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Rheumatoid arthritis
hyalin carilage invaded and replaced by synovial CT
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Chondronectin
adhesion protein (as opposed to fibronectin)
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Aggrecan
- -Major carilage proteoglycan (with chrondroitin sulfate, kereatan sulfate) bind hyaluronic acid (backbone)
- -100 million Da, size of bacterium
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Joint surface (articular cartilage) & parts of resp system
hyaline cartilage
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Perichondrium
- -DCT- type I
- -Outer: tpe I, fibroblasts, bv
- -Inner: chondrogenic, chondroblastsd
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Appositional growth
- New carilage added to surface of preexisting,
- differntiationS
- switch collegen types
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Interstitial growth
- New carilage ass WITHIN preesisting matrix
- Division of chondrocytes--> isogenous groups
- Cells separated by secrete matrix
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Cartilage mineralization (clacification)
Calcium phosphate (HYDROXYAPITITE): crystals within matrix
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Elastic cartilage
- Type II
- Elastic, flexible
- Auditory canal, epiglittis, larynx, vocal cords
- DOESN'T caclify
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Fibrocartilage
- Both types (I & II)- DCT & cart
- intervertebral discs
- NO perichondrium
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Bone- Mechanoresponsive
- Tension increases bone formation;
- Pressure increases bone resorption
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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)
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Vitamin D def
prevents calcium absorption
- child- rickets
- adult- osteomalacia- decrease stiffness, deformed bones
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Vit C def
sCurvy- insuff Collegen, thin, fragile shaft
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Osteocyotes
- maintain bone
- Regression of secretory phenotype,
- less rER, Golgi, non-dividing
- Gap junctions
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Newly synth bone (immature)
- Woven, primary
- Collegen fibril interlaced, no organization, not lamellar, low mineralization
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Remodeled (mature)
secondary--> compact, spongy
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Endosteum
- single variable layer of: osteogenic, osteoclast, osteoblast
- Lines 3 inner surfaces: Haversion canals, bone trabeculae, compact bone
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Shaft
Ends
- Shaft- compact bone (dense)
- predominates
- Ends- spongy bone (cancellous) predom
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Haversion systems/osteon
- 200 nm
- Canals- surrounded by concentric lamellae of bone (ouside-->in)
- Outer boundary of H system- cement lines
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Intersitial lamellae:
spaces between H systems, remnants of older ones
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Volkmann's canal:
H canals interconnected by these
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Osteoblasts
- Cuboidal cells, secrete osteoid- eosinophilic cuz protein>>proteoglycan
- Eestablish canaliculi
- Regulate osteoclast by osteoclast-differentiation factors
- Release matriz vesicles- CA4P2--> crystallized for
- Osteocalcin
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Osteocalcin
bind Calcium, ABUNDANT non-collenagenous glycoprotein, serum marker for bone turn over
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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
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Intrammebranous ossification
- CT-->directly to Bone
- (flat bones, skull, face)
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Endochondral ossification
CT-->cartilage-->bone
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Estrogen
Inhibits osteoblasts activation of osteoclast differntiation, promotes osteoclast apoptosis
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