SmoothSmooth musclemuscle (HE)(HE)

SkeletalSkeletal musclemuscle ((crosscross sectionsection HE)HE)

SkeletalSkeletal musclemuscle ((longitudinallongitudinal sectionsection HE)HE)

SmoothSmooth musclemuscle HM, HM, 40x 40x (HE)(HE)SmoothSmooth musclemuscle cellcell ((oneone nucleusnucleus, , thinthin, , bobbinbobbin shapeshape))The The cellscells arrangedarranged inin fasciculifasciculi..The The nucleusnucleus is is localisedlocalised inin thethe centre of centre of thethe cellcell. . ThereThere areare no no striatedstriated

Smooth muscle nucleus

The The functionalfunctional unit of unit of itit is is thethe muscularmuscular fibrefibreThereThere is a is a fusionfusion of of thethe myoblastmyoblast cellscells duringduring thethe ontogenesisontogenesisThe The numbernumber of of nucleinuclei maymay be more be more thanthan 100100

Epimysium

EndomysiumPerimysium

(Cohnheim field)

SkeletalSkeletal musclemuscle crosscross sectionsection, 20x (HE), 20x (HE)

SkeletalSkeletal musclemuscle crosscross sectionsection, 40x (HE), 40x (HE)

The The bandsbands, , whichwhich areare dyeddyed darkdark, show a , show a doubledouble refractionrefraction of of lightlight. . ThatThat sswhywhy thesethese areare AnisotropesAnisotropes (A)(A)The The bandsbands, , whichwhich areare dyeddyed lightlight, , havehave singlesingle refractionrefraction of of lightlight IsotropesIsotropes (I)(I)ThereThere is a is a thinthin line line inin thethe middlemiddle of of thethe II--bandband, , whichwhich is is calledcalled ZZ--bandbandThereThere is a is a lighterlighter line line inin thethe middlemiddle of of thethe AA--bandband, , whichwhich is is calledcalled HH--bandbandand int he and int he middlemiddle of of thisthis lighterlighter line line therethere is a is a darkdark line, line, thethe MM--line.line.The The II--bandband becomesbecomes shortershorter whenwhen thethe musclemuscle contractscontracts

ThoseThose contractilecontractile elementselements whichwhich show show striatedstriated patternpattern is is calledcalledmyofibrilsmyofibrils..The The placeplace whichwhich is is betweenbetween twotwo ZZ--bandsbands isis calledcalled sarcomersarcomerThe The myofibrillummyofibrillum consistsconsists of of myofilamentsmyofilaments..

thinthin (9 nm (9 nm actinactin))

thickthick (12(12--15 nm 15 nm myosinmyosin))

HarHaráántcsntcsííkolt izom HM, 40x (HE)kolt izom HM, 40x (HE)

Muscle cell nuclei

Striated pattern

Fibrocyte nucleus

SkeletalSkeletal musclemuscle ((longitudinallongitudinalsectionsection, 40x (HE), 40x (HE)