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20 Cards in this Set
- Front
- Back
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How does enamel differ from other hard tissues?
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It has no collagen and is ectodermally derived as opposed to CT dervied like others. (its formation and destruction follows similar format though)
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Common marker protein for all cells secreting bone matrix?
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Alkaline phosphatase
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Calcium hydroxyapatite crystals vary in size in hard tissues, which are bigger?
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enamel crystals are biggest, then dentin, then bone and cementum
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What prohibits spontaneous precipitation of calcium and phosphate in body fluids?
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Inhibitor molecules present in fluids. Also, there is an energy barrier because crystal formation is unstable.
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What is homogeneous nucleation?
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local increase in ion concentration that drives the crystal forming reaction in bone
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What is heterogeneous mineralization?
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Nucleating substance drives the crystal forming reaction without increasing the ion concentration (takes place within matrix vessicles)
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What are matrix vessicles?
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Membrane bound structures containing proteins necessary for matrix mineralization. This is how homogeneous nucleation is accomplished when vessicles lyse (MV absent in enamel)
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Why do crystals form in the gaps of tropocollagen molecules?
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The gaps contain proteoglycans that bind calcium
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What is the role of alkaline phosphatase in matrix mineralization?
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It dephosphorylates phosphoproteins to provide additional phosphate for nucleation and crystal growth.
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What molecule acts as the controller and inhibitor of crystal growth?
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Pyrophosphate accumulates on the surface of crystals and inhibits growth
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Where is most of the mineral located in bone?
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70-80% is located within collagen fibers, the rest is packed in the ground substance between fibers.
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What would you find in a Howship's lacuna?
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Large multinucleate osteoclasts
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What is the enzyme marker for all osteoclasts?
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Acid phosphatase
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What acids are elaborated from the ruffled border of osteoclasts?
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Carbonic and citric acid. There is also a proton pump to help lower pH of the area.
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What are the hydrolytic enzymes used by osteoclasts to degrade organic bone matrix?
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acid phosphatase, cathepsin B, and collagenase
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What surrounds osteocytes in lacunae?
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The lamina limitans surrounds the cell and separates it from the mineral interface
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What are the 4 regions of an active osteoclast?
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Basal zone, ruffled border, clear zone, and vesicular zone.
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Describe intramembranous bone formation
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This happens spontaneously in the flat bones of the skull in the CT membranes (no Haversian systems)
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Describe endochondral bone formation.
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Cartilage template is invaded by blood vessels, which brings in osteogenic cells that replace cartilage template with bone (happens in long bones)
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What is the role of the perichondrium in endochondral bone growth?
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It lays down a bony outer collar (intramembraneously) while the cartilage in the center is deteriorating.
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