組織學與胚胎學06 肌肉組織

HistologyMUSCULARTISSUE肌肉組織1Ⅰ.Introduction1.Composition:musclecells(musclefibers)+connectivetissue.2.Musclefibers:肌纖維contractile.cellmembrane→sarcolemma肌膜,cytoplasm→sarcoplasm肌漿.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肌內(nèi)膜--delicatelooseCT,surroundseachmusclefibers.

skeletalmusle

骨骼肌34A.LMstructureofMusclefibers

1.Long,cylindrical

cells

長圓柱狀2.Multinucleated,多核

withnucleilying

beneathsarcolemma

3.Havingalternatingdarkandlightbands(crossstriations)

周期性橫紋Ⅱ.

SkeletalMuscle骨骼肌54.Myofibrils肌原纖維

Long,cylindricalinparallel

A

band,Iband,Zline,Hband,Mline

Sarcomere:肌節(jié)1/2I+A+1/2I,

shortestcontractileunitofskeletalmuscle.6B.Ultrastructure

MyofibrilSarcoplasmicreticulum

Mitochondrium

Transversetubule

7Myofibrils

肌原纖維thickfilaments

粗肌絲thinfilaments

細肌絲8madupofthickandthinfilaments9Thickfilaments

粗肌絲1.6μmlongand15nmindiameterOccupyingAbandMadeupofmyosinmolecules:肌球蛋白10豆芽狀twistedtogether,

Gobularprojectionsatone

endformthehead.頭部

ATPbindingsitehaveATPaseactivity.AbilitytobindtoactinCross-brige橫橋Arragement

rodportion桿部overlap;globularheadsdirecttowardeitheroftheends11b.Thinfilaments細肌絲

1μmlongand5nmindiameter;OneendisinsertedintotheZline,theotherisfreeandextendsintotheAband;一端固定于Z線，一端伸入粗肌絲間，中止于H帶外側(cè)

Composedofactin,

tropomyosinandtroponin(TnI,TnT,TnC).

12

Actin肌動蛋白

g-actin:globularmonomerscontainbindingsiteformyosin

有與肌球蛋白頭部結(jié)合的位點

F-actin:long

filamentouspolymersconsisting2strandsofg-actintwistedinadublehelicalformation13Tropomyosin原肌球蛋白long,thinmoleculecontains2polypeptidechains,runalongthegroovebetween2twistedactinstrands.Troponin肌鈣蛋白TnT:

attachtotropomyosinTnC:bindcalciumionsTnI:

inhibitsactin-myosininteraction

14c.Arrangement

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

fixationofthickfilaments152.Transverse(T)tubules橫小管

Formedbysarcolemmainvagination

atA-Ijunctions;肌膜向肌漿內(nèi)凹陷形成的管狀結(jié)構(gòu)

Formananastomosingtubulesencirclingeverymyofibril;與肌纖維長軸垂直，同一平面的橫小管分支吻合，環(huán)繞肌原纖維

Responsibleforrapidconductionofimpulses.將肌膜的興奮傳導至肌纖維內(nèi)部163.Sarcoplasmicreticulum(Ltubule)肌漿網(wǎng)

Networkofsmoothendoplasmicreticulum

Encirclingeachmyofibrilbetween2adjacentTtubules.滑面內(nèi)質(zhì)網(wǎng)，位于橫小管之間

Endsdilatedandfusedtoformterminalcisternae兩端擴大形成的扁囊稱終池17

StoringCa2+,regulatingconcentrationofCa2+withinsarcoplasm.膜中有鈣泵Ttubule+2terminalcisternae=atriad.每條橫小管與兩側(cè)的終池組成三聯(lián)體1819C.Mechanismofcontraction--slidingfilamenthypothesis

neuralimpulsessarcolemmaTtubularsystem.thereleaseofcalciumionsfromtheSarcoplasmicreticulumcisternaetothesarcoplasmsurroundingthemyofibrils.CalciumionsinthesarcoplasmbindtotheTnCsubunitsoftroponin.

Thespatialconfigurationofthe3troponinsubunitschangesexposethemyosin-bindingsite.actinisboundtothemyosinmovementofthemyosinheadpullstheactinpastthemyosinfilament.20①運動神經(jīng)末梢將神經(jīng)沖動傳遞給肌膜；②肌膜的興奮經(jīng)橫小管迅速傳向終池；③肌漿網(wǎng)膜上的鈣泵活動，將大量Ca2+轉(zhuǎn)運到肌漿內(nèi)；④肌鈣蛋白TnC與Ca2+結(jié)合后，發(fā)生構(gòu)型改變，進而使原肌球蛋白位置也隨之變化；⑤原來被掩蓋的肌動蛋白位點暴露，迅即與肌球蛋白頭接觸⑥肌球蛋白頭ATP酶被激活，分解了ATP并釋放能量；⑦肌球蛋白的頭及桿發(fā)生屈曲轉(zhuǎn)動，將肌動蛋白拉向M線⑧細肌絲向A帶內(nèi)滑入，I帶變窄，A帶長度不變，但H帶因細肌絲的插入可消失，由于細肌絲在粗肌絲之間向M線滑動，肌節(jié)縮短，肌纖維收縮；⑨收縮完畢，肌漿內(nèi)Ca2+被泵入肌漿網(wǎng)內(nèi)，肌漿內(nèi)Ca2+濃度降低，肌鈣蛋白恢復(fù)原來構(gòu)型，原肌球蛋白恢復(fù)原位又掩蓋肌動蛋白位點，肌球蛋白頭與肌動蛋白脫離接觸，肌纖維舒張211.Ibandandsarcomerebecomeshorter,Hbandshortensordisappears,andAbandremainsconstantinlength.2.ThinfilamentsslideoverthickfilamentsandinsertfurtherintotheAband.3.Ca2+andATPplayanimportantrole.22AftercontractioncalciumionsreturntothecisternaeoftheSarcoplasmicreticulumactin-myosinbridgesbecomedetachedrelaxationoccur23

III.CardiacMuscle

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

Shortcolumninshapeandbranched;短圓柱狀，有分支2.showcrossstriationsandfibrils,butlessdistinct;周期性橫紋，肌原纖維3.One

centrallyplacednucleus;核1～2個，卵圓形，居中254.intercalateddiskslinkcellstooneanother.

細胞間以閏盤連接26C.EMstructure

largerTtubulesatZlinelevel;

橫小管發(fā)達位于Z線水平2.Simplesarcoplasmicreticulum,smallterminalcisternae;肌漿網(wǎng)稀疏，縱小管不發(fā)達，3.DiadsarecommonconsistingofTtubuleandterminalcisternaeononeside;終池小而少，多形成二聯(lián)體274.moremitochondriaandglycogenparticles;285.Intercalateddiscs閏盤

Specializedcelljunctions;

Tworegions:TransversportionLonggitudinalportion29Transverseportionhasdesmosomesandfasciaadherenstoenhanceintercellularjunction.橫位部分有中間連接和橋粒；Longitudinalportionhasgapjunctionprovidingsynchronouscontraction.

縱位部分存在縫隙連接，便于細胞間化學信息交流和電沖動傳遞，使心肌舒縮同步化

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

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