Muscles lecture for Anatomy

8/14/2019 Muscles lecture for Anatomy

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Muscle tissue consists of musclefibers that are capable of

contraction along their.


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Longitudinal Axis


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Functions of Skeletal Muscle

. Produce skeletal movement

Muscles move the bones of the skeleton by theirconnective tissue attachments. his enables all kindsvoluntary movement.

!. Maintains posture and body position

"hen not moving the various parts of the supportiveskeleton are held in position by isometric musclecontraction.

#. Supports soft tissue

he $eight of the abdominopelvic viscera is supporteby the muscles of the abdominal $all and the pelvicloor.

%. &uards entrances and exits

Skeletal muscle forms sphincters around orifices of thdigestive and urinary tracts.

'. Maintains body temperature

Muscle contraction generates heat that is involved inmaintaining normal body temperature.


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Anatomy of Skeletal Muscles


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Skeletal muscle can only exert forcon a structure if it is harnessed in

some $ay to that structure.

performsthis role.

he organi(ation of fibers $ithin themuscle gives rise to threeconcentric wrappingsofconnective tissue.


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)onnective issue

1.

!.

#.


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*ach individual muscle fiber issurrounded by a delicate net$orkof reticular fibers

called .

binds fibersto theirneighbors and supports thecapillariesthat supply the fibers.

1.


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*ndomysium


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he muscle fibers bound together bhe endomysiumform a bundle

called a .


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fascicle


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he fasciclesare surrounded byconnective tissue containingcollagenand elastic fibersthat

supports the blood vessels andnerves that serve the fibers of thefascicles. his connective tissue iscalled the .


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Perimysium


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he entire muscleis surrounded bydense irregular connective tissue

hat separates the muscle from thesurrounding tissue and organs. hiss the .


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*pimysium


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he fibers of the endomysium,perimysiumand epimysium

converge on the points of attachmenof the muscle to bone+ skin ormuscle.

his fibrous connection transfers theorce of contraction of the muscle tohe attachment point.

"hen the attachment is roundandesembles a thick cordor cableit i

called a . "hen theattachment is broadand forms asheetit is called ansing.-.


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1. endon

!. Aponeurosis


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Skeletal muscle uses and demandsnutrientsand oxygenthat aresupplied by blood vesselsthatenter the muscle along theconnective tissue partitionsand

eventual form capillary networksform capillary networkshat surround each muscle fiber.*ach muscle fiber is also controlledby a nerve that forms a single

attachment point $ith each fiberathe + a.k.a..


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neuromuscular unction

myoneural unction


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Skeletal muscle cells develop $henhundreds of individual embryoniccellscalled fuse.

he resulting cells/ cell membrane iscalled the and thecytoplasm is called .


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1. Myoblasts

!. Sarcolemma

#. Sarcoplasm


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Skeletal musclesare very large.

heir diameter is about 100microns,about 1# times thediameter of a red blood cell- and

hey can be as long as 30 to 40 cm,10 to 1 in.-.


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Skeletal muscles are

he nucleiof the myoblaststhatfuse to form the cell remain $ithinthe cell.

Some myoblastsdo not fuse but

remain associated $ith the fiber asthat can divideand differentiate to repairdamaged cells.


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1. Multinucleate

!. Satellite )ells


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here are internal tubularextensionsof the sarcolemmaint

the sarcoplasmcalledAka

2 .


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ranverse ubules

2ubules


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"ithin each skeletal muscle cell ofiber there are cylindricalstructurescalled .


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Myofibrils


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he are about 13100 thediameter of the cell but extend the fength of the cell and attach to the c

membrane at either end.

Contractionof the resn contraction of the entire cell.


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Myofibrils


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formloops around myofibrilsalong theentire length.


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ransverse ubules


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n betweenn betweenthe loops of transverseubule+ there is anetwork ofubulesof smooth endoplasmic

reticulumcalled the.

hesurrounds the myofibril like a sleeve


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Sarcoplasmic 4eticulum


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he sarcoplasmic reticulumoneither side of theloops of

ransverse tubulesfuse to formexpanded chambers called

.


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terminal cisternae


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he combination of atransverse tubuleflanked bytwo terminal cisternaeiscalled a .


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riad


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he energy for muscle contractionis supplied by the numerous

that surround themyofibrils.


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Mitochondria


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that alsosurround the myofibrils as a readysource of fuel.


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&lycogen &ranules


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he myofibrils are made2up of. he are

organi(ed in repeating units alongthe length of the myofibril called

.


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Myofilaments

Myofilaments

Sarcomeres


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he primary microfilaments in

myofibrils are ,thin- and,thickfilaments.

"ithin each sarcomerethere is aprecise arrangement of thesefilaments.

he sarcomeresof neighboringmyofibrilsare in alignment andthey create the banding patternvisible $ith the light microscope.


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1. Actin

!. Myosin


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he difference in the si(e and densi

of the thick and thin filaments isesponsible for the banding pattern.


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he center of the sarcomere has anarro$ band called the$here there are only thickfilaments.


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526and


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he 5 band is in the center of thethat includes a (one of

overlap bet$een the thick and thinfilaments.


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A 2 6and


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7n the (one of overlap+ each thickfilament is surrounded by six thin

filaments and each thin filament issurrounded by three thick filaments


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he is $here the thinfilaments do not overlap with the

thick filamentsat either end of thesarcomere+ and straddling the

.


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7 6and

8 Line


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itin

Muscles lecture for Anatomy

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