Histo Bones Lecture 2 part 1 slides 45-84

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    A: Haverson Canals , parallel to axis of bone.B. Volkman canal connecting 2 different Haverson canal systems; perpendicular to long axis of bone
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    VC- volkman's canal.
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    • Bone remodeling shown.
    • Bottom one layer of FLAT cells signal inactively. Superior on cell is cuboidal, actively resorbing; osteoclasts.
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    Osteon (O) some time found in a thick trabecula.  Big spicule.
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    Osteon (O) some time found in a thick trabecula.  Big spicule.
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    What type of tissue is on the left and right?
    • Left: Mature bone
    • Right: Immature woven bone.
    • •Mature bone (whether compact or spongy) is lamellated•Immature bone has no organized lamellated appearance (called WONEN; NONLAMELLAR; BUNDLE BONE) type I collagen in  bone is not organized in layers•due to collagen fiber interlacing•Contains more cells per unit area than mature•Cells tend to be randomly arranged•whereas in mature bone their long axis parallels lamellae
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    A: Mesenchymal Cells -> Osteoprogenitor cells to make another spiculeB. Flat Osteoprogenitor cells resting (flat cells)
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    • Os: Endosteum has Volkman Canals (rod), Haverson Canals (circles) and bone marrow (white with black dots are osteocytes in lacunae).
    • •(P) PERIOSTEUM•sheath of dense connective tissue •Consists Of two layers:•Outer fibrous layer•collagen fibers arranged parallel to surface (CT)•Inner cellular layer- bone making cells•contains osteoprogenitor cells•can undergo division and differentiation into osteoblasts to add bone to surface for APPOSITIONAL GROWTH
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    A: older Haverson System cells lighter colored cell means older bone showing high calcification/mineralizationB:  newer Haverson System – darker cell is newly formed – not mineralized yetC: White spaces underneath are old boneX-ray micrograph of calcification. White: highly mineralized. Dark- no minerals. Shows degree of calicification.  TM is opposite (positive image) so white is newer.
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    Osteocytes communicating with each other via canaliculi tunnels in bone matrix
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    • A: Haversian Canal
    • B. Lamelli layers with canaliculi
    • C. 1 osteocyte per lacuna
    • D. cement
    • E. Fibroblast
    • F. cellular processes
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    What kind and state is this cell in?
    •Quiescent (doing nothing)  osteocytes•little rER•small Golgi•mature calcified matrix •closely apposed to plasmalemma
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    A: Cannaliculi B. Osteocyte in lacunae C. Bone matrix surrounds Not doing much because cell nucleus has heterochromatin and cytoplasm you cannot see rER or Golgi- so low activity is indicated.
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    Formative osteocyte surrounded by newly formed bone. See rer and golgi because active osteocyte.
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    A: lots of Golgi indicating active osteocyte
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    • A: Osteoclast •Large multinucleated cell•function to resorb bone•rest directly on bone surface•
    • b: HOWSHIP’S LACUNA• cavity beneath osteoclast•cell is conspicuous due to:• size •marked acidophilia•strong histochemical reaction for acid phosphatase
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    • 3 ARROWS: 3 Osteoclasts resorbing boneA: CENTRAL REGION: Red area: cytoplasmic processes called central region, ruffled border with hydroxyl apatite crystals B: Clear zone (resorption): actin filaments form a zone at perimeter of cell at surface (ligher area) of osteoclast attachemnet to bone. Attached by focal adhesion.
    • •CENTRAL REGION •with many plasma membrane infoldings•microvillous-like structures •called RUFFLED BORDER•EM shows hydroxy apatite crystals in ruffled border processes
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    Rapid bone remodeling.  OC, osteoclast; OB, oseoblast; OY, osteocyte.  OC- multiple at surface of bone., round globs with multiple nucleus attached to bone surface. HL- howship’s lacuna white zoneOB is buildingOC is remodeling/resorbing
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Histo Bones Lecture 2 part 1 slides 45-84
Histo Bones Lecture 2 part 1 slides 45-84