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SELF-ASSESSMENTINHISTOLOGYQUESTIONS五,MUSCLE1Skeletalmusclefibresaremultinucleatecellsembryologicallyderivedbyfusionofnumerousmononucleatecells.(T)2Skeletalmusclecellsarehighlybranchedandformfunctionalconnectionswithsurroundingcellswhichpermitsimultaneouscontractionofgroupsofcells.(F)3Thenucleiofskeletalmusclecellsarecharacteristicallylocatedimmediatelysubjacenttotheplasmamembrane.(T)4Perimysiumisthedelicateconnectivetissuewhichseparatesindividualmusclefibres.(F)5Skeletalmusclefibreshaveasimilardiametertothatofsmallbloodcapillaries.(F)6Damagedskeletalmuscleregeneratesreadilybymitoticdivisionofmaturemusclecells.(F)182Inskeletalmuscle,eachmyofibrilismadeupofachainofsarcomeresconnectedendtoend.(T)7Thestriationsofskeletalmuscleseeninlightmicroscopyresultfromthefactthatthesarcomeresofadjacentmyofibrilsallieinregisterwithoneanother.(T)8DuringcontractionofmyofibrilstheAbandsshorteninlengthbuttheIbandsremainconstantinlength.(F)9Eachsarcomereisaboutthesamelengthasamusclecellnucleus.(F)10Theslidingfilamenttheoryofskeletalmusclecontractilityproposesthatmyosinfilamentscontracttherebyslidingwithrespecttoadjacentactinfilaments.(F)11TheZlinesofskeletalmusclerepresentzonesofattachmentforactinfilaments.(T)12Inskeletalmuscle,contractilestimuliareconductedtothecontractileunitsbyaspecialisationoftheplasmamembraneknownasthesarcoplasmicreticulum.(F)13Theslidingfilamentmechanismofskeletalmusclecontractionisactivatedbyreleaseofcalciumionsintothemusclecellcytoplasm.(T)14Mitochondrialenzymescanbeusedashistochemicalmarkersindistinguishingdifferentmusclefibretypesonthebasisoftheirpredominantmodeofenergymetabolism.(T)15Visceralmusclemayalsobedescribedbytheterms'smooth'or'involuntary'muscle.(T)16Incontrasttothemultinucleateskeletalmusclecells,visceralmusclecellsusuallycontainonlytwoorthreenuclei.(F)17Visceralmuscleappearsnon-striatedinlightmicroscopybutinelectronmicroscopycrossstriationsarereadilyvisible.(F)18Bundlesofvisceralmusclefibreswhichformasinglefunctionalunitareknownas'motorunits'.(F)19Forperistalticcontractiontooccur,theremustbeatleasttwolayersofvisceralmuscledisposedatrightanglestooneanother.(T)20Cardiacmusclefibrescontainoneortwonucleiwhicharemainlycentrallylocatedinthecell.(T)21Thecytoplasmofadjacentcardiacmusclefibresisconfluentthuspermittingsynchronouscontractionofthewholemusclemass.(F)22Themyofibrilsofcardiacmusclearebranchedincontrasttothoseofskeletalmusclewhichareunbranched.(T)23Reflectingtheirhighdemandforenergy,cardiacmusclefibrescontainnumerousmitochondriawhichhaveunusualtubularcristae.(F)24Incardiacmusclefibres,theconductingsystemforexcitatorystimuliisbasicallysimilartothatofmammalianskeletalmusclefibresexceptthatthetriadsofTtubulesandsarcoplasmicreticulumarelocatedattheZlinesinsteadofatthejunctionofAandIbands.(T)