ORAL MUCOUS MEMBRANE

• Oral Mucous Membrane


  Moist lining that lines the intestinal tract, nasal passage, and other body cavities that communicate with the exterior environment
• Locations of mucous membranes

  • Oral cavity
  • Nasal cavity & sinuses
  • Trachea
  • Stomach & intestines
  • Urinary bladder
  • Uterus
• Oral mucosa or oral mucous membrane


  Moist lining of the oral cavity that is in continuation with the exterior surface of skin on one hand & esophagus on the other end
• Layers of oral mucous membrane

  • Oral Epithelium
  • Connective Tissue
• Oral Epithelium


  The epithelium that forms the surface of oral mucosa
• Oral Epithelium


  • Forms the primary barrier between oral environment & deeper tissues
  • Ectodermal in origin (except the tongue, which is endodermal)
  • Maintains its structural integrity by a system of continuous cell renewal in which cells produced by mitotic division in the deepest layers migrate to the surface to replace those cells that are shed
• Cell types in oral epithelium

  • Progenitor cells
  • Maturing cells or keratinocytes
• Progenitor cells


  Divide & produce new cells
• Maturing cells or keratinocytes


  Undergo a process of continuous maturation or differentiation & form a protective surface layer
• Locations of oral mucous membrane

  • Faucial pillars
  • Sublingual tissues
  • Floor of mouth
  • Lips
  • Alveolar mucosa
  • Soft palate
  • Underside of the tongue
• Layers of keratinizing epithelium

  • Stratum basale (basal layer)
  • Stratum spinosum (Prickle layer)
  • Stratum granulosum
  • Stratum corneum
• Differences between keratinizing & non-keratinizing epithelium

  • Non-keratinized epithelium has stratum intermedium & stratum superficiale instead of stratum granulosum & stratum corneum
  • Intercellular spaces are less conspicuous in non-keratinized epithelia
  • Non-keratinizing epithelia do not produce a cornified surface layer & do not stain intensely with eosinophilic stain
  • Superficial layer cells in non-keratinizing epithelium contain nuclei, which are quite big and plump and not flattened
  • Turnover & mitotic ratio of the nonkeratinizing epithelium is higher than keratinized epithelium
  • Surface layer of non-keratinized epithelium consists of cells filled with loosely arranged filaments that are not loosely dehydrated
• Characteristics of non-keratinocytes in oral epithelium

  • Melanocyte
  • Langerhans cell
  • Merkel cell
  • Lymphocyte
• Keratinization


  Process by which epithelial cells exposed to the external environment lose their moisture & are replaced by horny tissue containing insoluble keratin protein
• Keratinized epithelium


  • More resistant to infections & irritation than nonkeratinized epithelium
• Layers of keratinized epithelium


  • Stratum Basale or Basal Layer
  • Stratum Spinosum
  • Stratum Granulosum
  • Stratum Corneum
• Stratum Basale or Basal Layer


  Also called the proliferative or germinative layer; cells are capable of division and synthesize DNA to undergo mitosis, providing new cells
• Stratum Spinosum


  Also called the prickle cell layer; cells are irregularly polyhedral, larger than basal cells, and joined by intercellular bridges with tonofibrils crossing between cells
• Stratum Granulosum


  Contains flatter & wider cells with keratohyalin granules that stain intensely; nuclei show signs of degeneration & pyknosis
• Stratum Corneum


  Keratinized layer with larger, flatter cells that have lost their nuclei and organelles
• Types of keratinization


  • Orthokeratinization or True keratinization
  • Parakeratinization
• Factors affecting keratinization


  • Linea alba
  • Palate of smokers
  • Presence of mild vs severe inflammation
• Lamina Propria or Corium


  Connective tissue layer supporting the oral epithelium, with irregular interface and connective tissue papillae interdigitating with epithelial ridges
• Divisions of lamina propria

  • Papillary portion
  • Reticular portion
• Submucosa


  Connective tissue layer that attaches the lamina propria to the underlying bone or muscle, containing glands, blood vessels, nerves, and adipose tissue
• Cell types in lamina propria

  • Fibroblast
  • Histiocyte
  • Macrophage
  • Monocyte
  • Mast cell
  • Polymorphonuclear leukocyte
  • Lymphocyte
  • Plasma cell
  • Endothelial cell
• Characteristics of masticatory mucosa - Hard Palate

  • Covering epithelium: Orthokeratinized (often parakeratinized in parts), stratified squamous epithelium
  • Thick palatine ridges (rugae)
  • Lamina propria
• Lymphocytes may be present in epithelium
• Lymphocyte Morphologic Characteristics


  • Round with dark-staining nucleus and scant cytoplasm with some mitochondria
• Lymphocyte Function


  Some lymphocytes participate in humoral or cell-mediated immune response
• Lymphocytes may be present in areas of acute and chronic inflammation
• Plasma Cell Morphologic Characteristics

  • Cartwheel nucleus; intensely pyroninophilic cytoplasm with abundant rough endoplasmic reticulum
• Plasma Cell Function


  Synthesis of immunoglobulins
• Plasma cells are often found in areas of chronic inflammation, often perivascularly
• Endothelial Cell Morphologic Characteristics

  • Normally associated with a basal lamina; contains numerous pinocytotic vesicles
• Endothelial Cell Function


  Lining of blood and lymphatic channels
• Endothelial cells are located throughout the lamina propria
• Masticatory Mucosa


  Covers the hard palate and gingiva
• Hard Palate Covering Epithelium

  • Orthokeratinized (often parakeratinized in parts), stratified squamous epithelium
  • Thick palatine ridges (rugae)
• Hard Palate Lamina Propria


  • Thick, dense collagenous tissue, especially under rugae, long papilla, moderate vascular supply