the skull.pdf

8/14/2019 The Skull.pdf

1/42

AnatomyTheSkullSveinnRnarSigursson,group5.

2009

[email protected]

MedicalUniversityofDebrecen

4/20/2009


2/42

Anatomy::Theskull

T h e

s k u l l

Page

2

ContentsIntroduction.................................................................................................................................... 5

Theskull::verybriefoverview........................................................................................................ 7

1.Thevertebralcolumn(bones,joints,ligaments,curvatures,movements).................................... 8

Commonfeaturesofthevertebrae.................................................................................................... 8

Cervicalvertebrae............................................................................................................................... 8

Generalfeatures

of

the

cervical

vertebrae

.....................................................................................

9

Typialcervicalvertebrae(otherthanC1,C2,C7)............................................................................ 9

Atlas(C1)......................................................................................................................................... 9

Axis(C2)........................................................................................................................................... 9

Vertebraeprominens(C7)............................................................................................................... 9

Thoracicvertebrae............................................................................................................................ 10

Lumbarvertebrae.............................................................................................................................. 10

TheSacrum........................................................................................................................................ 10

Joints.................................................................................................................................................. 11

Structure

of

the

intervertebrae

disks.

...........................................................................................

11

Synostosis...................................................................................................................................... 11

Ligaments.......................................................................................................................................... 11

Otherimportantligaments........................................................................................................... 12

Curves................................................................................................................................................ 12

Movement......................................................................................................................................... 12

2.Vertebrae.Craniovertebraljoints.............................................................................................. 13

3.Musclesandjointsofthethorax................................................................................................ 14

Musclesofthethorax........................................................................................................................ 14

Pectoralis....................................................................................................................................... 14

major.

............................................................................................................................................

14

Pectoralis....................................................................................................................................... 14

minor............................................................................................................................................. 14

Subclavius...................................................................................................................................... 14

Serratus......................................................................................................................................... 14

magnus.......................................................................................................................................... 14

Externalintercostals(eleveninnumber)...................................................................................... 14

Internalintercostals(eleveninnumber)....................................................................................... 14

Triangularis

....................................................................................................................................

14

sterni.............................................................................................................................................. 14

Levatorscostarum(twelveinnumber)......................................................................................... 14

Diaphragm..................................................................................................................................... 14

Jointsofthethorax............................................................................................................................ 15

Costovertebraljoints..................................................................................................................... 15

Costochondraljoints...................................................................................................................... 15


3/42

Anatomy::Theskull

T h e

s k u l l

Page

3

Interchondrialjoints...................................................................................................................... 15

Sternocostaljoints......................................................................................................................... 15

4.Extrinsicandintrinsicmusclesoftheback(withtheexceptionofthenuchalregion)................. 16

Theextrinsicmusclesoftheback...................................................................................................... 16

TheTrapeziusmuscle.................................................................................................................... 16

TheLatissimus

Dorsi

Muscle

.........................................................................................................

16

TheLevatorScapulaeMuscle........................................................................................................ 17

Theintrinsicmusclesoftheback...................................................................................................... 17

TheSpleniusMuscles(Superficiallayer)....................................................................................... 17

TheErectorSpinaeMuscle(Intermediatelayer).......................................................................... 17

ActionsoftheErectorSpinaeMuscles.......................................................................................... 18

5.Partsofthecranium;calvaria,fontanelles,parietalbone.......................................................... 19

Calvaria.............................................................................................................................................. 19

Fontanelles........................................................................................................................................ 19

Parietalbone

.....................................................................................................................................

19

6.Anteriorcranialfossa.Frontalbone........................................................................................... 20

Borders.......................................................................................................................................... 20

Structures...................................................................................................................................... 20

Openings........................................................................................................................................ 20

Thefrontalbone................................................................................................................................ 21

7.Middlecranialfossa.Temporalbone......................................................................................... 22

Structuresopenings........................................................................................................................ 22

Superiororbitalfissure.................................................................................................................. 22

Opticcanal..................................................................................................................................... 22

Foremanrotundum

.......................................................................................................................

22

Foremanovale............................................................................................................................... 22

Foremanspinosum........................................................................................................................ 23

Foremanlascerum......................................................................................................................... 23

Hiatusforlesserpetrosalcanal..................................................................................................... 23

Hiatusforthegreaterpetrosalnerve............................................................................................ 23

Sellaturcica(Eng:TheTurkishsaddle)......................................................................................... 23TheTemporalbone........................................................................................................................... 23

8.Posterior

cranial

fossa.

Occipital

bone.

......................................................................................

24

Theposteriorcranialfossa................................................................................................................ 24

Occipitalbone.................................................................................................................................... 24

Squamuspart................................................................................................................................ 24

9.Externalsurfaceofthecranialbase........................................................................................... 26

Externaloccipitalprotuberance.................................................................................................... 26

Superiornuchalline....................................................................................................................... 26

Inferiornuchalline........................................................................................................................ 26


4/42

Anatomy::Theskull

T h e

s k u l l

Page

4

Occipitalcrest................................................................................................................................ 26

Foramanmagnum......................................................................................................................... 26

Occipitalcondyles.......................................................................................................................... 26

Condylarfossa............................................................................................................................... 26

Mastoidprocess

............................................................................................................................

26

Mastoidnotch............................................................................................................................... 26

Mastoidforamen........................................................................................................................... 26

Styloidprocess............................................................................................................................... 26

Styleomastoidforamen................................................................................................................. 26

Hypoglossalcanal.......................................................................................................................... 27

Jugularfossa.................................................................................................................................. 27

Fossulapetrosa.............................................................................................................................. 27

Cochlearcanalicule

........................................................................................................................

27

Carotidcanal.................................................................................................................................. 27

Foremanlacerum.......................................................................................................................... 27

Scaphoidfossa............................................................................................................................... 27

Groovefortheauditorytube........................................................................................................ 27

Musculotubariancanal.................................................................................................................. 27

Pterygoidcanal.............................................................................................................................. 27

Mandibularfossa........................................................................................................................... 28

Inferiororbital

fissure

....................................................................................................................

28

Zygomaticotemporalforamen...................................................................................................... 28

Zygomaticofacialforeman............................................................................................................. 28

Greaterpalatinecanals................................................................................................................. 28

Lesserpalatinecanal..................................................................................................................... 28

Incisivecanal................................................................................................................................. 28

Zygomaticcanal............................................................................................................................. 28

10.Temporal,infratemporalandpterygopalatinefossae.............................................................. 29

11.Bonesofthefacialskeleton.Maxilla........................................................................................ 30

TheFrontalbone........................................................................................................................... 30

Zygomaticbone............................................................................................................................. 30

TheSphenoidbone........................................................................................................................ 30

TheMaxilla........................................................................................................................................ 30

12.Bonesofthefacialskeleton.Ethmoidalbone.......................................................................... 31

The5largestbonesofthefacialskeleton......................................................................................... 31

Frontalbone.................................................................................................................................. 31


5/42

Anatomy::Theskull

T h e

s k u l l

Page

5

Zygomaticbone............................................................................................................................. 31

Maxilla........................................................................................................................................... 31

Sphenoidbone.............................................................................................................................. 31

Thethreesmallerfacialbones.......................................................................................................... 32

Nasalbone..................................................................................................................................... 32

Lacrimalbone................................................................................................................................ 32

Palatinebone................................................................................................................................. 32

Ethmoidalbone................................................................................................................................. 32

13.Wallsandopeningsonthewallsoftheorbit........................................................................... 33

14.Nasalcavity,paranasalsinuses................................................................................................ 34

Entrance:Piriformicaperture....................................................................................................... 34

Thenasalcavity............................................................................................................................. 35

NasalMeati.................................................................................................................................... 35

Exitofthenasalcavity................................................................................................................... 36

Paranasalsinuses............................................................................................................................... 37

Sphenoidsinus............................................................................................................................... 37

Maxillarysinus............................................................................................................................... 37

Frontalsinus.................................................................................................................................. 37

Ethmoidsinus................................................................................................................................ 37

15.Mandible.Temporomandibularjoint....................................................................................... 38

TheTemporomandibularjoint.......................................................................................................... 38

Movementsatthejoint................................................................................................................. 39

Musclesthatmovethejaw........................................................................................................... 39

TheTemporalisMuscle................................................................................................................. 40

TheMasseterMuscle.................................................................................................................... 40

TheLateralPterygoidMuscle........................................................................................................ 40

TheMedialPterygoidMuscle........................................................................................................ 40

Additionalinformation.................................................................................................................. 41

Thecranialnerves............................................................................................................................. 41

Notestakendownfromhereandthere........................................................................................... 41

CranialForaminaandapertures........................................................................................................ 42

IntroductionThisdocumentcontainssuggestedanswerstoThetopicsofthe3rdselfcontroltest,aspreparedby

theAnatomydepartment.

Theskullisthemostcomplexboneinthebody.So,inordertounderstandeachtopicfullyandwith

lessefforts,itiscriticaltostartwithahighlevel overviewoftheskullitself.


6/42

Anatomy::Theskull

T h e

s k u l l

Page

6

Iusedvarioussourcestocreatethisdocument,rangingfromMoore,Netter,Graysanatomyand

teacherhandouts.IrecommendusingthissummaryasaguidelinealongsideanAnatomyAtlas,such

asNetter.Bones,ligamentsandotherstructuresaredescribedinentiresentences,insteadofsimply

listingthefeaturestobementionedonthetest.IthinkthisisabetterapproachthaninSamannotes

forexample,sinceanatomicallocationofeachanatomicalfeaturemustbedescribedontheexam,

butnotonlyitsname.Nevertheless,Ialsodecidedtoincludealotofanatomicdetailsfoundoneach

boneandincludethemasrawdata.Suchdetailsaredisplayedinlistsandwithasmallerfont.

Finally,therearedefinatellysomeerrorshereandthere,orsomethingsmissing...so,onceagain,use

thesummaryasaguide,alongsideanAtlas,inordertopasstheSCT.

SpecialthanxgotoCsabbaM.&TamasJ.forreviewingmynotes,providingmewithadditional

information,errorcorrectionsetc.

ReferencestoMooresClinicallyOrientedAnatomyweremadeusingthelatest,6th,edition.Same

appliestoNettersAnatomyAtlas.Thereferencesarenotvalidforothereditions.

Svenni


7/42

Anatomy::Theskull

T h e

s k u l l

Page

7

Theskull::verybriefoverviewBeforedivingintothetopicsthemselves,thefollowingbriefoverviewcanbeappliedasan

introductiontoallthetopics.

Theskullisthemostcomplexboneinourbody.Itismadeofseveralbonesanditisdividedintoa

fewsegments.

Theskullisreferredto,astheCranium,whichmeanstheskull+thelowerjaw.

TheNeurocraniumisthebonycaseforourbrain.Itisformedby8bones.Fourbonesthattouchthe

midline(frontal,ethmoidal,sphenoidal andoccipitalbones)andtwosetsofbonesthatcomeinbi

lateral(thatis,existonoppositelateralsides)temporal andparietalbones.

TheNeurocraniumhasaroof,whichlookslikethedomeofthechurchifyouwill.Itisalsoreferredto

toastheCalvaria(skullcap).Whenremovingthebrain,duringautopsyetc.,thisisthepartthatis

removedfromthehead,inordertoremovethebrain.Mostofthesebonesareunitedbyfibrous

interlockingsutures.

ThefloorofthecalvariaiscalledtheCranialbase.ThebonesthatmakeuptheCranialbaseare

mostlyirregularboneswhilemostofthebonesthatmakeuptheCalvariaaremainlyflatbones.

TheViscerocraniumcosistsof15irregularbonesandthisregionisusuallyreferredtoasthefacial

skeleton.


8/42

Anatomy::Theskull

T h e

s k u l l

Page

8

1.Thevertebralcolumn(bones,joints,ligaments,curvatures,movements).PAGESINNETTER::153,154,155,13,17,18,157,185,248

MOORE::19,982984,440448,477480

Structuretheanswerbyfirstnamingthesections,thengooverthecommonfeaturesofthevertebrae,thenspecialfeaturesofeachsection,thenjoints,ligaments,curvatureandmovementsendingwithblueboxesThevertebralcolumncanbesplitinto3sections.

Cervicalvertebrae(7bones,Atlas(C1),Axis(C2),Vertebraeprominens(C7))Thoracicvertebrae(T1T12)Lumbarvertebrae(L1L5)Sacrum(5fusedsacralvertebrae+coccyx)

Theaveragehumanhas between3335vertebrae.Thedifferencedependsonwhetherthecoccyx

has4or6vertebrae.

CommonfeaturesofthevertebraeThevertebraeofall3sections(cervical,thoracicandlumbar)havesomeelementsincommon.They

allhaveabodyandonthedorsalsidewefindanarch, Pedicles(means:asmallfoot)anda

vertabraeforamenthatformsthevertebraecanal.Insideit,wefindthespinalchord.

Allthevertebraehavedifferentprocesses.Someoftheseprocessesarepaired.Thespinous

(meaning:thorn)

process,

located

dorsally,

is

not

apaired

process.

Lateral

to

it,

we

find

aTransverse

processwhichisapairedprocessandanArticularprocesses.Wefindtwoarticularprocessesonthe

superiorsideofthevertebraeandtwoontheinferiorside,sototalof4exists.

CervicalvertebraeThereare7cervicalvertabraeinthehumanbody.The3rd6thvertebraearetypicalwhilethe1st,

2ndand7thareatypical1.Atypicalvertebraconsistsofavetrebralbody,vertebralarchandseven

processes.

1Containspecialfeatures.


9/42

Anatomy::TheskullGeneralfeaturesofthecervicalvertebraeThecervicalvertebraehaveaquadrangularshapedbody.Thecervicalvertebraehaveatriangularforamen.Onthetransverseprocesseswefindatransverseforamina.Insidethetransverseforaminawefindvertebraearteries.AtlasandAxisareadaptedtoallowmovementofthehead2attheAtlantooccipitaljoints(synovialjoint).Theythereforecontainsomefeatureswhichweneedtomentionspecifically. Rotationofthehead,takesplacebetweenAtlasandtheAxis,attheAtlantoaxialjoints.Typialcervicalvertebrae(otherthanC1,C2,C7)

Hasabodyinfront,Neuralarchbehind,togetherclosingtheVertebralForamen,Aspinousprocesswith2tubercles,atransverseprocessoneachsite.Thearticularsurfacesoneachsiteformtheintervertebraljoints.Thecervicalvertebraearejoinedbytheintervertebraldisk,infront,andtwointervertebraljointsbehind.

Atlas(C1)Thevertebraewhichconnectstotheskull,theAtlas,hasafewuniqueelements.Atlashasnobody.Instead,ithasananteriorandaposteriorarchwhichencloseanunusuallylargeforamen.Itsspinousprocessismissing.OntheAtlas,wefindthefoveadentis. Articularsurfacesmustbementionedandpointedout.TheyareshapedlikecupssothattheycanmatchthecondylesoftheOccipitalbone(towhichtheyconnect).

FRACTUREAND DISLOCATIONOF THE ATLAS:VERTICALFORCES(LIKEHITTINGTHE BOTTOMOF APOOLWITHYOURHEAD)CAN FRACTUREONE ORBOTHOFTHE ANTERIOROR POSTERIORARCHES./THETRANSVERSELIGAMENTCAN ALSORUPTURE.

Axis(C2)AxisisfoundrightbelowtheAtlas.CanbedistinguishedbytheOdontoidprocess3.Inrotation,theAtlasvertebraerotatesaroundthisprocess.TheAxishasaregularquadrangularshapedbody.Italsohastransverseprocesses.Ithasadenseaxis.

FRACTUREAND DISLOCATIONOF THE ATLAS:ONEOF THE MOSTCOMMONVERTEBRAEINJURIES.UPTO 40%.HYPEREXTENSION,USEDTO EXECUTECRIMINALSBY HANGING.THEKNOTIS PLACEDUNDERTHE CHIN,THEREFORESOMETIMESCALLEDHANGMANSINJURY.

Vertebraeprominens(C7)Thevertebraeprominensisthe7thcervicalvertebrae.Whatisimportanttomentionhereisthatitsspinousprocessisnotbifurcated.Anothernicewaytodistinguishthisvertebraistospotthebonyspiculedividingthetransverseforamenintotwoparts.

2Forwardandlateralflexion;extensionofthehead.3InNetter:theOdontoidprocessiscalledthedensofaxis


10/42

Anatomy::TheskullDISLOCATIONOF THE CERVICALVERTEBRAE:BECAUSEOF THE LARGECANAL,WECAN DISLOCATETHESEVERTEBRAEWITHOUTDAMAGINGTHE SPINALCHORD.CAN SLIPBACKINTOPLACE,RESULTINGONLYIN SOFTTISSUEDAMAGE.

ThoracicvertebraeNETTER:154Inthehumanbodywefind12thoracicvertebrae. Thebodyofthethoracicvertebraeisarchshaped.Theformeniscircularinshapeinthisregion.Inthisregionwefindobliquespinousprocesseswhichoverlapeachotherbetweenadjacentvertebrae. Inthethoracicregionwefindalargenotchbetweenthebodyandthespinousprocesses.Thisnotchiscalledtheintervertebraenotch.Thenotchparticipatesintheformationoftheintervertebraeforamina,whichisformedbetween2adjacentnotches.Theintervertebraeforaminacontainnerves(ganglion4/Properganglion).Inthethoracicregionwefindarticularsurfacesfortheribs(smoothsurfaces). Thissurfaceisexclusivelyfoundinthethoracicregion.Onthelateralsideofthebodyofthethoracicvertebrae,wefindanotherarticularsurfacefortheheadoftheribs5.LumbarvertebraeThereare5lumbarvertebraeinthehumanbody. Thelumbarvertebraehavealarge/massivebody.Thevertebraearekidneyshaped.Thevertebraeforaminaistriangularinshape.Thevertebraehaveahugespinousprocess,locatedinasagitalplane.Theprocessisflat.Costalprocesses6arefoundonthevertebrae.Thelumbarvertebraehave verysmalltransverseprocesses7.Thelumbarvertebraehavepairedarticularsurfaces.

LUMBARSPINALSTENOSIS: DESCRIBESANARROWVERTEBRALFORAMENIN ONE OR MORELUMBARVERTEBRAE.CAN CAUSEACOMPRESSIONOF ONE ORMOREOF THE SPINALNERVEROOTS.

TheSacrumThevertebraeoftheSacrumarefusedtogether.Inthiscontextitisimportanttomentionthefusionline.

The

fusion

line

is

seen

on

the

internal

surface

(which

is

smooth).

We

need

to

be

able

to

recognizeearshapedsmoothsurfaceandtheauricularsurface.DorsalsurfaceoftheSacrum:HerewefindtheSacrumcanal,Sacralhiatus.TheSacrumcanalcontainsmerelytherootsofthespinalchord8.OnthedorsalsurfaceweneedtorecognizeMediansacral(..) (fusedspinousprocesses).LaterallytoitwefindtheMedialsacralcrestsandfutherlaterallytoitwefindlateralsacralcrests.Wecannoticeossificationbetweenthetransverseprocesses.Therearegroupsofholes,foundanteriourlyandposteriourlyontheSacrum.ThesearetheSacralforamina.Betweenthe5thsacralvertebraeandthecoccyxwefindajoint,butinmales,itisfused.

4Ganglioncontainsmanyaxisofnervecells.5NospecificnamefoundinNetter/Moore.6Costalprocessesareremnantsoftheribs(notsure,needtocheckagain).7AlsoreferredtoasAccessoryprocessinthisregion8Thespinalchordsendsbelowthe2ndlumbarvertebrae.


11/42

Anatomy::Theskull

JointsTheintervertebralarticulations,speciallythecraniovertebraljointsatitssuperiorendprovidetheflexibilitynecessarytoallowpositioningofthehead.Theintervertebraljointsaresynovialjoints.Therefore(asinallsynovialjoints)eacharticularsurfaceiscoveredwithsmootharticularcartilage.Andthespacebetweenthecartilageisfilledwithsynovialfluid.Thefluidiscontainedwithinafibreousjointcapsule.Theintervertebraldisksaremadeoffibrocartilage.TheyallowminimummovementandarethereforenotfoundbetweentheAtlasandtheAxis,instead,onlysynovialjoints.Syndesmosis(notcategorizedasaarealjoint)isfoundbetweenbonesinthevertebralcolumn.Syncondrosisisaconnectionbetweenbonesbycartilage.Structureoftheintervertebraedisks.Anulusfibrosus(meaning:ring)consistsoffibrouscartilage.Inthemiddleoftheeachdiskisastructure,thenucleuspulposus.

THEINTERVERTEBRALDISKCAN SOMETIMESPROTRUDEINTOTHE VERTEBRAECANALAND PUSHTHE SPINALCHORD.SynostosisOssificationorabonyconnection.Includessynovialjoints.Inthevertebreacolumnwefindplanesynovialjoints.Zygophysialjoints9arefoundaswell.LigamentsWefind3ligamentsthatrunverticallythroughoutthevertebraecolumn.TheNuchalLigament(Latin:LigamentumNuchae).Itlimitstheforwardflexionofthehead.Fromtheanterioraspectweseetheanteriorlongitudinalligament.Itlookslikeabroadbandandconnectstothevertebraebodiesthroughoutthewholevertebraecolumn10.Originatefromtheforaminmagnum.Itliesontheanteriorsurfaceofeachvertebrae.Continuestotheperiosteum.

Thethirdligament,theposteriorlongitudinalligamentrunsinsidethevertebraecanalitself.ItoriginatesfromtheTectorialmembraneandconnectstothebackofthebodiesthroughouttheentirevertebraecolumn.

Supraspinousligaments,arefoundontheedgesontheneckandasadirectcontinuationofthenuchal.Ligamentumflavum(meaning:yellowligament)Locatedbetweentheneighboringarches.Onthesurfaceoftheseligamentsisahole(theintervertebraeforamen)

9Betweenneighboringvertebrae10Endsonatubercle,foundontheAtlas


12/42

Anatomy::TheskullOtherimportantligamentsThetransverseligamentoftheAtlas.ItisattachedontwooppositetuberclesandenclosestheOdontoidprocessoftheAtlas.Italsocontainsasuperiorandaninferiorband(thebandsarerefferedtoasthecruciformligaments11.Alarligamentsarefoundbehindthetransverseligament(limitmovementofhead,speciallylateralflexion).Theligamentsthatconnectthearchesofthevertebraearecalledligamentumflavum12.ArchesofatlasandAxisandedgesofForamenMagnumareheldtogetherbyAtlantooccipitalandAtlantoaxialligaments.CurvesThevertebraecolumnisroughlysshaped.Inthecolumnwemustdifferentiatebetweenseveralcurvations.Thesecurvaturesarecategorizedintotwogroups,namelylordosisandkyphosisandtheycorrespondtoanteriorandposteriorcurvature,respectivelyFromtoptobottomthecurvatureofthevertebraecolumncanbedescribedassuch:

Cervicallordosis Thoracickyphosis Lumbarlordosis Sacralkyphosis

Thecurvesarefurthermorecategorizedintoprimaryorsecondarycurves.Primarycurvesaredevelopedduringembryoniclifetimeandsecondarycurvesaredevelopedafterbirth.

SCOLIOSIS:THE VERTEBRAECOLUMN IS LOCATEDMORETO THE RIGHT,THE AORTAPRESSESTHE COLUMN.PEOPLEWITHSCOLIOSISHAVEASMALLCURVATUREOFTHE COLUMN.FURTHERMORE,PEOPLEWHO SUFFERFROMSCOLIOSISHAVEAHIGHER TENDENCYTO BE LEFTHANDED.

MovementWedifferentiatebetweenventralanddorsalflexions.Ventralflexionisgeneratedinthecervicalandlumbarpartofthecolumn.Torsion/rotationFinallyyouhavetobeabletoexplaintheyesandbendingmovementsofthehead,wherethismovementoriginatesetc.

11Behindthesuperiorcruciformband,wefindasmallligamentthatliesdeepest,theApicalligamentofdens12Yellowfribrouscartilage


13/42

Anatomy::Theskull

T h e

s k u l l

Page

13

2.Vertebrae.CraniovertebraljointsNETTER::

MOORE:982984,19,440444

Thistopicoverlapswiththe1sttopicofthissummary. So,inregardsofthevertebrae(bonesonthe

vertebralcolumn)

and

the

craniovertebral

joints

Irefer

to

the

text

in

topic

1Thevertebralcolumn

(bones,joints,ligaments,curvatures,movements).,andthesectionAdditionalinformationattheveryendofthissummary.

Aproperpresentationofthisstructureistostartbymentioningthenumberofvertebraefoundinthevertebralcolumn,thenthenumberofdifferentsegments,thenanatomicalfeaturesofeachsegments(startingwiththeSacrumandendingwithAtlas(C1),thengointothecraniovertebraljoints,theligamentsofthesejoints,movements/rotationsandfinally clinicalcorrelations.

Lumbosacralangle

occurs

at

the

junction

of

the

long

axes

of

the

lumbar

region

and

the

sacrum.

The

vertebraebecomelargerastheydescendtowardsthesacrum.


14/42

Anatomy::Theskull

T h e

s k u l l

Page

14

3.MusclesandjointsofthethoraxMOORE::7981,8283,8691

Eventhoughtheskeleton (ofthethoracicwall)isnotapatofthetopic.Itsusefultostartby

mentioningit,andthereforeenvelopingtheareaunderdiscussion.

Thethoracic

skeleton

forms

the

osteocartilaginous

thoracic

cage,

which

protects

the

thoracic

viscera.Thethoracicskeletonincludes12pairsofribsandcostalcartilages,12thoracicvertebrae

andintervertibrealdisksandfinally,thesternum.

Theribsandthecostalcartilageformthelargestpartofthethoraciccage.Theribsarecurved,flat

bonesthatformthelargestpartofthethoraciccage.Theyarelightinweightyetresilient.Eachrib

hasaspongyinteriorcontainingbonemarrow.Thereare3typesofribs:true,falseandfloating

ribs.

Trueribs:Thesearethe7firstribs.Theyarecalledsobecausetheyattachdirectlytothesternumthroughtheirowncostalcartilage.

Falseribs:Theseareribs810.Theircartilagesarejoinedtotheribabovethemsotheyindirectlyconnecttothesternum. Floatingribs:Theseareribs1112.THebasiccartilagesoftheseribsdonotconnectatalltothesternum.Theyendinthe

posteriorabdominalmusculature.

MusclesofthethoraxName. Position. Origin. Insertion. Action. NerveSupply.

Pectoralis

major.

Upperandforepartof

chest,andinfrontof

axilla.

Anteriorsurfaceofsternum,

clavicle,sevenuppercostal

cartilages.

Outermarginoccipital

grooveofhumerus.

Flexesarm,raises

bodytoarms,

rotatesinwards,

adducts.

Externalanterior

thoracic.

Pectoralis

minor.

Underpectoralis

major.Third,fourth,fifthribs.

Coracoidprocess

scapula.

Depressespointof

shoulder.

Internalanterior

thoracic.

Subclavius.

Betweenclavicleand

first

rib.

Cartilage,firstrib. Undersurfaceclavicle. Drawsdownclavicle.Fromfifthand

sixth

cervical.

Serratus

magnus.

Betweenribsand

scapulaatupperpart

andsideofchest.

Eightupperribs.Vertebralborderof

scapula.

Extendsarm

forwards,assistsin

raisingribsin

inspiration.

Posterior

thoracic.

External

intercostals

(elevenin

number).

Fillsintercostalspaces. Inferiorbordersofribs.Superiorbordersof

ribsbelow.

Raisesribsin

expiration.Intercostal.

Internal

intercostals

(elevenin

number).

Fillsintercostalspaces. Inferiorbordersofribs.Superiorbordersof

ribsbelow.

Depressesribsin

inspiration.Intercostal.

Triangularis

sterni.

Innerwall

of

front

of

chest.

Lowerthird,posterior

surfaceof

sternum,

ensiform

cartilage,costalcartilageof

fourlowertrueribs.

Bydigitationsinto

lowerborders

of

costal

cartilagesofsecondto

sixthrib.

Drawsdown

costal

cartilagesin

expiration.

Intercostal.

Levators

costarum(twelve

innumber).

Onthebackbetween

seventhcervicaland

elevenupperdorsal

vertebrae.

Transverseprocess,seventh

cervicalandelevenupper

dorsalvertebrae.

Eachtotheribbelow.Raiseribsin

inspiration.Intercostal.

Diaphragm.

Formsfloorofthorax

androofofabdomen.

Ensiformcartilage,sixlower

ribs,bodiesoflumbar

vertebrae.

intocentraltendon.Respirationand

expulsion.

Phrenic,lower

intercostals,and

phrenicflexus.


15/42

Anatomy::Theskull

T h e

s k u l l

Page

15

JointsofthethoraxMOORE:7981

CostovertebraljointsAtypicalribarticulateswithtthevertebralcolumnattwojoints.

Joints

of

the

heads

of

the

ribs

:

The

head

of

each

typical

rib

articulates

with

demifacets

or

costal

facets

of

two

adjacent

thoracic

vertebraeandtheintervertebraldiscbetweenthem.Theheadarcitulateswiththesuperiorpartofthecorresponding(same

number)vertebrae.Anarticularcapsulesurroundseachjointandconnectstheheadoftheribwiththecircumferenceofthe

jointcavity.Thefibrouscapsuleisstrongestanteriourlywhereitformsaradiateligamentthatfansouttoformtheanterior

marginofthetheheadoftheribtothesidesofthebodiesofthetwovertebraeandtheIVdiscbetweenthem.

Costotransversejoints:Thetubercleofatypicalribarticulateswiththetransversecostalfacetontheanteriorsurfaceoftheendofthetransverseprocessofitsownvertebra.Thesesmallsynovialjointsaresurroundedbythinarticularcapsulethat

attachestotheedgesofthearticularfacets.Acostotranserveligamentpassingfromthenecktotheribandthentothe

transverseprocess,andalateralcostotransverseligamentpassingfromthetubercleoftheribtothetipofthetransverse

process.Finally,alateralcostotransverseligamentgoesfromthetipofthetransverseprocess,straighteningtheanteriorand

theposterioraspectofthejoint.

CostochondraljointsThecostochondralarticulationsarehyalinecartilaginousjoints.Eachribhasacupshaped

depressionin

its

sternal

end

into

which

the

costal

cartilage

fits.

The

rib

and

its

cartilage

are

firmly

boundtogetherbythecontinuityoftheperiosteumoftheribwiththeperichondriumofthe

cartilage.Nomovementusuallyoccursatthesejoints.

Interchondrial jointsThesearticulationsbetweentheadjacentbordersofthe6th7th,8th8thand9thcostalcartilage

areplanesynovialjoints.Eachofthesejointsusuallyhaveasynovialcavitythatisenclosedbyan

articularcapsule.Thejointsarestrengthenedbyanarticularcapsule.Thejointsarealso

strenghtenedbyinterchondrialligaments.Thearticulationbetweenthe9thand10thcostal

cartilagesisafibrousjoint.

SternocostaljointsThe1stto7thribsarticulatewiththeircostalcartilageswiththelateralbordersofthesternumasfolllows.The1stpairofthecartilagesarticulatewiththemanubriumonly.The2ndpairofcartilages

articulateswiththemanubriumandthe1ststernalsegment.The3rdto5thpairsofcartilages

articulatewiththe2ndand3rdsternalsegment.The6thpairofcartilagesarticulateswiththe4th

sternalsegmentonly.Andfinally,the7thpairofcartilagesarticulateswiththe4thsternalsegment

andthexiphoisprocess.


16/42

Anatomy::Theskull

T h e

s k u l l

Page

16

4.Extrinsicandintrinsicmusclesoftheback(withtheexceptionofthenuchalregion).MOORE::482,484488

TheextrinsicmusclesofthebackMOORE

::

482

Thesemusclesaresuppliedbytheventralramiofcervicalnerves,notbydorsalrami.Theexplanationforthisisthatthesuperficialbackmusclesdevelopintheembryoasaventrolateralsheetthatmigratesposteriorlytogainattachmenttothevertebralcolumn.

TheTrapeziusmuscleThisisalarge,flat,triangularmusclethatcoverstheposterioraspectoftheneckandsuperiorhalfof

the

trunk.

It

was

given

its

name

because

the

muscles

of

the

two

sides

form

a

trapezion

(G.

irregular

foursidedfigure).Thetrapeziusmuscleattachesthepectoralgirdletotheskullandthevertebral

columnandassistsinsuspendingit.

Medialattachmentsare:medialthirdofsuperiornuchalline;externaloccipitalprotuberance,ligamentumnuchae,spinousprocessesofC7toC12vertebrae.

Lateralattachmentsare:lateralthirdofclavicle,acromionandspineofscapula. Innervation:spinalrootofaccessorynerve(CNXI)andcervicaln.(C3andC4).

Thesuperiorfibresofthetrapeziuselevate the scapula;itsmiddlefibresretract the scapula,

anditsinferiorfibresdepress the scapula and lower the shoulder.Thesuperiorandinferior

fibresacttogetherinthesuperiorrotationofthescapula.Thetrapeziusmusclesbracetheshoulders

bypullingthescapulaeposteriorly,henceweaknessofthesemusclesresultindroopingofthe

shoulders.

TheLatissimusDorsiMuscleThenameofthismuscleisderivedfromtheLatinmeaning"widestoftheback".Thisislarge,wide,

fanshapedmusclepassesbetweenthetrunkandthehumerusandactsontheshoulderjointand

indirectlyonthepectoralgirdle.

Medialattachmentsare:spinousprocessesoftheinferiorsixthoracicvertebrae,thoracolumbarfascia,iliaccrest,andinferior3or4ribs.

Lateralattachmentsare:floorofintertuberculargrooveofhumerus. Innervation:thoracodorsaln.(C6,C7,andC8).

Thelatissimus

dorsi

extends,

adducts,

and

medially

rotates

the

humerus

at

the

shoulder

joint.

Whenclimbing,thesemusclesraisethetrunk.Inconjunctionwiththepectoralismajormuscle,the

latissimusdorsimuscleraisesthetrunktothearm,whichoccurswhenperformingchipups.


17/42

Anatomy::Theskull

T h e

s k u l l

Page

17

TheLevatorScapulaeMuscleThesuperiorthirdofthisstraplikemuscleliesdeeptothesternocleidomastoidmuscle;theinferior

thirdisdeeptothetrapezius.

Medialattachmentsare:posteriortuberclesoftransverseprocessesofC1orC4vertebrae. Lateralattachmentsare:superiorpartofmedialborderofscapula. Innervation:dorsalscapular(C5)andcervical(C3andC4)nerves.

Thelevatorscapulaeelevatesthescapulaandhelpstotiltitsglenoidfossainferiorlybyrotatingthe

scapula.Italsohelpstoretractthescapulaandfixitagainstthetrunkandtoflextheneck.

TheintrinsicmusclesofthebackMOORE::484488

Theintrinsicordeepmusclesofthebackareconcernedwiththemaintenanceofpostureandmovementsofthevertebralcolumnandhead.Themusclesarenamedaccordingtotheirrelationshiptothesurface:(1)asuperficiallayer,(2)anintermediatelayer,and(3)adeeplayer.

TheSpleniusMuscles(Superficiallayer)Thesearebandagelikemuscles(G.splenion,bandage)are

appliedtothesidesandbackoftheneck,somewhatlikespiral

bandages.Theyascendfromthemedialplaneoftheneckand

thetransverseprocessesofthesuperiorcervicalvertebraeto

thebaseoftheskull.Eachmuscleisdividedintoacranial

portion(latin:spleniuscapitis)andacervicalportion(latin:spleniuscervicis).

Origin:inferiorhalfoftheligamentumnuchaeandthespinousprocessesofT1toT6vertebrae. Insertion:spleniuscapitisinsertsintothelateralaspectofthemastoidprocessandthelateralthirdofthesuperiornuchalline

oftheoccipitalbone(deeptothesternocleidomastoidmuscle).Spleniuscervicisinsetsintotheposteriortuberclesofthe

transverseprocessesofC1toC4vertebrae(posteriortothelevatorscapulaemuscle).

Innervation:dorsalramiofinferiorcervicalnerves.Actingalone,thespleniusmuscleslaterallyflexandrotatetheheadandnecktothesameside.

Actingtogether,theyextendtheheadandneck.

TheErectorSpinaeMuscle(Intermediatelayer)Thismassivemuscleformsaprominentbulgeoneachsideofthevertebralcolumn.Itlieswithina

fascialcompartmentbetweentheposteriorandanteriorlayersofthethoracolumbarfascia.The

erectorspinaeisarrangedinthreeverticalcolumns:

iliocostalis(lateralcolumn); longissimus(intermediatecolumn); spinalis(medialcolumn).

Thecommonoriginofthethreecolumnsisthoughabroadtendonthatisattachedinferiorlytothe

posteriorpartoftheiliaccrest,theposterioraspectofthesacrum,thesacroiliacligaments,andthe

sacralandinferiorlumbarspinousprocesses.


18/42

Anatomy::Theskull

T h e

s k u l l

Page

18

TheIliocostalisMuscle(Intermediatelayer)Thisisthelateralcolumnoftheerectorspinaeanditarisesfromthecommonoriginandinsertsinto

theanglesoftheribs.Itmaybedividedintothreepartsaccordingtotheregioninvolved.

Iliocostalislumborumisattachedtotheinferiorsixribs; iliocostalisthoracisisattachedtoalltheribs; iliocostaliscervicisisattachedtothesuperiorsixribsandtheposteriortuberclesofC4toC6vertebrae.

TheLongissimusMuscle(Intermediatelayer)Thisistheintermediatecolumnoftheerectorspinaemuscleanditarisesfromthecommonorigin

andisattachedtothetransverseprocessesofthethoracicandcervicalvertebrae,andthemastoid

processofthetemporalboneoftheskull.Thisgivesthismuscleaherringboneappearance.

Thelongissimuscanalsobedividedintothreepartsaccordingtotheregionsittraverses.

Longissimusthoracisinsertsintothetipsofthetransverseprocessesofallofthethoracicvertebrae,andintothetuberclesoftheinferiorninetotenribs;

longissimuscervicisextendsfromthesuperiorthoracictransverseprocessestothecervicaltransverseprocesses; longissimuscapitisarisesincommonwiththecervicalpartandattachestothemastoidprocessofthetemporalbone.

TheSpinalisMuscle(Intermediatelayer)Thisisthenarrowmedialcolumnoftheerectorspinaemuscleandisrelativelyinsignificant.Itarises

fromthecommonoriginandextendsfromthespinousprocessesinthesuperiorlumbarandinferior

thoracicregionstothespinousprocessesinthesuperiorthoracicregion.Itmayalsobedividedinto

threeparts

spinalisthoracis spinaliscervicis spinaliscapitis

ActionsoftheErectorSpinaeMusclesActingbilaterally,allthreecolumnsoftheerectorspinaeextendtheheadandpartorallofthe

vertebralcolumn.

Acting

unilaterally,

the

erector

spinae

laterally

flexes

the

head

or

the

vertebral

column. Inaddition,thelongissimuscapitismusclerotatestheheadsothatitisturnedtothesame

side.Theerectorspinaemusclesarethechiefflexorsofthevertebralcolumn.Theystraightenthe

flexedcolumnandcanbenditposteriorly.Theyalso"payout"(release)duringitsflexionsothatthe

movementisslowandcontrolled.


19/42

Anatomy::Theskull

5.Partsofthecranium;calvaria,fontanelles,parietalboneMOORE::21,822,838,840(CALVARIA),28,839,840(FONTANELLES),823,829,869CalvariaMOORE::21,822,838,840

FontanellesMOORE::28,839,840

ParietalboneMOORE::823,829,869


20/42

Anatomy::Theskull

T h e

s k u l l

Page

20

6.Anteriorcranialfossa.FrontalboneMOORE::822827

TheCranialbasecanbedividedintothreestairs/stepsorthe

anterior,posteriorandmiddlecranialfossae.TheAnteriorcranial

fossaisthetopicofdiscussioninthissegment.

Westartthetopicbydefiningthebonybordersthatdefinethe

anteriorcranialfossa.

Borders Anterior:Squamuspartofthefrontalbone Posterior:Posteriorfreeedgeofthesphenoidboneexcludingtheanteriorclinoidprocess,upperborderoftheopticcanal,

limbusofthesphenoidbone

Floor:Cerebralsurfaceoftheorbitalpartofthefrontalbone,cribiformplateoftheethmoidbone,thecerebralsurfaceofthelesserwingofthesphenoidbone.

StructuresTheChristagalli/doramateranchorshere.Thecribriformplate,whichformsthefloor

13oneither

sideoftheChristaGalli,andtheverynarrowroofofthenasalcavity,has22holes.11oneachsideof

thecrhistagalli,6inthemedialand5inthelateralrow.Thereisaconnectionbetweenthenasal

cavityandtheanteriorcranialfossa.Thefilaolfactoria,anteriorethmoidartery,vein,nerveenter

throughit.

Theanteriorethmoidalforemanprovidesaconnectionbetweentheorbitandtheanteriorcranial

fossa.Itcontainstheanteriorethmoidalartery,vein,nerve.Themeningealbranchessupplythedura

mater,thenasalbranchesenterthenasalcavitythroughthecribiformplate.

Posteriorethmoidalforemanprovidesaconnectionbetweentheorbitandtheanteriorcranial

fossa.Itscontentistheposteriorethmoidalartery,vein,nerve.

OpeningsWeneedtolookatthreeopeningsthatpassforwards,twoopeningsthatpassdownardsandone

thatpassesinanobliquemannerbackwards.

StructuresthatpassforwardsaretheOpticcanal(opticnerve), locatedjustinfrontoftheanterior

clinoidprocess.LateraltotheopticcanalwefindtheSuperiorOrbitalFissure(numerousnervesand

vesselspassthroughit,intotheorbit).BelowtheSuperiorOrbitalFissurewefindtheForamen

Rotundum(maxillarybranchofthetrigeminalnerve).TheForamenRotundumdoesnotgointothe

orbit14

.

TheopeningsthatpassdownardsaretheForamenOvale(Mandibularbranchofthetrigeminal

nerve)whichcomesoutjustnexttothelateralpterygoidplate, andbehindandlateraltoit,the

ForamenSpinosum(Middlemeningealartery) whichexitsbehindandabitlateraltotheexitofthe

ForamenOvale.

13Wecanalsocallit,thedepression,onbothsides.

14Itgoesintothepterygoidmaxillaryfissure


21/42

Anatomy::Theskull

T h e

s k u l l

Page

21

Thefifthopening(theobliqueone)istheForamenLacerum(Internalcarotidartery).Theforamen

appearstopassstraightdown,butitdoesnot.Inthelivingbodytheinferioropeningisfilledwith

densecartilageandfibroustissue.Whenthethecartilageisinplace(inthelivingbody)theforamen

takesinamorecircularshapetheopeningoftheCarotidcanal.Theexit(inferiourly)ofthiscanalis

justmedialtotheStyloidprocess.Infrontoftheopeningofthecanal(ontheinferiorside)thereis

anotheropeninginfrontofit,theopeningoftheAuditoryTube.TheAuditorytubespasses

backwardsandlaterallyandemergesinthemiddleear.Inthelivingbodythetubeislonger,because

itisextendedwithCartilageoftheAuditoryTube.Theauditorytubeopensintothenasalpharynx.

ThefrontalboneMOORE::822,823824,892

Thefrontalboneisaverylargebone.Thelowerpartofthe

frontalboneformsthebeginningoftherootofthenose,the

upperpartoftheorbitalmargin,asmallpartofthetemporal

fossaandalargepartoftheroofoftheorbit.Thefrontal

bonealsoformsthelargestpartofthefloor,oftheanterior

cranialfossa.

Thepartofthefrontalbonewhichisnearthemidline,is

hollow.Thisspaceiscalledthefrontalsinus15.

15Oneofparanasalsinuses


22/42

Anatomy::Theskull

T h e

s k u l l

Page

22

7.Middlecranialfossa.TemporalboneMOORE::822827,823,829

Borders

Anterior:Istheposteriorfreeedgeofthesphenoidbone,excludingtheanteriorclinoidprocess,upperborderoftheopticcanal,limbusofthesphenoidbone.

Posterior:Superiormarginofthepyramid,posteriorclinoidprocessanddorsumsallae. Floor:Lateralandanteriorpartofthepyramid,portionoftheSquamuspartofthetemporalbone,cerebralsurfaceofthe

greaterwingofthesphenoidbone.MiddleandlateralpartsofthewallsofthebodyofSphenoidboneandsellaturcia.

Thecomplicated andraisedareainthemiddleofthecranialfossa,istheSellaTurcica(Turkishsaddle).Themainfeaturesofthearea,arethedeepdepressioncalledPituitaryFossa

16,ashallow

grooveforthetwoopticnervesandthe4projections(AnteriorClinoidprocesses/Posterior

Clinoidprocesses).TheposteriorsurfaceofthisareaiscalledDorsumSellaeandthissurfaceis

continouswiththebaseoftheocciputbone.

Aswecanseeonthefloordefinitionforthisregionhereabove,thefloorofthisregionismarked

withtheopeningsofvariousnervesandbloodvessels.

StructuresopeningsSuperiororbitalfissureIt

is

located

between

the

lesser

and

greater

wings

of

the

sphenoid

bones.

Connection

between

Middlecranialfossaandtheorbit.Itconsistsof:oculomotor(III),trochlear(IV),ophtalmic(V/1),

abducensnerves

superiorophthalmicvein.

OpticcanalItservesasaconnectionbetweenthemiddlecranialfossaandOrbit.Itconsistsof:optic(II)nerve,

opthalmicartery.

ForemanrotundumItistheconnectionbetweenthemiddlecranialfossaandthePteryopalatinefossa.Contains:

Maxillary

(V/2)

nerve

ForemanovaleItistheconnectionbetweenthemiddlecranialfossaandinfratemporalfossa.Contains:

Mandibularnerve(V/3)

lesserpetrosalnerve(branchfromBlossophanyngealnerve)

accessorymengingealartery.

16ForthePituitarygland


23/42

Anatomy::Theskull

T h e

s k u l l

Page

23

ForemanspinosumConnectionbetweenmiddlecranialfossaandinfratemporalfossa.

Middlemeningealartery

meningealbranchofmandibularnerve

ForemanlascerumBetween

middle

cranial

fossa

and

infratemporal

fossa.

Invivothisopeningisclosedbythe

synchodrosisspehnopetrosa(fibrouscartilage).Borders:thebodyofsphenoidbone(medial),the

greatwingofthesphenoid(lateral),andthepyramidofthetemporalbone.

Greaterpetrosalnerve(fromtheVIInerve).

Exitofthecarotidcanal

Betweentheexternalcranialbaseandthemiddlecranialfossa.

Internalcarotidartery,

carotidnerveplexus(sympathetic)

HiatusforlesserpetrosalcanalBetween

the

tympanic

cavity

and

the

middle

cranial

fossa.

Lesserpetrosalnerve

HiatusforthegreaterpetrosalnerveBetweenthefacialcanalandthemiddlecranialfossa

GreaterPetrosalnerve

Sellaturcica(Eng:TheTurkishsaddle)Formedbymiddleclinoidprocess,hypophysealfossa,posteriorclinoidprocess,tuberculumand

thedorsumsellae.

Content

Hypophysis.Other

structures

found

here

as

well

:Fissure

sphenopetrosa17,

Tegman

tympani18,

Arcuteeminence19,Trigemnianimpression20

TheTemporalboneMOORE::823,829

17Lateraledgeofthef.Lacerum.

18Roofofthetympanycavity

19Thisistheanteriorpartofthepyramid

20Locatedonthetopofthepyramid


24/42

Anatomy::Theskull

T h e

s k u l l

Page

24

8.Posteriorcranialfossa.Occipitalbone.MOORE::822827,493,495,831,869,986,1032

TheposteriorcranialfossaMOORE::822827

OccipitalboneMOORE::822827,493,495,831,869,986,1032

TheOccipitalboneisasaucershapedlargebone,whichformstheposteriorinferiorpartofthe

cranialbase,theocciputandthemajorityoftheposteriorcranialfossa.

Ontheinferioraspectithasalargeovalopening,theforemanmagnum,throughwhichthecranial

cavitycommunicateswiththevertebralcanal.Also,theoccipitalcondylesarelocatedforarticulation

withthe

Atlas

(C1).

Theoccipitalboneconsistsof4parts.TheSquamuspart,thegreaterpartofthebone,whichlies

behindtheforemanmagnum.Twolateralparts,oneachsideoftheforemanmagnum.Andfinally,a

basilarpartwhichislocatedinfrontoftheforemanmagnum.

SquamuspartArticulateswiththeparietalboneatthelambdoidsutureandalsowiththemastoidprocessofthe

temporalbone(occipitomastoidsuture).Thatbonyregionthatliesatthelambdoidsutureiscalled

thesuperiorangle.Thepartthatliesattheasterion(wherethesuturesoftheparietal,temporaland

occipitalbonemeet)isthelateralangle.

Externalsurface

Externaloccipitalprotrubrence Externaloccipitalcrest Highest/supremenuchalline Superiornuchalline Inferiornuchalline

Internalsurface(dividedinto4surfaces)

2upperfossaearecalledthecerebralfossa(foroccipitallobesofthebrain) 2lowerfossaearecalledthecerebellarfossae

o Internaloccipitalprotruberenceo Grooveforthesuperiorsaggitalsinuso Groovesforthetransversesinuseso Groovesforthesigmoidsinuso Internaloccipitalcrest


25/42

Anatomy::Theskull

T h e

s k u l l

Page

25

Lateralpart

OccipitalcondyleswhicharticulatewiththeAtlas(atlatooccipitaljoint) Hypoglossalcanal Condylarfossa

o Condylarcanalo Interjugularspineo

Jugular

notch

o Jugulartubercleo Grooveforsigmoidsinus

Basilarpart

Itisfusedwithethebodyofthesphenoidbone(sphenooccipitalsynchondrosis21

).Itossifies

completelybytheageof25.Atthesides,itarticulateswiththepetrouspartofthetemporalbones

(petrooccipitalsynchondrosis).Structurestobespottedinthispartare:

Clivus Groovefortheinteriorpetrosalsinus Pharyngealtubercle

21Synchondrosisarejointswheretwobonesareconnectedbyapieceofcartilage.


26/42

Anatomy::Theskull

T h e

s k u l l

Page

26

9.ExternalsurfaceofthecranialbaseMOORE::829830

Structuresweneedtopinpointatthecranialbase.

Externaloccipitalprotuberance Located

on

the

Squamous

part

of

the

occipital

bone.

The

trapezius

muscle

originates

here.

SuperiornuchallinePassesthroughtheexternaloccipitalprotuberancehorizontally.

InferiornuchallineInferiortothesupernuchalline.

Theneckmusclesinsertonboththesuperiorandtheinferiornuchallines.

OccipitalcrestLongitudinalbonycrestfortheattachmentofthemucalligament.Locatedbetweentheexternal

occipitalprotuberance

and

the

foramen

magnum

(at

the

midline).

ForamanmagnumSurroundedbythesquamous,lateralandbasilarypartsoftheoccipitalbone.

OccipitalcondylesOvoidshapearticularsurfacefortheattachmentoftheatals.

CondylarfossaDepressionjustbehindthecondyles.Thecondylarcanalopenshere.Thiscanalcontainstheemissary

veins.

MastoidprocessLocatedatthemastoidpartofthetemporalbone.Thesternocleidomastoidmuscleandtheposterior

bellyofthedigastricmusclesoriginatehere.Theprocesscontainsmastoidaircellswhichopensinto

themiddleear.

MastoidnotchItislocatedjustlateraltothemastoidprocess.Thepostbellyofthedigastricmuscleoriginateshere.

MastoidforamenOpensattheposterolateralsideofthemastoidprocess.Communicateswithttheposteriorcranial

fossaandcontainsanemissaryvein.

StyloidprocessIsalong,slenderandtoothshapedprocess.Thestylomusclesoriginatehere.

Styloglossusandstylopharnygenusmuscles.

StyleomastoidforamenLocatedbetweenthestyloidandthemastoidprocesses.Itistheexitofthefacialcanal.Insideit,we

findthefacialnerve.


27/42

Anatomy::Theskull

T h e

s k u l l

Page

27

HypoglossalcanalLocatedbetweentheoccipitalcondyles.

JugularfossaLocatedattheinferioraspectofthejugularforamen.Formedpartiallybythepyramidandpartially

bythelateralpartoftheoccipitalbone.Insideit,wefindtheGlossoparyngealnerve,Vagusnerve

andaccessory

nerve.

We

also

find

the

Internal

jugular

vein.

FossulapetrosaTinyfossalocatedbetweenthejugularfossaandtheentranceofthecarotidcanal.Theinferior

ganglionoftheglossopharingealnerveishere.Attheroofofthefossulaatinycanaliculeoriginates,

whichconnectstheECBwithtthetympaniccavity.ThisistheTympaniccanalicule.Thetympanic

nerveiswithinthiscanal.

Thetympanicnerveentersthetympaniccavityandformsanerveplexuswithinit.Oneofits

branchesexitsthetympaniccavitythroughthecanalforthelesserpetrosalnerveasthelesser

petrosalnerve.

Thetympanicnerveisabranchoftheglossopharyngealnerve,andoriginatesat(from)theinferior

ganglionoftheglossopharangealnerve.

CochlearcanaliculeLocatedslightlylateraltothefossulapetrosa.Itcontainsthecochlearduct,whichcontainsthe

perilymph.

CarotidcanalRoundopeningjustmedialtothestyloidprocess.Theinternalcarotidarteryentersthiscanalto

reachtheMCF.Itsfunctionistoreducethepulsationwaveoftheblood.Insidethecanalwefind

InternalcarotidarteryandtheCarotidplexus.

ForemanlacerumThisopeningdoesntexistinvivo;itiscoveredbythesynchondrosissphenopetrosa.Locatedatthe

jointbetweentheapexofthepyramid,bodyofthesphenoidandthebacillarypartoftheoccipital

bone.Insideitwefindthegreaterandlesserpetrosalnerves.

ScaphoidfossaLocatedattheroofofthemedialplateofthepterygoldprocess.Themedialplateoriginateswiththe

tworoots,andasmallfossacanbefoundbetweentheseroots,thescaphoidfossa.

GroovefortheauditorytubeFormsthescaphoidfossa,ashallowgrooveextendstowardsthemiddletothebaseofthepyramid.

MusculotubariancanalThiscanalsleadsfromtheECBtotheinternalear.Itissubdividedintotwohalfcanals,theupper

semicanalforthetensortympanimuscleandthelowersemicanalfortheauditorytube.

PterygoidcanalThepterygoidcanalislocatedbetweenthemedialandlateralplatesofthepterygoidprocess.


28/42

Anatomy::Theskull

T h e

s k u l l

Page

28

MandibularfossaThefossalocatedattheroofofthezygomaticarch.Theheadofthemandibulaarticulateshere.At

theborderbetweenthetympanicandSquamouspartofthetemporalbone,wecanseeaslitlike

opening.Carefulobservationrevealsatinycrest,theTegmantympani(tegmentalcrest).

BetweentheSquamouspartofthetemporalboneandthetegmentalcrest,wecanfindanarrowslit

likeopening,

the

petrosquamous

fissure.

Betweenthetegmentalcrestandthetympanicpart,wecanseethepetrotympanicfissure.The

chordatympani,abranchofthefacialnerve,exitstheskullthroughthisfissure.

InferiororbitalfissureThisslitlikeopeningislocatedbetweenthebodyofthemaxillaandtheorbitalsurfaceofthegreater

wingofthesphenoidbone.Itsaconnectionbetweentheinfratemporal fossawiththeorbit,and

alsothepterygopalativefossawiththeorbit.Insideitwefindinfraorbitalvesselsandthemaxillary

nerve.

ZygomaticotemporalforamenSeenmedially.Thisistheexitofthezygomaticotemporalcanal,atthetemporalsurfaceofthe

zygomaticbone.Itcontainsthezygomaticotemporalnerve.

ZygomaticofacialforemanSeenanteriourly.Thisistheexitofthezygomaticofacialcanal,attheanteriorsurfaceofthe

zygomaticbone.Containsthezygomaticofacialnerve.

GreaterpalatinecanalsOriginatefromthepterygopalatine.ItcontainstheDescendingpalatinearteryandthegreater

palatinenerve.

LesserpalatinecanalOriginatefromthegreaterpalatinecanalandopenbesideit,withintheoralcavity.Containsthelesserpalatineartery,lesserpalatinevein,lesserpalatinenerve

IncisivecanalFormedattheanterior,mostareaofthemedianpalatinesuture,betweentheleftandrightpalatine

andalveolarprocessesofthemaxilla.Containsnasopalatineartery,nasopalatinevein,nasopalatine

nerve.

ZygomaticcanalIsanyshapedcanalrunninginthezygomaticbone.


29/42

Anatomy::Theskull

T h e

s k u l l

Page

29

10.Temporal,infratemporalandpterygopalatinefossae.


30/42

Anatomy::Theskull

T h e

s k u l l

Page

30

11.Bonesofthefacialskeleton.Maxilla.MOORE::823824,825,827,831,952,837

Incommonlanguage,Maxilla,isrefferredtoastheupperjaw.The

Maxillaisthefocusofthistopic,butwealsoneedtoreviewtheother

facialbonesaswell.

The5largestfacialbonesarethefrontalbone,Zygomaticbones,the

Maxilla,theSphenoidboneandtheEthmoidbone.

Someofthefacialboneshavealreadybeendiscussesinthissummary.

Gotothetableofcontentstofinddescriptionforthebonesthatare

leftout(ethmoidetc.).

TheFrontalboneLowerpartformstherootofthebeginningoftherootofthenose,upperpartoftheorbitalmargin,

smallpartofthetemporalfossaandalargepartoftheroofoftheorbit.Thefrontalbonealsoforms

mostoftheflooroftheanteriorcranialfossa.

ZygomaticboneFormsthebonypartofthecheek,lowerorbitalpartoftheorbitalmarginandapartofthelateral

orbitalwall.Itextendsbackwardstomeetthezygomaticprocessofthetemporalbone,forming the

Zygomaticarch.

TheSphenoidboneExtremelycomplex.Extendsfromonesideoftheskulltotheother.

Formsapartoftheorbitandalargepartoftheanteriorfloorofthe

cranium.

Ithas

acentral

part,

the

lesser

wing,

the

greater

wing

and

thePterygoidprocess.Thecentralpartishollow

TheMaxillaTherightandleftmaxilliarejoinedtogetherinthemidline.Oneachsidethemaxilliformthelower

medialpartoftheorbitalmarginandalmostalloftheflooroftheorbit.TheMaxillabearstheupper

teeth.Ontheundersideitformsthebiggestpartofthehardpalate.TheMaxillaishollow.Itcontains

thelargestsinuses.Ifweremovethezygomaticarchweseeacleftbehindit.Thisclefthasavertical

andahorizontalsurfaceandiscalledthePterygomaxillaryFissureandtheinferiorOrbitalFissure,

respectively.Theinferiororbitalfissureseparatestheflooroftheorbitfromitslateralwall.


31/42

Anatomy::Theskull

T h e

s k u l l

Page

31

12.Bonesofthefacialskeleton.Ethmoidalbone.MOORE::824,891

Inthistopiciprefertostartbydivingthefacialskeletonintotwocategories.The5largebonesofthe

facialskeletonandthe3smallbonesofthefacialskeleton.Finishingthetopicoffwithadetailed

discussionabouttheEthmoidbone.

The5largestbonesofthefacialskeletonFrontalboneThefrontalboneisaveylargebone.Thelowerpartofthefrontalboneformsthebeginningofthe

rootofthenose,theupperpartoftheorbitalmargin,asmallpartofthetemporalfossaandalarge

partoftheroofoftheorbit.Thefrontalbonealsoformsmostoftheflooroftheanteriorcranial

fossa.Theboneofthefrontalbone,nearthemiddlinecontainsahollowspace,theNasalSinus,

whichisoneoftheparanasalsinuses.

ZygomaticboneThe

Zygomatic

bone

forms

the

bony

prominence

of

the

cheek.

It

also

forms

the

lower

lateral

part

of

theorbitalmarginandapartofthelateralorbitalwall.TheZygomaticboneextendsbackwardsto

formthezygomaticarchbetweenthezygomaticandthetemporalbone.

MaxillaTherightandleftpartsoftheMaxillaarejoinedtogetheratthemidline.

Themaxillaformsthelowermedialpartoftheorbitalmarginandalmost

alloftheflooroftheorbit.Themaxillabearstheupper teath.Onthe

underside,itformsmuchofthehardpalate.TheMaxillaishollowandit

containsthelargestoftheparanasalsinuses,theMaxillarysinus.Atthe

posteriorsideofthemaxillawefindacleft.Thisclefthasaverticalpart

andahorizontal

part.

The

vertical

part

is

named

Pterygo

maxillary

Fissure.

The

horizontal

part

is

calledtheinferiorOrbitalFissure.TheinferiorOrbitalFissureseparatestheflooroftheorbitwith

thelateralwall.

SphenoidboneTheSphenoidboneisextremelycomplex.Itextendsallthe

wayfromonesideoftheskulltotheother.Itformsimportant

partsoftheundersideandoutsideoftheskull.Italsoformsa

partoftheorbitandalargeandacomplicatedpartofthefloor

ofthemiddlecranialfossa.Thesphenoidbonehasacentral

part,and

on

each

side,

3major

projections

:the

lesser

wing,

thegreaterwingandthepterygoidprocess.

Thecentralpartoftheboneincludesthefourclinoidprocesses,andthesphenoidfossa.Thecentral

partofthesphenoidboneishollow.Thelesserwing,whichisthehighestpartofthesphenoidbone,

formstheSphenoidRidgewhichseparatesthemiddleandtheanteriorcranialfossae.Theunderside

ofthelesserwingformsasmallbutanimportantpartonthebackoftheorbit.Thegreaterwingof

thesphenoidfomsthefrontwallandpartofthefloorofthemiddlecranialfossa.Ontheoutsidethe


32/42

Anatomy::Theskull

T h e

s k u l l

Page

32

greaterwingsformsapartoftheupperandinferiortemporalfossae.Italsoformsalargepartofthe

lateralwalloftheorbital.ThegreaterandlesserwingareseparatedmediallybytheSuperiorOrbital

Fissurewhichformsalargeopeningbetweentheorbitandtheinsideofthecranium.

ThePterygoidprocessofthesphenoidboneprojectsdownwardsbehindtheproxilla.ThePterygoid

processincludesthemedialandthelateralpterygoidplates.Theareabetweenthetwoplatesisthe

PterygoidFossa.

The

little

hook

at

the

end

of

the

Pterygoid

process

is

called

Pterygoid

Hamulus.

ThethreesmallerfacialbonesNasalboneThethinnasalbonesformjusttheupperpartofthenose.Theirstructuresupportstheprojectionof

thenose,whichismadeofcartilage22.

LacrimalboneTheLacrimalboneformsthemostmedialpartoftheorbitalwall.TheopeningbetweentheLacrimal

boneandtheethmoidboneiscalledNasolacrimalductwhichtakestearsfromtheeyeandmoves

them

to

the

nasal

cavity.

PalatineboneOneachside,thePalatineboneformstheposteriorpartofthehardpalateandpartofthesidewall

ofthenasalcavity.

EthmoidalboneTheEthmoidboneisafragilecoalitionofparts.

Theethmoidalboneisalittlebitdifficulttounderstandatfirst,because,on

anintactskull,itisnearlyoutofview.

ThePerpendicularPlateoftheethmoidboneformsalargepartofthe

bonynasalseptum.Theuppermostprojectionontopoftheseptumisthe

beginningoftheCristaGalli.OneachsiteoftheCristagalliarethe

cribriformplates.Themostlateralpartoftheethmoidboneisthepaper

thinLaminaPapyraceawhichformsapartofthemedialwalloftheorbit.

BetwentheLaminapapyraceaandtheupperpartofthenasalcavity,we

findtheethmoidaircells.TheSuperiorandmiddleconchaearealsoapart

oftheethmoidbone.

Theethmoidboneisjoinedtothefrontalboneabove,themaxillabelowandthecentralpartofthe

sphenoidbone

behind.

22Histology:Elasticcartilage.


33/42

Anatomy::Theskull

T h e

s k u l l

Page

33

13.Wallsandopeningsonthewallsoftheorbit.MOORE::891,952,889,905907,892,894895


34/42

Anatomy::Theskull

T h e

s k u l l

Page

34

14.Nasalcavity,paranasalsinuses.MOORE::823824

Entrance:PiriformicapertureBorders

Above:Nasalbone Lateral:frontalprocessofthemaxilla Inferior/lateral:alveolarprocessofthemaxilla Inferior:anteriornasalspine

Superiorwall(Anterior>posteriordirection)

Nasalbone Nasalpartofthefrontalbone(nasalspine) Cribiformplateoftheethmoidbone Anteriorandinferiorwallofthebodyofthesphenoid Wingofthewomer

Connections

Cribiformplate:FilaolfactoriaconnectionbetweentheACFandthenasalcavity. Sphenoethmoidrecess:sphenoidsinuswithtwoopenings.

Sphenoethmoidrecess thesphenoethnoidrecessistheanglebetweenthelesserwingofthe

sphenoidboneandtheanteriorwallofthebodyofthesphenoidbone.Itislocatedattheroofofthe

nasalcavity.

Inferiorwall(Hardplate)

Palatineprocessofthemaxilla Horizontalplateofthepalatineborder

Onthe

inferior

wall

we

find

the

incisive

canal

which

provides

aconnection

between

the

oral

nasal

cavities.Theincisivecanalcontainsthenasopalatinenerve,arteryandvein

Lateralwall

Frontalprocessofthemaxilla Nasalsurfaceofthebodyofthemaxilla Lacrimalbone Laminapapryacea(labyrinth)oftheethmoidbone Perpendicularpalteofthepalatinebone Medialplateofthepterygoidcanal Inferiornasalconcha

Structures

Bullaethmoidalis Uncinateprocess Semilunarhiatus Superior,middleandinferiornasalconcha Superior,middleandinferiornasalmeatus Sphenopalatineforeman Nasolacrimal duct


35/42

Anatomy::Theskull

T h e

s k u l l

Page

35

Connections

Frontalsinus:Throughtheethmoidinfundibulum.Itopensattheanteriorpartofthesemilunarhiatus. Maxillarysinus:Opensattheposteriorpartofthesemilunarhiatus Anteriorandmiddleethmoidaircells:opensatthebulaethmoidalis Posteriorethmoidaircells:Superiornasalmeatus Nasolacrimal canal:containsnasolacrimalduct.Connectionsbetweenorbitandnasalcavity. Sphenopalatineforamen:Containssphenopalatineartery,andposteriorsuperiornasalnerves.

ThenasalcavityTheopeningintothenasalcavityiscalledthePiriformaperture.Insideitwefindtwonasalcavities,

separatedinthemiddlebythenasalseptum.Theseptum,isalittleofcentre,resultinginthe

cavitiesbeingofdifferentsize. Thefloorofthenasalcavityandthewallformedbytheseptumhave

nofeaturesandaresmooth.Bycontrast,thelateralwallhasanumberoffeatures,mostnotable3

deligateprojections,knownastheConchae(Turbinatebones)23

.Thethreeconchaepartiallydivide

theairpassageintothreeparts,theinferiormeatus,middlemeatusandthesuperiormeatus.Atthe

top(mediallytotheorbitcavity)thenasalcavitybecomesmuchnarrower.Thenarrowingiscaused

theexistanceofsmall,hollowspaces,theethmoidaircells.

Alargepartoftheseptumisformedbytheethmoidbone,orthePerpendicularplateofEthmoid.An

inferiorandsmallerpartisformedbyanother,smallbone,thevomer.Thelowestpartisformedby

theMaxilla(anteriourly)andposteriourlybythePalatinebone.

Theroofofthenasalcavityreachesitshighestheightinthecribriformplate.Inthelateralwallthere

areseveralopenings.Theyarepartlyhiddenbytheconchae.Thelateralwallitselfispartlyformedby

themaxilla,ethmoidboneandpartlybythepalatinebone.Furtherback,wherethenasalcavity

becomesthenasalpharynx,thewallisformedbythemedialpterygoidplate.

Allthelargefacialbonesthatsurroundthenasalcavity,arehollowtosomeextent.Thehollow

spacesinthesebonescontaintheparanasalsinuses,which,inahealthylivingbody,arefilledwith

air.All

the

paranasal

sinuses

communicate

with

the

nasal

cavity.

The

sinuses

we

need

to

know

are

Theright/leftfrontalsinus,Maxillarysinus(thelargestsinus,extendsbackwardstothefissureand

downards,almosttotherootsoftheuppermolars.)24

,Left/rightSphenoidsinuses(occupy the

centralspaceofthesphenoidbone),Ethmoidaircells25

(extendtotheback,behindthemedialwall

oftheorbitandtheupperpartofthenasalcavity).

NasalMeatiThethreenasiaconchaformthreeairpassagesbelowthem.Thesepassagesarethenasalmeati.The

nasalmeatiareimportantinmoisturingandwarminguptheairbreathedin.Theyarethesuperior,

middleandinferiornasalmeatus.

Afourth

air

passag,

the

common

nasal

meatus

is

also

formed

between

the

conchae

and

the

medial

wallofthenasalcavity.

Structuresopeningintothenasalmeati

23Inferior,middleandsuperior(smallestofthethree)concha

24AlsoknownastheMaxillaryAntrum

25Alsoreferredtoastheethmoidsinus


36/42

Anatomy::Theskull

T h e

s k u l l

Page

36

Superiornasalmeatuso Posteriorethmoidaircellso Sphenoidalsinuso Sphenopalatineforamen

Middlenasalmeatuso Maxillarysinuso Frontalsinuso Anteriorandmiddleethmoidaircells

Inferiornasalmeatuso Nasolacrimalcanal

Commonnasalmeatuso Sphenoidprocess(atsphenoidrecess)o Incisivecanal

Medialwall

Formedbythenasalseptum.Itconsistsofthreeparts.Herelistedinaposterior>anterior

direction.

Bonynasalseptum Carilagenousnasalseptum Membranousnasalseptum

Thebodyofthenasalseptumisformedbytheperpendicularpalteoftheethmoidboneandthe

bladeofthevomer.

ExitofthenasalcavityBorders

Superior:inferiorsurfaceofthebodyofthesphenoidandthewingofthewomer. Lateral:medialplateofthepterygoidbone Inferior:horizontalplateofthepalatinebone Medial:bladeofthewomer


37/42

Anatomy::Theskull

T h e

s k u l l

Page

37

ParanasalsinusesParanasalsinusesareaircontainingcavitieslocatedwithinthebonesoftheskull.Thesecavitiesarelinedbyepithiliumofthenasalcavity.

SphenoidsinusLocatedwithinthebodyofthesphenoidbone.Thissinusispartiallydividedintotwopartsonthe

midline(incompletelydivided).Eachofthepartshasaseparateexit.Openstosphenoethmoid

recess.

MaxillarysinusThisislargestofthesinuses.Locatedwithinthebodyofthemaxilla.Itopensattheposteriorportion

ofthesemilunarhiatus.Theexitofthesinusisnotatthebottomofit,butatthemidwayofthe

medialsurfaceofthebone.

Asaresult,incaseofinfection,pusaccumulateswithinthesinusandneedstobewashedout.

FrontalsinusLocatedatthebaseoftheSquamuspartofthefrontalbone.Opensattheanteriorpartofthesemilunarhiatusthroughtheinfudibulumoftheethmoidbone.

EthmoidsinusThissinusisactuallynotanaircontainingspace,butagroupofaircells.

Posteriorethmoidcells:opensatsuperiornasalmeatus Middleandanteriorethmoidaircells:Openatthemiddlenasalmeatus,onthebulla

ethmoidalis.

CLINICAL::

BACTERIALINFECTIONOFTHE SINUSISVERYCOMMON.SINUSITUS


38/42

Anatomy::Theskull

T h e

s k u l l

Page

38

15.Mandible.Temporomandibularjoint.MOORE::827,945,986,1022,922,923

Inpractise,whenwespeakaboutthejawsinplural,weare

referringtoboththemaxilla(theupperjaw)andthemandible

(thelowerjaw).Whenwespeakofthejawwearealways

referringto

the

mandible.

Themandibledevelopsfrom2individuallyseparatebones.

TheyfusetogetherattheSymphysisoftheMandible.

TheMandibleisproperlydescribedbyreferringtoitsbody anditsleftanrightRamus.Thecorner

betweenthebodyandtheRamus,istheAngleoftheMandible(roughontheoutsideandthe

inside).TheroundedprojectionsthatarticulatewithetheTemporalbonearetheCondyle(orthe

Condylarprocess).ThenarrowingbelowthecondyleistheNeckoftheMandible.Thesharpand

slenderprojectioninfrontofthecondyleistheCoronoidprocess.Rightbehindit,wefindthe

condylarnotch.

ThebodyoftheMandibleisdescribedbyitssegments,

theBaseandtheAlveolarprocess26.Ontheinsideof

thejaw,weseethatthealveolarprocessbulges

medially,thisiscausedbytheSubmandibularFossa.

Belowthecentralteethwefindaprojection,the

MentalProtuberance(chin).Ontheinside,belowthe

centralteethaswell,wefindtheMentalSpine.Behind

themostposteriorpairofmolars(the8thpair),wefind

theButtress(ontheinneraspectofthejaw).Onthe

insideoftheRamusaswell,wefindtheMandibular

Foramen(at

the

same

horizontal

level

as

the

teeth).

Just

in

front

of

it,

there

is

an

upwards

projection,theLingula.TheMandibularforamenisthestartofatunnelfortheinferioralveolar

nerveandbloodvessels.Amajorbranchofthenervemergesfromtheoutside,throughtheMental

Foramen.

TheTemporomandibular jointItenablestheMandibletomove.ItisaSynovialjointwhichmeansthatwefindarticularsurfaceson

thebonesandajointcapsulethatenclosesthesynovialfluid.Itisadoublejointsincewehavetwo

separatesynovialcavities,withoneabovetheother.Thecavitiesareseparatedbyanarticulardisk27

whichisbothflexibleandhighlymovable.Thisarrangementpermitstwokindsofmovements.

Thearticular

surface

of

the

condyle

(of

the

Mandible)

is

curved

sharplyfromthefronttotheback.Itisalmostpointyonthe

top. ThearticularsurfaceoftheTemporalbonehasadouble

curve.Theconcavepartofit,istheMandibularFossawhilethe

convexpartofitiscalledArticularTubercle.

26TheAlveolarprocessprovidesthebonysocketforourteeth.

27Madeoffibroustissue.Itsthinatthefrontandthickbehind.Itsprettyflexible


39/42

Anatomy::Theskull

T h e

s k u l l

Page

39

Mostofthejointcapsuleisthinandloose.Thisarrangement allowsmoremovement.Onthelateral

aspect,thejointcapsuleismorethick.

Theligamentsassociatedwiththisjointsare:

Thefibrouscapsuleisthickenedlaterallytoformthelateral(temporomandibular)ligament.Itreinforcesthelateralpartofthiscapsule.

Thebaseofthistriangularligamentisattachedtothezygomaticprocessofthetemporalboneandthearticulartubercle. Itsapexisfixedtothelateralsideoftheneckofthemandible. Twootherligamentsconnectthemandibletothecraniumbutneitherprovidesmuchstrength. Thestylomandibularligamentisathickenedbandofdeepcervicalfascia. Itrunsfromthestyloidprocessofthetemporalbonetotheangleofthemandibleandseparatestheparotidandsubmandibular

salivaryglands.

Thesphenomandibularligamentisalongmembranousbandthatliesmedialtothejoint. Thisligamentrunsfromthespineofthesphenoidbonetothelingulaonthemedialaspectofthemandible.

MovementsatthejointThetwotypesofmovementpossiblefortheMandibleareaHingingmovement(topimage

totheright) andaforward/backwardsgliding(loweimagetotheright)movement.

TheHinging

movement

takes

place

between

the

condyles

and

the

articulate

disk.

The

back

wardandforwardmovementmainlytakesplacebetweenthediskandtheTemporal

surface.Anormalopening/closingmovementofthejaw,isacombinationofthetwo

movements.

Detailedmovementoverview

Thetwomovementsthatoccuratthisjointareanteriorglidingandahingelikerotation. Whenthemandibleisdepressedduringopeningofthemouth,theheadofthemandibleandarticulardiscmoveanteriorlyon

thearticularsurfaceuntiltheheadliesinferiortothearticulartubercle.

Asthisanteriorglidingoccurs,theheadofthemandiblerotatesontheinferiorsurfaceofthearticulardisc. Thispermitssimplechewingorgrindingmovementsoverasmallrange. Movementsthatareseeninthisjointare:depression,elevation,protrusion,retractionandgrinding.

MusclesthatmovethejawThemusclesarenotrequiredfortheselfcontrol.Aswithmostpretators,themusclesthatclosethejawaremuchmorepowerfulthanthosewho

openit. Alligatorsareanexcellentexampleofspecieshavingveryweakopenfunctionmusclesanda

verystrongclosingfunctionmuscles.

Closingthejawisajobperformedby3strongmusclesoneachside.

Movementsofthetemporomandibularjointarechieflyfromtheactionofthemusclesofmastication. Thetemporalis,masseter,andmedialpterygoidmusclesproducebitingmovements. Thelateralpterygoidmusclesprotrudethemandiblewiththehelpfromthemedialpterygoidmusclesandretrudedlargelyby

theposteriorfibresofthetemporalismuscle.

Gravityissufficienttodepressthemandible,butifthereisresistance,thelateralpterygoid,suprahyoidandinfrahyoid,mylohyoidandanteriordigastricmusclesareactivated.


40/42

Anatomy::Theskull

T h e

s k u l l

Page

40

TheTemporalisMuscleThisisanextensivefanshapedmusclethatcoversthetemporalregion.Itisapowerfulmasticatory

musclethatcaneasilybeseenandfeltduringclosureofthemandible.

Origin:flooroftemporalfossaanddeepsurfaceoftemporalfascia. Insertion:tipandmedialsurfaceofcoronoidprocessandanteriorborderoframusofmandible. Innervation:deeptemporalbranchesofmandibularnerve(CNV3). Thetemporaliselevatesthemandible,closingthejaws;anditsposteriorfibresretrudethemandibleafterprotrusion.

TheMasseterMuscleThisisaquadrangularmusclethatcoversthelateralaspectoftheramusandthecoronoidprocessof

themandible. Origin:inferiorborderandmedialsurfaceofzygomaticarch. Insertion:lateralsurfaceoframusofmandibleanditscoronoidprocess. Innervation:mandibularnerveviamassetericnervethatentersitsdeepsurface. Itelevatesandprotrudesthemandible,closesthejawsandthedeepfibresretrudeit.

TheLateralPterygoidMuscleThisisashort,thickmusclethathastwoheadsororigin.Itisaconical

musclewithitsapexpointingposteriorly.Actingtogether,thesemuscles

protrudethemandibleanddepressthechin.Actingaloneand

alternately,theyproducesidetosidemovementsofthemandible.

Origin:superiorheadinfratemporalsurfaceandinfratemporalcrestofthegreaterwingofthesphenoidbone,inferiorheadlateralsurfaceoflateralpterygoidplate.

Insertion:neckofmandible,articulardisc,andcapsuleoftemporomandibularjoint. Innervation:mandibularnervevialateralpterygoidnervefromanteriortrunk,whichentersitdeepsurface.

TheMedialPterygoidMuscleThisisathick,quadrilateralmusclethatalsohastwoheadsororigin.It

embracestheinferiorheadofthelateralpterygoidmuscle.Itislocated

deeptotheramusofthemandible.Ithelpstoelevatethemandibleand

closesthejaws.Actingtogether,theyhelptoprotrudethemandible.

Actingalone,itprotrudesthesideofthejaw.Actingalternately,they

produceagrindingmotion.

Origin:deepheadmedialsurfaceoflateralpterygoidplateandpyramidalprocessofpalatinebone,superficialheadtuberosityofmaxilla.

Insertion:medialsurfaceoframusofmandible,inferiortomandibularforamen. Innervation:mandibularnerveviamedialpterygoidnerve.


41/42

Anatomy::Theskull

T h e

s k u l l

Page

41

AdditionalinformationThecranialnerves

I. Olfactorynerve(cribiformplate)II. Opticnerve(opticcanal)III. Oculometernerve(superior orbitalfissure)IV. Trochlearnerve(superiororbitalfissre)V. Trigeminalnerve28VI. Abducentnerve(superiororbitalfissure)VII.Facialnerve(internalacousticmeatus)VIII.Vestibulocochlearnerve(internalacousticmeatus)IX. Glossopharyngealnerve(jugularforeman)X. Vagusnerve(jugularforeman)XI. Accessorynerve(jugularforeman)XII.Hypoglossalnerve(hypoglossalcanal)

NotestakendownfromhereandthereMovingthehead,thoracicandcervicalvertebrae,upperribs,theclaviclesandtheocciputpartofskull.

Skullconsistsofthecraniumandthefacialskeleton.Craniumisthebonycontainerforthebrainand

thefoundationforthefacialskeleton.Madeupoftheseveralbones,connectedbysutures,which

showthejointsofthejoints.

Principalbonesthatformthecranium,occipitalbone,theparietalbone,temporalbonex2,

sphenoidbone,andfrontalbone.

Occipitalbone

ThemoststrikingfeatureoftheoccipitalboneistheforamenMagnum,alargeopening,through

whichthespinalchordanditsaccompaniedstructuresgothrough.Thepartinfrontoftheopeni

the skull.pdf

Documents