Muscular Tissue Prof. Ji-Cheng Li (Zhejiang University School of Medicine)

1. Muscular TissueProf. Ji-Cheng Li(Zhejiang University School of Medicine)

2. General description 1) components: ---cell: muscle fiber--myofiber • elongated thread-liked • sarcolemma (cell membrane) • sarcoplasm (cytoplasm) • sarcoplasmic reticulum (SER ) ---extracellular G.S: CT with BV, LV and N

3. 2) classification According to the structure and function • skeletal muscle: striated voluntary m. • cardiac muscle: striated involuntary m. • smooth muscle: unstriated involuntary m. smooth muscle skeletal muscle cardiac muscle

4. Skeletal muscle

5. Often called striated or voluntary muscle • Has striations that are visible under light microscopy • Under voluntary control • Attached to skeleton ( skeletal)

6. Characteristics of Skeletal Muscles Muscle cells are elongated fibers with many peripheral nuclei Each muscle fiber contains many myofibrils Each myofibril contains many microfilaments

7. Connective tissue coverings (responsible for force transduction): Epimysium: surround entire muscle Perimysium: surround fascicle Endomysium: surround individual fibers

8. Epimysium Perimysium Entire muscle Endomysium Fasciculus of muscle fibres A muscle fibre

9. 1)Microstructure of skeletal muscle fiber ①long cylindrical 10-100um in diameter,1-40mm long ②multinucleate, nuclei are ovoid, distributed under sarcolemma ③ filled with longitudinal parallel-arranged myofibrils

10. Longitudinal section Transverse section

11. muscle fiber myofibril Thin Filaments Thick Filaments

12. myofibril: • 1-2um in diameter • cross striation: light band --I band, dark band-- A band

13. --A band: M-line, H-band --I band: Z-line I band A band H-band Z-line M-line

14. --A band (except H band): Thin Filaments Thick Filaments H band: only Thick Filaments --I band: only Thin Filaments

15. sacromere sacromere:1/2 I band, A band ,1/2 I band the smallest structural and functional unit of myofibril

16. 2)Ultrastructure of myofiber myofibril: ---thick myofilament: • Composed of myosin: ---thin myofilament: • Compose of • A. actin • B. tropomyosin • C.troponin:

17. Transverse tubule (T tubule): ---definition: sarcolemma and basement membrane invaginate into sarcoplasm to form a transverse distributed tubular system ---location:A-I junctional part ---function: transfer the information into cytoplasm

18. ③Sarcoplasmic reticulum: ---definition: A longitudinal distributed tubular system formed by smooth endoplasmic reticulum Sarcoplasmic reticulum

19. ---structure: • H-A band: longitudinal enclose myofibril-- longitudinal tubule • terminal cisternae: flattened sac, A-I junction • triad: one T-tubule + two terminal cisternae • ---function: there are calcium pump proteins (ATPase) on membrane, so it can store and release calcium ions triad

20. Cardiac muscle

21. 1) Microstructure of cardiac muscle • ①short column in shaped, 100um long,15um in diameter, with branches, the branches associated with each other to form a network • ②1-2 nuclei, centrally-located • ③striated, but no very clear • ④intercalated disc: junctional part • LM: dark striation across the cardiac fibers

22. Cardiac muscle

23. Cardiac muscle: show intercalated disc

24. 2) Ultrastructure of cardiac muscle similar to skeletal muscle, composed of thick, thin filament and have sarcomere Different: ① myofibril have different diameter, the boundary of myofibril is not very clear

25. diad ②transverse tubule are thicker, located at Z-line level (skeletal muscle : A-I junctional part) ③sarcoplasmic reticulum is not well-developed, form less terminal cisternae ④diad: one T-tubule + one terminal cisternae (skeletal muscle : triad) cardiac muscle triad skeletal muscle

26. ④ intercalated discs transverse portion longitudinal portion

27. transverse portion: connection -intermediate junction -desmosome longitudinal portion: communication -gap junction transverse portion longitudinal portion

28. Smooth muscle

29. microstructure of smooth muscle ①elongated, spindle-shaped cells, 8 um in diameter, 200( 20-500)um long ②only one nucleus ③no striation, no myofibril

30. smooth muscle Neuroanglion smooth muscle

31. 2) ultrastructure of smooth muscle ①caveola on sarcolemme invaginate into cytoplasm ②dense patch: under sarcolemma dense body: in sarcoplasm ③intermediate filament: caveola dense body dense pach

32. smooth muscle under SEM

33. Compare with three muscle tissues

34. 1. The location of T tubules of cardiac muscle differ from those of skeletal muscle, the former lie at the • A. A-I junctions B.I bands • C. A bands D.M lines • E. Z lines √

35. 2. Sarcoplasmic reticulum of muscle fiber is composed of • A. lysosome B. mitochondria • C. microsome D. RER • E. SER √

36. 3.The cell junction which transmit rapidly an electrical impulse between adjacent smooth muscle cells is • A. tight junction B. intermediate junction • C. gap junction D. desmosome • E. semidesmosome √

37. Questions: • Describe the characteristics of muscle tissue. • Compare the similar with the difference for three kinds of muscle cells according to their fine structure and ultrastructure.