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Anatomy 2 > Lect 6 Tooth Development > Flashcards

Lect 6 Tooth Development Flashcards

1
Q

ectoderm (epithelium)

A

one of three basic germ layers that forms skin, CNS, tooth enamel and many other structures

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2
Q

Endoderm (epithelium)

A

one of the three basic germ layers that forms sthe gut tube and its derivative

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3
Q

mesoderm

A

one of the three basic germ layers that forms blood vessels, bone, CT and other structures

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4
Q

Neural crest cells

A

cells of the neuropithelium that form the tips (crest) of the neural folds and then migrate to form many structures including: spinal ganglia, head and neck CT, dentin, support tissues of tooth and many other structures

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5
Q

ectomesenchyme

A

embryonic CT that is derived from neural crest cells (will form dentin, cementum, periodontal ligament, alveolar bone)

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6
Q

Primary epithelial band

A

proliferated epithelium at the site of the future dental arches
Day 37 of development

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7
Q

Day 42-48

A

Subdivisions form

  • Dental lamina
  • Vestibular lamina - cells enlarge an then degenerate to form the vestibule of the oral cavity
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8
Q

Oral cavity development key concepts

A
  • the ectoderm is epithelium, it has folded/proliferated into the embryo as the anterior aspect of the oral cavity
  • the mesenchyme that has been invaded by neural crest cells is called the ectomesenchyme
  • cell signaling occurs throughout tooth development
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9
Q

Dental lamina

A

each dental lamina develops 10 centers of proliferation,

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10
Q

Stages of tooth development

A

Initiation stage
Bud Stage
Cap Stage
Bell Stage

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11
Q

Initiation stage

A

6-7 weeks

primary epithelial band apparent

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12
Q

Bud stage

A

8-9 weeks
tooth buds grow into underlying ectomesenchyme
- buds are for deciduous teeth
-cells only proliferate, no change in function at this time

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13
Q

Cap Stage

A

10-11 weeks
deep surface of bud invaginates and becomes cap shaped, ectomes. condensation
-peripheral cells:become cuboidal and columnar shape
-As development continues in enamel organ, matrix has increasing amounts of glycoaminoglycans
-center area becomes hydrated, cells pulled apart and maintain contact via hemidesmisomes
-dental lamina is a sheet rather than a single layer

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14
Q

Bell Stage

A

12-14 weeks
tooth becomes bell shapes as the undersurface of the enamel cap deepens to form 4 recognizable regions: outer enamel epithelium, stellate reticulum, stratum intermedium, inner dental epithelium

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15
Q

enamel organ

A

=enamel
epithelial ingrowth
avascular

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16
Q

Dental papilla

A

dentin
condensed ectomesenchyme.
Vascularized during the Cap stage

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17
Q

dental follicle/sac

A

Condensed ectomesenchyme surrounding the enamel organ and the dental papilla
well vascularized

18
Q

enamel niche

A

created during cap stage by the cutting through of a curved lateral lamina so that the mesenchyme appears to be surrounded by dental epithelium

mitotic activity ceases at the site where dentin will first appear
under inductive influence of developing ameloblasts some of the ectomesenchymal cells become columnar and differentiate into odontoblasts

19
Q

outer enamel epithelium

A

thick basement membrane seperates it from ectomesenchyme

20
Q

stellate reticulum

A 
mechanical role (protects dental tissues and produces signaling molecules
blood vessels never penetrate stellate reticulum
21
Q

stratum intermedium

A

flattened cells overlying inner dental epithelium, role in producing proteins and transporting them to the inner dental epithelium

22
Q

inner dental epithelium

A

columnar shape cells, elongate prior to producing enamel and (functionally) change polarity to secrete adjacent to the basement membrane

23
Q

Cervical loop

A

inner and outer enamel epithelium are continuous at cervical loop
this is where the outer epithelium bends to meet the inner epithelium
gives rise to the epithelium that will signal root development

24
Q

Early events of bell stage

A

dental lamina and lateral lamina around the tooth germ begin to degenerate

25
Q

Early events of bell stage (and late cap stage)

A

dental lamina and lateral lamina around the tooth germ begin to degenerate

  • developing tooth loses connection with oral cavity
  • tooth will continue to develop in the underlying tissues of the oral cavity
  • cells of the laminas usually completely degenerate, if they dont, could lead to cyst (filled with keratin) and interfere with tooth eruption
  • crown assumes final shape
26
Q

Hard tissue formation

A

late cap stage though the bell stage is significant for HISTODIFFERENTIATION

  • inner dental epithelium differentiate into ameloblasts
  • dental papilla epithelium differentiate into odontoblasts
27
Q

ameloblasts

A

form enamel
formed thru inner enamel epithelial cells differentiation

contact with dentin induces the ameloblasts to begin secretion of the enamel matrix
becomes mineralized almost immediately
move away from odontoblasts and their blood supply

28
Q

odontoblasts

A

form dentin
dentin production always precedes enamel formation

begin to secrete predentin which calcifies (1 day) as dentin
As it calcifies, odontoblasts move toward papilla

29
Q

Reciprocal induction

A

the differentiation of the odontoblasts is initiated by an organizing influence from the ells of the inner enamel epithelium

  • the development of dentin and enamel requires ameloblasts and odontoblasts signal each other
  • if this does not occur the tooth will not develop normally
30
Q

Anhidrotic ectodermal dysplasia

A

reciprocal induction problem

31
Q

pre-ameloblasts

A

induce some cells of dental papilla to differentiate into odontoblasts

32
Q

dentinal tubules

A

long apical processes of odontoblasts reside in these canaliculi that extend the full thickness of dentin

33
Q

Early development vascularization/nutrient supply

A

cells of the avascular enamel organ received nourishment from two vascular sources

  • blood vessels of the dental papilla
  • blood vessels surrounding the enamel organ
34
Q

Later development vascularization/nutrient supply

A

layer of dentin interferes with diffusion from papilla

stellate reticulum collapses as compensation and brings peripheral blood vessels closer to the now active ameloblast layer

35
Q

DEJ

A

formed from process of ameloblasts moving outward and odontoblasts moving inward

36
Q

Maturation stage of ameloblasts

A

enamel is full thickness

cells from stratum intermedium, stellate reticulum and outer enamel epithelium reorganize and form the papillary layer

Ameloblast+papillary layer = reduced dental/enamel epithelium

37
Q

Cementum

A

supporting tissues of tooth form from dental follicle

some cells differentiate into cementoblasts
- poor regenerative capacity

38
Q

Sharpy’s fibers

A

found in periodontal ligament

39
Q

Periodontal ligament

A

embryology - derived from dental follicle (ectomesenchyme)
Anatomy- located between the cementum and alveolar bone of the tooth socket
Histology: CT with thick collagen type I fibers
-different than other ligaments in body (very cellular, well vascularized, highly innervated) dense regular collagenous tissue
-high rate of collagen turnover (vulnerable with nutritional deficiencies

CT of gingiva is continuous with CT of PDL

40
Q

tooth eruption

A

tooth covered by reduced enamel epithelium
bone overlaying tooth is resorbed
CT over tooth breaks down in advance
Reduced enamel epithelium and oral epithelium fuse
-central epithelial cells degenerate
-dentogingival junction formed (give rise to junctional epithelium of gingiva)

Anatomy 2 (8 decks)

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