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Muscular Tissue

Muscular Tissue. Jun Zhou ( 周俊 ) School of Medicine, Zhejiang University. 20140415. Overview 1) components : -- cell: muscle fiber-myofiber elongated thread-liked Sarcolemma （肌膜） Sarcoplasm （肌质） Sarcoplasmic reticulum （肌质网） : SER --extracellular G.S: CT with BV, LV and N.

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Muscular Tissue

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  1. Muscular Tissue Jun Zhou (周俊) School of Medicine, Zhejiang University 20140415

  2. Overview 1) components: --cell: muscle fiber-myofiber • elongated thread-liked • Sarcolemma（肌膜） • Sarcoplasm（肌质） • Sarcoplasmic reticulum（肌质网）: SER --extracellular G.S: CT with BV, LV and N

  3. 2) classification According to the structure and function • skeletal muscle (骨骼肌): striated, voluntary • cardiac muscle (心肌): striated, involuntary • smooth muscle (平滑肌): unstriated, involuntary

  4. Skeletal muscle

  5. Epimysium（肌外膜）: DCT • Perimysium（肌束膜） • Endomysium（肌内膜）

  6. LM: • long cylindrical 10-100um in diameter, 1-40mm long • multinucleate, nuclei are ovoid, distributed under sarcolemma • filled with longitudinal parallel- arranged myofibrils

  7. Skeletal Muscle • Cells are long multinucleate “cylinders”

  8. Endomysium Fascicle Myofiber Perimysium Identify: Endomysium, Perimysium, myofiber and fascicle

  9. Endomysium: connective tissue, nutrient capillaries, nerve endings and around each myofiber a basal or external lamina

  10. Myofiber

  11. Myofibril: • 1-2um in diameter • cross striation: • light band -I band • dark band- A band --A band: M-line, H-band --I band: Z-line

  12. Definitions Isotropic (各向同性) Anisotropic (各向异性)

  13. A band : Anisotropic (各向异性) I band: Isotropic (各向同性)

  14. H Band is light and in the center of the A Band

  15. Sacromere（肌节）: 1/2 I +A + 1/2 I the smallest structural and functional unit of myofibril

  16. EM: 1.Transverse tubule (T tubule): 横小管 • definition: sarcolemma invaginate into sarcoplasm to form a transverse distributed tubular system • location: A-I junctional part • function: transfer the information into cytoplasm

  17. 2.Sarcoplasmic reticulum: 肌质网 • smooth endoplasmic reticulum • longitudinal tubule ( L tubule ) • terminal cisternae (终池) • Triad (三联体): one T-tubule +two terminal cisternae • calcium pump proteins • store and release calcium ions

  18. 3.Myofibril (肌原纤维) • thick myofilament • thin myofilament

  19. Skeletal Muscle • Organizational Hierarchy Muscle is composed of fascicles Fascicle (smallest) is composed of myofibers Myofiber is composed of myofibrils Myofibril is composed of myofilaments

  20. Thick myofilament • 1.5 um long, 15 nm in diameter • composed of myosin (肌球蛋白) -rob: in bundles -head: cross bridge- binding site (ATPase activity)

  21. Thin myofilament • 1 um long, • 5 nm in diameter A. Actin (肌动蛋白)- binding site B. Tropomyosin (原肌球蛋白) C. Troponin (肌原/钙蛋白) -Tn T: bind to tropomyosin -Tn C: binds to calcium ions -Tn I: inhibit actin-myosin interaction

  22. Myofibril Is cross banding evident at the level of the myofibril? Define a sarcomere. A sarcomere is that portion of the contractile apparatus between and attaching to two Z lines.

  23. Myofibril Thick myofilaments consist of myosin. Myosin is ONLY found in the A Band The sarcomere is the smallest contractile unit. It consists of a precisely organized array of myofilaments.

  24. Myofibril Thin myofilaments consist of Actin, tropomyosin and troponin. Thin myofilaments are found in BOTH the A Band and I Band

  25. Myofibril M Line, in the center of the H Band, consists of proteins that hold myosin filaments together.

  26. Myofibril Z Line.

  27. Electron Micrograph of Human Skeletal Muscle Myofibril Dark granules are glycogen Micrograph Provided by Ernest Whitter

  28. Electron Micrograph of Human Skeletal Muscle Sarcomere Micrograph Provided by Ernest Whitter

  29. Electron Micrograph of Human Skeletal Muscle A Band Micrograph Provided by Ernest Whitter

  30. Electron Micrograph of Human Skeletal Muscle Z Line M Line in H Band I Band Micrograph Provided by Ernest Whitter

  31. Sliding filament hypothesis(肌丝滑动学说)

  32. Cardiac muscle

  33. LM • short column in shaped, 100um long,15um in diameter, with branches • 1-2 ovoid nuclei, centrally-located • striated, but no very clear • intercalated disc

  34. EM • T tubule at Z-line level • less terminal cisternae • diad(二联体): one T-tubule + one terminal cisternae • Numerous mitochondria

  35. intercalated discs

  36. Smooth muscle

  37. LM • elongated, spindle-shaped cells, 8um in diameter, 200( 20-500)um long • rob-liked or ovoid nucleus • no striation, no myofibril

  38. Cross Section Longitudinal Section Smooth Muscle

  39. EM • caveola: sarcolemme invaginate into cytoplasm • dense patch (密斑): under sarcolemma dense body (密体): in sarcoplasm • intermediate filament: /composed of desmin(结蛋白) /10nm in diameter /connect between dense body

  40. thick filament: myosin, 15 nm thin filament: actin, 5 nm-fixed on dense patch or body • contractile unit (肌丝收缩单位): several thick filament and thin filament aggregate

  41. THE END

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