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36 Cards in this Set
- Front
- Back
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Which cells are specific to CT? (4)
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1. Fibroblasts
2. Odontoblasts 3. Osteoblasts 4. Cementoblasts |
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Osteoblasts produce 3 general classes of ECM molecules?
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1. GAG
2 Proteins 3. Regulatory factors |
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What forms the ground substance of ECM?
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Proteoglycans, proteoglycan aggregates & GAGs
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What are proteoglycans?
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Negatively charged highly glycosylated glycoproteins containing GAGs
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Which molecules bind water & create flexibility & lubrcity?
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PGs & GAGs
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How is mature fibrillar collagen bonded?
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Covalently & hydrophobically to form very strong oriented fibers
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What takes compressional loads in bone?
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Hydroxyapatite
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What takes tensional loads in bone?
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Collagen
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Osteogenesis imperfecta arises from?
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Molecular defects in type I chains
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Chondroplasias arise from?
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Type II defects
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Ehlers-Danlos syndrome arises from?
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Type III defects-- failure to form fibrils from failure to process propeptides & improper crosslinking
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Which amino acids are involved in crosslinking?
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Histidines & lysins
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Why is crosslinking essential?
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Gives strength to collagen
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What is endochondrial bone formation?
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Bone mineralizes from previously formed cartilage model
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How does mineralization begin in endochondrial bone formation?
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From a central region & progresses towards ends of bone
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What is the growth plate?
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Endochondrial bone formation-- zone where transformation from cartilage to bone takes place
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2 models of mineralization studied?
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1. Endochondrial bone formation<br />2. Intramembranous bone formation
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What is similar between both models of mineralization?
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External regulators determine when & under what conditions calcification will occur
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What percentage of organic matrix is collagen in mineralizing tissues?
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90%
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What types of molecules are found in non-collagenous materials? (5)
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1. PGs-removed before mineral formation
2. GAGs- sulfated, phosphorylated 3. Osteocalcin 4. Osteonectin 5. Osteopontin |
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What are the 2 general models of biological mineralization?
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1. Homogenous nucleation
2. Heterogenous nucleation |
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What is the booster hypothesis? (2)
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Homogenous nucleation:
1. Matrix of mineralized tissue is same as non-mineralized tissue 2. Cellular activity boost Ca & P ions to drive seeding of mineral |
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What is the environmental hypothesis? (2)
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Heterogenous nucleation:
1. Ksp is exceeded in most tissues 2. Matrix must be different for mineralization to occur |
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How is Ca boosted in mineralizing tissues?
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Mitochondria accumulate Ca at expense of ATP
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What happens to Ca in mitochondria?
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Accumulates in matrix vesicles to make hydroxyapatite
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What increases phosphate in growth plate?
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Alkaline phosphatase
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How is mineral associated collagen different? (4)
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1. Type I= less cross linked
2. Has linkages to sugars 3. Phosphorylated in telopeptide regions 4. Fibril associated collagens associate w/ mineralization process |
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What enzymes & growth factors are located in matrix of mineralizing tissues? (6)
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1. Alkaline phosphatase, collagenase, plasminogen activator
2. FGF, IGF, TGF beta 3. Proteolipids 4. BMPs 5. Growth factors 6. Serum proteins |
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What inhibits mineralization at growth plate?
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Pyrophosphate
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How is pyrophosphate broken down?
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Increase pyrophosphatase --> break down pyrophosphate --> Increase phosphate
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Why is collagen glycosylation reduced at growth plate?
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Reduction in inhibition of mineralization by sugars
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What complexes appear to be critical in mineralization?
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Proteolipid (Ca-phospholipid-phosphate) complexes
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What happens to GAG levels during mineralization?
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Decrease
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What causes attachment to collagen?
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Osteonectin
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What regulates mineralization?
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Growth factors
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What drives modeling of the matrix?
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Osteocalcin
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