Oral Mucosa: Comprehensive Notes

Oral Mucosa Properties

• The oral cavity reflects an individual's health; changes in the mucosa can indicate systemic or local issues.

• Composed of stratified squamous epithelium, connective tissue proper (lamina propria), and possibly a submucosa with a basement membrane.

Oral Mucosa Types

• Three types: lining, masticatory, and specialized mucosa.

• Classified by histologic features.

Regional Differences in Oral Mucosa

• Histologic features vary regionally, causing clinical differences.

Epithelium of Oral Mucosa

• Three types of stratified squamous epithelium: nonkeratinized, orthokeratinized, and parakeratinized.

• Differ in surface layers; keratinocytes produce keratin, and nonkeratinocytes are present in smaller numbers.

• Microplicae (MPL) are surface folds, and keratin provides protection.

Lining Mucosa

• Soft, moist, stretchable; includes buccal, labial, and alveolar mucosa, ventral tongue surface, floor of the mouth, and soft palate.

• Smoother interface, elastic fibers, and usually a submucosa.

• Nonkeratinized stratified squamous epithelium with basal, intermediate, and superficial layers.

Labial Mucosa and Buccal Mucosa

• Opaque pink, shiny, moist, compressible; may have melanin or Fordyce spots; classified as lining mucosa.

• Thick nonkeratinized epithelium overlies a vascular lamina propria with irregular papillae; submucosa contains adipose tissue and minor salivary glands.

Buccal and Labial Mucosa: Fordyce Spots

• Yellowish bumps from misplaced sebaceous glands.

Nonkeratinized Epithelium: Hyperkeratinization

• Can transform into keratinizing type due to trauma; larger area can undergo hyperkeratinization with bruxism.

Buccal Mucosa: Linea Alba

• White ridge of calloused tissue at the occlusal plane.

Alveolar Mucosa

• Reddish-pink, shiny, moist, mobile; lines vestibules; classified as lining mucosa.

• Thin nonkeratinized epithelium overlies a vascular lamina propria with elastic fibers; submucosa has minor salivary glands and elastic fibers.

Ventral Surface of the Tongue and Floor of the Mouth

• Reddish-pink, moist, shiny, compressible; floor of the mouth has mobility, ventral surface is firmly attached; classified as lining mucosa.

• Lingual frenum, sublingual fold, and sublingual caruncle are present.

• Thin nonkeratinized epithelium overlies a vascular lamina propria.

Floor of Mouth:

• Mandibular Torus/Tori: bony nodule on lingual mandibular arch; Ankyloglossia: tongue-tied due to short lingual frenum.

Soft Palate

• Deep pink with yellowish hue, moist, compressible, elastic; classified as lining mucosa.

• Thin nonkeratinized epithelium overlies a thick lamina propria with elastic layer; thin submucosa with adipose tissue and minor salivary glands.

Masticatory Mucosa

• Rubbery surface texture; includes hard palate, attached gingiva, and dorsal tongue surface.

• Associated with keratinized stratified squamous epithelium.

• Highly interdigitated interface with thin or absent submucosa.

Hard Palate

• Whiter pink, immobile, firm anteriorly; cushioned feeling posteriorly.

• Palatine rugae and median palatine raphe are firm.

• Classified as masticatory mucosa.

• Thick orthokeratinized epithelium overlies a thick lamina propria.

• Submucosa with adipose tissue and minor salivary glands in lateral zones; absent in the medial zone.

• Mucoperiosteum.

Masticatory Mucosa: Orthokeratinized Stratified Squamous Epithelium

• Keratinization of epithelial cells throughout superficial layers; four layers: basal, prickle, granular, keratin.

Hard Palate:

• Palatal Torus: bony growth on midline; Nicotinic Stomatitis: hyperkeratinization due to heat.

Masticatory Mucosa: Parakeratinized Stratified Squamous Epithelium

• Associated with attached gingiva and lingual papillae.

• Similar layers to orthokeratinized epithelium, but keratin layer contains nuclei.

Attached Gingiva

• Opaque pink, may have melanin; dull, firm, immobile when dried; stippled surface.

• Classified as masticatory mucosa.

• Thick parakeratinized epithelium obscures vascular supply.

• No submucosa; lamina propria attached to alveolar process.

• Mucoperiosteum.

Mucogingival Junction

• Scalloped junction between attached gingiva and alveolar mucosa.

• Dividing zone between keratinized and nonkeratinized tissues.

Attached Gingiva:

• Exostoses: bony growths on maxilla; Periodontal Disease: enlarged gingiva; Gingival Recession: apical gingival margin; Gingival Graft: reduces recession; Gingival Hyperplasia: overgrowth due to certain drugs.

Lamina Propria of Oral Mucosa

• Deep to basement membrane; Type I collagen fibers and elastic fibers.

• Papillary and dense layers; capillary plexus.

• Fibroblasts are the most common cell.

Submucosa

• May or may not be present; contains loose connective tissue, adipose tissue, or salivary glands.

• May overlie bone or muscle.

Submucosa: Salivary Glands

• Epithelium and connective tissue; secretory cells (mucous and serous) in acini.

• Capsule and septa.

• Ranula: managed by removal of stone or gland.

Clinical Considerations for Oral Mucosa Pigmentation

• Melanin pigmentation gives localized flat areas of brown to brownish-black color.

• Melanin is formed by melanocytes with melanosomes.

Pigmentation: Pathology

• Nevus (mole) is a benign tumor of melanin; melanoma is a cancer involving melanin.

• Both can appear as a macule or papule.

Oral Mucosa Turnover

• Faster than skin; gingival epithelium has the fastest turnover (4-6 days), hard palate has the lowest (24 days).

Oral Mucosa Repair

• Clot forms, inflammatory response triggered, epithelial cells migrate to form new surface layer, fibroblasts produce granulation tissue, replaced by scar tissue.

Oral Mucosa Aging

• Reduction of stippling, increase in Fordyce spots, enlargement of lingual veins.

• Reduced lingual papillae and taste buds; diminished rete ridges; slowed turnover times.

Oral Mucosa Pathology: Oral Cancer

• Asymptomatic, flat lesion that can become exophytic.

• Most are squamous cell carcinomas.