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47 Cards in this Set

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