Tooth Development, Oral Cavity Anatomy: Ob Final

Front 1

1. What is critical to the formation of the primitive oral cavity?
2. What lines the oral cavity anterior to the oropharyngeal membrane?
3. What lines it posterior to the oropharyngeal membrane?

Back 1

the head fold is critical to the formation of the primitive oral cavity ectoderm lines the oral cavity anterior to the oropharyngeal membrane endoderm lines posterior to the oropharyngeal membrane

Front 2

What are the 2 parts of the adult oral cavity?

Back 2

1. oral vestibule- slit-like space between the teeth and mucosa of the lips and cheeks
2. oral cavity proper- between the upper and lower dental arches, roof is the palate, communicates posteriorly with the oral pharynx

Front 3

What are the major functions of the oral cavity?

Back 3

-propulsion and digestion
-protection
-secretion through major and minor salivary gland. Von Ebner's gland is around the circumvallate papillae and is a purely serous minor salivary gland.

-protection: lingual tonsil, palatine, pharyngeal

Front 4

What papillae has a purely mechanical function?

Back 4

Filiform - helps to move food around the oral cavity.

Fungiform, foliate, and vallate all have other functions.

Front 5

What are the 2 types of mucosa in the oral cavity?

Back 5

1. masticatory - adapted for chewing (25%), keratinized or parakeratinized (presence of some nuclei in some superficial cells- usually at surface)
2. lining mucosa- makes of the majority of the oral cavity mucosa (60 %), stratified squamous non-keratinized epithelium
In addition-regions of the oral mucosa that have taste buds are covered by specialized mucosa (15%)

Front 6

Where is the keratinized mucosa?

Back 6

palate, gingiva, and dorsal surface of the tongue

Front 7

Where is the lining mucosa?

Where's the only place in the mouth where absorption takes place?

Back 7

All the rest - much thicker than kertainzed. However, the floor of the oral cavity and under the tongue has thinner epithelium. This is the only place where absorption takes place.

Front 8

1. When do the salivary glands develop?
2. How do they develop?
3. When does secretion begin?

Back 8

Develop from 6-7 weeks.
They arise from ectoderm! These row into the underlying mesenchyme layer.

-distal end expands and becomes secretory acini.
-cords canalize and lumen is formed
-secretion begins at week 18.

-CT is neural crest cell derived

Front 9

Parotid gland

Back 9

• completely serous with a well developed duct system
• enclosed in a tough connective tissue capsule
• fatty tissue allows flexibility

Front 10

Submandibular glands

Back 10

• mixed glands, predominant serous acini

Front 11

Sublingual glands?

Back 11

• mostly mucus-secreting glands (serous demilunes present, but rarely serous acini).
• multiple ducts (very small) empty to submandibular duct or floor of the mouth

Front 12

Each tooth consists of
1. anatomical crown
2. root
3. pulp cavity
4. What does the apical foramen allow?
5. Name 3 specialized tissues of the tooth

Back 12

Each tooth consists of:
Anatomical crown- covered by enamel
Root- one or more dependent on the shape of the tooth, housed in alveolar bone
• junction between the crown and root is the cervical margin or neck
Pulp cavity -connective tissue filled space, narrows as the root canal
• the apical foramen allows passage of blood vessels and nerves
three specialized tissues:
1. enamel 2. dentin 3. cementum

Front 13

In regard to tooth development, what happens during the following time periods..
1. Day 37
Day 42
Day 55
14 weeks
18 weeks
32 weeks

Back 13

Day 37:
primary epithelial band
Day 42: dental lamina
Day 55: bud stage (deciduous teeth)
14 weeks: bell stage (deciduous teeth)
18 weeks: dentin and functional ameloblasts (deciduous)
32 weeks - dentin and functional ameloblasts (permanent)

Front 14

Which of the following structures perforate (puncture) the epithelium in the human body ?
1. hair
2. nails
3. teeth
4. sweat gland (secretory acini)
5. sweat gland (ductal portion)

Back 14

Teeth! The only structure that perforates the epithelium.

Front 15

What are the 2 parts of the gingiva?

Back 15

oral mucosa surrounding an erupted tooth, often called the gums
divided 2 parts:
gingiva mucosa
1. gingival mucosa- faces oral cavity, lined with masticatory mucosa with type I collagen fibers deep to the epithelium
2. junctional epithelium-
faces the tooth- adheres firmly to the to the enamel/cementum of the tooth via hemidesmosomes

Front 16

Name the structures through which teeth develop from?

Back 16

• oral ectoderm- enamel
• mesoderm/mesenchyme and neural crest cells (ectomesenchyme)
• all other tissues (dentin, cementum and peridontal ligament)

Front 17

What is Day 37 crucial for?

Back 17

•formation of the primary epithelial band (proliferated epithelium at the site of the future dental arches)

- where the jaw is developing

Front 18

Day 42-48?

Back 18

Subdivisions from the epithelial band form
1. dental lamina
2. vestibular lamina

Front 19

What happens with the vestibular lamina?

Back 19

• the vestibular lamina proliferates- the cells enlarge and then degenerate

• the cleft that remains is the vestibule of the oral cavity- the area between the teeth and gums

Front 20

What happens with the dental lamina?

Back 20

•derivative of oral (surface) epithelium
•follow the curves of the primitive jaws
•dental lamina cells proliferate and form ingrowths into the ectomesenchyme
•ectomesenchyme influences the proliferative activity of surface epithelium of the dental lamina

Front 21

Day 55: Stage I bud stage

Back 21

From each dental lamina, you get 20 total tooth buds growing into the ectomesenchyme.

-these are the buds for the deciduous teeth (shed during childhood)
-cells only proliferate here. There's NO change in function here.

Front 22

cap Stage

Back 22

condensation - cluster of cells coming together that have a different function than the cells outside of the cluster..

Deep surface of bud invaginates and fomrs a cap.
The dragged down dental lamina is called lateral lamina.

• the epithelial ingrowth is called the enamel organ (enamel)
• the ball of condensed ectomesenchyme is now called the dental papilla (dentin)
• condensed ectomesenchyme surrounding the enamel organ and the dental papilla is the dental follicle/sac (cementum and peridontal ligament)

All together form a dental organ or tooth germ

Front 23

Describe the bell stage at 14 weeks.

Back 23

• assumes shape of bell as the undersurface of the enamel cap deepens
Four recognizable layers
1. outer dental/enamel epithelium
2. inner dental/enamel epithelium- borders the dental papilla-columnar
3. stratum intermedium-
internal to the inner enamel epithelium
4. stellate reticulum
• cells in the center of the enamel organ that secrete an extracellular matrix (GAGS) that pull in water.
• cells are pulled apart but stay connected by
desmosomes- this results in star shaped cells.

Front 24

What is the cervical loop?
What types of epithelium forms this?
What other types of cells form here, and what does this eventually give rise to?

Back 24

• inner and outer enamel epithelium are continuous where the outer epithelium bends to meet the inner epithelium
• this is the zone of reflection or the cervical loop
• some dental papilla cells accumulate here
• gives rise to the epithelium that will signal root development

Front 25

In bell stage..
1. What happens to the dental and lateral lamina?

Back 25

•dental lamina and lateral lamina around the tooth germ begin to degenerate •the developing tooth has lost its connection with the oral cavity •the tooth will continue to develop in the underlying tissues of the oral cavity •the cells of the dental/lateral lamina usually completely degenerate
•persistence of these cells may form small cysts over the developing tooth and could interfere with tooth eruption

Front 26

Crown pattern formation
1. What folds and shapes the crown?
2. What is the shape determined by?
3. When do cells stop dividing?
4. What does this result in?

Back 26

Dentin = always develops first.

• inner enamel epithelium folds and shapes the crown of the tooth
• the shape of the tooth is determined by differential rates of mitotic divisions of the inner enamel epithelial cells.
• the cells stop dividing as they differentiate into enamel producing cells.
• results in the differentiation of dental papilla cells into odontoblasts and they begin to produce dentin

Front 27

Where do blood vessels develop, and when?

Back 27

• Blood vessels develop in the dental papilla during the cap stage and continue to increase throughout development.
• the dental sac also is well vascularized

Front 28

Is the enamel organ vascular or avascular?

Back 28

Its avascular

Front 29

Hard tissue formation
1. What's the late cape stage through the bell stage significant for?
2. What does the inner dental epithelium differentiate into?
3. What do cells of dental papilla differentiate into?

Back 29

The late cap stage through the bell stage is significant for histodifferentiation (cells transforming into morphologically and functionally distinct components)

Front 30

What's reciprocal induction?

Back 30

the differentiation of the odontoblasts is initiated by an organizing influence from the cells of the inner enamel epithelium Reciprocal induction: •the development of dentin and enamel requires the ameloblasts and odontoblasts signal each other- if this does not occur the tooth will not develop normally

Front 31

Inner enamel epithelium
1. When does mitotic activity cease?
2. What type of epithelium elongates?

Back 31

•mitotic activity ceases at the site where dentin will first appear
•the columnar epithelium will elongate
•changes will occur within the cell
•the cells of the inner enamel epithelium induce the dental papilla cells to differentiate into odontoblasts

Front 32

How long does it take odotoblasts to secrete predentin that calcifies into dentin?

Back 32

1 day. As it calcifies, odontoblasts move towards papilla

Front 33

What does the name of the dental papilla change to during formation of dentin?

Back 33

Now its called the pulp cavity.

Front 34

Where do long apical process of odontoblasts reside in
Where do they extend?

Back 34

• long apical processes of the odontoblasts reside in dentinal tubules (canaliculi)
• dentinal tubules extend the full thickness of the dentin

Front 35

What type of bone formation is invovled in tooth development?

Back 35

Intramembranous ossification

Front 36

What gets thinner and gest very close to the develping bone? What cells differentiate into cementum and other periodontal structures?

Back 36

• odontoblasts are in contact with ectomesenchyme of the now pulp cavity • the enamel organ is getting thinner and is very close to developing bone (B)

• some ectomesenchymal cells around the enamel organ will differentiate into cells of cementum and other periodontal structures

Front 37

1. Where do ameloblasts come from?
2. What induces the secretion of enamel matrix?
3. In what direction to the ameloblasts move?

Back 37

• inner enamel epithelial cells continue to differentiate into ameloblasts
• contact with dentin induces the ameloblasts to begin secretion of the enamel matrix
• enamel becomes mineralized almost immediately
• ameloblasts are moving away from the odontoblasts and fro

Front 38

early in development
Where does enamel organ nourishment come from? (2 sources)

Back 38

1. blood vessels of dental papilla
2. blood vessels surrounding the enamel organ

Front 39

Later in development, were does enamel oran get nourishment from?

Back 39

• layer of dentin interferes with diffusion from papilla
• stellate reticulum collapes as compensation and brings peripheral blood vessels closer to the now active ameloblast layer

Front 40

1. When does maturation stage begin?
2. What cells from which layers form the papillary layer?
3. What layers form the reduced dental/enamel epithelium?

Back 40

• when enamel is full thickness the ameloblasts enter the maturation stage.
• cells from the stratum intermedium, stellate reticulum and outer enamel epithelium reorganize and form the papillary layer.
• ameloblast layer + papillary layer form the reduced dental/enamel epithelium.

Front 41

Name the 5 steps in root development

Back 41

1. cells of the cervical loop region proliferate and form Hertwig’s root sheath
2. the sheath encloses the dental pulp region
3. this double layered sheath is epithelial/ectoderm derived
4. inner epithelial cells induce the ectomesenchyme cells to differentiate into dentin producing odontoblasts
5. as the tooth grows, the root sheath is stretched, cells disassociate, and clusters of small epithelial cells persist

Front 42

1. What tissues from the dental follicle?
2. Where do cementoblasts come from?
3. Where does periodontal ligament derive from?
4. How about alveolar bone?

Back 42

• supporting tissues of the tooth form from the dental follicle.
• some cells differentiate into cementoblasts and form cementum.
• some cells form the peridontal ligament
• some cells may contribute to alveolar bone

Front 43

Describe the embryology, anatomy (location), and histology of PDL

Back 43

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

Front 44

Tooth eruption
1. What is tooth covered by?
2. What hapens to the bone overlying the tooth, and what already happened to the CT here?
3. Name 2 types of epithelium that fuse

Back 44

• tooth is covered by the reduced enamel epithelium • bone overlying the tooth is resorbed • connective tissue over the tooth has already broken down (G) • reduced enamel epithelium and oral epithelium fuse: - central epithelial cells degenerate
- dentogingival junction formed (gives rise to junctional epithelium of gingiva)