2.0 ORAL MUCOUS MEMBRANE

• Oral Mucous Membrane


  The moist lining of the oral cavity that is in continuation with the exterior surface of the skin on one hand & esophagus on the other end
• Oral Mucous Membrane


  • It is found lining the oral cavity, the nasal cavity & sinuses, the trachea, the stomach & intestines, the urinary bladder, and the uterus
• Oral Epithelium


  Forms the surface of oral mucosa and the primary barrier between oral environment & deeper tissues
• Oral Epithelium


  • 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
• Progenitor cells


  Cells that divide and produce new cells
• Maturing cells or keratinocytes


  Cells that undergo a process of continuous maturation or differentiation and form a protective surface layer
• Proliferation & maturation


  Progenitor cells divide & produce new cells & maturing cells 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 keratinized epithelium

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


  Proliferative or germinative layer. The cells are capable of division. Consists of a layer of cuboidal or columnar cells adjacent to the basement membrane. Cells synthesize DNA & undergo mitosis, providing new cells
• Stratum Spinosum


  Prickle cell layer. Irregularly polyhedral & these are larger than the basal cells. Cells are joined by intercellular bridges. Tonofibrils cross from one cell to the next across intercellular bridges
• Stratum Granulosum


  Contains flatter & wider cells. These cells are larger than spinous cells. This layer contains a number of small granules that stain intensely with basic dyes, such as hematoxylin. These granules are called keratohyalin granules (basophilic in nature)
• Stratum Corneum


  This layer is keratinized & the cells are larger & flatter than granular cells & are eosinophilic in nature. In this layer all the nuclei & other other organelles like mitochondria & ribosomes disappear
• Orthokeratinization or True keratinization

  One of the two types of maturation of keratinized cells
• Parakeratinization


  The other type of maturation of keratinized cells, sometimes present in the hard palate & usually all of the gingiva
• Factors Affecting Keratinization


  • Linea alba-sometimes a non- keratinized area in the cheek opposite the occlusal plane, gets keratinized due to continuous stress of friction
  • The palate of smokers-becomes hyperkeratotic due to imitation produced by tobacco smoke
  • Presence of mild inflammation increases keratinization but severe inflammation reduces the degree of keratinization
• Lamina Propria or Corium


  The connective tissue supporting the oral epithelium
• Lamina Propria


  • The interface between epithelium & connective tissue is usually irregular & upward projections of connective tissue, called the connective tissue papillae, interdigitate with epithelial ridges or pegs, sometimes called the rete ridges or pegs
• Parts of Lamina Propria

  • Papillary portion
  • Reticular portion
• Papillary portion


  It is associated with epithelial ridges. The papillary layer consists of finger-like projections of connective tissue that interlock with similar epithelium projections
• Reticular portion


  It is named because of the reticular fibers
• Submucosa


  A connective tissue layer that attaches the lamina propria of the oral mucosa to the underlying bone or muscle
• Components of Submucosa


  • Glands
  • Blood vessels
  • Nerves
  • Adipose tissue
• Large blood vessels


  They enter the submucosa & divide here into smaller branches, which then enter the lamina propria, where these branches again divide into further smaller branches
• Main cell types in Connective Tissue

  • Fibroblast
  • Histiocyte
  • Macrophage
  • Monocyte
  • Mast Cell
  • Polymorphonuclear Leukocytes
• Fibroblast


  Stellate or elongated with abundant rough endoplasmic reticulum, secretes fibers and ground substance, located throughout lamina propria
• Histiocyte


  Spindle-shaped or stellate; often dark-staining nucleus; many lyosomal vesicles, resident precursor of functional macrophage, located throughout lamina propria
• Macrophage


  Round with pale-staining nucleus; contains lysosomes and phagocytic vesicles
• Keratinization is a process by which epithelial cells exposed to the external environment lose their moisture & are replaced by horny tissue. This horny tissue contains keratin which is fibrous in nature & contains protein. This protein is insoluble in most solvents including gastric juice
• Keratinized epithelium is more resistant to infections & irritation than nonkeratinized epithelium
• Main cell types


  • Fibroblast
  • Histiocyte
  • Macrophage
  • Monocyte
  • Mast Cell
  • Polymorphonuclear Leukocytes
• Fibroblast


  Stellate or elongated with abundant rough endoplasmic reticulum
• Fibroblast function


  Secretion of fibers and ground substance
• Fibroblast location


  Throughout lamina propria
• Histiocyte


  Spindle-shaped or stellate; often dark-staining nucleus; many lyosomal vesicles
• Histiocyte function


  Resident precursor of functional macrophage
• Histiocyte location


  Throughout lamina propria
• Macrophage function


  Mobile phagocytic cell; involved in antigen processing
• Macrophage location


  Areas of chronic inflammation
• Monocyte


  Round with dark-staining kidney-shaped nucleus and moderate amount of cytoplasm