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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