16.2FirstLinesofDefense

Listanddescribethephysicalfactorsofthefirstlineofdefenseofthehumanimmunesystem.a)  Howdoskinandthemucousmembranes

provideimmunity?b)  Howdotears,saliva,urinaCon,perspiraCon

andvaginalsecreConsprovideprotecCon?c)  HowistheprotecConprovidedbyhair(nose

hairs,eyelashes)differentfromthatprovidedbycilia?

1stLinesofDefense:Skin&MucousMembranes•  MechanicalprotecCon‐Barrier

–  skin(epidermis)closelypacked,keraCnizedcells

•  sheddinghelpsremovemicrobes

•  Hardtopenetratethrough–  mucousmembranesecretesmucus:trap&

movemicrobesasa“ciliary

escalator”

1stLinesofDefense:Hair

•  MechanicalprotecCon–Barrier

•  Nose,eyelashes,eyebrows,ear•  BlockentrybyparCclesintothemoistenvironmentsoftheeye,outerearandrespiratorytract

Earhairchampion!

1stLinesofDefense:SecreCons‐Rinsing

•  Tears,vaginalsecreCons,perspiraCon&salivaconCnuallyrinseorwashsurfacestopreventmicrobesfromcolonizing

•  ExpellingofmaterialsbydefecaCon,urinaCon,emesis,sneezing,coughingachievesasimilareffect

1stLinesofDefense:SecreCons‐Chemical

•  SomesecreConshavealowpHthat

createsaninhospitableenvironmentformanymicrobes–  Gastricjuice:pH3–  VaginalsecreCons/lacCcacid:pH4.0–  Urine:pH6

•  Lysozymeisanenzymepresentinsaliva,tears,urine,nasalmucus,sweat–  EnzymethatmetabolizespepCdoglycan–  PepCdoglycanisacomponentofbacterialcellwalls

– MoreeffecCveagainstGramposiCve

1stLinesofDefense:Microflora

•  10xasmanymicrobialcellscolonizingoursurfacesastherearehumancellsintheenCrebody

•  Skin&hair–  Harmlessmicrobesfeedonsebum,othersecreCons&deadskin

cells–  Acinetobacterjohnsonii,Staphylococcusaureus,Candida

albicans,Demodexfolliculorum–  CompeCConforterritoryexcludespathogens

•  GItract–  Lactobacillusacidophilus,Escherichiacoli,Bifidobacterium

bifidum–  Acids&anCmicrobialchemicalsreleasedtopreventpathogens

•  Vagina–  Lactobacillusacidophilus–  ProduceslacCcacidasaresultofglycogenmetabolism