Lecture 18: Bones

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Lecture 18: Bones
2011-01-27 20:20:04
Cell Bio Midterm

cartilage and bones
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  1. Rheumatoid arthritis
    hyalin carilage invaded and replaced by synovial CT
  2. Sizes: Type I, Type II
    • 20nm
    • 50-200nm
  3. Chondronectin
    adhesion protein (as opposed to fibronectin)
  4. Aggrecan
    • -Major carilage proteoglycan (with chrondroitin sulfate, kereatan sulfate) bind hyaluronic acid (backbone)
    • -100 million Da, size of bacterium
  5. Joint surface (articular cartilage) & parts of resp system
    hyaline cartilage
  6. Perichondrium
    • -DCT- type I
    • -Outer: tpe I, fibroblasts, bv
    • -Inner: chondrogenic, chondroblastsd
  7. Appositional growth
    • New carilage added to surface of preexisting,
    • differntiationS
    • switch collegen types
  8. Interstitial growth
    • New carilage ass WITHIN preesisting matrix
    • Division of chondrocytes--> isogenous groups
    • Cells separated by secrete matrix
  9. Cartilage mineralization (clacification)
    Calcium phosphate (HYDROXYAPITITE): crystals within matrix
  10. Elastic cartilage
    • Type II
    • Elastic, flexible
    • Auditory canal, epiglittis, larynx, vocal cords
    • DOESN'T caclify
  11. Fibrocartilage
    • Both types (I & II)- DCT & cart
    • intervertebral discs
    • NO perichondrium
  12. Bone- Mechanoresponsive
    • Tension increases bone formation;
    • Pressure increases bone resorption
  13. Bone
    • Organic- osteoid (80-90% type I)
    • Inorganic- calcium phosphate (hydroxyapitite): 50% dry weight

    • collegen- tenisile strength, elasticity (difficult to deform)
    • Hydroxyapitite- stiffness

    Collegen + hydrogyapitite = rigitity (= resist in all directions)
  14. Vitamin D def
    prevents calcium absorption

    • child- rickets
    • adult- osteomalacia- decrease stiffness, deformed bones
  15. Vit C def
    sCurvy- insuff Collegen, thin, fragile shaft
  16. Osteocyotes
    • maintain bone
    • Regression of secretory phenotype,
    • less rER, Golgi, non-dividing
    • Gap junctions
  17. Newly synth bone (immature)
    • Woven, primary
    • Collegen fibril interlaced, no organization, not lamellar, low mineralization
  18. Remodeled (mature)
    secondary--> compact, spongy
  19. Endosteum
    • single variable layer of: osteogenic, osteoclast, osteoblast
    • Lines 3 inner surfaces: Haversion canals, bone trabeculae, compact bone
  20. Shaft
    • Shaft- compact bone (dense)
    • predominates
    • Ends- spongy bone (cancellous) predom
  21. Haversion systems/osteon
    • 200 nm
    • Canals- surrounded by concentric lamellae of bone (ouside-->in)
    • Outer boundary of H system- cement lines
  22. Intersitial lamellae:
    spaces between H systems, remnants of older ones
  23. Volkmann's canal:
    H canals interconnected by these
  24. Osteoblasts
    • Cuboidal cells, secrete osteoid- eosinophilic cuz protein>>proteoglycan
    • Eestablish canaliculi
    • Regulate osteoclast by osteoclast-differentiation factors
    • Release matriz vesicles- CA4P2--> crystallized for
    • Osteocalcin
  25. Osteocalcin
    bind Calcium, ABUNDANT non-collenagenous glycoprotein, serum marker for bone turn over
  26. Osteoclast
    • Differntaite from monocytes, multinucleate, fusion of many cells
    • Attachment region-- ruffled border
    • Secretory vesicles (reg by Homrones)->
    • a. carbon/citrate, inc pH, dissolve CaP
    • b. lysosmal hydrolases degrade matrix
    • Parathyroid- inc osteoclast, promote osteoblasts secretion of osteoclast-differention factors
    • Calcitonin- red osteoclasts, inhib ruffle border
  27. Intrammebranous ossification
    • CT-->directly to Bone
    • (flat bones, skull, face)
  28. Endochondral ossification
  29. Estrogen
    Inhibits osteoblasts activation of osteoclast differntiation, promotes osteoclast apoptosis