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No.11.IntroductionofHumanAnatomy2.IntroductionofOsteology(BonySystem)IntroductionofHumanAnatomy

Definition:Humananatomyisthesciencewhichdealswiththegrossmorphologyandspacialinterrelationsofthestructuresofthebody.Theterm“anatomy”isderivedfromtheGreekwordsmeaning“apart”and“tocut.”

Significance:

Formedicalstudents,humananatomyisthebasiccourseofpreclinicalandclinicalcurriculum.

Classification:

Owingtodifferentmethodsandpurposesofstudy,humananatomyisclassifiedintosystematicanatomy,andregionalanatomy.Ⅰ.Fieldsofanatomy(classification)

GrossanatomyandmicroscopicanatomyThestudyofanatomyinvolvesexaminationofthegeneralstructuresofthebody(grossanatomy)aswellasthosestructuresthatcanbeseenonlywiththeaidofamicroscope(microscopicanatomy).Microscopicanatomyincludesthestudyofcells(cytology)andthestudyoftissues(histology).Whenanatomyisstudiedundertheextremelyhighmagnificationspossiblewiththeelectronmicroscope,itisreferredtoasfinestructureorultrastructure.

Regionalanatomyandsystematicanatomy:Grossanatomycanbestudiedbyregions,suchasthehead,neck,thorax,abdomen,pelvis,orlimbs.Thisapproach,referredtoasregionalanatomy,isoftenusedindissection,inwhichallstructuresinaregionarestudiedsimultaneously.However,forourpurposesthestudyofanatomybyorgansystemsthatperformcommonfunctions(systemicanatomy)ismostbeneficialandthisbookusesthatapproach.Developmentalanatomy:Thissubdivisionofanatomy,focusesonthedevelopmentofthebodyfromthefertilizedeggtotheadultform.Developmentalanatomyincludesembryology,whichislimitedtoprenataldevelopment.Radiographicanatomyisparticularlyvaluableinthediagnosisofdisordersandinjuries.Ⅱ.Thegeneralstructureofthehumanbody

Therearefourstructurallevelsinthebody:cells,tissues,organs,andsystems.Eachlevelofbodystructurehasspecificfunctionsthatcontributenotonlytothestructureitselfbutalsotothegeneralwell-beingoftheentirebody.Cell:Thehumanbodyconsistsofinnumerablecells.Tissue:

Groupsofcellsbecomedifferentiatedandbuiltupvarioustissuesofthebody.Thehumanbodyiscomposedofonlyfourbasictypesoftissue:Epithelialtissue,Connectivetissue,Musculartissue,Nervoustissue.Organ:Thesetissuesdonotexistasisolatedunits,butratherinassociationonewithanotherandinvariableproportionsandcombinations,formingdifferentorgansandstructures.

System:Aseriesoforgansandstructurescanbearrangedinasystemaccordingtotheircommonfunction.locomotorsystem、alimentarysystem、respiratorysystem、urinarysystem、genital

system、endocrinesystem、circulatorysystem(angiology)、nervoussystem、senseorgansⅢ.Anatomicalposition,Relationalplane,Termofdirection

1.Anatomicalposition

Forthepurposeofdescription,thehumanbodyisassumedtobeinerectposition,the“anatomicalposition”,withthefaceandtoesdirectedforward,theheelsandtoestogether,andupperlimbshangingbythesideofthebodywiththepalmsofthehandfacingforward.

2.Relationalplane

Therearethreekindsofrelationalplanes.SagittalplaneCoronalplaneHorizontalplaneTheseplanesdividethebodyintoleftandrightparts,anteriorandposteriorpartsandsuperiorandinferiorparts,respectively.mediansagittalplanethatpassesthroughthemidlineofbodyanddividesthebodyintoequalleftandrightparts.3.Termsofdirection

Thetermsofdirection(position)commonlyusedinclinicalpracticeandanatomyareillustratedinFig.1-1.PositionDescriptionAnteriorPosteriorInfrontofanotherstructureBehindanotherstructureSuperiorInferiorAboveanotherstructureBelowanotherstructure

PositionDescription

SuperficialDeepClosertothebodysurfaceFurtherawayfromthebodysurfaceMedialLateralClosertothemedianplaneFurtherawayfromthemedianplaneInternalExternalNearertothecenterofaholloworganorbodycavityFurtherawayfromthecenterofaholloworganorbodycavityProximalDistalClosertothetrunkororiginFurtherawayfromthetrunkororiginPARTⅠTHELOCOMOTORSYSTEMConstitution:

Thelocomotorsystemincludesbones,jointsandmuscles.Thegeneralframework(skeleton)ofthebodyisbuiltupmainlyofaseriesofbonestogetherwitharticulation.Functions:

Thelocomotorsystemnotonlyprovidestheframeworkforthebody,butalsocarriesoutthefunctionofmotion,supportandprotection.Chapter1Osteology(BonySystem)

Section1introduction

Osteologyisthestudyofboneandbones,thehardsupportingtissueofthebody.Bonesinadultare206innumber.Eachlivingboneisanorgan,ithaspropershapeandcarriesoutcertainfunctions.Itisahardandresilientorgan,andisabundantinbloodandnervesupply.Functions:Itpossessestheabilityofreconstruction,repairingandregeneration.Infact,livingbonesareplastictissueswithorganicandinorganiccomponents.Ⅰ.TheShapeandClassificationofBones

Bonesaredifferentinshapebecauseofthedisparityoftheirfunctions.Accordingtotheirshape,fourkindsofbonesareclassified.LongbonesshortbonesflatbonesIrregularbonesⅠ)LongbonesEachlongboneconsistsofashaftorbodyandtwoendsorextremities.Shaft:Theshaftisaslendertubeofcompactbonetissue.Thereisacavityintheinneroftheshaft,knownasmedullarycavity:Thecavitycontainsbonemarrowinlivingbones.Extremity:Theextremitiesarewiderandknownasepiphyses.Thesmoothsurfaceoftheendiscalledarticularsurfacewhichiscoveredbyarticularcartilage.Theshaftisconnectedwiththeepiphysesbycartilageknownasepiphysialcartilageinyoungman.Aftertheossificationoftheepiphysialcartilageshasfinishedinadult,theepiphysesfusewithmetaphysesoftheshaft,andbecometheepiphysiallines.Longbonesarefoundinlimbs,theyactastheleversinlocomotion.Ⅱ)ShortBones

Theshortbonesareroughlyincuboidshape.Theydistributeinwristandfootincludingthecarpalandtarsalbones.Thesebonesarecomposedofspongybonewithathinlayerofcompactbone.Theshortbonescanbearstrongerpressureandplayanimportantroleofsupport.Ⅲ)FlatbonesTheflatbonesconsistoftwoplatesofcompactbonewithspongyboneandmarrowbetweenthem.Inthecranialbones,thelayerofcompactboneareknownastheplatesoftheskull;theouterplateisthickandtough,theinnerplateisthin,denseandbrittle.Theinterveningspongysubstanceiscalledthedioploё.Theyincludetheribs,sternum,scapulae,andmanybonesoftheskull.Thefunctionsofthemareusuallytoprotecttheimportantorganssuchasthebrain,theheart,thelungs,theliverandthespleenetc,orprovidebroadsurfacesformuscularattachment.Ⅳ)IrregularBonesTheirregularbonesaregreatlyvariedinshape,carryoutdifferentfunctions,andcannotbeclassifiedintheprecedinggroups.Theyincludemanyofthecranialbones,thevertebrae,andthehipbones.Somecranialbonescontainair-filledcavitiesorsinusesandareknownaspneumaticbones,maxillaearetheexample.Ⅱ.TheStructureofBonesLivingbonesconsistofbonysubstance,periosteumandbonemarrow,andareabundantinbloodandnervesupply.Ⅰ)BonySubstanceThebonysubstanceincludecompactordenseboneandcancelousorspongybone.Compactbone:Thecompactboneformstheshaftofthelongboneandtheexternallayeroftheepiphysesandoutcasingofotherkindsofbone.Italsoformstheouterandtheinnerplatesoftheflatcranialbones.Thecompactboneiscapableofresistingstressesandbending.Cancellousorspongybone:Thecancellousorspongyboneconsistsofalotoftrabeculae,whichinterweavewitheachotherandarrangeintoanexpandedmeshworklikethesponge.Thetrabeculaerunindirectionssuitedtotheirfunction,andarearrangedinlineofthepressureandoftension,andinaX-rayphotographthepressurelinesareseentopassacross

jointsfrombonetobone.

Thespongybonedistributesinepiphysisandfillsintheinteriorofallbones.Thespongyboneinthecranialbonesisknownasthedioploё.Ⅱ)PeriosteumThewholeofthebone,exceptthearticularpart,isinvestedbyamembranouscoveringofperiosteum.Itconsistsoftwolayers:anouterorfibrousmembraneandaninnerorvascularmembranelinedwithbone-formingcells,theosteoblasts.Thefunctionofthesecellsismostactiveduringtheperiodofthedevelopment,growth,reconstructionandrepairingofthebones.Theperiosteumaboundswithvessels,nervesandlymphaticvessels,andplaysimportantroleintheregenerationofthebones.Sothat,forthepurposeofpreventionofthebonynecrosisordelayedhealing,itisnecessarytopreservetheperiosteumasmuchaspossiblewhentheoperationonthebonesiscarriedout.Endosteum:Itlinestheinneraspectofthemedullarycavity.Ⅲ)Bonemarrow

Therearetwokindsofbonemarrow,redandyellow.Redmarrow:Theredmarrowiscapableofmakingbloodcells.Itconsistsofmanydevelopingbloodcellsofvariedperiods.Yellowmarrow:Theyellowmarrowcomprisesalotoffat.

Atbirth,thecancellousboneandthemedullarycavitiesoflongbonesarefilledwithred(blood-forming)marrow.Bythesixthyear,theredmarrowinthemedullarycavitiesaregraduallyreplacedbyyellowmarrow.Atabout18thyear,redmarrowisalmostentirelyreplacedbyyellowoneinthebonesoflimbs,thereafter,itisconfinedtotheaxialskeleton(skull,vertebrae,ribs,sternum)andthehipbones,theupperendsoffemurandhumerus,andcarriesoutcontinuouslythefunctionofblood-forming.TheRedandwhitebloodcellsareformedintheredbonemarrow.Apunctureoniliaccrest(orspinousprocessoflumbarvertebra,orsternum)toexaminethemarrowisausefulmethodtomakeadiagnosisofsomeblooddiseases.Insometypesofanemia,thedeathrateoftheredcellsishigh,theyellowmarrowrevertstoredinanendeavortosupportthebirthrate.Ⅲ.TheChemicalCompositionandPhysicalPropertiesofBonesLivingbonesareplastictissueswithorganicandinorganiccomponents.Boneshaveanorganicframeworkoffibroustissueandcells,amongwhichinorganicsaltsaredeposited.Organicmaterial:Theorganicmaterial(themainoneiscollagen)forms30～40percentandgivesthebonesresilienceandtoughness;Inorganicmaterial:Theinorganicmaterial,mineralsalts,(themainoneiscalciumphosphate)60～70percentofthedryweightoftheboneandgivestheboneshardnessandrigidityandmakethemopaquetoX-rays.Thephysicalpropertiesofthebonesdependuponthechemicalcomponentswhichchangewithage.Ininfantandchild,theorganiccomponentsarerelativelymorethanthoseinadult,sotheirbonesaresofter,andareeasytobedeformed.Butintheoldpeople,theinorganiccomponentsarecomparativelymore,andbonefractureintheagedpeopleismoreoften.Atestcanbetakentodemonstratetherelationshipbetweenthechemicalcomponentsandthephysicalpropertiesofthebones.Bysubmergingaboneinamineralacidthesaltsareremoved,buttheorganicmaterialremainsandstilldisplaysindetailtheshapeoftheuntreatedbone.Suchaspecimenisflexible.Forexample,adecalcifiedfibulacanbetiedinaknot.Byburningabonewithfire,theorganicmaterialisremoved,thisboneismorebrittlethanporcelain,crumbleandfracturedeasily.Ⅳ.TheBloodandNerveSupplyofBones

1.Thebonesarefurnishedwithanabundanceoffinearterioles.(1)Inthelongbones,thearterialsupplyconsistsof:①periostealtwigsenteringtheshaftatmanypoints;②twigsfromarticulararteriessupplyingtheepiphyses;③thenutrientartery,whichentersthemedullarycavitythroughanutrientforamen,supplyingtheshaftandthemarrow.

(2)Theshortbonesreceivenumerousfinebloodvesselsfromtheperiosteum.(3)Flatbonesaresuppliedbynumerousvesselswhichentertheboneatvariouspointsfromthecoveringperiosteum.(4)Largeirregularboneslikethescapulaandhipbonereceivebothsuperficialvesselsfromperiosteumandnutrientarteries.

2.Lymphaticvesselsareabundantintheperiosteum,andarepresentwithinthebonesubstances.3.Numerousnervefibersaccompanythebloodvesselsofbones,theydistributewidelytoperiosteum,bonesubstanceandadventitiaofthearteries.Ⅴ.TheFunctionsofBones

Thefunctionsofbonescanbesummedupasfollows:(1)Support:Theskeletonactsastheframeworkofthebody,givingsupporttothesofttissuesandprovidingpointsofattachmentformostofthebodymuscles.(2)Movement:Becausemanyofthemusclesattachtotheskeleton,andmanyofthebonesmeetinmovablejoints,theskeletonplaysanimportantroleindeterminingthekindandextentofmovementofwhichthebodyiscapable.Chapter2ArthrologySection1IntroductionThebonesareconnectedtogetherbyfibrous,cartilaginousorosseoustissuesatdifferentpartsoftheirsurfaces,andsuchaconnectionisdesignatedbythenameofjointorarticulation.Accordingtothemovementtheyareclassifiedintotwotypesofjoints,i.e.synarthroses(syn=together;arthron=joint)anddiarthroses.Ⅰ.Synarthroses

Thesynarthroses(immovablearticulations)includethefibrousjoints,thecartilaginousjointsandsynostoses.However,slightmovementis,infact,permittedinsomesynarthroses.Ⅰ)TheFibrousJoints

Thefibrousjointsincludeallthearticulationsinwhichthebonesareheldtightlytogetherbyfibrousconnectivetissue.Thebonesareunitedbyfibroustissuewithoutanycavity.Therearetwotypesoffibrousjoints,suturesandsyndesmoses,dependinginpartonthelengthoftheconnectivetissuefibersthatholdthebonestogether.1.Sutures

Theseparatedbonesareheldtogetherbyathinlayeroffibroustissue.Theunionisextremelytightandthereislittleornomovementbetweenthebones.Thiskindofjointisfoundonlybetweentheflatbonesoftheskullandcanbefusedbyossificationfromtheearly20sandprogressesthroughoutthelife.

2.SyndesmosesThebonesareunitedbyaligamentorasheetoffibroustissue,e.g.,theyellowligamentsjointheadjacenttwovertebralarches,andtheinteroseousmembranejoinstheradiuswiththeulna.Bonesjoinedbysyndesmosesarenotheldasfirmlyasthosejoinedbysutures.Syndesmosescanpermitsomemovement.Ⅱ)CartilaginousJoints

Thebonesareunitedbycartilage.Theyallowlittleornomovement.Therearetwotypesofcartilaginousjoints:

synchondrosessymphyses.

1.Synchondroses

Thebonesofasynchondrosisjointarejointedbyhyalinecartilage.Forexample,theepiphysialcartilageplateconnectstheendsandtheshaftofalongbone.Manysynchondrosesaretemporaryjoints,withthecartilageeventuallybeingreplacedbybone.Thisreplacementoccursbetweentheepiphysesandthediaphysisoflongbones(wheretheepiphysealcartilagesarereplaced)andbetweencertainskullbones.Thejointsformedbetweenthefirsttenribsandtheircostalcartilagesarepermanentsynchondroses.

2.Symphyses

Theconnectingmaterialisabroad,flatdiscoffibrocartilage.Thiskindofjointisfoundbetweenthebodiesofvertebrae.Thepubicsymphysisisanotherexampleofthesejoints.Thesymphysisdoesnotossifythroughoutthelife.Ⅲ)Synostoses

Thebonesareunitedbytheossificationofthefibrousjointorsynchondrosisbetweenthem,e.g.,thesynostosesbetweentheilium,ischiumandpubisofthehipbone.Ⅱ.Diarthroses

TheDiarthroses(movablearticulations,synovialjoints)thereisaspacebetweenthearticulatingbones,calledthesynovialcavity.Thiskindofjointsnormallyprovidefreemovement.Thebonesareconnectedbythejointcapsuleandligament.Thereisaspacebetweenthearticulatingbones,calledthesynovialcavity.Thiskindofjointsnormallyprovidefreemovement.WecalledthemasSynovialJointsⅠ)TheEssentialStructuresofaSynovialJoint

Theessentialstructuresareasfollows:Articularsurface,Articularcapsule,Articularcavity.

1.ThearticularsurfacesTheyareusuallycoveredbythearticularcartilage.Thearticularcartilageisathinlayerofhyalinecartilagethatcoversthesmootharticularsurfacesofthebones.Itisverysmoothbutuneveninthethickness.2.Thearticular(joint)capsuleThearticularcapsuleisadouble-layeredmembranethatsurroundsandenclosesthejoint.Itisattachedtotheperipheryofthearticularsurfaceandadjacentbonesurface.Theouterlayerofthecapsule(fibrousmembrane)isformedbydenseconnectivetissuewhosefibersarefirmlyjoinedtotheperiosteumofthebonesandisrichedinbloodvesselsandnerves.Itsthicknessiscorrespondingtothefunctionsofthejoint.Theinnerlayerofthearticularcapsuleisreferredtoasthesynovialmembrane.Itconsistsofloseconnectivetissuewhoseinnersurfaceiswellsuppliedwithcapillaries.Themembrane,whichisoftenthrownintofoldsthatprojectintothejointcavity,investstheinsideofthefibrousmembrane,exceptforthesurfaceofthearticularcartilages.Itisverythin,glisteningandslippery.

Thesynovialmembranesecretesathickfluidcalledsynovialfluid(synovia).Synovialfluidprovidesnourishmenttothearticularcartilages,andlubricatesthejointsurfaces.

3.Thearticular(joint)cavityItisaclosedcavityformedbythesynovialmembraneandthearticularcartilage.Itcontainsaproperamountofsynovia.Itspressureisnegativetotheatmospherepressure.Ⅱ)TheAccessoryStructuresofSynovialJoints

Theaccessorystructuresareasfollows:TheligamentsThearticulardisc(orcartilage)Thearticularlabrum(lip)1.TheligamentsThejointsareusuallystrengthenedbyaccessoryligamentswhichareeitherinsideoroutsidethejoint(theintracapsularandextracapsularligament).Theseligamentsaredesignedtolimitmovementsofthejointinundesirabledirection.

2.Thearticulardisc(orcartilage)Itisusuallyafibrocartilageanddividesthejointcavitypartiallyorcompletelyintotwoparts.Functions:Itmakesthearticularsurfacesmorefittingwitheachotheranddiminishestheshockofthejoint.3.Thearticularlabrum(lip)Itisapliable,fibrocartilaginousringthathelpstodeepenthearticularsurfaceforthebones,e.g.,thelabrumoftheglenoidcavityofthescapula.Ⅲ)TheMovementofJointThebasicmovementsofjointsareasfollows:1.Flexionandextension2.Adductionandabduction3.Rotation4.Circumduction1.Flexionandextension

Thesetwoantagonisticmovementsareperformedinthecoronalaxis.The

flexiondecreasestheanglebetweentheadjoiningbones,whereastheextensionincreasestheangle.2.AdductionandabductionThemovementsareperfomedinthesagittalaxis.Theadductionmeansthemovementofabonetowardthemidlineofthebody.Theabductionmeansthemovementofapartawayfromthemidlineofthebody.3.RotationItmeansmovingabonearounditsverticalaxis.Itincludesmedialrotationandlateralrotation.Pronationandsupination:Themovementsarespeciallyfortheforearm.Thepronationisamovementoftheforearminwhichthepalmofthehandisturnedbackward.Thesupinationisthemovementinwhichthepalmisturnedforward.4.CircumductionItisamovementinwhichthedistalendofabonemovesinacirclewhilethepositionofproximalendremainsrelativelystable.Ⅳ)ThetypesofSynovialJointsTheycanbeclassifiedaccordingtothenumberofbones,theaxisandthetypeofmovementortheshapeofarticularsurfaceetc.1.TheuniaxialjointsTheypermitmovementonlyinoneaxis(coronal,sagittalorvertical).1)Thehingejoints(ortrochlearjoints)Theypermitflexionandextension,e.g.,theinterphalangealjoints.2)ThepivotjointsTheyallowrotationaroundalongaxis,e.g.,theproximalradioulnarjointpermitsrotationoftheheadofradius.2.Thebiaxialjoints

Theyallowmovementintwoaxeswhichmeetatrightangletoeachother.1)Theellipsoidjoints(orcondyloidjoints)Theypermitflexionandextension,adductionandabduction,aswellascircumduction.Theirarticularsurfacesareellipsoidalorovalinshape,e.g.,theradiocarpaljoint.2)ThesaddlejointsTheirarticularsurfacesareconcaveandconvex,oppositetoeachother.Theyallowmovementofflexion,extention,adduction,abductionandcircumduction.Thecarpometacarpaljointofthethumbisagoodexample.Chapter3MyologySection1IntroductionMuscletissueconstitutesalmostone-halfofthetotalbodyweight.Muchofthebody’sformisduetothenumerousmusclesthatattachtotheskeletonandunderlietheskin.Othermusclesarelocatedwithinthewallsofholloworgansandbloodvessels.Muscletypes:Thebodycontainsthreetypesofmuscles--

skeletalmuscle,

smoothmuscle,

cardiacmuscle.Musclescanbefurtherclassifiedasvoluntaryandinvoluntary,onthebasisofthetypeofcontrolexercisedovertheiractivity.Voluntarymuscles:Thecontractionsofvoluntarymusclesarenormallyundertheconsciouscontroloftheindividual.Voluntarymusclesarecontrolledbytheportionofthenervoussystemknownasthesomaticnervoussystem.Involuntarymuscles:Thecontractionsofinvoluntarymusclesaregenerallynotundertheconsciouscontroloftheindividual.Rather,theyaregovernedbytheportionofthenervoussystemknownastheautonomicnervoussystem,aswellasbyhormonesandbyfactorsintrinsictothemusclesthemselves.

Skeletalmuscles:Themusclesoflocomotorapparatusaretheskeletal(orstriated)muscles.Allofthemareattachedbyatleastoneendtosomepartoftheskeleton.Theskeletalmuscleisvoluntarymusclebecauseitscontractionisunderthevoluntarycontrol.About40%ofthebodyweightissharedbytheskeletalmuscle.Eachskeletalmusclepossessesadefiniteshape,structure,locationandaccessoryapparatus,andissuppliedbyabundantbloodvessels,lymphaticsandnerves,sothat,itcanberegardedasanorgan.Smoothmuscles:Smoothmuscleissonamedbecauseitscellslackthestriationsevidentinskeletalmusclecells.Itisalsocalledvisceralmusclebecauseitisfoundinthewallsofholloworgansandtubessuchasthestomach,intestines,andbloodvessels.Smoothmuscleisinvoluntarymuscle,anditscontractionsgovernthemovementofmaterialsthroughtheorgansystemsofthebody.Cardiacmuscles:Cardiacmuscleisaspecializedtypeofmusclethatformsthewalloftheheart.Itisinvoluntary,likesmoothmuscle,andstiated,likeskeletalmuscle.Ⅰ.TheMorphologyofSkeletalMuscleMusclefiber:Eachmuscleiscomposedofacollectionofmusclefibers(cells).Themusclefiber,bundleofmusclefibersandthemusclearewrappedbyconnectivetissue.1.Connective-tissuecoveringsMusclefibersareheldtogetherbythinsheetsoffibrousconnective-tissuemembranescalledfascia.Thefasciathatenvelopsanentiremuscleiscalledtheepimysium.Fasciaalsopenetratesmuscle,separatingthemusclefibersintobundlescalledtheperimysium.Wecansaythattheperimysiumistheconnectivetissuethatsurroundseachbundleofmusclefibers.Theendomysiumenvelopsthecellmembraneofeachmusclefiber.2.BellyandtendonThefleshypartofamuscleisoftencalledthebelly.Ateachendofaskeletalmuscletheconnectivetissueblendswiththestrongcollagenbundlestoformthetendonthatanchorsittothebone,cartilageorarticularcapsule.Themusclesvaryextremelyintheirshape.Itmaybelong,short,broadandcircularband-like(sphincter).Somemuscleshavemorethanonebellyoroneorigin.Thefibersofsomemusclesareobliquetothelongaxisofthemuscle.Becauseoftheirresemblancetofeathers,theyarecalledpinnatemuscles.Ⅱ.TheOrigin,InsertionandActionofSkeletalMuscle1.OriginandInsertion:Mostofmusclesareattachedeitherdirectlyorbymeansoftheirtendonsofaponeurosestobones,cartilages,ligaments,fasciaeortosomecombinationofthese.Somemusclesareattachedtoorgans,suchastheeyeball,andsomeareattachedtoskinormucousmembrane.Whenamusclecontractsandbecomesshort,oneofitsattachmentsusuallyremainsfixedandtheotheronemoves.Thefixedattachmentiscalledtheorigin,themovableonethe

insertion.Inthelimbs,themoredistalpartsareusuallymobile.Thereforethedistalattachmentisusuallycalledtheinsertion.However,thetermsoriginandinsertionareconvenientmerelyforpurposesofdescription.Sometimestheanatomicalinsertionremainsfixedandtheoriginmoves.Sometimesbothendsremainfixed,themusclethenstabilizesajoint.2.Primemovers(agonists)andantagonist,synergistandfixators:Duringmovementsofthebody,certainprincipalmusclesarecalledintoaction.Thesemuscles,calledprimemoversoragonists,contractactively(shortenandthicken)andproducethedesiredmovement.Amusclethatopposestheactionofaprimemoveriscalledanantagonist.Themuscleswhichcooperateinperforminganactionarecalledsynergist.Othermuscles,called

fixators,steadytheproximalpartsofalimbwhilemovementsareoccurringindistalparts.Amusclemayactasaprimemover,antagonist,synergistorfixatorunderdifferentconditions.Ⅲ.TheNomenclatureofMuscleThenamesofmusclesusuallyindicatedsomestructuralorfunctionalfeature.Anamemayindicateshape,e.g.,rhomboid,trapezius,orgracilis.Anamemayrefertolocation,e.g.,tibialisposterior.Thenumberofheadsoforiginisindicatedbythetermsbiceps,triceps