Anatomy and Histology of salivary glands

Anatomy and Histology of salivary glands

1. Type of acini (p = serous, smg = all three >80% serous, slg = mostly mucous)

   • Serous
     • Extensive RER, Golgi and secretory granules (amylase, lysozyme)
     • Many basal invaginations (as more continuous)
     • Lots of junctional complexes
   • Mucous
     • Fewer basal invaginations compared to serous - less "basal" level of secretion
     • Secrete mucin glycoprotein - less enzymatic secretions more carbohydrate
     • More prominent Golgi than serous, less extensive RER + mito
   • Mixed
     • Serous "sit" on top of mucous cells
   • Myoepithelial cells surround acinus - joined to acinus by DESMOSOMES - squeeze acini to increase salivary flow

2. Developmental origin

   • ECTODERMALLY derived from stomatodeum lining
   • Oral epithelial cells proliferate into surrounding ectomesenchyme and form buds with epithelial cords to OE surface
   • 4-6-8-12 weeks pattern formation (largest to smallest glands)
   • Surrounding condensed mesenchyme induces differentiation of oral epithelial invaginated tissue
   • Surrounding condensed mesenchyme becomes fibrous capsule - lymph nodes frequently become trapped because this condensation is delayed
   • Duct system forms from epithelial cords - further branching for different duct types
   • Epithelial parenchymal tissue forms the lobules

3. Duct system - Acinus - intercalated - striated - excretory (terminal)

   • Intercalated (INTRAlobular)
     • Smallest duct
     • Simple cuboidal epithelium
     • Secretory proteins such as lysozyme
   • Striated (INTRAlobular)
     • Striated due to high infolded basolateral membrane containing elongated mitochondria
     • Modification of saliva occurs here
     • Columnar cells
   • Excretory (terminal - INTERlobular)
     • End part of the duct system
     • Pseudostratified columnar epithelium
     • Embeddded in connective tissue between the lobules
   • Interlobular = in septal connective tissue outside paremchyma, Intralobular = inside paremchyma

4. Age changes

   • Stroma becomes fibrotic and accumulates lymphocytes
   • More fat cells in parotid
   • Linked to xerostomia / sjogrens

5. Minor glands

   • 8-10% of all saliva production
   • Palatal, lingual, labial, buccal, retromolar location
   • None in gingiva + anterior palate