SALIVARY GLANDS

• Oral cavity environment


  Moist, with a film of fluid (saliva) constantly present
• Saliva


  Complex fluid secreted in the oral cavity by salivary glands
• Approximately 700 ml of saliva is secreted daily by a healthy adult person
• Saliva production by gland type

  • 60% by submandibular
  • 30% by parotid
  • 5% from lingual
  • 5% from minor salivary glands
• Types of salivary glands

  • Major salivary glands
  • Minor salivary glands
• Major salivary glands


  • Situated outside the oral cavity, have a long ductal system, 3 bilaterally present paired glands: Parotid, Submandibular, Sublingual
• Minor salivary glands


  • Present in groups beneath the oral epithelium, generally open by very small ductules
• Both major and minor salivary glands are epithelial in origin
• Functions of saliva

  • Protection
  • Digestion
  • Buffering
  • Taste
  • Antimicrobial
  • Tooth integrity
  • Soft tissue repair
• Lubrication


  Saliva lubricates the oral cavity, protecting the mucosa from friction during mastication
• Lavage


  Saliva acts to flush the oral cavity by mechanical washing action, preventing the collection of food particles and debris
• Pellicle formation


  A thin, resistant layer of glycoproteins and salivary proteins forms on the tooth surface
• Water proofing


  The viscosity of saliva forms a somewhat waterproof layer on the tooth surface
• Bolus formation


  Saliva helps form food into a bolus that can be easily swallowed and digested
• Digestion of starch


  Salivary amylase and alpha amylase enzymes catalyze the hydrolysis of starch into smaller carbohydrate molecules
• Neutralization of esophageal contents


  Phosphates and bicarbonates in saliva neutralize the esophageal contents
• Maintenance of pH


  Saliva maintains the pH of the oral cavity, creating an environment unfavourable for the growth of certain bacteria
• Buffering capacityof saliva


  Due to bicarbonate and phosphate ions, protects the oral cavity by preventing colonization of pathogenic bacteria and demineralization of teeth
• Sialin


  A negatively charged salivary protein peptide that acts as a buffer, raising the pH of plaque and preventing demineralization and cavitation of enamel
• Solution of molecules


  Saliva acts as a solvent, helping taste buds detect food flavors
• Taste bud growth and maturation

  Saliva helps in the growth and maturation of taste buds
• Antibodies


  Many immunoglobulins are present in saliva. Among them important are IgA, IgG & IgM.
• Hostile environment


  Substances in saliva like lysozyme and lactoferrin create an environment hostile to pathogenic microorganisms
• Barrier effect


  Glycoproteins in saliva form a protective barrier, preventing bacterial adherence and facilitating their removal
• Enamel maturation


  Saliva's high calcium and phosphate content increases enamel hardness, decreases permeability, and increases resistance to caries
• Remineralization


  The high calcium and phosphate content in saliva allows remineralization of enamel lesions
• Decreased susceptibility


  When fluoride is present, the repaired enamel becomes more acid resistant
• Reduction in bleeding time


  The viscosity of saliva helps check bleeding of oral tissues
• Wound contraction and healing


  Saliva increases the rate of wound contraction and healing, due to epidermal growth factor
• Blood clot formation


  Saliva helps in the clotting of blood, aiding in the repair of wounds in the oral cavity
• Structure and anatomy of salivary glands

  • Parenchyma consists of ducts ending in terminal secretory end pieces, the functional unit is the alveolus or acinus
• Types of terminal end piece cells


  • Serous
  • Mucous
  • Seromucous
  • Myoepithelial
• Serous cells


  Secrete mostly proteins and small amounts of carbohydrates, with a watery consistency
• Mucous cells


  High in carbohydrates and low in proteins, secrete a viscous product called mucin
• Myoepithelial cells


  Contractile epithelial cells that originate from the oral epithelium, function to contract and squeeze the acinus, facilitating secretion
• Duct system


  • Intercalated ducts
  • Striated ducts
  • Excretory or collecting ducts
• Intercalated ducts


  Have low cuboidal cells with metabolic function, containing mitochondria, rough endoplasmic reticulum, and secretory granules
• Striated ducts


  Cells are slightly taller and more columnar than intercalated ducts, have striations caused by basal membrane enfolding, allowing increased ion exchange and sodium resorption/potassium secretion
• Terminal secretory (collecting) ducts

  Ducts through which salivary fluid is secreted into the oral cavity, also function to alter salivary fluid composition by changing electrolyte concentration
• Excretory or collecting duct

  Excretory or collecting ductow cuboidal cells