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47 Cards in this Set
- Front
- Back
two phases of amelogenesis?
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secretory and maturation
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what happens during the secretory phase of ameogenesis
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ameloblasts sectrete a proteinaceous enamel matrix which undergoes preliminary mineralization
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maturation phase?
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modifications are made in the enamel matrix. completion of mineralization
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after maturation what happens to the ameloblasts?
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they become a protective epithelial membrane that covers the surface of the crownuntil thetooth emerges.
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what are the stages of the ameloblast life cycle?
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Inner enamel epithelium, pre ameloblast, secretory ameloblast, maturational ameloblast, REE
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what do ameloblasts and other scleroblasts have in common
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they all secrete protien as well as deposit an organic matrix. they also take part in mineralization of the matrix by introducing mineral ions for hydroxy apatite.
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how does amelogenesis differ from other mineralized tissue formation?
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ameloblasts are not mesoderm derived,ameloblasts have a separate maturation phase, enamel matrix has no collagen fibers, the hydroxyapatite crystals are larger?
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do other mineralized tissue development include a maturation phase? do other mineralized tissue have as big of crystals? are other mineralized tissues derived from mesoderm or ectoderm? do other mneralized tissues have collagen?
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yes
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what is cytodifferentiation and when does it occur?
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it occurs after the shape of the tooth is established. it is the termination of epitherlial mitotic activity combined with cytoplasmic changes to prepare for secretory activity..
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what are the two steps of cytodifferentiation
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iee-preameloblasts
preameloblasts to secretory |
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which cytodifferentiation requires a cell free mineralizing dentin
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the preameloblast to secretory requires a cell free mineraliqind dentin matrix
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what cellular events characterize the change from IEE to secretory ameloblast?
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development of polarity- nucleus moves to basal or proximal end of the cell, elongation to a tall columnar shape, appearance of the tomes process at the distal secretory end.
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what causes the end of the secretory phase
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the odontoblasts lay down dentin and the basal lamina that was between the preameloblasts and the pre odontoblasts breakes down.
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what happens to the organelles in the cell before change from IEE to secretory
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increase in the number of organelles- including the ones that are involved in protien synthesis and secretion
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what is found at the basal and apical ends of the preameloblasts?
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junctional complexes are found
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what are junctional complexes?
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they have tight junctions and plaques at the basal end. tight junctions regulate the paracellular transport of ions, small solutes and water. protien composition varies by stage. regulate permeability creating the environment suitable for enamel depostion and maturation
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what other type of junctions ar ein the junctional complexes?
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gap junctions-permittng related cells to communicate with one another. enable cells to coordinate secretory activity.
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whats the deal with the cytoskeleton?
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present through out the cell and tomes process.
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terminal web?
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runs transversely across the cell- contains actin myosin, tropomyosin, alpha actinin. it is the stabilizer of the differentiating ameloblast.
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tomes process?
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only in secretory stage of secretory ameloblast.- it is a cell process with no organelles- it does have an extensive tubulovesicular system.
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what are the other activities of the secretory ameloblast besides secretion.
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produces enamelmelysin, kallikrein(enamel serin protienase), acid phosphatase
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when is kallikrein produced
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by secretory ameloblasts also called enamel matrix serine proteasee
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name somematrix protien
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amelongenin enamelin, tuftelin, ameloblastin- concentrateed in the golgi and then transported to the apical plasma membrane via secretory vesicles
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what is the ratio of mineral to fluid in secretory vs. mature enamel
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10% mineral initially and the mature- 90%
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what gene family do amelogenins belong to?
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secretoy calcium binding phosphoprotien- scpp- located on the x and y chromosome.
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where are amelogenins secreted?
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between hydroxyapatite crystals- form micelles by self organizing nanospheres
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how do they form micelles
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hydrophobic cores with hydrophillic c termini on peripheries
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up to 149
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yes
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ameloblastin
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first on the scene of the enamel matrix- adjacent to the tomes process cell membrane.
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where are ameloblastins located
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next to the tomes process
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what is the function of ameloblastins
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adhesion of secretory ameloblasts to the developing matrix when there is no basal lamina to attach to- responsible for maintenance of the differentiation state
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how does it end
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after they are secreted they are cleaved in their n-terminal halves that accumulate in the interprismatic space
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enamelins
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acidic, hydrophobic- larger than amelogenins
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where are enamelins located
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at the mineralization front
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what role do enamelins play
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crystal elongation
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what happens to the products of enamelin cleavage
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they are unstable. those that remain are attached to hydroxyapatite and contunue to be present in the enamel prisms of mature enamel
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tuftelin
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low abundance. most acidic backbone
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where is tuftelin located
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DEJ and tufts
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is tuftelin specific to enamel
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no it is also found in kidney, liver, lungs
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what is the role of tuftelin
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it is a nucleator in the mineralization process -acts as the phosphoprotiens do in bone and dentin
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what chromonsomes are amelogenin, enamelin and tuftelin found on
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ameloblastin is on 4q 21. enamelin is on 4q and tuftelin is on chromosome 1
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name 2 enamel protienases that are in immature enamel
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enamelmysin and kallikerin( enamel matrix serine protease)
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what is the lingual papilla
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anterior 2/3
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what is the lingual tonsil
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posterior 1.3
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taste buds
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on3 of the 4 lingual papilla types
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epithelium
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non-keratinized- various thicknesses
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ventral surface
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lining mucosa
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