantchange of the dissociationcurve below Po₂of 40 mmHg ensuresthatwithany furtherdecline inPo₂there willoccura disproportionatelygreaterrelease of oxygenfrom the haemoglobin. Factors Affecting Oxygen Dissociation Curveof Haemoglobin :- 1. H⁺ concentration.
  19. 19. 2. Carbondioxide tension. 3. Temperature. 4. Erythrocyte concentrationof 2,3 diphosphoglycerate( DPG). Increase inthese factorsbringsrightwardshiftof the curve therebydecreasingthe affinityof haemoglobinforoxygen. Bohr Effect  Carbondioxide reactswithwatertoformcarbonic acidthat lowerthe pH inactive tissue & inducesoxyhaemoglobintogive upmore of its O₂.This phenomenoniscalled BohrEffect.  The Bohr effectstatesthathaemoglobin’soxygenbindingaffinityisinverselyrelatedbothto acidity& to the concentrationof carbon dioxide,i.e.,anincrease inbloodCO₂ concentration,whichleadstoadecrease inbloodpH,will resultinaloweraffinityof haemoglobinforoxygen.  Conversely,adecrease incarbondioxide provokesanincrease inpH,whichresultsin haemoglobinpickingupmore oxygen.  Since carbondioxide reactswithwatertoformcarbonic acid,an increase inCO₂resultsina decrease inbloodpH.  Bohr effectplaysacrucial role in enhancingoxygenationof the bloodinthe lungs&also in the release of oxygeninthe tissues.Fromatissue capillarybed,the deoxygenatedblood entersthe veinsasvenousblood. Mechanism  DecreasesinbloodpH,meaningincreasedH⁺concentration,are likelythe directcause of lowerhaemoglobinaffinityforoxygen.  Specifically,the associationof H⁺ionswiththe aminoacidsof haemoglobinappearto reduce haemoglobin’saffinityforoxygen.  Because changesinthe carbon dioxide partial pressure canmodifybloodpH,increased partial pressuresof carbondioxide canalsoresult inright-wardshiftsof the oxygen- haemoglobindissociationcurve.  The relationshipb/wcarbondioxide partial pressure &bloodpHismediatedbycarbonic anhydrase whichconvertsgaseouscarbondioxide tocarbonicacidthat inturn releasesa free hydrogenion,thusreducingthe local pHof blood.
  20. 20. Significance  The Bohr effectallowsforenhancedunloadingof oxygeninmetabolicallyactiveperipheral tissuessuchas exercisingskeletalmuscle.Increasedskeletalmuscle activityresultsin localizedincreasesinthe partial pressure of CO₂whichinturnreducesthe local bloodpH.  Because of the Bohr effect,thisresultsinenhancedunloadingof boundoxygenby haemoglobinpassingthroughthe metabolicallyactivetissue&thusimprovesoxygen delivery.  Importantly,the Bohreffectenhancesoxygendeliveryproportionallytothe metabolic activityof the tissue.  As more metabolismtakesplace,the carbondioxidepartial pressure increasesthuscausing largerreductionsinlocal pH & inturn allowingforgreateroxygenunloading.Thisis especiallytrue inexercisingskeletal muscles whichmayalsorelease lacticacidthatfurther reduceslocal bloodpH& thus enhancesthe Bohreffect. Transport of Carbon dioxide  Carbondioxide iscarriedbythe bloodinthree forms:- physical solution,bicarbonate ions& carbaminohaemoglobin. (i) Physical Solution:-  A verysmall amountof carbon dioxide ( about7% ) dissolvesinthe plasma&iscarriedas a physical solution.
  21. 21. (ii) Bicarbonate Ions:-  About70% of carbon dioxide releasedbyrespiringtissuecellsdiffusesintothe plasma& thencarriedintothe red bloodcorpuscles.  Here,CO₂ combineswithwatertoformcarbonicacid.The reactioniscatalyzedbya zinc- containingenzyme carbonicanhydrase.  Carbonicacid dissociatesintobicarbonate &hydrogenions.  Hydrogenionsare pickedupby proteins&bicarbonate ionsare joinedbybases( Na⁺, K⁺ ) to maintainpHof the blood. CO₂ + H₂O CarbonicAnhydrase H₂CO₃ CarbonicAcid H₂CO₃ H⁺ + HCO₃⁻ CarbonicAcid HydrogenIon Bicarbonate Ion  A small amountof bicarbonate ionsistransportedinthe RBCs,whereasmostof them diffuse intoplasmatobe carriedbyit. Chloride Shift  It isalso knownasthe Hamburger’sshift orHamburger’s phenomenon.  Exitof bicarbonate ionsconsiderablychangesionicbalance b/w the plasma&the erythrocytes.Torestore the ionicbalance,the chlorideionsdiffusefromthe plasmaintothe erythrocytes.Thismovementof chlorideionsisknownas Chloride Shift.
  22. 22.  It isa processwhichoccursin a cardiovascularsystem&referstothe exchange of bicarbonate ( HNO₃¯) & chloride ( Cl¯) across the membrane of redbloodcells( RBCs ).  The movementof chloride ionsfromthe plasmaintoredbloodcellsasaresultof the transferof carbondioxide fromtissuestothe plasma,a processthatservestomaintain bloodpH.  Bicarbonate & chloride ionsare transportedacrossthe redbloodcell membrane inopposite directionsbythe bicarbonate-chloride carrierprotein.  The chloride shiftisextremelyrapid,occurringwithin1second.  The chloride shiftresultsinthe chloride contentof venousbloodbeinggreaterthanthatof arterial blood. Mechanism  Carbondioxide ( CO₂ ) generatedintissuespassivelydiffusesintocapillariesviathe interstitialfluid( lymph).Once incirculation,CO₂entersredbloodcells( RBCs) to balance the intracellular&extracellularCO₂partial pressures.  RBCs containappreciable quantitiesof carbonicanhydrase,anenzyme whichcatalyzesthe conversionof CO₂to carbonicacid & whichisnot highlyexpressedininterstitial fluid& plasma.  RBC carbonicanhydrase catalyzesthe conversionof dissolvedCO₂&intracellularwaterto carbonicacid ( H₂CO₃ ),whichspontaneouslydissociatestoformbicarbonate ( HCO₃¯) & a hydrogenion( H⁺ ) inresponse tothe fall of intracellularpCO₂,more CO₂passivelydiffuses intothe cell.  Redbloodcell membranesare impermeable tohydrogenionsbutare able toexchange bicarbonate ionsforchloride ionsusingthe anionexchangerproteinBand3.  The rise in intracellularbicarbonate leadstobicarbonate export&chloride intake.The term ‘‘chloride shift’’referstothisexchange.  As a result,plasmachloride concentrationislowerinsystemicvenousbloodthaninsystemic arterial blood:- highvenouspCO₂leadstobicarbonate productioninRBCs,whichthen leavesthe RBCinexchange forchloride comingin.
  23. 23.  The opposite processoccursinthe pulmonarycapillariesof the lungswhenthe pO₂rises& pCO₂falls,& the Haldane effect occurs( release of CO₂from haemoglobinduring oxygenation).Thisreleaseshydrogenionsfromhaemoglobin,increasesH⁺concentration withinRBCs,& shiftsthe equilibriumtowardsCO₂&waterformationfrombicarbonate .  The subsequentdecreaseinintracellularbicarbonate concentrationreverseschloride- bicarbonate exchange :- bicarbonate movesintothe cell inexchangeforchloride moving out.  Inwardmovementof bicarbonate via the Band3 exchangerallowscarbonicanhydrae to convertit to CO₂for expiration.  The chloride shiftmayalsoregulate the affinityof haemoglobinforoxygenthroughthe chloride ionactingasan allostericeffector. (iii) Carbaminohaemoglobin:-  About23% of CO₂ enteringthe RBCslooselycombineswiththe aminogroup( -NH₂) of the reducedhaemoglobin( Hb) to formcarbaminohaemoglobin.  The reactionreleasesoxygenfromoxyhaemoglobin. HbO₂ + CO₂ HbCO₂ + H⁺ + O₂ Haemoglobin as a Buffer :-  Additionof hydrogenionswouldmake the bloodveryacidic.  However,mostof the hydrogenionsare neutralizedbycombinationwithhaemoglobin, whichisnegativelycharged,forming acidhaemoglobin.Thisreducesthe acidityof the blood,& alsoreleasesadditionaloxygen. HbO₂⁻ + H⁺ HHb + O₂  If the bloodbecomestoobasic,acidhaemoglobindissociates,releasinghydrogenions.Thus, the haemoglobinalsoactsasa buffer,asubstance thatkeepsthe pH fromfluctuating.
  24. 24. HHb H⁺ + Hb Release of Carbon Dioxide :-  The venousbloodloadedwithcarbondioxide inthe tissuesreturnstothe lungsviaheart. Here,itis oxygenated.  Its oxygenationhelpsinthe release of carbon dioxide fromit.ThisCO₂iseliminatedfromthe lungsduringexpiration. Haldane Effect  Bindingof oxygenwithhaemoglobintendstodisplacecarbondioxide fromthe blood.This phenomenoniscalled Haldane Effect.  It resultsfromthe simple factthatcombinationof oxygenwithhaemoglobincausesitto become a strongeracidwhich,inturn,displacescarbondioxide fromthe blood.  Haldane effectplaysfarimportantrole inpromotingcarbondioxide transportthanisthe Bohr effectinpromotingoxygentransport. Mechanism  Carbondioxide islesssolubleinarterial bloodthaninvenousblood.Therefore,somecarbon dioxide diffusesfromthe bloodplasmaof the lungcapillariesintothe lungalveoli.  Oxyhaemoglobinisastrongeracid thandeoxyhaemoglobin.Therefore,itdonateshydrogen ion( H⁺ ) whichjoinsbicarbonate ion( HCO₃⁻ ),formingcarbonicacid ( H₂CO₃ ). Then,the carbonicacid issplitintowater& carbon dioxide bythe enzyme carbonicanhydrase. H₂CO₃ CarbonicAnhydrase H₂O + CO₂ The bicarbonate ionspassintothe RBCsfor hydrolysisbycarbonicanhydrase .  HighPo₂ inthe pulmonarycapillariesdue tooxygenationof haemoglobinfavoursseparation of carbondioxide fromcarbaminohaemoglobin.Thus,the reactionsthatbindcarbondioxide intobicarbonate & carbaminohaemoglobininthe tissuecapillariesare reversedinthe pulmonarycapillaries&the free carbondioxide.  The carbon dioxide diffusesintothe lungalveoli because the Pco₂of venousbloodishigher than that of alveolarair. Hypoxia  It isa respiratorydisorder.  Hypoxiaisa conditionof oxygenshortage inthe tissues.   It isof twotypes:-
  25. 25. (i) Artificial Hypoxia:- Itresultsfromthe shortage of oxygeninthe air as at high( over 2400 m ) altitudes.Itcausesmountainsicknesscharacterisedbybreathlessness, headache,dizziness,nausea,vomiting,mental fatigue &bluishtingeonthe skin& mucousmembranes. (ii) AnaemicHypoxia:- Itresultsfromthe reducedoxygencarryingcapacityof the blood due to anaemia( decreasedhaemoglobincontentinblood) orcarbon monoxide poisioning( some haemoglobinoccupiedbyCO).In bothcases,lesshaemoglobinis available forcarryingO₂. 

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