Breathing and Exchange of Gases - Detailed Notes

Breathing and Exchange of Gases

  • O2O_2 is utilized by organisms to indirectly break down simple molecules (glucose, amino acids, fatty acids) to derive energy.

  • CO2CO_2, a harmful byproduct, is released during catabolic reactions.

  • O2 must be continuously provided by cells for CO2 to be released.

  • Breathing (respiration) is the exchange of O<em>2O<em>2 from the atmosphere with CO</em>2producedbycells.</p></li></ul><h3id="f440184a−f789−4f25−96ca−45c29fe2c5eb"data−toc−id="f440184a−f789−4f25−96ca−45c29fe2c5eb"collapsed="false"seolevelmigrated="true">RespiratoryOrgans</h3><ul><li><p>Breathingmechanismsvaryamonganimalsbasedonhabitatandorganizationlevel.</p></li><li><p>Lowerinvertebrates(sponges,coelenterates,flatworms)exchangegasesbysimplediffusionovertheirentirebodysurface.</p></li><li><p>Earthwormsusemoistcuticle;insectsusetrachealtubes.</p></li><li><p>Aquaticarthropodsandmolluscsusegills(branchialrespiration).</p></li><li><p>Terrestrialformsuselungs(pulmonaryrespiration).</p></li><li><p>Vertebrates:fishesusegills;amphibians,reptiles,birds,andmammalsuselungs.</p></li><li><p>Amphibians(frogs)canalsorespirethroughmoistskin(cutaneousrespiration).</p></li></ul><h4id="b05a3d49−6ca9−415b−971b−bd07bfd9e969"data−toc−id="b05a3d49−6ca9−415b−971b−bd07bfd9e969"collapsed="false"seolevelmigrated="true">HumanRespiratorySystem</h4><ul><li><p>Externalnostrilsopenabovetheupperlips,leadingtothenasalchamberviathenasalpassage.</p></li><li><p>Nasalchamberopensintothepharynx(commonpassageforfoodandair).</p></li><li><p>Pharynxopensthroughthelarynx(soundbox)intothetrachea.</p></li><li><p>Epiglottiscoverstheglottisduringswallowingtopreventfoodentryintothelarynx.</p></li><li><p>Tracheaextendstothemid−thoraciccavity,dividingintorightandleftprimarybronchiatthe5ththoracicvertebra.</p></li><li><p>Bronchidivideintosecondaryandtertiarybronchi,thenbronchioles,endinginterminalbronchioles.</p></li><li><p>Trachea,bronchi,andinitialbronchiolesaresupportedbyincompletecartilaginousrings.</p></li><li><p>Terminalbronchiolesgiverisetothin,irregular−walled,vascularizedalveoli.</p></li><li><p>Lungsconsistofthebranchingnetworkofbronchi,bronchioles,andalveoli.</p></li><li><p>Twolungsarecoveredbyadouble−layeredpleurawithpleuralfluidtoreducefriction.</p></li><li><p>Outerpleuralmembranecontactsthethoraciclining;theinnermembranecontactsthelungsurface.</p></li></ul><h4id="9b43113f−9f8a−4141−95ee−ae1155b553e5"data−toc−id="9b43113f−9f8a−4141−95ee−ae1155b553e5"collapsed="false"seolevelmigrated="true">Conductingvs.RespiratoryParts</h4><ul><li><p>Conductingpart:fromexternalnostrilstoterminalbronchioles.</p><ul><li><p>Transportsatmosphericairtoalveoli.</p></li><li><p>Clearsforeignparticles,humidifies,andadjustsairtemperature.</p></li></ul></li><li><p>Respiratory/exchangepart:alveoliandtheirducts.</p><ul><li><p>SiteofactualdiffusionofCO</em>2 produced by cells.</p></li></ul><h3 id="f440184a-f789-4f25-96ca-45c29fe2c5eb" data-toc-id="f440184a-f789-4f25-96ca-45c29fe2c5eb" collapsed="false" seolevelmigrated="true">Respiratory Organs</h3><ul><li><p>Breathing mechanisms vary among animals based on habitat and organization level.</p></li><li><p>Lower invertebrates (sponges, coelenterates, flatworms) exchange gases by simple diffusion over their entire body surface.</p></li><li><p>Earthworms use moist cuticle; insects use tracheal tubes.</p></li><li><p>Aquatic arthropods and molluscs use gills (branchial respiration).</p></li><li><p>Terrestrial forms use lungs (pulmonary respiration).</p></li><li><p>Vertebrates: fishes use gills; amphibians, reptiles, birds, and mammals use lungs.</p></li><li><p>Amphibians (frogs) can also respire through moist skin (cutaneous respiration).</p></li></ul><h4 id="b05a3d49-6ca9-415b-971b-bd07bfd9e969" data-toc-id="b05a3d49-6ca9-415b-971b-bd07bfd9e969" collapsed="false" seolevelmigrated="true">Human Respiratory System</h4><ul><li><p>External nostrils open above the upper lips, leading to the nasal chamber via the nasal passage.</p></li><li><p>Nasal chamber opens into the pharynx (common passage for food and air).</p></li><li><p>Pharynx opens through the larynx (sound box) into the trachea.</p></li><li><p>Epiglottis covers the glottis during swallowing to prevent food entry into the larynx.</p></li><li><p>Trachea extends to the mid-thoracic cavity, dividing into right and left primary bronchi at the 5th thoracic vertebra.</p></li><li><p>Bronchi divide into secondary and tertiary bronchi, then bronchioles, ending in terminal bronchioles.</p></li><li><p>Trachea, bronchi, and initial bronchioles are supported by incomplete cartilaginous rings.</p></li><li><p>Terminal bronchioles give rise to thin, irregular-walled, vascularized alveoli.</p></li><li><p>Lungs consist of the branching network of bronchi, bronchioles, and alveoli.</p></li><li><p>Two lungs are covered by a double-layered pleura with pleural fluid to reduce friction.</p></li><li><p>Outer pleural membrane contacts the thoracic lining; the inner membrane contacts the lung surface.</p></li></ul><h4 id="9b43113f-9f8a-4141-95ee-ae1155b553e5" data-toc-id="9b43113f-9f8a-4141-95ee-ae1155b553e5" collapsed="false" seolevelmigrated="true">Conducting vs. Respiratory Parts</h4><ul><li><p>Conducting part: from external nostrils to terminal bronchioles.</p><ul><li><p>Transports atmospheric air to alveoli.</p></li><li><p>Clears foreign particles, humidifies, and adjusts air temperature.</p></li></ul></li><li><p>Respiratory/exchange part: alveoli and their ducts.</p><ul><li><p>Site of actual diffusion ofO2andandCO2betweenbloodandair.</p></li></ul></li></ul><h4id="04719435−ec8b−4a4d−b2e9−d8b6c85f0092"data−toc−id="04719435−ec8b−4a4d−b2e9−d8b6c85f0092"collapsed="false"seolevelmigrated="true">ThoracicChamber</h4><ul><li><p>Lungsaresituatedintheair−tightthoracicchamber.</p></li><li><p>Thoracicchamberisformedby:</p><ul><li><p>Vertebralcolumn(dorsally).</p></li><li><p>Sternum(ventrally).</p></li><li><p>Ribs(laterally).</p></li><li><p>Dome−shapeddiaphragm(lowerside).</p></li></ul></li><li><p>Changesinthoraciccavityvolumereflectinthepulmonarycavity,essentialforbreathing.</p></li></ul><h4id="fc83b29c−1678−4596−a0c7−46aea9faf6b1"data−toc−id="fc83b29c−1678−4596−a0c7−46aea9faf6b1"collapsed="false"seolevelmigrated="true">StepsinRespiration</h4><ol><li><p>Breathing/pulmonaryventilation:atmosphericairin,between blood and air.</p></li></ul></li></ul><h4 id="04719435-ec8b-4a4d-b2e9-d8b6c85f0092" data-toc-id="04719435-ec8b-4a4d-b2e9-d8b6c85f0092" collapsed="false" seolevelmigrated="true">Thoracic Chamber</h4><ul><li><p>Lungs are situated in the air-tight thoracic chamber.</p></li><li><p>Thoracic chamber is formed by:</p><ul><li><p>Vertebral column (dorsally).</p></li><li><p>Sternum (ventrally).</p></li><li><p>Ribs (laterally).</p></li><li><p>Dome-shaped diaphragm (lower side).</p></li></ul></li><li><p>Changes in thoracic cavity volume reflect in the pulmonary cavity, essential for breathing.</p></li></ul><h4 id="fc83b29c-1678-4596-a0c7-46aea9faf6b1" data-toc-id="fc83b29c-1678-4596-a0c7-46aea9faf6b1" collapsed="false" seolevelmigrated="true">Steps in Respiration</h4><ol><li><p>Breathing/pulmonary ventilation: atmospheric air in,CO_2−richalveolarairout.</p></li><li><p>Diffusionofgases(-rich alveolar air out.</p></li><li><p>Diffusion of gases (O2andandCO2)acrossthealveolarmembrane.</p></li><li><p>Transportofgasesbytheblood.</p></li><li><p>Diffusionof) across the alveolar membrane.</p></li><li><p>Transport of gases by the blood.</p></li><li><p>Diffusion ofO2andandCO2betweenbloodandtissues.</p></li><li><p>Utilizationofbetween blood and tissues.</p></li><li><p>Utilization ofO2bycellsforcatabolicreactions,releasingby cells for catabolic reactions, releasingCO2(cellularrespiration).</p></li></ol><h3id="6cda19dc−e6b6−48e0−954b−7cc016e11d04"data−toc−id="6cda19dc−e6b6−48e0−954b−7cc016e11d04"collapsed="false"seolevelmigrated="true">MechanismofBreathing</h3><ul><li><p>Inspiration:atmosphericairisdrawnin.</p></li><li><p>Expiration:alveolarairisreleasedout.</p></li><li><p>Airmovementisdrivenbyapressuregradientbetweenlungsandatmosphere.</p></li><li><p>Inspirationoccurswhenintra−pulmonarypressureislessthanatmosphericpressure(negativepressure).</p></li><li><p>Expirationoccurswhenintra−pulmonarypressureishigherthanatmosphericpressure.</p></li><li><p>Diaphragmandintercostalmuscles(externalandinternal)generatethesegradients.</p></li></ul><h4id="a675c94b−270b−4682−aa1d−597ce910125c"data−toc−id="a675c94b−270b−4682−aa1d−597ce910125c"collapsed="false"seolevelmigrated="true">Inspiration</h4><ul><li><p>Initiatedbydiaphragmcontraction,increasingthoracicchambervolumeintheantero−posterioraxis.</p></li><li><p>Contractionofexternalintercostalmusclesliftsribsandsternum,increasingthoracicvolumeinthedorso−ventralaxis.</p></li><li><p>Increasedthoracicvolumeleadstoincreasedpulmonaryvolume.</p></li><li><p>Increasedpulmonaryvolumedecreasesintra−pulmonarypressure,forcingairintothelungs.</p></li></ul><h4id="e2493d88−ded4−4a08−80ab−156f8ab245e8"data−toc−id="e2493d88−ded4−4a08−80ab−156f8ab245e8"collapsed="false"seolevelmigrated="true">Expiration</h4><ul><li><p>Relaxationofdiaphragmandintercostalmusclesreturnsthemtonormalpositions,reducingthoracicvolume.</p></li><li><p>Reducedthoracicvolumedecreasespulmonaryvolume.</p></li><li><p>Increasedintra−pulmonarypressureexpelsairfromthelungs.</p></li><li><p>Additionalabdominalmusclescanincreasethestrengthofinspirationandexpiration.</p></li><li><p>Ahealthyhumanbreathes12−16times/minuteonaverage.</p></li><li><p>Aspirometerestimatesairvolumeinbreathingmovementsforclinicalassessmentofpulmonaryfunctions.</p></li></ul><h4id="060d9b5b−473a−4c0c−a98d−628367700811"data−toc−id="060d9b5b−473a−4c0c−a98d−628367700811"collapsed="false"seolevelmigrated="true">RespiratoryVolumesandCapacities</h4><ul><li><p><strong>TidalVolume(TV)</strong>:Volumeofairinspiredorexpiredduringnormalrespiration.Approx.500mL.(6000−8000mL/minute).</p></li><li><p><strong>InspiratoryReserveVolume(IRV)</strong>:Additionalairvolumeduringforcibleinspiration.Averages2500mL−3000mL.</p></li><li><p><strong>ExpiratoryReserveVolume(ERV)</strong>:Additionalairvolumeduringforcibleexpiration.Averages1000mL−1100mL.</p></li><li><p><strong>ResidualVolume(RV)</strong>:Airvolumeremaininginthelungsafterforcibleexpiration.Averages1100mL−1200mL.</p></li><li><p><strong>InspiratoryCapacity(IC)</strong>:Totalairvolumeapersoncaninspireafternormalexpiration.(cellular respiration).</p></li></ol><h3 id="6cda19dc-e6b6-48e0-954b-7cc016e11d04" data-toc-id="6cda19dc-e6b6-48e0-954b-7cc016e11d04" collapsed="false" seolevelmigrated="true">Mechanism of Breathing</h3><ul><li><p>Inspiration: atmospheric air is drawn in.</p></li><li><p>Expiration: alveolar air is released out.</p></li><li><p>Air movement is driven by a pressure gradient between lungs and atmosphere.</p></li><li><p>Inspiration occurs when intra-pulmonary pressure is less than atmospheric pressure (negative pressure).</p></li><li><p>Expiration occurs when intra-pulmonary pressure is higher than atmospheric pressure.</p></li><li><p>Diaphragm and intercostal muscles (external and internal) generate these gradients.</p></li></ul><h4 id="a675c94b-270b-4682-aa1d-597ce910125c" data-toc-id="a675c94b-270b-4682-aa1d-597ce910125c" collapsed="false" seolevelmigrated="true">Inspiration</h4><ul><li><p>Initiated by diaphragm contraction, increasing thoracic chamber volume in the antero-posterior axis.</p></li><li><p>Contraction of external intercostal muscles lifts ribs and sternum, increasing thoracic volume in the dorso-ventral axis.</p></li><li><p>Increased thoracic volume leads to increased pulmonary volume.</p></li><li><p>Increased pulmonary volume decreases intra-pulmonary pressure, forcing air into the lungs.</p></li></ul><h4 id="e2493d88-ded4-4a08-80ab-156f8ab245e8" data-toc-id="e2493d88-ded4-4a08-80ab-156f8ab245e8" collapsed="false" seolevelmigrated="true">Expiration</h4><ul><li><p>Relaxation of diaphragm and intercostal muscles returns them to normal positions, reducing thoracic volume.</p></li><li><p>Reduced thoracic volume decreases pulmonary volume.</p></li><li><p>Increased intra-pulmonary pressure expels air from the lungs.</p></li><li><p>Additional abdominal muscles can increase the strength of inspiration and expiration.</p></li><li><p>A healthy human breathes 12-16 times/minute on average.</p></li><li><p>A spirometer estimates air volume in breathing movements for clinical assessment of pulmonary functions.</p></li></ul><h4 id="060d9b5b-473a-4c0c-a98d-628367700811" data-toc-id="060d9b5b-473a-4c0c-a98d-628367700811" collapsed="false" seolevelmigrated="true">Respiratory Volumes and Capacities</h4><ul><li><p><strong>Tidal Volume (TV)</strong>: Volume of air inspired or expired during normal respiration. Approx. 500 mL. (6000-8000 mL/minute).</p></li><li><p><strong>Inspiratory Reserve Volume (IRV)</strong>: Additional air volume during forcible inspiration. Averages 2500 mL - 3000 mL.</p></li><li><p><strong>Expiratory Reserve Volume (ERV)</strong>: Additional air volume during forcible expiration. Averages 1000 mL - 1100 mL.</p></li><li><p><strong>Residual Volume (RV)</strong>: Air volume remaining in the lungs after forcible expiration. Averages 1100 mL - 1200 mL.</p></li><li><p><strong>Inspiratory Capacity (IC)</strong>: Total air volume a person can inspire after normal expiration.IC = TV + IRV</p></li><li><p><strong>ExpiratoryCapacity(EC)</strong>:Totalairvolumeapersoncanexpireafternormalinspiration.</p></li><li><p><strong>Expiratory Capacity (EC)</strong>: Total air volume a person can expire after normal inspiration.EC = TV + ERV</p></li><li><p><strong>FunctionalResidualCapacity(FRC)</strong>:Airvolumeremaininginlungsafternormalexpiration.</p></li><li><p><strong>Functional Residual Capacity (FRC)</strong>: Air volume remaining in lungs after normal expiration.FRC = ERV + RV</p></li><li><p><strong>VitalCapacity(VC)</strong>:Maximumairvolumeapersoncanbreatheinafteraforcedexpiration,orbreatheoutafteraforcedinspiration.</p></li><li><p><strong>Vital Capacity (VC)</strong>: Maximum air volume a person can breathe in after a forced expiration, or breathe out after a forced inspiration.VC = ERV + TV + IRV</p></li><li><p><strong>TotalLungCapacity(TLC)</strong>:Totalairvolumeaccommodatedinthelungsattheendofaforcedinspiration.</p></li><li><p><strong>Total Lung Capacity (TLC)</strong>: Total air volume accommodated in the lungs at the end of a forced inspiration.TLC = RV + ERV + TV + IRVororTLC = VC + RV</p></li></ul><h3id="df9a3faa−d5ac−4d06−9ab8−30c3e8a88f33"data−toc−id="df9a3faa−d5ac−4d06−9ab8−30c3e8a88f33"collapsed="false"seolevelmigrated="true">ExchangeofGases</h3><ul><li><p>Alveoliaretheprimarysitesofgasexchange.</p></li><li><p>Gasexchangealsooccursbetweenbloodandtissues.</p></li><li><p></p></li></ul><h3 id="df9a3faa-d5ac-4d06-9ab8-30c3e8a88f33" data-toc-id="df9a3faa-d5ac-4d06-9ab8-30c3e8a88f33" collapsed="false" seolevelmigrated="true">Exchange of Gases</h3><ul><li><p>Alveoli are the primary sites of gas exchange.</p></li><li><p>Gas exchange also occurs between blood and tissues.</p></li><li><p>O2andandCO2areexchangedbysimplediffusionbasedonpressure/concentrationgradients.</p></li><li><p>Solubilityofgasesandmembranethicknessalsoaffecttherateofdiffusion.</p></li><li><p>Partialpressure:pressurecontributedbyanindividualgasinamixture.</p><ul><li><p>are exchanged by simple diffusion based on pressure/concentration gradients.</p></li><li><p>Solubility of gases and membrane thickness also affect the rate of diffusion.</p></li><li><p>Partial pressure: pressure contributed by an individual gas in a mixture.</p><ul><li><p>pO_2foroxygen.</p></li><li><p>for oxygen.</p></li><li><p>pCO_2forcarbondioxide.</p></li></ul></li><li><p>Concentrationgradientforoxygen:alveolitobloodtotissues.</p></li><li><p>Gradientforfor carbon dioxide.</p></li></ul></li><li><p>Concentration gradient for oxygen: alveoli to blood to tissues.</p></li><li><p>Gradient forCO_2:tissuestobloodtoalveoli.</p></li></ul><h4id="1289ad34−5602−4f56−b191−69afd08f22db"data−toc−id="1289ad34−5602−4f56−b191−69afd08f22db"collapsed="false"seolevelmigrated="true">DiffusionFactors</h4><ul><li><p>: tissues to blood to alveoli.</p></li></ul><h4 id="1289ad34-5602-4f56-b191-69afd08f22db" data-toc-id="1289ad34-5602-4f56-b191-69afd08f22db" collapsed="false" seolevelmigrated="true">Diffusion Factors</h4><ul><li><p>CO2solubilityis20−25timeshigherthansolubility is 20-25 times higher thanO2.</p></li><li><p>Theamountof.</p></li><li><p>The amount ofCO2thatdiffusesthroughthemembraneishigherthanthat diffuses through the membrane is higher thanO2perunitdifferenceinpartialpressure.</p></li><li><p>Diffusionmembranelayers:</p><ul><li><p>Thinsquamousepitheliumofalveoli.</p></li><li><p>Endotheliumofalveolarcapillaries.</p></li><li><p>Basementsubstance(basementmembranessupportingepitheliumandendothelium).</p></li></ul></li><li><p>Totalthicknessislessthanamillimeter.</p></li><li><p>Allfactorsfavordiffusionofper unit difference in partial pressure.</p></li><li><p>Diffusion membrane layers:</p><ul><li><p>Thin squamous epithelium of alveoli.</p></li><li><p>Endothelium of alveolar capillaries.</p></li><li><p>Basement substance (basement membranes supporting epithelium and endothelium).</p></li></ul></li><li><p>Total thickness is less than a millimeter.</p></li><li><p>All factors favor diffusion ofO2fromalveolitotissuesandfrom alveoli to tissues andCO2fromtissuestoalveoli.</p></li></ul><h3id="ab1ef052−70b8−4efe−ba5b−245f8d200e2b"data−toc−id="ab1ef052−70b8−4efe−ba5b−245f8d200e2b"collapsed="false"seolevelmigrated="true">TransportofGases</h3><ul><li><p>Bloodisthetransportmediumforfrom tissues to alveoli.</p></li></ul><h3 id="ab1ef052-70b8-4efe-ba5b-245f8d200e2b" data-toc-id="ab1ef052-70b8-4efe-ba5b-245f8d200e2b" collapsed="false" seolevelmigrated="true">Transport of Gases</h3><ul><li><p>Blood is the transport medium forO2andandCO2.</p></li><li><p>97.</p></li><li><p>97% ofO_2istransportedbyRBCs.</p></li><li><p>3is transported by RBCs.</p></li><li><p>3% ofO_2iscarriedinadissolvedstatethroughplasma.</p></li><li><p>20−25is carried in a dissolved state through plasma.</p></li><li><p>20-25% ofCO_2istransportedbyRBCs.</p></li><li><p>70is transported by RBCs.</p></li><li><p>70% ofCO_2iscarriedasbicarbonate.</p></li><li><p>7is carried as bicarbonate.</p></li><li><p>7% ofCO_2iscarriedinadissolvedstatethroughplasma.</p></li></ul><h4id="b01c1383−04cb−43c0−afea−5a422e211cdf"data−toc−id="b01c1383−04cb−43c0−afea−5a422e211cdf"collapsed="false"seolevelmigrated="true">TransportofOxygen</h4><ul><li><p>Hemoglobin:red−colored,iron−containingpigmentinRBCs.</p></li><li><p>is carried in a dissolved state through plasma.</p></li></ul><h4 id="b01c1383-04cb-43c0-afea-5a422e211cdf" data-toc-id="b01c1383-04cb-43c0-afea-5a422e211cdf" collapsed="false" seolevelmigrated="true">Transport of Oxygen</h4><ul><li><p>Hemoglobin: red-colored, iron-containing pigment in RBCs.</p></li><li><p>O_2bindsreversiblywithhemoglobintoformoxyhemoglobin.</p></li><li><p>Eachhemoglobinmoleculecancarryamaximumoffourbinds reversibly with hemoglobin to form oxyhemoglobin.</p></li><li><p>Each hemoglobin molecule can carry a maximum of fourO_2molecules.</p></li><li><p>Bindingisprimarilyrelatedtomolecules.</p></li><li><p>Binding is primarily related topO_2.</p></li><li><p>Otherfactors:.</p></li><li><p>Other factors:pCO_2,hydrogenionconcentration,andtemperature.</p></li><li><p><strong>OxygenDissociationCurve</strong>:Sigmoidcurveofpercentagesaturationofhemoglobinwith, hydrogen ion concentration, and temperature.</p></li><li><p><strong>Oxygen Dissociation Curve</strong>: Sigmoid curve of percentage saturation of hemoglobin withO2plottedagainstplotted againstpO2.</p><ul><li><p>Usefulforstudyingeffectsof.</p><ul><li><p>Useful for studying effects ofpCO2,,H^+concentration,etc.,onconcentration, etc., onO2binding.</p></li></ul></li><li><p>Inalveoli(highbinding.</p></li></ul></li><li><p>In alveoli (highpO2,low, lowpCO2,lesser, lesserH^+concentration,lowtemperature):factorsfavoroxyhemoglobinformation.</p></li><li><p>Intissues(lowconcentration, low temperature): factors favor oxyhemoglobin formation.</p></li><li><p>In tissues (lowpO2,high, highpCO2,high, highH^+concentration,hightemperature):factorsfavoroxygendissociationfromoxyhemoglobin.</p></li><li><p>Every100mlofoxygenatedblooddeliversaround5mlofconcentration, high temperature): factors favor oxygen dissociation from oxyhemoglobin.</p></li><li><p>Every 100 ml of oxygenated blood delivers around 5 ml ofO_2totissuesundernormalconditions.</p></li></ul><h4id="b91a885b−d8cb−4f4b−b04f−3a5f74395cd4"data−toc−id="b91a885b−d8cb−4f4b−b04f−3a5f74395cd4"collapsed="false"seolevelmigrated="true">TransportofCarbonDioxide</h4><ul><li><p>to tissues under normal conditions.</p></li></ul><h4 id="b91a885b-d8cb-4f4b-b04f-3a5f74395cd4" data-toc-id="b91a885b-d8cb-4f4b-b04f-3a5f74395cd4" collapsed="false" seolevelmigrated="true">Transport of Carbon Dioxide</h4><ul><li><p>CO_2iscarriedbyhemoglobinascarbamino−hemoglobin(20−25is carried by hemoglobin as carbamino-hemoglobin (20-25%).</p></li><li><p>Binding is related topCO_2.</p></li><li><p>.</p></li><li><p>pO_2isamajoraffectingfactor.</p></li><li><p>Intissues(highis a major affecting factor.</p></li><li><p>In tissues (highpCO2,low, lowpO2):more): moreCO_2binding.</p></li><li><p>Inalveoli(lowbinding.</p></li><li><p>In alveoli (lowpCO2,high, highpO2):):CO_2dissociationoccurs.</p></li><li><p>RBCscontainahighconcentrationofcarbonicanhydrase;smalleramountsinplasma.</p></li><li><p>Carbonicanhydrasefacilitatesthefollowingreaction:<br>dissociation occurs.</p></li><li><p>RBCs contain a high concentration of carbonic anhydrase; smaller amounts in plasma.</p></li><li><p>Carbonic anhydrase facilitates the following reaction:<br>CO2 + H2O \rightleftharpoons H2CO3 \rightleftharpoons HCO_3^- + H^+ </p></li><li><p>Attissuesite(high</p></li><li><p>At tissue site (highpCO2duetocatabolism):due to catabolism):CO2diffusesintobloodandformsdiffuses into blood and formsHCO_3^-andandH^+.</p></li><li><p>Atthealveolarsite(low.</p></li><li><p>At the alveolar site (lowpCO2):thereactionproceedsintheoppositedirection,forming): the reaction proceeds in the opposite direction, formingCO2andandH_2O.</p></li><li><p>Every100mlofdeoxygenatedblooddeliversapproximately4mlof.</p></li><li><p>Every 100 ml of deoxygenated blood delivers approximately 4 ml ofCO_2tothealveoli.</p></li></ul><h3id="df3b7259−6784−47be−9ab3−e436e2fdb34e"data−toc−id="df3b7259−6784−47be−9ab3−e436e2fdb34e"collapsed="false"seolevelmigrated="true">RegulationofRespiration</h3><ul><li><p>Humanscanmaintainandmoderaterespiratoryrhythmtosuitbodytissuedemands.</p></li><li><p>Neuralsystemcontrolsthisregulation.</p></li><li><p>RespiratoryRhythmCenter:inthemedullaregionofthebrain,primarilyresponsibleforregulation.</p></li><li><p>PneumotaxicCenter:intheponsregion,moderatesthefunctionsoftherhythmcenter.</p><ul><li><p>Neuralsignalsfromthiscenterreducethedurationofinspiration,alteringrespiratoryrate.</p></li></ul></li><li><p>ChemosensitiveArea:adjacenttotherhythmcenter,highlysensitivetoto the alveoli.</p></li></ul><h3 id="df3b7259-6784-47be-9ab3-e436e2fdb34e" data-toc-id="df3b7259-6784-47be-9ab3-e436e2fdb34e" collapsed="false" seolevelmigrated="true">Regulation of Respiration</h3><ul><li><p>Humans can maintain and moderate respiratory rhythm to suit body tissue demands.</p></li><li><p>Neural system controls this regulation.</p></li><li><p>Respiratory Rhythm Center: in the medulla region of the brain, primarily responsible for regulation.</p></li><li><p>Pneumotaxic Center: in the pons region, moderates the functions of the rhythm center.</p><ul><li><p>Neural signals from this center reduce the duration of inspiration, altering respiratory rate.</p></li></ul></li><li><p>Chemosensitive Area: adjacent to the rhythm center, highly sensitive toCO_2andhydrogenions.</p><ul><li><p>Increaseinthesesubstancesactivatesthecenter.</p></li><li><p>Signalstherhythmcentertoadjustrespiratoryprocesstoeliminatethesesubstances.</p></li></ul></li><li><p>Receptorsassociatedwiththeaorticarchandcarotidarteryalsorecognizechangesinand hydrogen ions.</p><ul><li><p>Increase in these substances activates the center.</p></li><li><p>Signals the rhythm center to adjust respiratory process to eliminate these substances.</p></li></ul></li><li><p>Receptors associated with the aortic arch and carotid artery also recognize changes inCO_2andandH^+$$ concentration.

    • Send signals to the rhythm center for remedial actions.

  • The role of oxygen in regulating respiratory rhythm is insignificant.

Disorders of Respiratory System

  • Asthma: Difficulty in breathing causing wheezing due to inflammation of bronchi and bronchioles.

  • Emphysema: Chronic disorder with damaged alveolar walls, decreasing respiratory surface.

    • Major cause: Cigarette smoking.

  • Occupational Respiratory Disorders: Long exposure to dust in certain industries can cause inflammation leading to fibrosis (proliferation of fibrous tissues) and serious lung damage; workers should wear protective masks. In certain industries, especially those involving grinding or stone-breaking, so much dust is produced that the defense mechanism of the body cannot fully cope with the situation. Long exposure can give rise to inflammation leading to fibrosis (proliferation of fibrous tissues) and thus causing serious lung damage. Workers in such industries should wear protective masks.