Histology of developing bone part I

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  1. embryogically, cartilage derive from
    mesenchymal cells
  2. mesenchyme forms
    • the cells of connective tissue, such as chondroblasts, osteoblasts and
    • fibroblasts.
  3. Osteogenesis
    Intramembranous Ossification 

    Endochondral Ossification
  4. intramembranous ossification
    produce flat bone
  5. endochondral ossigication
    long bone
  6. how is chondroblast, osteoblast and fibroblast similar?
    produce some kind of collagen

    derive from mesenchyme
  7. bilaminar perichondrium
    develops around the growing cartilage.  This will contain the blood supply and stem cells for the cartilage.
  8. chondroblasts secret
    type II collagen and cartilage-specific matrix components.
  9. tendon is made up of
    type I collagen produce by fibroblast in one direction 

    resist shear force
  10. Type I vs type II
    shear force vs compression force
  11. fibroblast produce and  found in
    type I collagen 

    found in ligament, osteoblast in bone
  12. Bone consist of
    type I collagen (Strength) and mineralized matrix (hardness)
  13. Flat bone consist of ...layers
    3 layers: outer table, Diploe and inner table
  14. intramembrananous ossification - process
    1. Mesenchymal cells condense into a vascularized sheet of cells, and differentiate into osteoblasts.

    2. osteoblast begin secreting and calcifying osteoid

    3. Some osteoblasts become completely surrounded by osteoid, and differentiate into osteocytes.  This process produces islands of woven bone.

    4. Trabecular bone forms, a rudimentary periosteum forms from mesenchyme, blood vessels grow into bone islands.

    5. Woven bone is remodeled to compact bone around the periphery to create inner, outer circumferential lamellae, which are represented by the outer and inner tables
  15. Osteocyte's job
    maintain bones
  16. woven bone
    one direction
  17. Intramembranous Ossification - fontanelles
    The process of forming the bones of the skull is not complete by birth. 

    As a result, the incompletely ossified areas between the bones are covered only by periosteum and primitive connective tissue. 

    • We know these areas as “soft spots” or fontanelles.
    • Rationale: child birth and cerebral growth
  18. Osteoid
    unmineralized bone matrix
  19. Woven bone end up becoming
    cavity where bone marrow reside 

    trabecular bone
  20. Long bone - anatomy
    • Development of a long bone – requires
    • that the articular surface remain largely unchanged throughout process, plus subject must comply with birth canal size restrictions, but still have bones capable of being used and capable of
    • increasing in length
  21. Endochondral Ossification - process
    1. The process of forming a long bone begins with the construction of a template made from cartilage.

    2. Osteoblasts differentiate from cells in the perichondrium, secrete osteoid around the center of the cartilage, forming a bone collar.

    3. The bone collar blocks nutrients from reaching chondrocytes located within the cartilage. These chondrocytes swell up and degenerate.  They secrete alkaline phosphatase (a bone matrix mineralization enzyme) and enlarge their lacunae.

    • 4. Blood vessels from  the perichondrium
    • infiltrate this tissue, they bring osteoprogenitor cells (these cells differentiate into osteoblasts).

    • 5. .  Osteoblasts adhere to the mineralized cartilaginous matrix and secrete osteoid,
    • which is transformed into woven bone.
  22. long bone - developing property
    child birth: right shape but not big size 

    continue to development
  23. Secondary Ossification center
    • will form between the metaphysis and
    • the epiphysis. 

    • –This process is initiated by the growth of blood vessels into the epiphysis, which
    • brings a supply of  osteoprogenitor
    • cells into the center of the epiphyseal cartilage.

    • –The cartilage in the epiphysis will be gradually replaced with bone marrow in a
    • similar manner as the primary ossification center.

    –The articular cartilage will be spared from ossification.
  24. The Epiphyseal Plate
    Located in the metaphysis

    Site at which chondrocytes proliferate, degenerate, and are replaced by bone resulting in increases in bone length during adolescence and young adulthood.
  25. Epiphyseeal plate: 4 layers
    –1  Resting Zone

    –2  Proliferating Zone: chondroblast 

    –3  Hypertrophic and Degenerative Zone: dying cell and enlarger lacunnae 

    –4  Calcification and Ossification Zone
  26. Secondary site of ossification: time line
    form after birth
  27. vertical vs horizontal septa zone
    vertical: maintain trabecullae integrity

    Horizontal: got compressed and dense
  28. Resting zone
    small nuclei, 

    equal spacing

    inactive metabolically
  29. proliferative zone
    isogenic group

    evidence of growth

    unequal pacing
  30. hypertrophic zone
    vertical and horizontal septa

    hypertrophic and dying cell

    compressed trabecullae
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Histology of developing bone part I
2013-07-16 18:50:54

histology of developing bone, part I
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