Oral 2

• Oral mucous membrane (oral mucosa)


  The surface of the oral cavity is a mucous membrane
• Oral mucosa


  • It is continuous with the skin of the lip through the vermilion border
  • It is continuous with the mucosa of the pharynx posteriorly
  • Its structure varies in an apparent adaptation to function in different regions of the oral cavity
  • Areas involved in the mastication of food, such as the gingiva and the hard palate, have a much different structure than does the floor of the mouth or the mucosa of the cheek
• Oral cavity


  Described as a mirror that reflects the health of the individual
• Changes indicative of disease are seen as alterations in the oral mucosa lining the mouth, which can reveal systemic conditions, such as diabetes or vitamin deficiency, or the local effects of chronic tobacco or alcohol use
• Functions of oral mucosa


  • Defense
  • Lubrication
  • Sensory
• Defense


  • The integrity of the oral epithelium is an effective barrier for the entry of the microorganisms
  • The oral mucosa is impermeable to bacterial toxins
  • It secretes antibodies and has an efficient humoral and cell mediated immunity
• Lubrication


  • The secretion of salivary glands keeps the oral cavity moist and thus prevents the mucosa from drying and cracking thereby ensuring an intact oral epithelium
  • A moist oral cavity helps in speech, mastication, swallowing and in the perception of taste
• Sensory


  • The oral mucosa is sensitive to touch, pressure, pain and temperature
  • The sensitivity of these sensations vary in different regions
• Swallowing, gagging, retching and salivating reflexes are initiated by receptors in the oral mucosa
• Touch sensations in the soft palate result in gag reflex
• Protection


  The oral mucosa protects the deeper tissues from mechanical forces resulting from mastication and from abrasive nature of food stuffs
• Types of the Oral Mucosa


  • Masticatory Mucosa
  • Lining Mucosa
  • Specialized Mucosa
• Masticatory Mucosa


  • It is a part that is adapted to need friction produced by mastication
  • It is keratinized or parakeratinized oral epithelium like gingiva (free, attached and interdental) and hard palate
  • It forms about 25% of total mucosa
• Lining Mucosa


  • It forms about 60% of total mucosa
  • It covers the floor of mouth, ventral (underside) tongue, alveolar mucosa, cheeks, lips and soft palate
  • It does not function in mastication and therefore has minimal attrition
  • Its non-keratinized epithelium is soft and pliable
• Specialized Mucosa


  • It forms about 15% of total mucosa
  • It covers dorsal tongue and is composed of cornified epithelial papillae
  • It holds the taste buds
• How is the oral mucosa different from skin?


  • Color
  • Moist surface
  • Absence of adnexal skin structures: hair follicles, sweat glands and sebaceous glands (exception in Fordyce's spots)
  • Fordyce's spots: Sebaceous glands in oral cavity predominantly in upper lip, buccal mucosa and alveolar mucosa
  • Presence of minor salivary glands in oral mucosa
  • Texture of surface: Oral mucosa is smoother than the skin (few exceptions: dorsal tongue – due to papillae; hard palate – rugae area; gingiva – stippling)
  • Firmness: Oral mucosa varies in its firmness. buccal mucosa and lips are loose and pliable whereas the gingiva and hard palate are firm so critical clinically while giving injections
• Structure of Oral Mucosa


  • Overlying oral epithelium
  • Underlying connective tissue (lamina propria and submucosa)
• Oral epithelium


  • It is keratinized or parakeratinized or non-keratinized stratified squamous epithelium
  • Epithelial cell-cell contact is made through desmosomes. These are anchored intracellularly by tonofibrils

  
• يطاخلما ءاشغلا


  Oral mucosa
• يقدشلا يطاخلما ءاشغلا


  • Flexible
  • Loose
• بلصلا كنحلاو ةثللا


  • Firm
  • Inelastic
• Structure of Oral Mucosa


  1. Overlying oral epithelium

  2. Underlying connective tissue (lamina propria and submucosa)
• Epithelium


  Keratinized or parakeratinized or non-keratinized stratified squamous epithelium

  
• Epithelial cell-cell contact


  • Made through desmosomes
  • Anchored intracellularly by tonofibrils

  
• Basement membrane


  Interface between epithelium and connective tissue
• Basement membrane


  • Irregular
  • Composed of downward projections of epithelium (rete ridges or rete pegs)
  • Upward projection of connective tissue (connective tissue papillae)
• Junction between oral epithelium and lamina propria is more obvious than that between lamina propria and submucosa
• Submucosa


  • Loose fat and glandular tissue
  • Blood vessels and nerves
  • Provides flexibility
• Gingiva and hard palate


  • No submucosa
  • Lamina propria directly attached to the periosteum of the underlying bone
  • Firm, inelastic attachment (oral mucoperiosteum)
• Basal lamina


  • Membrane separating the epithelium and lamina propria
  • Basal cells attached to it by hemidesmosomes

  
• Basal lamina under electron microscopic level


  • Cell free zone about 1-4 micron width
  • Composed of lamina lucida (clear cell free zone toward epithelium) and lamina densa (dark zone toward connective tissue, filamentous and granular, contain fine collagen fibers called anchoring fibers)

  
• Characteristic features of cells of oral epithelium


  • Keratinocytes (90% of epithelium cells)
  • Non-keratinocyte cells (melanocytes, Langerhans, Merkle's and lymphocyte cells)
  • Deeper layers (basal and supra basal) have ability of active mitotic division to replace continuously degenerated surface cells (cell renewal or cell turnover)
• Types of oral epithelium

  • Keratinized oral epithelium (orthokeratinized)
  • Basal cell layer
  • Spinous or prickle cell layer
  • Stratum germinativum layer (basal cell layer and supra basal)
• Basal cell layer


  • Single cuboidal or short columnar cells
  • Attached to each other by desmosomes
  • Attached to connective tissue by hemidesmosomes
  • Consists of serrated cells (heavily packed with tonofilaments) and non-serrated stem cells

  
• Spinous or prickle cell layer


  • Irregular, polyhedral or large oval shaped cells
  • Joined together by intercellular bridges (desmosomes and tonofilaments)
  • Intercellular spaces contain glycoprotein and fibronectin

  
• Stem cells


  Slowly dividing cells which serve to protect genetic information of the tissue
• Two groups of basal cells


  • Stem cells (slowly dividing)
  • Non-stem cells (rapidly dividing)
• Stem cells


  • Highly filled with tonofilament threads which are adaptations for attachment
• Spinous or prickle cell layer (stratum spinosum)


  • Cells are irregular, polyhedral or large oval in shape, about 20-25 layers of cells
  • Joined together by intercellular bridges or processes which are desmosomes and tonofilaments
  • The intercellular spaces contain glycoprotein and fibronectin, and these spaces are large in keratinized epithelium which made the desmosomes more prominent and given the cells prickles appearance

  
• Basal cell layer and supra basal (2-3 cell layers from stratum spinosum just beyond the basal cell layer)

  Able to undergo mitotic division, so they are termed as stratum germinativum layer