LECTURE7:• Knowallthecomponentsoftherespiratorysystem

andtheirmajorfunctionsWeneedtotransferO2fromtheatmospheretoourtissuesandCO2fromthetissuesintotheatmosphere.Respiratorysystemalso:

• AssistspHhomeostasis• Producesvocalsounds• Filtersairandprovidesforasenseof

smell• Assistsregulationofheatandwater

Theupperrespiratorysystemincludes:• Pharynx• Nose

Thelowerrespiratorysystemincludes:• Larynx• Trachea• Rightmainbronchus• Lungs

Principalorgansoftherespiratorysystem:• Nose-producesmucus,filters,warmsandmoistensincomingair• Paranasalsinuses-sameasnose.Mucosa-lined,airfilledcavities.• Pharynx-passageforairandfood.Connectsnasalcavitytolarynxandoralcavityto

esophagus.Has3subdivisions:nasopharynx,oropharynx,andlaryngopharynx.Thenasopharynxhelpswarmandhumidifyandfiltertheair.

• Larynx-airpassageway;preventsfoodfromenteringlowerrespiratorytract.Itprotectstheglottis(largecartilages)andproducessound(smallcartilagestructuresandvocalfolds).Thereare3largecartilages:thyroid,cricoidcartilageandepiglottis.

• Trachea-airpassageway;cleans,warmsandmoistensincomingair

• Bronchialtree-airpassagewayconnectingtracheawithalveoli;cleans,warmsandmoistensincomingair.Thebronchicontainincompleteringsofcartilageandarelinedbypseudostratifiedciliatedcolumnarepithelium.Consistsofrightandleftmainbronchi,whichsubdividewithinthelungstoformlobarandsegmentalbronchiandbronchioles.Platesofcartilagegraduallyreplacetheincompleteringsofcartilagefrommainbronchiandfinallydisappearinthe

distalbronchioles.Astheamountofcartilagedecreases,theamountofsmoothmuscleincreases.

• Alveoli-mainsitesforgasexchange.Comprisedofwallsofsimplesquamousepithelium.

• Lungs-houserespiratorypassagessmallerthanthemainbronchi.Composedprimarilyofalveoliandrespiratorypassageways.Stromaisfibrouselastic

connectivetissue,allowinglungstorecoilpassivelyduringexpiration.• Pleurae=producelubricatingfluidandcompartmentaliselungs.Comprisedofserous

membranes.TheLowerRespiratorySystem:

• Conductingairwaysandgasexchangesurfaces• Thereare3lobesintherightlungand2lobesintheleftlung

Conductingairways:

• Cartilagetopreventairwayscollapsing

• Smoothmusclewhichcannarrowtheairways

• Respiratoryepithelium(conditionandcleantheair)

Levelsoftherespiratorytree:

• Cartilagebecomeslessprominentasbranchesgetsmaller.

• Branchingofthebronchialtree:tracheaàmainbronchiàlobarbronchiàsegmentalbronchi(cartilagepresent)àbronchioles(nocartilage)àterminalbronchioles(smoothmusclecells)

Respiratoryepithelium:

• Cleansandmoistensairbeforeitreachesthealveoli

• Therespiratoryregionislinedwithpseudostratifiedciliatedcolumnarepitheliumwithnumerousgobletcells,whichisfrequentlycalledtherespiratoryepitheliumAlveoli:

• Respiratorybronchiolesàalveolarductsàalveolarsacsàalveoli

• Alveoliparticipateingasexchange,andthusrespiratorybronchiolesbegintherespiratoryzoneoftherespiratorysystem.

• Respiratorybronchiolessubdivideintoseveralalveolarducts(simplesquamousepithelium).

• Aroundthealveolarductsarenumerousalveoliandalveolarsacs.Analveolarsacconsistsoftwoormorealveolithatshareacommonopening.

• Wallsofthealveoliconsistof2typesofalveolarepithelialcells:typeIalveolarcells(squamouspulmonaryepithelialthatformtheliningofthealveolarwall)andtypeIIalveolarcells.

• TypeIalveolarcellsarethemainsitesofgasexchange.• TypeIIalveolarcells(cuboidalepithelial)secretealveolarfluidwhichkeepsthe

surfacebetweenthecellsandairmoist.Inthealveolarfluidissurfactant-acomplex

mixtureofphospholipidsandlipoproteins.Surfactantlowersthesurfacetensionofalveolarfluid.

• Alveolarmacrophages(dustcells)arealsoassociatedwiththealveolarwall-thesearephagocytesthatremovefinedustparticlesandotherdebrisfromthealveolarspaces.

• ExchangeofO2andCO2betweentheairspacesinthelungsandthebloodoccursthroughdiffusionacrossthealveolarandcapillarywalls.Thealveolarandcapillarywallsformtherespiratorymembrane.