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THECRANIUM
NEUROCRANIUM&VISCEROCRANIUM
THECRANIUM
THECRANIUM
Thebonesofthecraniumaredividedintothreegroups:
•  8cranialbonesformtheneurocranium,whichprotectsthebrain
•  14facialbonesformtheviscerocranium,whichprovidesthesubstructureforthe
face
•  6auditoryossicles(malleus,incus,andstapes),threeineach.
8CRANIALBONES:
8CRANIALBONES
14FACIALBONES
6AUDITORYOSSICLES
Thesingularbonescenteredonthemidline:
•  frontal
•  ethmoidal
•  sphenoidal
•  occipital
Thetwosetsofbonesoccurringasbilateralpairs:
•  temporal
•  parietal
THENEUROCRANIUM
THECRANIALFOSSAE
THEROOF-THECALVARIA(SKULLCAP)
thecalvariaareprimarilyflatbones:
•  frontal
•  parietal
•  occipital
THENEUROCRANIUM
THECRANIALFOSSAE:
THEFLOOR-THECRANIALBASE(BASICRANIUM):
•  THEANTERIORFOSSA
•  THEBUTTERFLY-SHAPEDMIDDLECRANIALFOSSA
•  THELARGESTPOSTERIORCRANIALFOSSA
THEANTERIORFOSSA
isformedby:
•  thefrontalboneanteriorly
•  theethmoidboneinthemiddle
•  andthebodyandlesserwingsofthesphenoidposteriorly.
THECRANIUM
THEFONTANELSOFCRANIUM
TherearealsosixlargeareasofconnecRveRssuemembrane
thatcoverthegapsbetweenthedevelopingbones.
Thesemembranoussheetsarecalledfontanels,meaning“liTlefountains”.
Thenamederivesfromthefactthatababy’spulsecanbefeltsurginginthese“soW
spots”ontheskull.
Thefontanelspermittheskulltoundergochangesinshape,calledmolding,during
parturiRon(childbirth).
OssificaUonofthefontanelsisnormallycompleteby24monthsofage.
Thefontanelsare:
1.Anterior(frontal)fontanel
2.Posterior(occipital)fontanel
3.Anterolateral(sphenoid)fontanels
4.Posterolateral(mastoid)fontanels
THECRANIUM
Thefontanelsare:
1.Anterior(frontal)fontanel
Theanteriorfontanelisdiamond-shapedandisthemostprominent.Itislocatedon
theanteromedianporRonoftheskull.Closureapprox.12-18months
2.Posterior(occipital)fontanel
TheposteriorfontanelisposiRonedatthebackoftheskullonthemedianline.Itis
alsodiamond-shaped,butsmallerthantheanteriorfontanel.Closureapprox.2-3
months
3.Anterolateral(sphenoid)fontanels
Thepairedanterolateralfontanelsarefoundonbothsidesoftheskull,directly
lateraltotheanteriorfontanel.TheyarerelaRvelysmallandirregularlyshaped.
Closureapprox.3-6months
4.Posterolateral(mastoid)fontanels
Thepairedposterolateralfontanels,alsoirregularlyshaped,arelocatedonthe
posterolateralsidesoftheskull.Closureapprox.6-18months
THECRANIUM
OSSIFICATIONOFTHESKULL
BonesdevelopedbyendochondralossificaUon:
•  ethmoidbone
•  inferiornasalconcha
•  sphenoidbone(exceptforlateralpartofgreaterwing)
•  petromastoidandstyloidpartsoftemporalbone
•  occipitalbone(belowsuperiornuchalline)
TherestoftheskullbonesdevelopbyintramembranousossificaUon.
THECRANIUM
THESUTURESOFTHECRANIUM:
• 
• 
• 
• 
SAGITTALSUTURE
CORONALSUTURE
LAMBDOIDSUTURE
SQUAMOUSSUTURE
SAGITTALSUTURE
AprominentsagiTalsutureextendstheanteroposteriormedianlengthoftheskull
betweentheanteriorandposteriorfontanels.
CORONALSUTURE
Acoronalsutureextendsfromtheanteriorfontaneltotheanterolateralfontanel.
LAMBDOIDSUTURE
Alambdoidsutureextendsfromtheposteriorfontaneltotheposterolateral
fontanel.
SQUAMOUSSUTURE
Asquamoussutureconnectstheposterolateralfontaneltotheanterolateral
fontanel.
THECRANIUM
CRANIALBONES:
Theyconsistof:
•  1frontal
•  2parietals
•  2temporals
•  1occipital
•  1sphenoid
•  1ethmoid
bones.
THECRANIUM-THEFRONTALBONE
FRONTALBONE:
Thefrontalbonedevelopsintwohalvesthatgrowtogether.
Generally,theyarecompletelyfusedbyage5or6.Theforamencecumgives
passagetovesselsduringfetaldevelopment.
Thefrontalboneforms:
•  theanteriorroofofthecranium
•  theforehead
•  theroofofthenasalcavity
•  thesuperiorarches(margins)oftheorbits
•  theroofoftheorbits
•  Insomeadultsametopicsuture,apersistentfrontalsuture,isvisibleinthe
midlineoftheglabella,thesmooth,slightlydepressedareabetweenthe
superciliaryarches
•  theglabellaissuperiorlytothenasion
THECRANIUM-THEFRONTALBONE
FRONTALBONE:
Thenasionisoneofmanycraniometricpointsthatareusedradiographicallyin
medicine
THEFRONTALBONEARTICUATESWITH:
• 
• 
• 
• 
• 
• 
• 
parietal
sphenoid
zygomaRc
maxilla
ethmoid
nasal
lacrimal
ThefrontalboneDOESNOT
arUculatewith:
•  temporal(!)
•  occipital
THECRANIUM-THEFRONTALBONE
FRONTALBONE:
AhorizontalporRonofthefrontalbone(orbitalpart)forms:
•  boththeroofoftheorbitand
•  partoftheflooroftheanterior
partofthecranialcavity
Theunpairedfrontalbonehasfourparts:
•  theunpairedsquamouspart
•  thepairedorbitalpartsand
•  theunpairednasalpart
Thesupra-orbitalmarginofthefrontalbonehasasupra-orbitalforamenornotch
forpassageofthesupra-orbitalnerveandvessels
Thefrontalbonealsocontainsfrontalsinuses,whichareconnectedtothenasal
cavityandareopenedintomiddlenasalmeatus(betweenmiddleandinferior
conchae)
THECRANIUM-THEPARIETALBONE
THEPARIETALBONEARTICUATESWITH:
• 
• 
• 
• 
• 
frontal
parietal
temporal
occipital
sphenoid
ThetemporalboneDOES
NOTarUculatewith:
•  zygomaRc
•  maxilla
•  ethmoid
•  nasal
Thetwoparietalbonesformtheuppersidesandroofofthecranium
Thecoronalsutureseparatesthefrontalbonefromtheparietalbones,andthe
sagiTalsuturealongthesuperiormidlineseparatestherightandleWparietals
fromeachother.Thelambdoidsutureseparatestheparietalandtemporalbones
fromtheoccipitalbone.
Theinnerconcavesurfaceofeachparietalboneismarkedbyshallowimpressions
fromconvoluRonsofthebrainandvesselsservingthebrain.
THECRANIUM-THEPARIETALBONE
PARIETALBONE:
BregmaisthecraniometriclandmarkformedbytheintersecRonofthesagiTaland
coronalsutures
Vertex,themostsuperiorpointofthecalvaria,isnearthemidpointofthesagiTal
suture
THECRANIUM-THETEMPORALBONE
THETEMPORALBONEARTICUATESWITH:
• 
• 
• 
• 
• 
parietal
occipital
sphenoid
zygomaRc
mandible
ThetemporalboneDOES
NOTarUculatewith:
•  frontal
•  maxilla
•  ethmoid
Eachtemporalboneisjoinedtoitsadjacentparietalbonebythesquamoussuture
Eachtemporalbonehasfourparts:
1.Squamous
2.Tympanic
3.Mastoid
4.Petrous
THECRANIUM-THETEMPORALBONE
THETEMPORALBONE:
1.Squamous
ThesquamouspartistheflaTenedplateofboneatthesidesoftheskull.ProjecRngforward
isazygomaRcprocessthatformstheposteriorporRonofthezygomaRcarch.Ontheinferior
surfaceismandibularfossa,whichformsajointwiththecondyleofthemandible.This
arRculaRonisthetemporomandibularjoint(TMJ).
2.Tympanic
ThetympanicpartofthetemporalbonecontainstheexternalacousRcmeatus,orearcanal,
whichisposteriortothemandibularfossa.Athin,pointedstyloidprocessprojectsinferiorly
fromthetympanicpart.
3.Mastoid
Themastoidprocess,aroundedprojecRonposteriortotheexternalacousRcmeatus,
accountsforthemassofthemastoidpart.Themastoidforamenisdirectlyposteriortothe
mastoidprocess.Thestylomastoidforamen,locatedbetweenthemastoidandstyloid
processes,providesthepassageforpartofthefacialnerve.
4.Petrous
Thepetrouspartcanbeseeninthefloorofthecranium.
Thestructuresofthemiddleearandinnereararehousedinthisdensepartofthetemporal
bone.ThecaroRdcanalandthejugularforamenborderonthemedialsideofthepetrous
partatthejuncRonofthetemporalandoccipitalbones.
THECRANIUM-THETEMPORALBONE
THEZYGOMATICARCH
ThezygomaUcarchisformedby:
•  theunionofthetemporalprocessofthezygomaRcbone
•  andthezygomaRcprocessofthetemporalbone
Thetemporalfossaisbounded:
•  superiorlyandposteriorlybythesuperiorandinferiortemporallines
•  anteriorlybythefrontalandzygomaRcbones
•  inferiorlybythezygomaRcarch
THECRANIUM-THETEMPORALBONE
THEINFRATEMPORALFOSSA
Theinfratemporalfossaisanirregularspace:
•  inferioranddeeptothezygomaRcarchandthemandible
•  andposteriortothemaxilla
THEPTERION
TheH-shapedformaRonofsuturesthatunite:
•  frontal
•  parietal
•  sphenoid(greaterwing)
•  andtemporalbones
THECRANIUM-THETEMPORALBONE
THEMASTOIDPROCESS:
Themastoidprocessofthetemporalboneisposteroinferiortotheexternal
acousRcopening
ThesternocleidomastoidmuscleaTachestothemastoidprocess
Themastoidprocessofthetemporalbonecanbeeasilypalpatedasabonyknob
immediatelybehindtheearlobe.Thisprocesscontainsanumberofsmallair-filled
spacescalledmastoidcellsthatcanbecomeinfectedinmastoidiRs,asaresult,for
example,ofaprolongedmiddle-earinfecRon.
THECRANIUM-THEOCCIPITALBONE
THEOCCIPITALBONEARTICUATESWITH:
• 
• 
• 
• 
parietal
temporal
sphenoid
atlas(C1)
TheoccipitalboneDOES
NOTarUculatewith:
•  frontal
•  maxilla
•  ethmoid
•  zygomaRc
ItarRculateswiththeparietalbonesatthelambdoidsuture.
THECRANIUM-THEOCCIPITALBONE
THEFORAMENMAGNUM:
Theforamenmagnumisthelargeholeintheoccipitalbonethroughwhichthe
spinalcordpassestoaTachtothebrainstem.
Contentsoftheforamenmagnum:
•  medullaandmeninges
•  vertebralarteries
•  CNXI
•  duralveins
•  anteriorandposteriorspinalarteries
Fromthedorsumsellaethereisamarkedincline,theclivus,inthecenterof
theanteriorpartofthefossaleadingtotheforamenmagnum.
THECRANIUM-THESPHENOIDBONE
THESPHENOIDBONEARTICUATESWITH:
• 
• 
• 
• 
• 
• 
• 
• 
• 
frontal
parietal
temporal
occipital
zygomaRc
maxilla
ethmoid
palaRne
vomer
isanirregularunpairedbonethatconsistsof:
•  abody
•  greaterwings
•  lesserwings
•  andpterygoidprocesses
ThesphenoidboneDOES
NOTarUculatewith:
•  nasal
•  lacrimal
•  mandible
THECRANIUM-THESPHENOIDBONE
SPHENOIDBONE:
Thebodyofthesphenoidbonehousessphenoidsinus,whichopenstothemiddle
nasalconchae.
Thegreaterandlesserwingsofthesphenoidspreadlaterallyfromthebody
Thegreaterwingshave:
•  orbital
•  temporal
•  infratemporal
•  cerebral
surfaces
Thepterygoidprocesses,consisRngof
lateralandmedialpterygoidplates,
extendinferiorlyoneachside
THECRANIUM-THESPHENOIDBONE
SPHENOIDBONE:
Thewedgelikebodycontainsthesphenoidalsinusesandaprominentsaddlelike
depression,thesellaturcica.Commonlycalled“Turk’ssaddle”thesellaturcica
housesthepituitarygland.
Thesellaturcicaiscomposedofthreeparts:
1.Thetuberculumsellae(hornofsaddle)
2.Thehypophysialfossa(pituitaryfossa)
3.Thedorsumsellae(backofsaddle)
Thedorsumsellaeformstheposteriorboundaryofthesellaturcica,andits
prominentsuperolateralanglesmakeuptheposterior
clinoidprocesses.
THECRANIUM-THESPHENOIDBONE
THESPHENOIDBONE:
Severalforaminaareassociatedwiththesphenoidbone:
1.TheopRccanal
2.Thesuperiororbitalfissure
3.Theforamenovale
4.Theforamenspinosum
5.Theforamenlacerum
6.Theforamenrotundum
THECRANIUM-THESPHENOIDBONE
THESPHENOIDBONE
1.THEOPTICCANALisalargeopeningthroughthelesserwingintothebackofthe
orbitthatprovidespassagefortheopRcnerveandtheophthalmicartery.
2.THESUPERIORORBITALFISSUREisatriangularopeningbetweenthewingsof
thesphenoidbonethatprovidespassagefortheophthalmicnerve,abranchofthe
trigeminalnerve,andfortheoculomotor,trochlear,andabducensnerves.
3.THEFORAMENOVALEisanopeningatthebaseofthelateralpterygoidplate,
throughwhichthemandibularnervepasses.Itislocatedposterolateraltothe
foramenrotundum.
4.THEFORAMENSPINOSUMisasmallopeningattheposteriorangleofthe
sphenoidbonethatprovidespassageforthemiddlemeningealvessels.
5.THEFORAMENLACERUMisanopeningbetweenthesphenoidandthepetrous
partofthetemporalbone,throughwhichtheinternalcaroRdarteryand
themeningealbranchoftheascendingpharyngealarterypass.
6.THEFORAMENROTUNDUMisanopeningjustposteriortothesuperiororbital
fissure,atthejuncRonoftheanteriorandmedialporRonsofthesphenoidbone.
Themaxillarynervepassesthroughthisforamen.
THECRANIUM-THESPHENOIDBONE
THESPHENOIDBONE:
Severalforaminaareassociatedwiththesphenoidbone:
•  OPTICCANALS-OpUcnerves(CNII)andophthalmicarteries
•  SUPERIORORBITALFISSURE-Ophthalmicveins;ophthalmicnerve(CNV1);
CNIII,IV,andVI;andsympatheUcfibers
•  FORAMENROTUNDUM-Maxillarynerve(CNV2)
•  FORAMENOVALE-Mandibularnerve(CNV3)andaccessorymeningeal
artery
•  FORAMENSPINOSUM-Middlemeningealarteryandveinandmeningeal
branchofCNV3
•  FORAMENLACERUMA-Deeppetrosalnerveandsomemeningealarterial
branchesandsmallveins
THECRANIUM-THESPHENOIDBONE
SPHENOIDBONE:
Locatedontheinferiorsideofthecranium,thesphenoidbonewouldseemtobe
wellprotectedfromtrauma.Infactthesphenoidisthemostfrequentlyfractured
boneofthecranium.
THEETHMOIDBONEARTICUATESWITH:
• 
• 
• 
• 
• 
• 
• 
• 
frontal
sphenoid
maxilla
palaRne
vomer
nasal
lacrimal
inferiornasalconcha
TheethmoidboneDOES
NOTarUculatewith:
•  temporal
•  parietal
•  occipital
•  mandible
THECRANIUM–THEETHMOIDBONE
ETHMOIDBONE:
TheethmoidboneislocatedintheanteriorporRonofthefloorofthecranium
betweentheorbits,whereitformstheroofofthenasalcavity
Theethmoidbonehas:
1.  Theperpendicularplate
2.  Thecristagalli
3.  Thesuperiorandmiddlenasalconchae
4.  Thecribriformplate
THECRANIUM–THEETHMOIDBONE
THEETHMOIDBONE
1.Theperpendicularplate
AninferiorprojecRon,whichformsthesuperiorpartofthenasalseptumthat
separatesthenasalcavityintotwochambers
2.Thecristagalli
posteriortotheforamencecum,projectssuperiorlyintothecranialcavityand
servesasanaTachmentforthemeningescoveringthebrain
3.Thesuperiorandmiddlenasalconchae
areonbothlateralwallsofthenasalcavity,
alsoknownasturbinates
4.Thecribriformplate
hasnumerouscribriformforaminaforthepassageofolfactorynerves(CNI)fromthe
epithelialliningofthenasalcavity
THECRANIUM–THEFACIALBONES
THEFACIALBONES
• 
• 
• 
• 
• 
• 
• 
• 
LACRIMALBONE
NASALBONE
INFERIORNASALCONCHA
VOMER
ZYGOMATICBONE
MAXILLA
PALATINEBONE
MANDIBLE
THECRANIUM–THEFACIALBONES
THEFACIALBONES
WiththeexcepRonsofthevomerandmandible,allofthefacialbonesarepaired.
THELACRIMALBONE
Thethinlacrimalbonesformtheanteriorpartofthemedialwallofeachorbit.
Eachonehasalacrimalsulcus-agroovethathelpsformthenasolacrimalcanal.
Thisopeningpermitsthetearsoftheeyetodrainintothenasalcavity.
THENASALBONE
Thesmall,rectangularnasalbonesjoinatthemidlinetoformthebridgeofthenose.
FracturesofthenasalbonesorfragmentaRonoftheassociatedcarRlagesare
commonfacialinjuries.
THECRANIUM–THEFACIALBONES
THEINFERIORNASALCONCHA
Thetwoinferiornasalconchaearefragile,scroll-likebonesthatprojecthorizontally
andmediallyfromthelateralwallsofthenasalcavity
Theinferiornasalconchaearethelargestofthethreepairedconchae
Theyextendintothenasalcavityjustbelowthesuperiorandmiddlenasalconchae,
whicharepartoftheethmoidbone.
THECRANIUM–THEFACIALBONES
THEVOMER
Thevomerisathin,flaTenedbonethatformsthelowerpartofthenasalseptum
Alongwiththeperpendicularplateoftheethmoidbone,itsupportsthelayerof
septalcarRlagethatformsmostoftheanteriorandinferiorpartsofthenasal
septum
THEZYGOMATICBONE
ThetwozygomaRcbones(“cheekbones”)formthelateralcontoursoftheface.
AposteriorlyextendingtemporalprocessofthisboneuniteswiththezygomaRc
processofthetemporalbonetoformthezygomaUcarch
SmallzygomaUcofacialforamen,locatedontheanterolateralsurfaceofthisbone,
allowspassageofthezygomaRcnervesandvessels.
THECRANIUM–THEFACIALBONES
THEMAXILLA
Thetwomaxillaeuniteatthemidlinetoformtheupperjaw,whichsupports
theupperteeth
ThepalaRneprocess,ahorizontalplateofthemaxilla,formsthegreaterporRonof
thehardpalateorroofofthemouth.
Theincisiveforamenislocatedintheanteriorregionofthehardpalate(behindthe
incisors),intowhichtheincisivecanalorcanalsopen.
Theinfraorbitalforamenislocatedundereachorbitandservesasapassagewayfor
theinfraorbitalnerveandarterytothenose
Theinferiororbitalfissureislocatedbetweenthemaxillaandthegreaterwingof
thesphenoid
Thelargemaxillarysinuslocatedwithinthemaxillaisoneofthefourparanasal
sinusesandentersintothemiddlenasalconchae(thesameenteringasthesphenoid
sinus)
THECRANIUM–THEFACIALBONES
THEPALATINEBONE
ThepalaRnebonesform:
•  theposteriorthirdofthehardpalate
•  apartoftheorbits
•  apartofthenasalcavity.
AttheposteriorangleofthehardpalateisthelargegreaterpalaUneforamenthat
providespassageforthegreaterpalaRnenerveanddescendingpalaRnevessels
TwoormoresmallerlesserpalaRneforaminaareposteriortothegreaterpalaRne
foramen.BranchesofthelesserpalaRnenervepassthroughtheseopenings.
THECRANIUM–THEFACIALBONES
THEMANDIBLE
Atthesuperiormarginofeachramusisthecondylarprocess,whicharRculateswith
themandibularfossaofthetemporalbone.
Thementalnerveandvesselspassthroughthementalforamen.
TheinferioralveolarnerveandvesselsaretransmiTedthroughthemandibular
foramen