WITH CORRECT ANSWERS GRADED A+ FOR
1
ExambSectionb1:bItemb1bofb50
NationalbBoardbofbMedicalbExaminers®
ComprehensivebBasicbSciencebSelf-Assessment
1.bShortlybafterbdelivery,babfull-
termbmalebnewbornbisbfoundbtobhavebblackbhairbwithbabwhitebforelock.bHisbmother,babbrunette,bals
obhasbabwhitebforelockbandbwearsbhearingbaids.bPhysicalbexaminationbshowsbheterochromiabofbirid
es.bOtoacousticbemissionsbtestingband
brainbstembauditorybevokedbresponsesbshowbbilateralbsensorineuralbhearingbloss.bWhichbofbthebfol
lowingbisbthebmostblikelybcausebofbthebfindingsbinbthisbpatient?
A)bAbnormalbneuralbcrestbdevelopment
B)bAbnormalitybofbconnexins
C)bDeficiencybofbhomogentisicbacidboxidasebactivity
D)bDeficiencybofbtyrosinasebactivity
E)bFailurebofbinternalizationbofbmelaninbgranulesbbybkeratinocytes
F)bFailurebofbmelanosomebtransportationbalongbdendritesb-bbCORRECTbANSWERSA.
AbnormalbneuralbcrestbdevelopmentbleadsbtobWaardenburgbsyndrome.bWaardenburgbsyndromebi
sbabsyndromebofbpatchybdepigmentationbofbthebskin,bhair,birises,bandbcochlearbdysfunctionbthatbpri
marilybillustratesbanbautosomalbdominantbinheritancebpattern.bBecausebof
geneticbmutationsbofbgenesbencodingbtranscriptionbfactors,bneuralbcrestbcellsbdobnotbproperlybdiff
erentiatebintobmelanoblastsb(melanocytebprecursors),borbmelanoblastsbdobnotbmigratebtobtheirbap
propriateblocation.bPatientsbtypicallybhavebabwhitebforelockbandbeyelashes,
,depigmentedbskinbpatches,biridicbheterochromia,bandbsensorineuralbdeafness.bThebeyesbmaybalsob
beblaterallybdisplaced.bThebclinicalbdiagnosisbmaybbebconfirmedbwithbgeneticbtesting.bTreatmentbin
cludesbaudiologicbevaluationbandbgeneticbconsultation.
IncorrectbAnswers:bB,bC,bD,bE,bandbF.
Anbabnormalitybofbconnexinsb(ChoicebB)bwouldbleadbtobabnormalbformationbofbthebplasmabmembr
anebchannelsbofbdiversebcellbtypes.bDifferentbcombinationsbofbsensorineuralbhearingbloss,bichthyos
is,balopecia,bandbperipheralbneuropathybmayboccur.bDepigmentation
wouldbbebatypical.
Deficiencybofbhomogentisicbacidboxidasebactivityb(ChoicebC)bwouldbleadbtobdecreasedbmetabolismb
ofbthebaminobacidsbphenylalaninebandbtyrosine,bwhichbinsteadbdegradebintobhomogentisicbacid.bH
omogentisicbacidbaccumulatesbinbthebskinbandbjoints,bcausingbincreased
pigmentationbandbarthritis,brespectively.bDepigmentationbwouldbbebatypical.
Deficiencybofbtyrosinasebactivityb(ChoicebD)boccursbinboculocutaneousbalbinism,bwhichbpresentsbw
ithbuniformlybhypopigmentedbhairbandbskinb(versusbthebpatchybdepigmentationbofbWaardenburgbs
yndrome)bandbeyebabnormalitiesb(eg,birisbhypopigmentation,brefractive
errors,bnystagmus).bInbtyrosinasebdeficiency,bmelanocytesbarebunablebtobsynthesizebmelaninbfromb
thebaminobacidbtyrosine.bIridicbheterochromiabandbsensorineuralbdeafnes
2
ExambSectionb1:bItemb2bofb50
NationalbBoardbofbMedicalbExaminers®
ComprehensivebBasicbSciencebSelf-Assessment
2.bDuringbanbexperiment,babsolutionbofbmixedbfattybacidsbisbinjectedbintobthebduodenumbofbanbexp
erimentalbanimal.bUnderbthesebconditions,bthebclearancebratebofbanbintravenousbglucosebloadbfro
mbthebcirculationbisbdoubled.bInbcontrast,banbinjectionbofbanbequal
volumebamountbofb0.9%bsalinebintobthebduodenumbhasbmuchblessbeffectbonbthebplasmabclearanceb
ratebofbglucose.bThesebfindingsbarebmostblikelybcausedbbybthebsecretionbofbwhichbofbthebfollowingb
hormones?
A)bGastrin
B)bGlucose-dependentbinsulinotropicbpeptide
,C)bMotilin
D)bSecretin
E)bSomatostatinb-bbCORRECTbANSWERSB.
Glucose-
dependentbinsulinotropicbpeptideb(GIP)bisbsecretedbbybKbcellsbinbthebduodenumbandbjejunumbandb
functionsbtobdecreasebgastricbacidbproductionbandbstimulatebinsulinbreleasebfrombthebpancreas.bIt
sbsecretionbisbpromotedbbybthebpresencebofbfattybacids,bamino
acids,bandbintestinalbglucose.bWhilebserumbglucosebalsobstimulatesbinsulinbsecretionbbybthebpancr
eas,bthebeffectbofbintraluminalbglucosebonbGIPbandbsubsequentbinsulinbsecretionbleadsbtobincrease
dbconcentrationsbofbinsulinbcomparedbtobparenteralbglucose
administration.bInsulinbpromotesbperipheralbtissuebuptakebofbglucose,bglycolysis,bglycogenbsynthe
sis,bproteinbsynthesis,bandbfattybacidbsynthesis,bresultingbinbdecreasedbglucosebconcentrationbinbth
ebserum.
IncorrectbAnswers:bA,bC,bD,bandbE.
Gastrinb(ChoicebA)bisbproducedbbybGbcellsbinbthebgastricbantrumbandbstimulatesbparietalbcellsbwithi
nbthebgastricbbodybtobproducebhydrochloricbacid.bGastricbacidbhasbnobeffectbonbserumbglucosebcon
centration.
Motilinb(ChoicebC)bisbsecretedbbybthebsmallbintestinebandbstimulatesbintestinalbperistalsis.bMotilinbr
eceptorsbarebtargetedbbyberythromycinbandbmetoclopramide,busedbtherapeuticallybinbgastropares
is.
Secretinb(ChoicebD)bisbproducedbbybduodenalbSbcells.bItbpromotesbthebreleasebofbbicarbonate-
richbpancreaticbsecretionsbandbbilebandbinhibitsbgastricbacidbproduction.
Somatostatinb(ChoicebE)bisbabregulatorybpeptidebsecretedbbybDbcellsbofbthebpancreasbandbgastroint
estinalbmucosabthatbinhibitsbgastricbacidbandbpepsinogenbsecretion,bgallbladderbcontraction,bandbi
nsulinbandbglucagonbrelease.bSomatostatinbwouldbhavebanbindirect
effectbonbglucosebthroughbcounterregulatorybactionbofbbothbinsulinbandbglucagon.
EducationalbObjective:bGlucose-
dependentbinsulinotropicbpeptideb(GIP)bisbsecretedbbybKbcellsbinbthebduodenumbandbjejunum,band
bitbfunctionsbtobdecreasebgastricbacidbproductionband
3
, ExambSectionb1:bItemb3bofb50
NationalbBoardbofbMedicalbExaminers®
ComprehensivebBasicbSciencebSelf-Assessment
3.bAb53-year-oldbmanbcomesbtobthebphysicianbbecausebofbab6-
daybhistorybofbshortnessbofbbreath,bcough,bandbpleuriticbchestbpain.bHisbtemperaturebisb38.9°Cb(10
2°F),bandbrespirationsbareb35/min.bSputumbisbpurulentbandbrustbcolored.bPhysicalbexaminationbsho
ws
decreasedbbreathbsounds,bandbcracklesbarebheardbatbthebleftbbase.bAbGrambstainbofbsputumbshows
bgram-positivebdiplococci.bAbchestbx-raybshowsbleft-
sidedblobarbconsolidation.bWhichbofbthebfollowingbanatomicbstructuresbmostblikelyballowedbrapidbs
preadbof
organismsbbetweenbalveolibtobinvolvebthebentirebleftblobebinbthisbpatient?
A)bAlveolarbcapillaries
B)bGerminalbcenters
C)bLymphaticbcapillaries
D)bPoresbofbKohn
E)bVascularbsinusoidsb-bbCORRECTbANSWERSD.
ThebporesbofbKohnbformbconnectionsbbetweenbalveolibandbarebpresentbinbnormalblungbtissue.bThey
barebcomposed,batbleastbinbpart,bofbtypebIlbalveolarbcellsbandballowbforbthebpassagebofbair,bfluid,bpha
gocytes,bandbinbthebsettingbofbpneumonia,bbacteriabbetweenbadjacent
alveoli.bByballowingbequilibrationbbetweenbadjacentbalveoli,bthebporesbofbKohnbaidbinbnormalboxyg
enationbandbinbthebpreventionbofbatelectasis.bHowever,binfectiousborganismsbandbinflammationbm
aybalsobspreadbbetweenbadjacentbalveolibthroughbthesebapertures.
IncorrectbAnswers:bA,bB,bC,bandbE.
Alveolarbcapillariesb(ChoicebA)bsurroundbeachbalveolusbandbarebcrucialbforbgasbexchange.bHowever,
btheybdobnotbprovidebabdirectbconnectionbbetweenbadjacentbalveoli,bprovidedbthatbthebalveolarban
dbcapillarybendotheliabremainbintact.
Germinalbcentersb(ChoicebB)ballowbforbthebdevelopmentbofbBblymphocytesbandbarebimportantbinbm
ountingbanbadaptivebimmunebresponsebtobpulmonarybpathogens.bTheybdobnotbformbconnectionsb
betweenbalveoli.
1
ExambSectionb1:bItemb1bofb50
NationalbBoardbofbMedicalbExaminers®
ComprehensivebBasicbSciencebSelf-Assessment
1.bShortlybafterbdelivery,babfull-
termbmalebnewbornbisbfoundbtobhavebblackbhairbwithbabwhitebforelock.bHisbmother,babbrunette,bals
obhasbabwhitebforelockbandbwearsbhearingbaids.bPhysicalbexaminationbshowsbheterochromiabofbirid
es.bOtoacousticbemissionsbtestingband
brainbstembauditorybevokedbresponsesbshowbbilateralbsensorineuralbhearingbloss.bWhichbofbthebfol
lowingbisbthebmostblikelybcausebofbthebfindingsbinbthisbpatient?
A)bAbnormalbneuralbcrestbdevelopment
B)bAbnormalitybofbconnexins
C)bDeficiencybofbhomogentisicbacidboxidasebactivity
D)bDeficiencybofbtyrosinasebactivity
E)bFailurebofbinternalizationbofbmelaninbgranulesbbybkeratinocytes
F)bFailurebofbmelanosomebtransportationbalongbdendritesb-bbCORRECTbANSWERSA.
AbnormalbneuralbcrestbdevelopmentbleadsbtobWaardenburgbsyndrome.bWaardenburgbsyndromebi
sbabsyndromebofbpatchybdepigmentationbofbthebskin,bhair,birises,bandbcochlearbdysfunctionbthatbpri
marilybillustratesbanbautosomalbdominantbinheritancebpattern.bBecausebof
geneticbmutationsbofbgenesbencodingbtranscriptionbfactors,bneuralbcrestbcellsbdobnotbproperlybdiff
erentiatebintobmelanoblastsb(melanocytebprecursors),borbmelanoblastsbdobnotbmigratebtobtheirbap
propriateblocation.bPatientsbtypicallybhavebabwhitebforelockbandbeyelashes,
,depigmentedbskinbpatches,biridicbheterochromia,bandbsensorineuralbdeafness.bThebeyesbmaybalsob
beblaterallybdisplaced.bThebclinicalbdiagnosisbmaybbebconfirmedbwithbgeneticbtesting.bTreatmentbin
cludesbaudiologicbevaluationbandbgeneticbconsultation.
IncorrectbAnswers:bB,bC,bD,bE,bandbF.
Anbabnormalitybofbconnexinsb(ChoicebB)bwouldbleadbtobabnormalbformationbofbthebplasmabmembr
anebchannelsbofbdiversebcellbtypes.bDifferentbcombinationsbofbsensorineuralbhearingbloss,bichthyos
is,balopecia,bandbperipheralbneuropathybmayboccur.bDepigmentation
wouldbbebatypical.
Deficiencybofbhomogentisicbacidboxidasebactivityb(ChoicebC)bwouldbleadbtobdecreasedbmetabolismb
ofbthebaminobacidsbphenylalaninebandbtyrosine,bwhichbinsteadbdegradebintobhomogentisicbacid.bH
omogentisicbacidbaccumulatesbinbthebskinbandbjoints,bcausingbincreased
pigmentationbandbarthritis,brespectively.bDepigmentationbwouldbbebatypical.
Deficiencybofbtyrosinasebactivityb(ChoicebD)boccursbinboculocutaneousbalbinism,bwhichbpresentsbw
ithbuniformlybhypopigmentedbhairbandbskinb(versusbthebpatchybdepigmentationbofbWaardenburgbs
yndrome)bandbeyebabnormalitiesb(eg,birisbhypopigmentation,brefractive
errors,bnystagmus).bInbtyrosinasebdeficiency,bmelanocytesbarebunablebtobsynthesizebmelaninbfromb
thebaminobacidbtyrosine.bIridicbheterochromiabandbsensorineuralbdeafnes
2
ExambSectionb1:bItemb2bofb50
NationalbBoardbofbMedicalbExaminers®
ComprehensivebBasicbSciencebSelf-Assessment
2.bDuringbanbexperiment,babsolutionbofbmixedbfattybacidsbisbinjectedbintobthebduodenumbofbanbexp
erimentalbanimal.bUnderbthesebconditions,bthebclearancebratebofbanbintravenousbglucosebloadbfro
mbthebcirculationbisbdoubled.bInbcontrast,banbinjectionbofbanbequal
volumebamountbofb0.9%bsalinebintobthebduodenumbhasbmuchblessbeffectbonbthebplasmabclearanceb
ratebofbglucose.bThesebfindingsbarebmostblikelybcausedbbybthebsecretionbofbwhichbofbthebfollowingb
hormones?
A)bGastrin
B)bGlucose-dependentbinsulinotropicbpeptide
,C)bMotilin
D)bSecretin
E)bSomatostatinb-bbCORRECTbANSWERSB.
Glucose-
dependentbinsulinotropicbpeptideb(GIP)bisbsecretedbbybKbcellsbinbthebduodenumbandbjejunumbandb
functionsbtobdecreasebgastricbacidbproductionbandbstimulatebinsulinbreleasebfrombthebpancreas.bIt
sbsecretionbisbpromotedbbybthebpresencebofbfattybacids,bamino
acids,bandbintestinalbglucose.bWhilebserumbglucosebalsobstimulatesbinsulinbsecretionbbybthebpancr
eas,bthebeffectbofbintraluminalbglucosebonbGIPbandbsubsequentbinsulinbsecretionbleadsbtobincrease
dbconcentrationsbofbinsulinbcomparedbtobparenteralbglucose
administration.bInsulinbpromotesbperipheralbtissuebuptakebofbglucose,bglycolysis,bglycogenbsynthe
sis,bproteinbsynthesis,bandbfattybacidbsynthesis,bresultingbinbdecreasedbglucosebconcentrationbinbth
ebserum.
IncorrectbAnswers:bA,bC,bD,bandbE.
Gastrinb(ChoicebA)bisbproducedbbybGbcellsbinbthebgastricbantrumbandbstimulatesbparietalbcellsbwithi
nbthebgastricbbodybtobproducebhydrochloricbacid.bGastricbacidbhasbnobeffectbonbserumbglucosebcon
centration.
Motilinb(ChoicebC)bisbsecretedbbybthebsmallbintestinebandbstimulatesbintestinalbperistalsis.bMotilinbr
eceptorsbarebtargetedbbyberythromycinbandbmetoclopramide,busedbtherapeuticallybinbgastropares
is.
Secretinb(ChoicebD)bisbproducedbbybduodenalbSbcells.bItbpromotesbthebreleasebofbbicarbonate-
richbpancreaticbsecretionsbandbbilebandbinhibitsbgastricbacidbproduction.
Somatostatinb(ChoicebE)bisbabregulatorybpeptidebsecretedbbybDbcellsbofbthebpancreasbandbgastroint
estinalbmucosabthatbinhibitsbgastricbacidbandbpepsinogenbsecretion,bgallbladderbcontraction,bandbi
nsulinbandbglucagonbrelease.bSomatostatinbwouldbhavebanbindirect
effectbonbglucosebthroughbcounterregulatorybactionbofbbothbinsulinbandbglucagon.
EducationalbObjective:bGlucose-
dependentbinsulinotropicbpeptideb(GIP)bisbsecretedbbybKbcellsbinbthebduodenumbandbjejunum,band
bitbfunctionsbtobdecreasebgastricbacidbproductionband
3
, ExambSectionb1:bItemb3bofb50
NationalbBoardbofbMedicalbExaminers®
ComprehensivebBasicbSciencebSelf-Assessment
3.bAb53-year-oldbmanbcomesbtobthebphysicianbbecausebofbab6-
daybhistorybofbshortnessbofbbreath,bcough,bandbpleuriticbchestbpain.bHisbtemperaturebisb38.9°Cb(10
2°F),bandbrespirationsbareb35/min.bSputumbisbpurulentbandbrustbcolored.bPhysicalbexaminationbsho
ws
decreasedbbreathbsounds,bandbcracklesbarebheardbatbthebleftbbase.bAbGrambstainbofbsputumbshows
bgram-positivebdiplococci.bAbchestbx-raybshowsbleft-
sidedblobarbconsolidation.bWhichbofbthebfollowingbanatomicbstructuresbmostblikelyballowedbrapidbs
preadbof
organismsbbetweenbalveolibtobinvolvebthebentirebleftblobebinbthisbpatient?
A)bAlveolarbcapillaries
B)bGerminalbcenters
C)bLymphaticbcapillaries
D)bPoresbofbKohn
E)bVascularbsinusoidsb-bbCORRECTbANSWERSD.
ThebporesbofbKohnbformbconnectionsbbetweenbalveolibandbarebpresentbinbnormalblungbtissue.bThey
barebcomposed,batbleastbinbpart,bofbtypebIlbalveolarbcellsbandballowbforbthebpassagebofbair,bfluid,bpha
gocytes,bandbinbthebsettingbofbpneumonia,bbacteriabbetweenbadjacent
alveoli.bByballowingbequilibrationbbetweenbadjacentbalveoli,bthebporesbofbKohnbaidbinbnormalboxyg
enationbandbinbthebpreventionbofbatelectasis.bHowever,binfectiousborganismsbandbinflammationbm
aybalsobspreadbbetweenbadjacentbalveolibthroughbthesebapertures.
IncorrectbAnswers:bA,bB,bC,bandbE.
Alveolarbcapillariesb(ChoicebA)bsurroundbeachbalveolusbandbarebcrucialbforbgasbexchange.bHowever,
btheybdobnotbprovidebabdirectbconnectionbbetweenbadjacentbalveoli,bprovidedbthatbthebalveolarban
dbcapillarybendotheliabremainbintact.
Germinalbcentersb(ChoicebB)ballowbforbthebdevelopmentbofbBblymphocytesbandbarebimportantbinbm
ountingbanbadaptivebimmunebresponsebtobpulmonarybpathogens.bTheybdobnotbformbconnectionsb
betweenbalveoli.
