Histology of the Oral Cavity and Associated Structures

Overview

• Continuation of discussion on histology of the oral cavity.
• Importance of understanding the skin in relation to oral structures.

Skin Structure

• Layers of Skin:
  1. Epidermis: Stratified squamous keratinized epithelium.
  2. Dermis: Underlying connective tissue.
• Five Layers of Epidermis:
  1. Stratum Basale:
     • Nearest to the basement membrane.
     • Composed of cuboidal or columnar cells.
  2. Stratum Spinosum:
     • Multiple layers of cells with tonofilaments (appear spiny).
  3. Stratum Granulosum:
     • Contains keratohyalin and lamellar granules (water regulation).
  4. Stratum Lucidum:
     • Translucent appearance; found in thick skin (palms and soles).
  5. Stratum Corneum:
     • Most superficial layer, constantly shed.
• Thick vs. Thin Skin:
  • Thick skin: Contains all five layers (includes stratum lucidum).
  • Thin skin: Lacks stratum lucidum (only four layers).

Oral Cavity Structure

• Consists of the mouth, tongue, teeth, salivary glands, and tonsils.
• Divisions of Oral Cavity:
  • Oral Cavity Proper: Space within clenched teeth.
  • Vestibule: Space between teeth and cheek (buccal mucosa).
• Lining of Oral Cavity:
  • Stratified squamous epithelium (oral mucosa).
  • Classified into three types:
    1. Specialized Mucosa: Contains taste buds (dorsal surface of the tongue).
    2. Masticatory Mucosa: Stratified squamous keratinized epithelium; covers gums and hard palate.
    3. Lining Mucosa: Stratified squamous non-keratinized epithelium; covers softer areas (lips, floor of mouth).

Types of Oral Mucosa

1. Specialized Mucosa:
   • Only found on the dorsal surface of the tongue; contains taste buds.
2. Masticatory Mucosa:
   • Found in gums and hard palate; keratinized for protection against friction.
3. Lining Mucosa:
   • Found in lips, cheeks, and soft palate; non-keratinized for mobility.

Tongue Anatomy

• Divisions:
  • Anterior two-thirds (taste perception) and posterior one-third (lingual tonsils).
• Papillae Types:
  1. Filiform Papillae:
     • Highly keratinized, mechanical role, no taste buds.
  2. Fungiform Papillae:
     • Mushroom-shaped, contains taste buds on dorsal surface.
  3. Foliate Papillae:
     • Located on lateral sides, poorly developed in adults.
  4. Circumvallate Papillae:
     • Largest, located along the sulcus terminalis, contain taste buds on lateral side.

Histology of Taste Buds

• Structure: Ovoid bodies within lingual papillae.
• Cell Types in Taste Buds:
  1. Gustatory Cells: Perceive taste; have microvilli.
  2. Supporting Cells: Provide support, do not perceive taste.
  3. Basal Cells: Stem cells that replace other cells every 10 days.

Teeth Anatomy

• Two sets: 20 deciduous (milk) teeth and 32 permanent teeth.
• Parts of a Tooth:
  1. Crown: Visible part above the gums.
  2. Neck: Covered by gingiva.
  3. Root: Embedded in the jawbone.
• Hard Parts of Tooth:
  • Enamel: 96-98% calcium hydroxyapatite; hardest substance.
  • Dentin: 70% calcium hydroxyapatite; supports enamel and root.
  • Cementum: Covers neck and root; connects to bone via periodontal ligaments.

Embryology of Teeth

• Derived from oral cavity epithelium.
• Stages of development:
  1. Bud Stage: Oral cavity epithelium invaginates into mesoderm to form dental papilla.
  2. Cap Stage: Dental papilla invaginates into enamel organ.
  3. Bell Stage: Developing tooth detaches from oral cavity epithelium.
• Ameloblasts (from inner enamel epithelium) produce enamel, while odontoblasts (from dental papilla) produce dentin.

Conclusion

• Understanding the histology of the oral cavity and associated structures is essential for future medical professionals.