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1团队合作游戏
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Striated Muscle—Thyrohyoid Muscle
The characteristic striation is bad on the structure and arrangement of the myofibrils,which traver the sarcoplasm lengthwi.This longitudinal c-tion of the thyrohyoid muscle shows the parallel orientation of the myofibrils and the resulting fine longitudinal striation.There are alternating li
ght and dark bands,with the dark bands being wider than the light ones.The dark cross-striations appear strongly birefringent in polarized light (anisotropic,A-bands ).The light bands are refringent (isotropic,I-bands ).Inside the I-bands are very narrow anisotropic bands with a larger refractive index (Z-bands or intermediary layer).In suitable preparations,a very thin M-band (center membrane)is discernible inside the A-bands.The layers between concutive Z-bands are called sarcomeres .The are the functional units of myofibrils.It should be noted that the nuclei are located at the cell periphery 1.The (blue-stained)endomysium 2(cf.Fig.226),which contains capil-laries and nerve fibers,should also be noted.
1Nucleus of a skeletal muscle fiber 2Endomysium
Stain:azan;magnification:×1125
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Striated Muscle—Psoas Muscle
Cross-ction of skeletal muscle fibers with evenly distributed myofibrils that are not bundled (simple fibril pattern ).Note the long,oval nuclei clo to the cell surface 1(cf.Fig.229)in the muscle fiber.The two darker-stained nu-clei in the connective tissue belong to fibrocytes 2.
1Nucleus in a muscle fiber 2Fibrocyte
3Collagenous (den)connective tissue
Stain:Heidenhain iron hematoxylin;magnification:×1125
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Striated Muscle—Psoas Muscle
This cross-ction shows striated muscle fibers about 10–100µm thick.Size and morphology depend on muscle function and workload.The nuclei 1are clearly located in the periphery of the cells.The plasmalemma envelops the cytoplasm (sarcoplasm ).The crevices between the muscle fibers contain the loo connective tissue of the endomysium ,which consists mostly of reticular fibers.The even,den and only softly stained dots in this cross-ction re-flect the even distribution of myofibrils (cf.Fig.228).Occasionally,depend-ent on the fixation,the fibrils show a grouping pattern (Cohnheim’s fields,groups ).The plasmalemma is often called sarcolemma.This terminology was coined in light microscopy.In fact,the sarcolemma consists of the plasma-lemma,the basal lamina and a network of delicate reticular fibers.The are not distinct components in light microscopic evaluations.
1Nucleus of a skeletal muscle fiber 2Capillary
3Nucleus of a connective tissue cell
Semi-thin ction;stain:methylene blue-azure II;magnification:×800
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Striated Muscle—Psoas Muscle
Longitudinal ction through striated myofibrils with conspicuous sar-comere organization.A sarcomere extends from one Z-band 1to the next 1.In Z-bands,the actin filaments of two successive sarcomeres twist together and are cross-linked.Actin filaments in the form of I-bands (isotropic bands )flank both sides of the Z-band 2.The thicker myosin filaments form the A-band (anisotropic band )3of the myofibril.Actin and myosin filaments form a twisted helix and leave only the H-band 4(light zone)in the middle of the A-band.The H-band consists only of myosin filaments,the I-bands only of actin filaments.The dark centerline in the H-zone is the centermembrane .Cross-linking of the myosin filaments creates this line.Note the peripheral nucleus 6clo to the fiber surface under the sarcolemma (plasmalemma)(e Figs.226,227).
鲻鱼
1Z-band
2I-bands (isotropic)3A-bands (anisotropic)
门卫招聘
当代著名书法家4H-band (H-zone;Henn’s bands)with M-band (M-line)5Mitochondria
6Nucleus of the muscle fiber
7Extracellular matrix with collagen fibrils Electron microscopy;magnification:×6000
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Striated Muscle—Psoas Muscle
Longitudinal ction through veral sarcomeres in a skeletal muscle fibril (cf.Fig.230).The space between two adjacent Z-bands 1is called sarcomere.By this definition,a sarcomere consists of an A-band and the two halves of the adjacent I-band 2on each side.
The Z-band 1is electron-den.It runs through the center of the I-band 2.The somewhat lighter stained H-band goes through the middle of the A-band 3.In the center of the H-band is the M-band or M-line (center membrane)(cf.Fig.230).Between neighboring A-bands are cuts through smooth ER membranes (sarcoplasmic reticulum =L-system).Crista-type mitochondria occur at the level of the I-bands.
1Z-bands or Z-disk 2I-bands (isotropic)3A-bands (anisotropic)
Electron microscopy;magnification:×25000
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山药炖牛肉的做法4电煮锅的危害
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