Salivary Glands Lecture Notes

Classification of Salivary Glands

• Major Salivary Glands: Larger glands
• Minor Salivary Glands: Smaller glands
• Types of Secretions:
  • Serous Salivary Glands
  • Mucous Salivary Glands
  • Mixed Salivary Glands

Development of Salivary Glands

• Origin: Ectodermal
• Process: Epithelial cells proliferate into ectomesenchyme leading to branching morphogenesis, requiring epithelial-mesenchymal interaction.
• Lumen Formation: Central cell degeneration, starting from distal and proximal portions.
• Development Timeline:
  • Parotid Gland: Begins at 5 weeks in utero
  • Submandibular Gland: 6 weeks in utero
  • Sublingual Gland: 8 weeks in utero
  • Minor Salivary Glands: 3rd month of fetal life

Histology of Salivary Glands

• Components:
  • Acini: Secreting end pieces
    • Types: Serous, Mucous, Serous Demilune
  • Duct System: Carries saliva to the oral cavity
    • Includes: Intercalated ducts, Striated ducts, Excretory ducts
  • Myoepithelial Cells: Located adjacent to acini and intercalated ducts
• Basement Membrane: Lining the entire salivary structure

Types of Acini

• Serous Acini:
  • Shape: Spherical
  • Cells: 8-12 serous cells, pyramidal shape
  • Features: Small lumen, intercellular canaliculi, dark cytoplasm due to protein-rich granules
  • Location: Parotid, von Ebner, submandibular glands
• Mucous Acini:
  • Shape: Tubular
  • Cells: 10-16 mucous cells
  • Features: Larger lumen, lacks intercellular canaliculi, appears empty on staining due to carbohydrate-rich mucus
  • Location: Submandibular, sublingual, minor glands (except von Ebner)
• Serous Demilune:
  • Structure: Mucous acini capped by crescent-shaped serous acini
  • Features: Intercellular canaliculi for saliva passage
  • Location: Mixed glands like submandibular

Duct System

• Intercalated Ducts:
  • Location: Adjacent to secretary end pieces
  • Epithelium: Simple cuboidal
  • Features: Few microvilli, first to receive saliva
• Striated Ducts:
  • Function: Receives saliva from intercalated ducts
  • Epithelium: Simple columnar
  • Features: Striations due to infoldings and mitochondria
• Excretory Ducts:
  • Function: Saliva reaches oral cavity
  • Epithelium: Pseudostratified, turns stratified near oral cavity
  • Features: Includes goblet and tuft cells

Myoepithelial Cells

• Location: Between acini/duct cells and basement membrane
• Shape:
  • Acini: Stellate or basket cells
  • Intercalated ducts: Fusiform
• Structure: Contains actin filaments for contraction
• Function: Support acini and prevent backflow of saliva, contract to increase saliva outflow