1. Muscle Tissue Xing Wenying 邢文英

2. Introduction Components: Muscle cells(muscle fibers) Elongated, thread-like, containing myofilaments and being contractile cell membrane → sarcolemma; cytoplasm → sarcoplasm; SER → sarcoplasmic reticulum CT: contain blood vessels, lymphatics and nerves.

3. classification : According to the structure and function striated unstriated striated functionstructure

4. Skeletal muscle

5. Long cylindrical, 1-40mm long, 10-100um in diameter Multinucleate, ovoid nuclei, just under the sarcolemma Cross-striations: alternating dark and light bands Histological features of skeletal muscle fibers

6. Dark bands--A bands ： H band, M line Light bands--I bands ： Z line Histological features of skeletal muscle fibers

7. sarcomere: The sarcomere is the basic contractile unit of striated muscle. It is the segment of a myofibril between two adjacent Z line. 1 sacromere = 1/2 I band+1 A band+1/2 I band

8. Myofibrils: Sarcoplasm is filled with long cylindrical filamentous bundles called myofibrils.

9. Myofibril Sarcoplasmic reticulum Mitochondrium Transverse tubule Ultrastructure of skeletal muscle fibers

10. Myofibrils are composed of bundles of myofilaments. Thick filaments and thin filaments. myofibrils and myofilaments

12. 1.5μm long and 10nm in diameter Occupy A band Made up of myosin molecules: --rods: overlap --heads: cross bridges, have ATPase activity. Thick filaments

14. 1um long, 5nm in diameter situated in both ending sides of each sarcomere; Run between and parallel to thick filaments; One end attached to the Z line, the other is free at H band composed of actin, tropomyosin, troponin Thin filaments

15. A. Actin : binding site for myosin. Thin filaments

16. B. Tropomyosin Thin filaments

17. C. Troponin: is a complex of three sub-units. Tn T(troponin T) Tn C(troponin C) Tn I(troponin I) Thin filaments

19. I band -- only thin filaments A band -- both thick and thin filaments H band -- only thick filaments Z line -- anchor for thin filaments M line – fixation of thick filaments Arrangement

20. Transverse tubule (T tubule)  Definition: A transverse distributed tubular system formed by Sarcolemma invaginating into sarcoplasm, encircling each myofibrils.  Location: A-I junctional part  Function: Rapidly conduct impulses for contraction to every myofibrils

21. Transverse tubule (T tubule) Sarcolemma with opening to T-tubule T tubule

22. Sarcoplasmic reticulum (SR)  Definition: A longitudinal distributed tubular system formed by SER, encircling each myofibril between 2 adjacent T tubules.  Terminal cisternae: Ends of L tubule dilate and fuse to form flattened sac.

23. Sarcoplasmic reticulum (SR)  Triad: 1 T tubule + 2 terminal cisternae  Function: store and release calcium ions regulating concentration of Ca 2+ within sarcoplasm

24. providing the energy necessary for the reactions involved in contraction. Other organelles and inclusion Mitochondria Glycogen lipid droplet

25. Mechanism of contraction -- sliding filament hypothesis  The thin filaments slide past the thick filaments and insert further into the A band.  I band and sarcomere become shorter, H band shortens or disappears, whereas A band remains the same length.  Ca 2+ and ATP play an important role.

27. Cardiac muscle Mainly distributed in the wall of heart; Has more connective tissue and capillaries; Some specialized as Purkinje fibers.

28. Microstructure of cardiac muscle Short cylindrical, 80-150um long,10-20um in diameter, with branches, associated with each other; 1 or 2, ovoid, centrally-located pale-staining nuclei; Exhibit cross striations, but less distinct;

29. Intercalated disk: unique characteristic

30. Ultrastructure of cardiac muscle Myofibril have different diameter, the boundary of myofibril is not very clear. T tubules are larger, located at Z-line level.

31. Ultrastructure of cardiac muscle Sarcoplasmic reticulum is not well-developed, forms less and smaller terminal cisternae, so Diads are common consisting of 1 T tubule and 1 terminal cisternae on one side.

32. Intercalated discs Specialized cell junctions at Z lines. Ultrastructure of cardiac muscle

33. rich in mitochondria, glycogen,pigment.

34. Smooth muscle Seen in blood vessels and hollow viscera, arranged in layers.

35. Structure of Smooth Muscle fiber

37. Summary The structure of skeletal muscle. The structure of cardiac muscle. The structure of smooth muscle. Mechanism of contraction -- sliding filament hypothesis

38. Summary The structure of cardiac muscle.

39. Summary The structure of smooth muscle.

40. Homework  Review the characteristics of skeletal muscle and cardiac muscle.  Prepare for nerve tissue.