MuscleII.Skeletal muscle：OrganizationMuscle fasciculus-skeletalmusclefibers-surrounded by CT.The individual musclesMuscletiberHzAofgrossanatomyarebandbandbandbandorgans.MyofibrilM lineThey are mainlyG-actin moleculetcomposed of skeletalMyofilamentsmusclefibres arranged58894868995908888inregularbundlesorF-ectin flamentfascicule.MyosinflamentMyosin light chai.XXMyosinheavyche
6 Ⅱ. Skeletal muscle v Organization -skeletal muscle fibers -surrounded by CT. v The individual muscles of gross anatomy are organs. v They are mainly composed of skeletal muscle fibres arranged in regular bundles or fascicule
SkeletalmuscleA.Organization of skeletalmuscleCT:* Epimysium - a dense CTEpsheath,surrounds theFentiremusclePerimysium-athinlayer福of CT, surrounds theEdbundlesofmusclefibersPe福Endomysium-adelicate.layerofCT,surroundseachmusclefiber
7 A. Organization of skeletal muscle CT: v Epimysium – a dense CT sheath , surrounds the entire muscle. v Perimysium – a thin layer of CT, surrounds the bundles of muscle fibers. v Endomysium – a delicate layer of CT, surrounds each muscle fiber. Skeletal muscle Ed Ep F Pe
EndomysiumEpimysiumPerimysiumCross sectionof striatedmusclestained to showcollagenstypeIandIllandcell nuclei.The endomysiumis indicated by arrowheads and theperimysium by arrows. At left is a piece of epimysium8
8 v Cross section of striated muscle stained to show collagens type I and III and cell nuclei. v The endomysium is indicated by arrowheads and the perimysium by arrows. At left is a piece of epimysium
Skeletalmuscle(cell boundaryB.Histological featuresMusdeSbMyofibrils(cortractioncontractonPerimysiuntainsbundlescuscle fibers)ofskeletalmusclefibersCapllary (nutritiorcovers the musdleEndomysiu(separalesmusclefibersnurtionLM: Microstructure offibersShape:long cylindrical shape Size: 10-100um in diameter,1-40mm long* Nucleus:* ovoid & fairly elongated;*numerous;* distributed at the periphery of the celllocated just underthe sarcolemmaSarcoplasm:* filled with longitudinal parallel-arranged myofibrils cross striations :muscle fibers show regularcrossstriations of alternating dark and light bands
9 B. Histological features of skeletal muscle fibers LM：Microstructure of fibers v Shape: long cylindrical shape v Size: 10-100um in diameter,1-40mm long v Nucleus: * ovoid & fairly elongated; * numerous; * distributed at the periphery of the cell; located just under the sarcolemma v Sarcoplasm: * filled with longitudinal parallel-arranged myofibrils v cross striations :muscle fibers show regular cross striations of alternating dark and light bands Skeletal muscle
SkeletalMuscleH&ESkeletal MuscleH&Eirisdiaphragmopentransverselycutmusclefibresstriationsperipherallyplaced nucleicapillariescut longitudinallycuttransverselymusclefibresThe nuclei can be seen inthe periphery of the cell,just10underthecellmembrane
10 v The nuclei can be seen in the periphery of the cell, just under the cell membrane