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Musculoskeletal System

Musculoskeletal System

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Musculoskeletal System

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  1. Musculoskeletal System SugitoWonodirekso, MS, Dr Department of Histology FMUI

  2. Materials • Skeletal muscle • Joint • Joint types • Bone • Cartilages • Supporting tissues Musculoskeletal System

  3. Objectives of the muscle tissue • Identify skillfully the skeletal muscle structure • Identify the structural and functional different between 3 major types of muscle tissue • Comprehend the relationships between muscle fascicles, muscle fibers, myofibrils, and myofilaments • Explain the structure and function of T-tubule in skeletal muscle • Analyze the relationships between normal structure and function of skeletal muscle • Explain the regeneration process of skeletal muscle Musculoskeletal System

  4. General features of muscle tissues • Terminology • Prefixes: Sarco- and or myo- • Specialized for contraction • Myofilaments: actin (thin) and myosin (thick) • Mesodermal origin • Exception: iris smooth muscle arise from ectoderm • Cell shape • May reach 4 cm long  called fibers (myofibers) • Organization • Works in groups or separately • Two major types • Smooth and striated Musculoskeletal System

  5. Muscle types and characteristics Musculoskeletal System

  6. Skeletal muscle (this is our concern now) • Histogenesis • Mesenchymal cells of mesodermal origin fuse to each other to make • Myoblasts which then fuse to make • Myotubes which later • Elongate by incorporating additional myoblasts • Eventually accumulated myofilaments which are organized into myofibrils and displaced nuclei and other cytoplasmic components peripherally Musculoskeletal System

  7. Skeletal muscle cells • Mature skeletal muscle fibers: • Elongated • Unbranched • Cylindrical • Multinucleated • Flattened peripherally displaced nuclei, lie just under sarcolemma (muscle cell plasma membrane) • Most organelles and sarcoplasm (muscle cells cytoplasm) are displaced near the nuclei’s poles • Sarcoplasm contains mitochondria, glycogen granules, and myoglobin (oxygen-binding protein). It accumulates lipofuscin pigment with age • Mature skeletal cell are end cells and cannot divide Musculoskeletal System

  8. Skeletal muscle tissue • Cross-cut of skeletal muscle to show connective tissue partitioning of muscle into groups or bundles of fibers. Endomysium is very delicate and lies between individual fibers, while perimysium is more visible and lies around a group of fibers. Epimysium is not seen here but ensheaths a whole muscle. In this picture notice the presence of small blood vessels in both perimysium and endomysium. Notice also the cross-cuts of myofibrils within the muscle cells, making them look grainy. Musculoskeletal System

  9. Higher power of skeletal muscle for details of cross-striations. Notice thin Z discs and heavy A bands. From one Z disc to the next is a sarcomere, the unit of muscle contraction. In the upper muscle cell notice shadowy myofibrils running longitudinally. Musculoskeletal System

  10. Skeletal muscle cells (fibers), with cross-striations and peripheral nuclei. Musculoskeletal System

  11. Muscle fibers organization Musculoskeletal System

  12. Sarcomeres (contraction units) Musculoskeletal System

  13. Sarcomere and the cross sections Musculoskeletal System

  14. Myofilament • Thin filaments (actin) • Filamentous actin (F-actin) is polymeric chain of globular actin(G-actin)monomer. Each thin filament consist of 2 double helix wound F-actin strands • Tropomyosinis long, thin, double-helical polipeptides that wrap around the actin double helix, lies in grooves on its surface, and spans 7 G-actin monomers • Troponin is a complex of 3 globular proteins. • TnT (Troponin T) attaches each complex to specific site on each tropomyosin molecule, • TnC binds calcium ions, and • TnI inhibits the interaction between the thin and thick filaments Musculoskeletal System

  15. Actin filaments Musculoskeletal System

  16. Myofilament • Thick filaments (myosin): • Long golf-club-shaped polypeptide • A bundles of myosin molecules with their shafts pointing toward and overlapping in the bundle’s middle and their heads projecting from the bundle’s ends • This arrangement leaves a headless region in the center of each filament corresponding to the H band • Treating myosin molecule with papain (a proteolytic enzyme) cleaves them, at a point near head, into 2 pieces • The piece containing most of the thin shaft is termed light meromyosin; the head and the associated portion of the shaft make up the heavy meromyosin • The head portion of heavy meromyosin has an ATP-binding site and an actin binding site, which are necessary for contraction Musculoskeletal System

  17. Actin and myosin filaments relationship Musculoskeletal System

  18. Myofilament • Organization • The banding pattern of skeletal muscle reflects the grouping of myofilaments into parallel bundles of thin and thick filaments called myofibrils. Each muscle fiber may contain several myofibrils; the number depending on its size. • Take special attention on the appearance of myofibrils in cross- and longitudinal section, especially in EM images and its schematic version Musculoskeletal System

  19. Sarcomere and muscle contraction • Diagram of contraction of skeletal muscle. On the left is the view with light microscopy. On the right are the thin actin filaments and thick myosin filaments seen in EM. Notice that the total width of the A band stays the same throughout and that the sliding in or out of the actin filaments determines the width of the H band. Consider which filaments you would see if you cut the muscle cross-wise through the I band, A band, or H band. Musculoskeletal System

  20. T-tubules and the Triads • Drawing of relationship (at EM level) of myofibrils to sarcoplasmic reticulum (smooth ER) and T-tubules in skeletal muscle. In this drawing the sarcoplasmic reticulum is labelled "sarcotubules" and "terminal cisternae". Notice that T-tubules are extensions of the sarcolemma (cell membrane, seen at right-hand edge), so that depolarization can spread along this part of the sarcolemma as well. (See diagrams and further explanation in your textbook.) Musculoskeletal System

  21. The sarcomere and the diads • Same diagram, for cardiac muscle. • Note differences with skeletal muscle in: • their amount and arrangement of sarcoplasmic reticulum • the presence or near-absence of terminal cisterns (next to the T-tubules) • the position of T-tubules in relation to the A, I, and Z bands seen at the left. • A triad consists of two terminal cisterns with a T-tubule in the middle. When the cisterns are not well developed, a true triad does not exist. A diad means two elements are together, as with one T-tubule and a neighboring bit of sarcoplasmic reticulum. NOTE: sarcoplasmic reticulum is just a form of smooth endoplasmic reticulum (SER). In muscle it is particularly associated with the release of calcium ions needed for contraction. Musculoskeletal System

  22. The sarcomere • EM of several myofibrils running longitudinally through skeletal muscle cell. Between individual myofibrils lie the mitochondria (M) and glycogen (G) of the cytoplasm. Within each myofibril are the typical striations: • A= A band; • I= I band; • Z= Z line; and • H= H band. • The banding is formed by the arrangement of myosin and actin filaments. Musculoskeletal System

  23. Sarcomere and the contraction Musculoskeletal System

  24. Skeletal muscle regeneration Musculoskeletal System

  25. Skeletal muscle regeneration Musculoskeletal System

  26. Skeletal muscle regeneration Musculoskeletal System

  27. Contraction process-1 Musculoskeletal System

  28. Contraction process-2 Musculoskeletal System

  29. Contraction process-3 Musculoskeletal System

  30. Muscle fibers organization Musculoskeletal System

  31. Joints Basic joint components are: Bone Hyaline Cartilage Dense collagen tissues Musculoskeletal System

  32. BoneEndochondral bone formation Musculoskeletal System

  33. BoneEndochondral bone formation Musculoskeletal System

  34. Bone growth and remodelling Musculoskeletal System

  35. Compact bone with Haversian system Musculoskeletal System

  36. HaversianLamelae and the remnant Musculoskeletal System

  37. Osteocytes’ lacunae and its canaliculi Musculoskeletal System

  38. Osteocyte and the canaliculi Musculoskeletal System

  39. Osteocyte EM. Osteocyte in its lacuna. Notice the pericellular space, organell some of which are globules containing Calcium, and the cell processes Musculoskeletal System

  40. Tight junction between osteocytes’ processes in its canaliculus Musculoskeletal System

  41. Muscle-bone attachment Musculoskeletal System

  42. Younger compact bone tissue Musculoskeletal System

  43. Bone dynamics Appositional growth Bone vascular system Musculoskeletal System

  44. Bone Osteocytes Compact bone tissue Musculoskeletal System

  45. Hyaline cartilage Musculoskeletal System

  46. Cartilage Chondrocyte Appositional growth Musculoskeletal System

  47. Cartilage Hyalin cartilage Elastic cartilage Musculoskeletal System

  48. Cartilage Elastic cartilage Fibrous cartilage Musculoskeletal System

  49. Cartilage Hyalin cartilage Hyalin cartilage on the joint surface Musculoskeletal System

  50. Joint Musculoskeletal System