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Muscle tissue

Muscle tissue. Specialized for contractility. Striated. Classification of muscle tissue. Functional classification based on neural control Voluntary Involuntary Structural classification based on the presence of striations Striated Non-striated. Non-striated. Types of muscle.

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Muscle tissue

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  1. Muscle tissue Specialized for contractility

  2. Striated Classification of muscle tissue • Functional classification based on neural control • Voluntary • Involuntary • Structural classification based on the presence of striations • Striated • Non-striated Non-striated

  3. Types of muscle • Skeletal muscle • Voluntary & Striated • Hypertrophy only • Cardiac muscle • Involuntary & Striated • Hypertrophy only • Smooth muscle • Involuntary & Non-striated • Hypertrophy and hyperplasia

  4. Largest fiber type Cylindrical Unbranched Heavy cross striations Multiple, peripheral nuclei Skeletal muscle fibers (cells) Longitudinal sections Cross sections

  5. Skeletal muscle fibers Fibers contain numerous longitudinally arrayed myofibrils composed of myofilaments (actin and myosin) Myofibrils Cross sections

  6. Skeletal muscle fibers Cross sections Longitudinal sections SER

  7. Muscle fibers Banding pattern A band (dark) - Myosin and actin I band (light) - Actin only Z line - Alpha actinin H band – Myosin only Sarcomere Z-line to Z-line Contractile unit BV A I Z Myofibrils I Z A H Myofilaments Sarcomere

  8. Actin 70,000x Myosin Organization of myofilaments

  9. Changes in bands during contraction Sarcomeres shorten Z-line interval narrows

  10. H H Changes in bands during contraction Sarcomeres shorten Z-line interval narrows H and I bands narrow

  11. Changes in bands during contraction Sarcomeres shorten Z-line interval narrows H and I bands narrow A band is unchanged

  12. T-tubule Ca+ Ca+ Ca+ Regulation of skeletal muscle contraction Triads: T-tubule (sarcolemma) Terminal cisterns of SER (sarcoplasmic reticulum)

  13. 1. Segregate the muscle fibers into fascicles 2. Transmit the force of contraction to the point of muscle insertion Connective tissues of skeletal muscle Endomysium - reticular fibers plus the external (basal) lamina produced by the muscle fiber Perimysium - dense connective tissue surrounding a group of fibers and dividing the muscle into fascicles Epimysium - dense connective tissue surrounding the entire muscle, blends with the deep fascia and tendons

  14. Connective tissues of skeletal muscle Perimysium Epimysium Epimysium Endomysium RF Endomysium Fiber EL EL

  15. Neuromuscular junction (Motor end plate)

  16. Cardiac muscle Most restricted distribution (myocardium) Intermediate size Cylindrical fibers Fibers branch, forming interwoven bundles Single, centrally located nucleus Moderate striations Myofibrils and myofilaments similar to skeletal muscle Highly vascular Large numbers of mitochondria Glycogen Cardiac muscle fibers Longitudinal section, 400x Cross section, 1000x

  17. Cardiac muscle fibers M Nucleus M Myofibrils M

  18. Cardiac muscle - Intercalated discs Unique to cardiac muscle fibers Composed of: Adherent junctions Gap junctions (ionic coupling)

  19. Regulation of contraction T tubules No triads, reduced sarcoplasmic reticulum Contraction regulated by calcium Contraction spreads to adjacent cells due to current flow through gap junctions

  20. Smooth muscle Organized into sheets forming much of the wall of hollow organs and blood vessels Smallest fiber type Spindle shaped Single, centrally placed nucleus Non-striated, no myofibrils External lamina Gap junctions Hypertrophy& hyperplasia Smooth muscle fibers

  21. Longitudinal layers Longitudinal section Circular layer Cross section Smooth muscle

  22. Myofilament organization Actin and myosin present No myofibrils Myofilaments arranged as reticulum Dense bodies in cytoplasm Relaxed Dense body Contracted “Inchworm nuclei”

  23. Coordination of contraction Small fibers, T-tubules are absent (caveolae) Sarcoplasmic reticulum is rudimentary Ionic coupling via gap junctions Contraction initiated by calcium release Contraction occurs by sliding filament mechanism unique to smooth muscle Caveolae Desmo- some Gap junction Dense bodies Nucleus Smooth muscle fiber (EM)

  24. Skeletal Cardiac Smooth

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