cartilage and bone

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cartilage and bone
2010-09-17 00:57:16
cartilage bone

cartilage and bone
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  1. hylaine cartilage
    • clear,
    • most common type, matrix contains collagen II
  2. elastic cartilage
    • conatins
    • collagen II, high concentration of elastic fibers
  3. fibrous cartilage
    • fibrocartilage,
    • tendone with chondrocytes replacing fibroblasts, contains high concentration of

    TYPE I collagen
  4. chondrogenic cells
    • will
    • give rise to cartilage
  5. chondroblast cells
    • immature
    • proliferating, grow cartilage
  6. chondrocytes
    can still be proliferative
  7. chondronectin
    • adhesive
    • glycoprotein holds matrix in place
  8. histogenesis
    • Begins with
    • mesenchymal connective tissue (embryonic)

    • Change shape
    • and start to round up, proliferate, mitotsis, beigin to secrete matrix (rich in
    • chondronectin)

    • As the begin
    • to secrete matrix, they are called chondroblasts
  9. interstitial growth
    • expansion
    • of matrix from within, chrondrosblasts aggregate, forms centers of
    • chondrification, secrete matrix around cells and separate
  10. appositional growth
    • adds
    • new cartilage to periphery, surface, fusiform chondrogenic cells (chondroblast
    • precursors) reside in perichondrium (fibrous coating outside cartilage); secrete matrix at periphery
  11. perichondrium
    • protective
    • envelope- 2 layers:

    • Fibrous-
    • outer layer, more fibrillar less cellular

    • Cellular-
    • inner layer, less fibrillar, more cellular, less conspicuous after cessation of
    • growth
  12. growth hormone
    • stimulates cartilage growth, acts thru insulin-like
    • growth Factor-1 (IGF-1, somatomedin-C)
  13. thyroid hormone
    • stimulates cartilage growth, acts directly, and thru
    • IGF-1
  14. glucocorticoids
    • inhibit cartilage growth, down-regulate type I
    • collagen, up-regulate collagenase II
  15. testosterone
    stimulates growth
  16. estradiol
    inhibits cartilage growth
  17. vitamin A deficiency
    slows cartilage growth & calcification
  18. vitamin C defeiciency
    inhibits collagen synthesis (scurvy)
  19. vitamin D deficiency
    inhibits calcification (rickets, osteomalacia)
  20. boen functions
    • support, protect,
    • site of attachment for muscles/tendons/ligaments, readily mobilize stroes of
    • Ca2+
  21. bone properties
    • inert
    • (mineralized portion is nonreactive); as tissue- NOT inert, dynamic, living
    • tissue, Strength/rigidity of cast iron- but only weights 1/3 as much, relatively
    • brittle

    • Richly
    • vascularized
  22. compact bone
    • cortical,
    • more stress placed on boneà
    • more bone will develop in that area
  23. cancellous bone
    • spongy,
    • adapts to stress lines placed on bone
  24. Wolffs law
    • bone adapts
    • to loads placed on it, change in mechanical stress dictates structure of living
    • bone

    • Bony
    • elements: place/displace themselves in direction of functional pressure

    • Increase or
    • decrease mass to reflect functional pressure

    • *a bony
    • protuberance is there bc a bone has reorganized its elements to support
    • function
  25. matrix
    • 90% of
    • organic material is collagen

    Collagen fibers are radially arranged

    • Collagen fibers of one lamella
    • are perpendicular to those in next lamella

    • 5% is polysaccharide: rich in aggrecans
    • (chondroitin-4 sulfate, chondroitin-6 sulfate, heperan sulfate), rich in
    • glycoproteins )osteocalcin, osteopontin, bone sialoprotein)

    • 62% inorganic, forms plate which
    • align with collagen, mostly hydroxyapatite salt (see slide 16)
  26. lamellae
    • calcified interstitial substance deposited in
    • layers (lamellae)

    • lacunae - small cavities within
    • each lamella, “uniformly” spaced, lenticular-shaped

    • canelliculi- canals,
    • communication btw osteocyte and haversian systems

    • *spongy
    • bone has trabelcullae and spicules, NO haversian canals

    Bony cells reside in lacunae- tiny tubular passages radiate from lacunae
  27. canaliculi
    life lines of osteocytes, cells receive nutrients thru canaliculli
  28. osteon
    • AKA haversian systems, majority of boen
    • arranged in osteons, contain haversian canal

    • Haversian
    • canal- central point of haversian system

    • Central
    • canal containing blood vessels

    • Runs
    • parallel with longitudinal axis of bone

    • Surrounded
    • by concentrical lamellae
  29. periosteum
    fibrous connective tissue associated with outer surface of bone, envelop and tightly adhere to bone

    Sharpy’s fibers: anchor periosteum to underlying bone, collagen from outer layer embed into bone........ Very important!

    Fibrous periosteum: Dense, fibrous, relatively acellular, only FIBROBLASTS are present

    • Cellular periosteum: inner layer, loose, less fibrous, more cellular, undifferentiated,
    • osteogenic cells (bone precursor cells)à may transform into osteoblasts
  30. endosteum
    thin singlular, cellular layer lining bony walls of adjoining marrow cavity, osteogenic cells

    Line all bone cavities (including Haversian canals and marrow spaces)

    Have osteogenic potential
  31. osteoblasts
    form osseous tissue, lay down bony matrix

    Arise from mesenchymal cells (embryo)

    • Osteoprogenitor cells (in adults)- sit on bony surface, basophilic sytoplasm, nucleus away from
    • bony surface Of periosteum

    Endosteal cells lining bone
  32. why is sytoplasm basophilic
    • they are full of ER, ribosomes made of RNA, ACIDIC,
    • highly active, producing bone matrix (lots of collagen protein)
  33. osteocyte
    reside WITHIN lacunae, small lenticular cell, sparse RER and Golgi, long cytoplasmic processes

    Maintain health of boen

    Participate in Ca and PO4 transport

    Cytoplasmic processes connect adjacent osteocytes by way of CANALICULI
  34. osteoclast
    specialized macrophages that fuce (multiple nuclei), job is to eat bone

    Located in concave areas- HOWESHIP’S lacunae

    Can release calcium into bloodstream

    Ruffled cell edge to increase SA to internalize whatever it eats up

    Clear zone has many polyribosomes to break down calcium salts
  35. endochondral growth
    • within
    • cartilage model of bone, starts in connective tissue matrix
  36. intramembranous growth
    • mesenchymal-
    • happens within connective tissue membrane
  37. conditions needed for osteogenesis
    • presence of pre-existing connective tissue in 1 of 2 forms:
    • in a loose primitive mesenchymal form
    • as a cartilagenous model

    rearrangement of underlying CT

    increased vascularity (ingrowth of capillaries)

    osteogenic stem cells
  38. osteoid
    • thin layer of uncalcified preosseous tissue,
    • surrounds osteocyte adjacent to active osteoblast (osteoblasts secrete osteoid)
  39. spicules
    • - first deposition of bone, spike like shard
    • of new bone
  40. trabeculae
    • bony spicules radiating from ossification
    • center, spicules have merged
  41. intramembranouse growth
    occurs in flat bones of skull (e.g. frontal, occipital and temporal)

    pre-existing tissue scaffold, including:

    mesenchymal cells-à osteoblastic

    primitive fibrous CT

    fibers (collagen type I)

    cells differentiate and bcome osteoblasts, secrete organic matrix, matrix calcifies

    traps cells in lacunae, becoming osteocytes
  42. endochondral growth
    • occurs in long bones (extremities and vertebral column), pre-existing cartilage anlage
    • model

    Osseous cuffs form: calcification of midregion cartilage

    death and resorption of central chondrocytes

    • blood
    • vessels penetrate diaphysis (cuff)

    • osteogenic
    • cells migrate into cavity

    transformation of chondrocytes

    develop primary ossification site

    marrow cavity enlarges

    • remaining cartilage anlage forms “plate”
    • epiphyseal cartilage plate

    secondary center of ossification: blood vessels penetrate epiphysis
  43. zone of resting cartilage
  44. relatively translucent, maintain cartilage of
    growing bone, pool of chonsrocytews
  45. zone of proliferation-
  46. active proliferation, many many stacks
    of cartilage cells, not much space
  47. zone of hypertrophy-
    • actively secreting matrix, start laying matrix
    • down (blue tint)
  48. zone of calcifying cartilage
    • begin to lay Ca2+ salts, calcified
    • connective tissue
  49. zone
    of resorption/ossification
    • large number of osteoclasts to chew away
    • calcified cartilage and blasts move in to lay down true bony matrix, pink stain
    • is the norm for calcified bone
  50. bone repair
    • at fracture, new hyaline cartilage gets laid into wound, callus (new tissue develops in and
    • around fracture site), general same schema as osteogenesis, new bony tissue
    • laid down

    *repaired bone is often stronger than regular bony areas

    callus- area of inflammation around injury