Lecture: Oral Cavity & Teeth Flashcards by Chiazom Ezenekwe

Functions of the oral cavity

Beginning of digestion
Immune protection
Barrier protection
Sensation
Secretion
Speech

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What makes up the oral cavity?

Lips
Teeth + Periodontal Tissues
Tongue
Hard and Soft Palate
Cheeks

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Masticatory Mucosa

Structure:
Stratified Squamous Keratinized or Stratified Squamous Parakeratinized

Location:
Gingiva and hard palate

Function:
Protects from frictional forces

● Can be stratified squamous keratinized or parakeratinized
● Found in areas with the most immediate chewing forces (hard palate and gingiva)
● Mucosal layers present: epithelium and lamina propria

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Lining Mucosa

Structure:
Stratified Squamous Nonkeratinized

Location:
Lips, cheeks, ventral tongue, floor of mouth, soft palate, mucosal surfaces around alveolar bone

Function:
Protect underlying tissues/withstands stretch

● Thick, stratified squamous nonkeratinized
● Protects underlying structures
● The majority of the oral mucosa in the oral cavity (inside of lips, cheeks, floor of mouth, soft palate, surrounding most of the alveolar bone)
● Mucosal layers present:
epithelium and lamina propria

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Specialized Mucosa

Structure:
Modified, elongated epithelial cells

Location:
Dorsal surface of the tongue,
soft palate and pharynx

Function:
Transmission of sensory information to CNS

● SSK or SSNK with elongated epithelial cells
● Specialized functions (taste sensation and mechanical function)
● Places where there are taste buds (dorsal surface of tongue, soft palate and pharynx)
● Mucosal layers present: epithelium and lamina propria

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Parakeratinized

Similar to keratinized but the
outer layer of cells do not lose
nuclei

Cytoplasm stains similar to
keratin layer in SSK (keratin)

Found in transition areas
between lining and
masticatory mucosa

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Gingiva

oral mucosa surrounding areas immediately around the teeth

Has two different parts:
1. Masticatory mucosa
2. Junctional epithelium

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Junctional epithelium

Junction where epithelium and tooth are connected

The junctional epithelium is a modified basement membrane that seals this opening to prevent microorganisms and other pathogens from entering

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Hemidesmosomes

Connects the internal basal lamina to the tooth enamel

Connects the external basal lamina to surrounding connective tissue

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Vermilion Border

The transition between skin epithelium (SSK) and lips (lining mucosa - SSNK) is referred to as the Vermilion Border

*Chapped lips - vermilion zone
lacks salivary glands, required
moisture from inside oral cavity

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What are the different LINGUAL PAPILLAE?

Filiform, Foliate, Fungiform, and Circumvallate

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Filiform Papillae

keratinized projections that lack taste buds and have mechanical function (like scooping in cats)

Epithelium:
Stratified squamous keratinized epithelium

Taste buds:
no taste buds (dorsal surface of the tongue serves as a masticatory mucosa)

Location:
anterior 2/3rds of the tongue

Main Function:
compress and break food (mechanical role )

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Foliate Papillae

contain many taste buds (less prominent in adults)

Epithelium:
stratified squamous nonkeratinized (or lightly keratinized)

Taste buds:
taste buds located at the apical surface of papillae

Location:
tip and two sides of tongue

Main Function:
chemoreceptor (detects taste)

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Fungiform Papillae

numerous, mushroom-shaped with taste buds

Epithelium:
stratified squamous non-keratinized epithelium

Taste buds:
taste buds (most numerous) located lateral surface of papillae

Location:
in a V-shaped row just anterior to the terminal sulcus

Main Function:
chemoreceptor (detects taste)

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Circumvallate Papillae

Large structures with mucous secreting Von Ebner’s glands

Epithelium:
stratified squamous non-keratinized epithelium

Taste buds:
taste buds located on lateral surface of papillae

Location:
posterior lateral surface of the tongue

Main Function:
chemoreceptor (detects taste)

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terminal sulcus

a groove that separates the tongue into a superior oral surface and a posterior pharyngeal surface

Two sets of teeth in our lifetime

Primary - Deciduous teeth (20)
Secondary - Permanent teeth (32)

*in most cases, primary teeth don’t erupt until 6 months post birth

Crown

Tooth covered by enamel (anatomical crown and clinical crown)

Cervix

aka neck
between crown and root cementoenamel junction

Root

Tooth covered by cementum

Pulp Cavity

connective tissue (vascularized and innervated)

Enamel

Origin: ameloblasts
Composition: 96% inorganic hydroxyapatite

● Small, translucent layer that surrounds the crown of the tooth
● Most mineralized tissue in the body
- Bone - 65% mineralized
- Enamel - 95% mineralized
● Avascular, cannot be repaired
● Ameloblasts (ectoderm) form the enamel
- Degenerate after tooth eruption

**Does not show up on H&E stains

Dentin

Origin: odontoblasts (secrete unmineralized predentin)
Composition: 65% inorganic hydroxyapatite

● Makes up a majority of the hard tissue in the tooth
● Odontoblasts secrete unmineralized predentin that will subsequently become mineralized into dentin
- Odontoblasts tay on inner surface towards the pulp cavity
- Dentinal tubule processes remain in the dentin (connected to odontoblasts)

Cementum

Origin: cementoblasts
Composition: 50% inorganic hydroxyapatite

● Surrounds the root dentin
● Cementoblasts produce cementum, cementocytes are the resident cells of cementum
● Sharpey’s Fibers - perpendicular collagen fibers from the periodontal ligament connecting to cementum and alveolar bone (on both sides, connecting to both cementum and alveolar bone)

Periodontium

The structures surrounding and supporting the teeth 1. Gingiva 2. Cementum 3. Periodontal Ligament 4. Alveolar Bone

Periodontal Ligament

● Specialized connective tissue that connects tooth to surrounding bone ● Highly cellular, very vascularized and lots of innervation ● Sharpey’s fibers - mainly type I collagen

How do permanent teeth come in?

Deciduous teeth can't grow to accommodate developing jaw + muscles of mastication exert higher forces on the PDL of deciduous teeth Permanent teeth will begin to erupt the pressure will stimulate the process of tooth resorption Odontoclasts, similar origin to osteoclasts, aid in the process of tooth resorption of the deciduous teeth roots The tooth will loosen and eventually fall out, being replaced by permanent teeth

Stages of Tooth Development

Dental Lamina Stage, Cap Stage, Bell Stage, Root Stage

Dental Lamina Stage

Ridge of oral epithelium (ectoderm) will begin to invaginate into the underlying mesenchymal tissue, specifically termed ectomesenchyme Centers of proliferation, termed the dental lamina, will form on both the developing upper and lower jaws Once permanent teeth grow in, you will never get another dental lamina

Cap Stage

The deeper surface of the dental lamina invaginates and creates a cap shape with an enclosed space referred to as the enamel organ Basal - inner enamel epithelium + stratum intermedium Other epithelial regions - outer enamel epithelium Cells inside sac - stellate reticulum ● The inner enamel epithelium contains pre-ameloblasts which will become ameloblasts post differentiation ● The fluid pressures hold the shape of the developing tooth ● Dental follicle - cementum, PDL and alveolar bone ● Dental papilla - dentin ● Enamel organ - enamel

Bell Stage

The enamel organ will deepen, creating a “bell shape” The cervical loop appears in this stage and the dental lamina begins to degenerate The elongation of epithelial cells at this stage will eventually signal the start of root development

Root Stage

Root development is what causes the tooth to eventually erupt through the oral epithelium Does not begin until enamel and dentin have already started to be secreted Forms the cementum converted structure of the tooth root

Cervical Loop

where the inner and outer enamel epithelium are continuous with one another

Hard Tissue Formation

Towards the end of cap stage and during bell stage cells with undergo histodifferentiation and begin hard tissue formation ● Inner enamel epithelium - ameloblasts (enamel) ● Dental papilla - odontoblasts (pre dentin) *dentin is always formed before enamel!

Hard Tissue Formation - Odontoblasts

Odontoblasts will secrete pre-dentin towards the ameloblasts As the predentin calcifies, the odontoblasts will move towards the developing pulp cavity

Hard Tissue Formation - Ameloblasts

Before secretion, the polarity of the ameloblast will reverse Ameloblasts will secrete enamel onto the surface of dentin Where the enamel and dentin meet is referred to as the dentinoenamel junction

Reduced Enamel Epithelium

Once the ameloblasts have finished secreting enamel, the reduced enamel epithelium is formed Formerly: Inner and outer enamel epithelium, stellate reticulum and stratum intermedium Protects the tooth as it erupts and degenerates after

Hard Tissue Formation - Cementoblasts

After the enamel and dentin form the shape of the crown Ectomesenchymal cells are stimulated by dentin secretion to differentiate into cementoblasts which will cover dentin with cementum forming a cementoenamel junction

Hertwig’s root sheath

Hertwig’s root sheath is the extension from the cervical loop that guides dentin formation during the root stage