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Muscle Tissue Xing Wenying Slide 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. Slide 3 classification : According to the structure and function striated unstriated striated functionstructure Slide 4 Skeletal muscle Slide 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 Slide 6 Dark bands--A bands H band, M line Light bands--I bands Z line Histological features of skeletal muscle fibers Slide 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 Slide 8 Myofibrils: Sarcoplasm is filled with long cylindrical filamentous bundles called myofibrils. Slide 9 Myofibril Sarcoplasmic reticulum Mitochondrium Transverse tubule Ultrastructure of skeletal muscle fibers Slide 10 Myofibrils are composed of bundles of myofilaments. Thick filaments and thin filaments. myofibrils and myofilaments Slide 11 Slide 12 1.5m long and 10nm in diameter Occupy A band Made up of myosin molecules: --rods: overlap --heads: cross bridges, have ATPase activity. Thick filaments Slide 13 Slide 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 Slide 15 A. Actin : binding site for myosin. Thin filaments Slide 16 B. Tropomyosin Thin filaments Slide 17 C. Troponin: is a complex of three sub-units. Tn T(troponin T) Tn C(troponin C) Tn I(troponin I) Thin filaments Slide 18 Slide 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 Slide 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 Slide 21 Transverse tubule (T tubule) Sarcolemma with opening to T-tubule T tubule Slide 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. Slide 23 Sarcoplasmic reticulum (SR) Triad: 1 T tubule + 2 terminal cisternae Function: store and release calcium ions regulating concentration of Ca 2+ within sarcoplasm Slide 24 providing the energy necessary for the reactions involved in contraction. Other organelles and inclusion Mitochondria Glycogen lipid droplet Slide 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. Slide 26 Slide 27 Cardiac muscle Mainly distributed in the wall of heart; Has more connective tissue and capillaries; Some specialized as Purkinje fibers. Slide 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; Slide 29 Intercalated disk: unique characteristic Slide 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. Slide 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. Slide 32 Intercalated discs Specialized cell junctions at Z lines. Ultrastructure of cardiac muscle Slide 33 rich in mitochondria, glycogen,pigment. Slide 34 Smooth muscle Seen in blood vessels and hollow viscera, arranged in layers. Slide 35 Structure of Smooth Muscle fiber Slide 36 Slide 37 Summary The structure of skeletal muscle. The structure of cardiac muscle. The structure of smooth muscle. Mechanism of contraction -- sliding filament hypothesis Slide 38 Summary The structure of cardiac muscle. Slide 39 Summary The structure of smooth muscle. Slide 40 Homework Review the characteristics of skeletal muscle and cardiac muscle. Prepare for nerve tissue.