OCB02-1010 Late tooth development Flashcards
Where is the PEK formed?
Right in centre of the enamel organ in the IEE
When is the PEK formed?
Cap stage
What does it mean by the cells in the PEK are ‘non-proliferative’?
Cells in the PEK do not divide
What signalling molecules do the PEK secrete?
BMPs, FGFs, Wnts, Shh
What is the Enamel knot known as?
The ‘signalling centre’ as it doesn’t contain receptors
What cusp does the PEK mark the position of in molars?
The first bucker cusp of the molars
What occurs in the early bell stage?
The IEE has further invaginated
The stellate reticulum has expanded
What is the enamel cord?
A string of epithelial cells that links the inner and outer epithelium on the monocuspid and mutlicuspid
What are the 3 layers of the dental follicle?
Inner layer
Loose connective tissue layer
outer layer
What layers form the periodontal ligament?
outer and inner
Where do secondary enamel knots appear?
In multicuspid teeth
What do the numbers of SEK determine?
Number of cusps
What is a successional tooth?
Permanent tooth with a tooth predecessor
What is an accessional tooth?
Permanent tooth with no predecessor
What happens to the dental lamina in the late bell stage?
It breaks down
What remains after the dental lamina breaks down? and what can they cause?
Some epithelial clusters called epithelial pearls of Serres
These can cause cysts odontomas (tumours) or supernumerary teeth
Why do humans have only 2 dentitions?
The dental lamina contains the stem cells that are able to produce new teeth
Therefore after the second dentition has formed, the dental lamina breaks down and prevents the formation of new teeth
What are monophyodont beings?
Mouse, chameleon
Single generation of teeth, no replacement
What are diphyodont beings?
Humans
SEcond generation of teeth
What are polyphyodont beings?
snakes
multiple generation of teeth
What is histogenesis?
The terminal differentiation of specialised cells that gives rise to fully formed dental tissues
What is mineralised tissue?
Enamel, dentin
What is non-mineralised tissue?
Dental pulp
When does formation of hard tissues begin?
Late bell stage
What do cells at the periphery of the dental papilla differentiate into?
Odontoblasts
What do odontoblasts do?
Secrete predentin, which is mineralised into dentin
What cells do the IEE differentiate into?
Ameloblasts
What do ameloblasts do?
Lay down enamel
How do ameloblasts and odontoblasts diffrentiate?
There is elongation and polarisation of the IEE
This causes diffrentiation of odontoblasts
They lay down one layer of predentin which send signals to the pre-ameloblasts to become ameloblasts
The ameloblasts become fully functional
They then begin to lay down enamel
Why do ameloblasts not get nutrients from blood vessels in mesenchyme within dental papilla?
When odontoblasts lay down predentin and dentin, there will be a barrier between the odontoblasts and ameloblasts
The ameloblasts will not get nutrients for the dental pulp anymore
How do ameloblasts get nutrients?
When mineralising occurs at the tip of the cusp during amelogenesis, the stellate reticulum collapses
Outside the epithelial bell, are mesenchyme which contains blood vessels for nutrient diffusion
