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Muscle Tissue

Muscle Tissue. Mamoun Kremli Al- Maarefa College. Objectives. Identify basic structure of Muscles Recognize types of muscular tissues and the difference between them Recognize the relation between structure and function of various muscular tissues. Tissues.

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Muscle Tissue

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  1. Muscle Tissue MamounKremli Al-Maarefa College

  2. Objectives • Identify basic structure of Muscles • Recognize types of muscular tissues and the difference between them • Recognize the relation between structure and function of various muscular tissues

  3. Tissues • Four fundamental tissues are recognized: • Epithelial tissue • Connective tissue • Muscular tissue • Nervous tissue

  4. Muscle Tissue - Characteristics • Cells are referred to as fibers because they are elongated • Contracts or shortens with force when stimulated • Contraction depends on myofilaments • Actin • Myosin • Plasma membrane is called sarcolemma • Sarcos = flesh • Lemma = sheath

  5. Special functional characteristics • Contractility • Only one action: to shorten • Shortening generates pulling force • Excitability • Nerve fibers cause electrical impulse to travel • Extensibility • Stretch with contraction of an opposing muscle • Elasticity • Recoils passively after being stretched

  6. Muscle Tissue Types • Skeletal: • attached to bones • Cardiac: • muscle of the heart • Smooth: • muscles associated with tubular structures and with the skin

  7. Muscle Tissue Types

  8. Skeletal Muscle - Units Muscle Fascicle Fiber

  9. Skeletal Muscle - Coverings Epimysium surrounds whole muscle Epimysium surrounds whole muscle

  10. Skeletal Muscle - Coverings Perimysium Perimysium is around fascicle

  11. Skeletal Muscle - Coverings Endomysium Endomysium is around each muscle fiber

  12. Skeletal Muscle - Coverings • Epimysium, Perimysium, Endomysium

  13. Skeletal Muscle - Coverings

  14. Skeletal Muscle – Blood Supply • Muscles must have plenty of blood supply • High demand for O2 and nutrients Vessels injected with plastic material

  15. Skeletal Muscle • Voluntary movement • Long and cylindrical • Transverse striations • Each fiber is multi-nuclear (multinucleated cells – embryonic cells fuse) • 40% of body weight

  16. Skeletal Muscle Figure 4.14a

  17. Skeletal Muscle • Large, elongated, multinucleated fibers. • Nucleii are in periphery of cells, just under cell membrane

  18. Skeletal Muscle • A band (dark-stained) • I band (light-stained) • Z line A band I band Z line Giemsa stain

  19. Skeletal Muscle • A bands (dark-stained) • I bands (light-stained) • Z lines A bands I bands Z line

  20. Skeletal Muscle • A-band (actin & myosin ) • I-band( actin only) • Z lines(attachment of actin) • H-band(myosin only) • M-line (Myomesin, creatine kinase)

  21. Skeletal Muscle Structure • Invaginations of the T system at transition between A and I bands (twice in every sarcomere) • They associate with terminal cisternae of the sarcoplasmic reticulum (SR)(which is the specialized calcium-storing smooth endoplasmic reticulum). • Abundant mitochondria is present between myofibrils.

  22. Skeletal Muscle Structure Bloom W, Fawcett DW: A Textbook of Histology, 9th ed, Saunders

  23. Skeletal Muscle – Sarcomere structure Bloom W, Fawcett DW: A Textbook of Histology, 9th ed, Saunders

  24. The Thin Filament - Actin

  25. Skeletal muscle • Fibers have striations • Myofibrils are organelles of the cell: these are made up of filaments • Sarcomere • Basic unit of contraction • Myofibrils are long rows of repeating sarcomeres • Boundaries: Z discs (or lines) -an organelle

  26. Myofibrils • Made of three types of filaments (or myofilaments): • Thick (myosin) • Thin (actin) • Elastic (titin) ______actin _____________myosin titin_____

  27. Sliding Filament Model __relaxed sarcomere__ _partly contracted_ fully contracted Sarcomere shortens because actin pulled towards its middle by myosin cross bridges “A” band constant because it is caused by myosin, which doesn’t change length Titin resists overstretching

  28. Sliding Filament Model

  29. Sarcoplasmic reticulum is smooth ER • Tubules surround myofibrils • Cross-channels called “terminal cisternae” • Store Ca++ and release when muscle stimulated to contract • Two thin filaments triggering sliding filament mechanism of contraction • T tubules are continuous with sarcolemma, therefore whole muscle (deep parts as well) contracts simultaneously

  30. Neuromuscular Junction • Motor neurons innervate muscle fibers • Motor end plate is where they meet • Neurotransmitters are released by nerve signal: this initiates calcium ion release and muscle contraction

  31. Neuromuscular Junction • Motor Unit: a motor neuron and all the muscle fibers it innervates (these all contract together)

  32. Motor Unit

  33. Motor Unit

  34. Motor End-plate

  35. Types of Skeletal Muscle: • Type I fibres (red fibres). • Red muscles (large amounts of myoglobin and mitochondria). • Type II fibres(white fibers). • White muscles (less amounts of myoglobin and mitochondria). • Type III Fibres (Intermediate). • Have characteristics between type I & II In humans, skeletal muscles are composed of mixtures of these 3 types of fibres.

  36. Red muscles are used when sustained production of force is necessary, e.g. in the control of posture. • White muscles are for rapid accelerations and short lasting maximal contraction e.g. extraocularmuscles of the human eye)

  37. Cardiac Muscle • Striations • Involuntary • One nucleus • Deep center • Heart muscle

  38. Cardiac muscle • Bundles form thick myocardium • Cardiac muscle cells are single cells (not called fibers) • Cells branch • Cells join at intercalated discs • 1-2 nuclei in center • Here “fiber” = long row of joined cardiac muscle cells • Rhythmicity: • More T-Tubules

  39. Cardiac Muscle Figure 4.14b

  40. Cardiac Muscle

  41. Cardiac Muscle

  42. Cardiac Muscle

  43. Cardiac Muscle

  44. Smooth muscle • Muscles are spindle-shaped cells • One central nucleus • Grouped into sheets: often running perpendicular to each other • Peristalsis • No striations (no sarcomeres) • Contractions are slow, sustained and resistant to fatigue • Does not always require a nervous signal: can be stimulated by stretching or hormones • 6 major locations: • inside the eye 2. walls of vessels 3. respiratory tubes • 4. digestive tubes 5. urinary organs 6. reproductive organs

  45. Smooth Muscle • Spindle shaped • Not striated • Single nucleus • Involuntary movement • Internal organs

  46. Smooth Muscle

  47. Smooth Muscle • Centrally located nucleii

  48. Smooth Muscle • Cells are surrounded by a net of reticular fibers

  49. Smooth Muscle • Cytoplasmic filaments insert on dense bodies located in the cell membrane and deep in the cytoplasm. • Contraction of these filaments decreases the size of the cell and promotes the contraction of the whole muscle. • During the contraction the cell nucleus is deformed.

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