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MUSLE

MUSLE. MUSCULOSKELETAL BLOCK. HISTOLOGY LECTURE BY PROF. MASOOD AHMED. main objectives:. Skeletal Muscle Tissue and Organization. Describe the light and electron microscopic features of skeletal muscle.

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MUSLE

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  1. MUSLE MUSCULOSKELETAL BLOCK. HISTOLOGY LECTURE BY PROF. MASOOD AHMED

  2. main objectives: Skeletal Muscle Tissue and Organization Describe the light and electron microscopic features of skeletal muscle. Describe the light and electron microscopic features of muscle spindle and motor end plate. Differentiate between white and red types of skeletal muscle fibers.

  3. Muscle tissue vs. Muscle as an organ Made up of _____ tissue types. Word roots: sarco myos One of the 4 primary tissue types How many subtypes?

  4. Function of Skeletal Muscles • Skeletal movement • Posture and body position • Support of soft tissues • Guarding of entrances & exits • Maintenance of body temperature

  5. Gross Anatomy Each skeletal muscle is wrapped by 3 concentric layers of connective tissue.

  6. Epi-, Peri-, and Endomysium Are interwoven - Go over into tendon Distinguish between: Tendon Aponeurosis Ligament Function: Protection Blood supply Innervation

  7. Connective Tissue Wrappings big green arrow = Perimysium; Small green arrows = Endomysium

  8. Fluorescence stained section • Green = Perimysium • Redish brown = Myotubes

  9. Microanatomy of Skeletal Muscle Fibers Some vocabulary: Skeletal muscle fiber or myofiber Sarcolemma Sarcoplasm Sarcoplasmic reticulum Myofibril Myofilaments

  10. Nerveand Blood Vessel Supply Skeletal muscles are rich in nerves and blood vessels Chemical communication at Synapsis (neuromuscular junction) Synaptic terminal of axon meets motor end plate of muscle cell Coiled capillaries are able to adapt to changes in length of muscle fiber

  11. Skeletal Muscle

  12. Myofilaments Myofiber ( 100µm) Myofibrils ( 1-2 µm) Myofilaments Actin & Myosin

  13. Sarcomere Structure Z - line I - band = LIght band A- band = dArk band

  14. Sarcomeres Thick and Thin Filaments are organized in repeating functional units = ______ Each myofibril has linear arrangement of ~ 10,000 sarcomers Banded appearance (striation) due to arrangement of thick and thin filaments Interaction of thick and thin filaments responsible for skeletal muscle fiber contraction

  15. TEM of a Skeletal Muscle Sarcomere Z-Line M-Line I-Band A-Band

  16. Thin Filament: Actin F-actin G-actin

  17. Thick Filament: Myosin

  18. TEM of Skeletal Muscle High magnification view of of a sarcomere

  19. TEM of Skeletal Muscle in cross section

  20. TEM of Skeletal Muscle – t-tubule and triads SR = sarcoplasmic reticulum T = t-tubule Mi = mitochondria

  21. Motor Units = All muscle fibers that are controlled by a single motor neuron The lower the ratio of muscle fibers to neurons, the more precise the movement can be! Few cases 1: 1 relationship. Where? Most cases: many muscle fibers (up to 2,000) : 1 motor neuron. Where?

  22. TEM of a Myoneurojunction

  23. Three Types of Muscle Fibers 1) Fast (or White) Fibers Fast contraction after nervous stimulation Large diameter large glycogen reserve few mitochondria densely packed myofibrils Fatigue fast due to mainly anaerobic respiration

  24. 2) Slow (or Red) Fibers Slower but continuous contraction for extended periods Smaller diameter (~ half) contain myoglobin more capillaries more mitochondria Do not fatigue as fast due to ?

  25. 3) Intermediate Fibers Have attributes inbetween fast and slow types Most skeletal muscles contain mixture of fiber types. Proportion of fast to slow depends on ___________? One motor unit only contains one fiber type Eye, hand: ____ fibers dominate Back, calf: ____ fibers dominate

  26. THANX

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