组织学与胚胎学06 肌肉组织

HistologyMUSCULARTISSUE肌肉组织1Ⅰ.Introduction1.Composition:musclecells(musclefibers)+connectivetissue.2.Musclefibers:肌纤维contractile.cellmembrane→sarcolemma肌膜,cytoplasm→sarcoplasm肌浆.3.Connectivetissue:supporting,bringinbloodvessels,lymphaticsandnerves.4.Classification:3types:skeletal,cardiac,andsmoothmuscle.2Muscles:

madeupofskeletalmusclefiberssurroundedbyCT.EpPeEdF1.Epimysium肌外膜--denseCT,surroundsentiremuscle.2.Perimysium肌束膜--fibroussheath,surroundsmusclebundles.3.Endomysium肌内膜--delicatelooseCT,surroundseachmusclefibers.

skeletalmusle

骨骼肌34A.LMstructureofMusclefibers

1.Long,cylindrical

cells

长圆柱状2.Multinucleated,多核

withnucleilying

beneathsarcolemma

3.Havingalternatingdarkandlightbands(crossstriations)

周期性横纹Ⅱ.

SkeletalMuscle骨骼肌54.Myofibrils肌原纤维

Long,cylindricalinparallel

A

band,Iband,Zline,Hband,Mline

Sarcomere:肌节1/2I+A+1/2I,

shortestcontractileunitofskeletalmuscle.6B.Ultrastructure

MyofibrilSarcoplasmicreticulum

Mitochondrium

Transversetubule

7Myofibrils

肌原纤维thickfilaments

粗肌丝thinfilaments

细肌丝8madupofthickandthinfilaments9Thickfilaments

粗肌丝1.6μmlongand15nmindiameterOccupyingAbandMadeupofmyosinmolecules:肌球蛋白10豆芽状twistedtogether,

Gobularprojectionsatone

endformthehead.头部

ATPbindingsitehaveATPaseactivity.AbilitytobindtoactinCross-brige横桥Arragement

rodportion杆部overlap;globularheadsdirecttowardeitheroftheends11b.Thinfilaments细肌丝

1μmlongand5nmindiameter;OneendisinsertedintotheZline,theotherisfreeandextendsintotheAband;一端固定于Z线，一端伸入粗肌丝间，中止于H带外侧

Composedofactin,

tropomyosinandtroponin(TnI,TnT,TnC).

12

Actin肌动蛋白

g-actin:globularmonomerscontainbindingsiteformyosin

有与肌球蛋白头部结合的位点

F-actin:long

filamentouspolymersconsisting2strandsofg-actintwistedinadublehelicalformation13Tropomyosin原肌球蛋白long,thinmoleculecontains2polypeptidechains,runalongthegroovebetween2twistedactinstrands.Troponin肌钙蛋白TnT:

attachtotropomyosinTnC:bindcalciumionsTnI:

inhibitsactin-myosininteraction

14c.Arrangement

Iband--onlythinfilamentsAband--boththickandthinfilamentsHband--onlythickfilaments(rod-likeportionsofmyosinmoleculeZline--anchorforthinfilamentsMline–

fixationofthickfilaments152.Transverse(T)tubules横小管

Formedbysarcolemmainvagination

atA-Ijunctions;肌膜向肌浆内凹陷形成的管状结构

Formananastomosingtubulesencirclingeverymyofibril;与肌纤维长轴垂直，同一平面的横小管分支吻合，环绕肌原纤维

Responsibleforrapidconductionofimpulses.将肌膜的兴奋传导至肌纤维内部163.Sarcoplasmicreticulum(Ltubule)肌浆网

Networkofsmoothendoplasmicreticulum

Encirclingeachmyofibrilbetween2adjacentTtubules.滑面内质网，位于横小管之间

Endsdilatedandfusedtoformterminalcisternae两端扩大形成的扁囊称终池17

StoringCa2+,regulatingconcentrationofCa2+withinsarcoplasm.膜中有钙泵Ttubule+2terminalcisternae=atriad.每条横小管与两侧的终池组成三联体1819C.Mechanismofcontraction--slidingfilamenthypothesis

neuralimpulsessarcolemmaTtubularsystem.thereleaseofcalciumionsfromtheSarcoplasmicreticulumcisternaetothesarcoplasmsurroundingthemyofibrils.CalciumionsinthesarcoplasmbindtotheTnCsubunitsoftroponin.

Thespatialconfigurationofthe3troponinsubunitschangesexposethemyosin-bindingsite.actinisboundtothemyosinmovementofthemyosinheadpullstheactinpastthemyosinfilament.20①运动神经末梢将神经冲动传递给肌膜；②肌膜的兴奋经横小管迅速传向终池；③肌浆网膜上的钙泵活动，将大量Ca2+转运到肌浆内；④肌钙蛋白TnC与Ca2+结合后，发生构型改变，进而使原肌球蛋白位置也随之变化；⑤原来被掩盖的肌动蛋白位点暴露，迅即与肌球蛋白头接触⑥肌球蛋白头ATP酶被激活，分解了ATP并释放能量；⑦肌球蛋白的头及杆发生屈曲转动，将肌动蛋白拉向M线⑧细肌丝向A带内滑入，I带变窄，A带长度不变，但H带因细肌丝的插入可消失，由于细肌丝在粗肌丝之间向M线滑动，肌节缩短，肌纤维收缩；⑨收缩完毕，肌浆内Ca2+被泵入肌浆网内，肌浆内Ca2+浓度降低，肌钙蛋白恢复原来构型，原肌球蛋白恢复原位又掩盖肌动蛋白位点，肌球蛋白头与肌动蛋白脱离接触，肌纤维舒张211.Ibandandsarcomerebecomeshorter,Hbandshortensordisappears,andAbandremainsconstantinlength.2.ThinfilamentsslideoverthickfilamentsandinsertfurtherintotheAband.3.Ca2+andATPplayanimportantrole.22AftercontractioncalciumionsreturntothecisternaeoftheSarcoplasmicreticulumactin-myosinbridgesbecomedetachedrelaxationoccur23

III.CardiacMuscle

心肌A.Generalfeatures1.Foundonlyinthewallofheartandtheproximalportionoftheaortaandthevenae.2.Hasmoreconnectivetissueandcapillaries;Pu24B.LMstructure

Shortcolumninshapeandbranched;短圆柱状，有分支2.showcrossstriationsandfibrils,butlessdistinct;周期性横纹，肌原纤维3.One

centrallyplacednucleus;核1～2个，卵圆形，居中254.intercalateddiskslinkcellstooneanother.

细胞间以闰盘连接26C.EMstructure

largerTtubulesatZlinelevel;

横小管发达位于Z线水平2.Simplesarcoplasmicreticulum,smallterminalcisternae;肌浆网稀疏，纵小管不发达，3.DiadsarecommonconsistingofTtubuleandterminalcisternaeononeside;终池小而少，多形成二联体274.moremitochondriaandglycogenparticles;285.Intercalateddiscs闰盘

Specializedcelljunctions;

Tworegions:TransversportionLonggitudinalportion29Transverseportionhasdesmosomesandfasciaadherenstoenhanceintercellularjunction.横位部分有中间连接和桥粒；Longitudinalportionhasgapjunctionprovidingsynchronouscontraction.

纵位部分存在缝隙连接，便于细胞间化学信息交流和电冲动传递，使心肌舒缩同步化

30Electronmicrographofanatrialmusclecellshowingthepresenceofnatriureticgranulesaggregatedatthenuclearpole.分泌心房钠尿肽31Ⅳ.SmoothMuscle平滑肌1.Seeninbloodvesselsandhollowviscera,arrangedinlayers;2.Spindleinshape,withanoval,centrallylocatednucleus;

323.Mostsarcoplasmisfilledwithmyofilaments,Thebundlesofmyofilamentscrisscrossobliquelythroughthecell,formingalattice-likenetwork.4.TheTt