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DBCS 311 > Histology: Tooth Development > Flashcards

Histology: Tooth Development Flashcards

1
Q

Name the 6 Stages of Tooth Development and the aproximate time table for when each stage occurs.

A
  1. Initiation Stage 6th-7th week of development
  2. Bud Stage 8th week
  3. Cap Stage 9th-10th week
  4. Bell Stage 11th-12th week

Terminal Differentiation

  1. Apposition Stage varies per tooth
  2. Maturation Stage varies per tooth
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2
Q

Dental lamina grows deep into the __________

A

ectomesenchyme

“Before birth, it is called ectomesenchyme. After birth, it is called epithelium”.

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3
Q

tooth development is reffered to as?

A

odontogenesis

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4
Q

vestibular lamina proliferates into _______, and then degenerates to form a ______.

A

mesenchyme

cleft=vestibule

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5
Q

Localized proliferations of the ____________ into the surrounding ____________ forms the intitial tooth buds.

A

dental lamina

mesenchyme

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6
Q

Describe the Bud Stage

A
  • initial stage of definitive tooth development
  • round localized cluster of oral epithelium of the dental lamina
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7
Q

Describe the Cap Stage

A
  • beginning of morphogenesis
  • oral epithelium forms a cap over a mesenchymal condensation forms the dental papilla
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8
Q

Describe the Bell Stage

A
  • histodifferentiation
  • epithelial cells differentiate into ameloblasts
  • cells within the dental papilla differentiate into odontoblasts
  • eventual shape of crown becomes distinct

dental lamina breaks up into discrete islands

developing tooth is now separate from the overlying oral epithelium

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9
Q

Describe the Termination (Crown) Phase

A
  • final differentiation of odontoblasts and ameloblasts
  • secretion of dentin and enamel in apposition
  • Hard tissue formation of the teeth
    • Dentinogenesis
    • Amelogenesis (enamel formation)
  • Dental follicle differentiates into alveolar bone forming around the tooth germ
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10
Q

Rooth Sheath development is intitiated in the _______

A

cervical loop region

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11
Q

Describe Root Formation

A
  • Epithelial cells from the inner and outer dental epithelium proliferate from the cervical loop of the enamel organ to form Hertwig’s Epithelial Root Sheath.
  • The root sheath extends down to encompass all but the basal portion of the pulp
  • Ectomesenchymal cells of the pulp which face the root sheath differentiate to form odontoblasts
  • The odontoblasts will eventually form root dentin.
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12
Q

Epithelial cells from the inner and outer dental epithelium proliferate from the cervical loop of the enamel organ to form ___________.

A

Hertwig’s Epithelial Root Sheath (HERS)

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13
Q

Root development begins after the enamel and dentin formation has reached the future _________.

A

cementoenamel junction

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14
Q

What determines the morphological characteristics of the root (number of roots, length, curvature etc)?

A

HERS (Hertwig’s Epithelial Root Sheath)

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15
Q

Ectomesenchymal cells of the pulp which face the root sheath differentiate to form _______

A

odontoblasts

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16
Q

Odontoblasts will form _______.

A

root dentin

17
Q

The root sheath encompasses everything except the _________of the pulp.

A

basal portion of the pulp

18
Q

The ________ differentiates into alveolar bone forming around the tooth germ.

A

dental follicle

19
Q

The tooth originally develops from _______, a specialized region of ________?

A

dental lamina

oral ectoderm

20
Q

Tooth development begins with the formation of a continuous band of thickened ______ called _______.

A

oral epithelium

Primary Epitheliual Band

21
Q

Describe the primary epithelial band

A
  • a continuous band of thickened oral epithelium
  • tooth development begins with its formation
  • formed by a change in the orientation of mitotic spindles and their increased proliferation activity.
  • subdiivides into 2 areas that ingrow the underlying mesenchyme colonized by neural crest
    • 1st- dental lamina
    • 2nd- vestibular lamina
22
Q

______ develops lateral to Dental Lamina and will become the ______.

A

Vestibular Lamina

oral vestibule

23
Q

What is the oral vestibule and from which tissue does it develop?

A
  • the cleft between the cheeks and the tooth-bearing area
  • develops from the vestibular lamina
24
Q

The dental lamina gives rise to ______by localized proliferation of the ________ into the surrounding _________, through a continuous process known as ______.

A
  • teeth
  • epithelium
  • mesenchyme
  • odontogenesis
25
Q

Name the stage of odontogenesis and identify each number

A

Bud Stage

  1. Tooth bud
  2. Oral epithelium
  3. Ectomesenchyme
26
Q

Describe which stage occurs during the 8th week of development

A
  • Teeth begin to develop
    • Formation of tooth bud.
  • Cells proliferate.
  • Neural crest cells migrate to 10 deciduous tooth sites along the future upper and lower jaws.
    • These cells induce the overlying oral epithelium, or ectoderm, to become a tooth forming organ, the tooth bud.
27
Q

Describe the stage of tooth development that occurs in the 9th week of development

A
  • Early Cap Stage
  • Each tooth bud undergoes a downward growth to form an epithelial structure called the enamel organ that is cap shaped.
  • Histo-differentiation occurs.
  • The tooth germ also begins to take on form – the start of morpho-differentiation.
28
Q

Identify the Stage and the labeled aspects

A

Early Cap Stage 9th week

  1. enamel organ
  2. Dental Papilla
  3. Dental sac (dental follicle)

All 3 make up the Tooth Germ

Note: The tooth bud differentiates further to form the tooth germ.

29
Q

Describe the Stage of Tooth Development that begins in the 10th week of development

A

Late Cap Stage

  • Enamel organ produces future enamel.
  • Dental papilla produces future dentin and pulp.
  • Basement membrane separates enamel organ and dental papilla to form future DEJ
  • Remaining ectomesenchyme around the enamel organ will form dental sac, cementum, PDL, alveolar bone.
30
Q

Name the 2 cell types the tooth bud originates from

A

Ectoderm

Ectomesenchyme.

31
Q

Name the 6 cell types the tooth germ originates from

A

The first 4 epithelium derived from the enamel organ

  1. Outer Enamel Epithelium (OEE) - forms the outer border
  2. Stellate Reticulum - forms the middle portion
  3. Stratum Intermedium - a border of cells between the Stellate Reticulum and Inner Enamel Epithelium.
  4. Inner Enamel Epithelium (IEE) - forms the inner border.
  5. DP: Dental papilla (dentinogenesis)
  6. DF: Dental follicle (sac) (periodontal ligament, alveolus, cementum)
32
Q

Inner Enamel epithelium is composed of functional cells that will differentiate into __________ and make future _________.

A

ameleoblasts

enamel

33
Q

Within the dental papilla, cells near the Inner Enamel Epithelium will differentiate into _______ to make future ______.

The remaining cells in the dental papilla will form ______.

A

odontoblasts

dentin

dental pulp

34
Q

As we transition from Cap to Bell stage, which 2 newly formed cells can be identified.

A

Ameloblasts and Odontoblasts

Also start to see in the bell stage, the columnar shape of IEE to form Ameloblasts.

35
Q

WHich 2 major events occur during the 11th week of development or early bell stage.

A

Defining feature of early bell stage= tooth germ assumes a bell-like shape

  • Enamel Organ differentiates into 4 types of cells
  1. Inner dental epithelium-forms future ameloblasts
  2. Outer dental epithelium
  3. Stellate reticulum
  4. Stratum intermedium
  • Dental papilla differentiates to 2 types of cells:
  1. Outer cells of the DP – forms future odontoblasts
  2. Central cells of the DP – forms future pulp
36
Q

The entire dental organ is made of epithelial tissue and is avascular. Describe how it obtains nutrients to grow and develop into enamel.

A

The nutrients must come from the supporting cells.

Forming enamel requires a lot of energy, that is why Stellate Reticulum, Stratum Intermedium, and Outer Enamel Epithelium help supply nutrients to the developing Ameloblasts (from Inner Enamel/ Dental Epithelium).

  • Stellate Reticulum has a large cytoplasm, where it stores nutrients and resources.

Also between the dental papila and the Inner Enamel Epithelium is a basement membrane (cell-free zone)

DBCS 311 (17 decks)

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