Salivary glands
Normal histology

Author: Sally Tanakchi, M.B.Ch.B. (see Authors page)
Editor: F. Zahra Aly, M.D., Ph.D.

Revised: 21 October 2015, last major September 2015

Copyright: (c) 2002-2015,, Inc.

PubMed Search: Salivary glands [title] histology
Definition / General
  • Exocrine glands with ductal and acinar portions
  • Acinar portion is serous, mucinous or mixed
  • Acini are lined by luminal cells, which are enclosed by myoepithelial cells

  • Serous acini:
    • Dense, basophilic, PAS+ intracytoplasmic secretory granules containing amylase
    • Have central lumen that is rarely visible by H&E
  • Mucinous / mucous acini:
    • Larger than serous acini
    • Irregular pattern
    • Cells have abundant cytoplasm with clear mucin, well rounded basal nuclei, and are arranged around empty lumina
    • Produce acid (positive for Alcian blue and mucicarmine) and neutral (PAS+) sialomucins
  • Myoepithelia cells:
    • Surround acini and intercalated ducts and mediate contraction
    • Have both epithelial and mesenchymal structures and functions, and are important in the morphology of most salivary gland tumors
    • Myoepithelial cells surrounding intercalated ducts are more spindled and have fewer processes than those surrounding acini
  • Ducts:
    • Either intercalated, striated or interlobular, all with outer basal cells and inner luminal cells
    • Intercalated ducts have reserve cells that regenerate acinar tissue and terminal duct system
    • All epithelium is PAS+ (Pathol Int 1999;49:500)
    • Sebaceous glands are attached to parotid and submandibular ducts, and are considered part of normal holocrine differentiation [holocrine secretions are produced within the cell, then are released into the lumen after rupture of the plasma membrane], based on the occurrence of salivary tumors with sebaceous differentiation (Am J Surg Pathol 1989;13:879)
  • Parotid Gland:
    • Serous acini only; contain numerous basophilic zymogen granules; nuclei are uniform, round and in the basal half of the cell
    • Intercalated ducts are long in comparison to striated ducts
    • Striated ducts are larger than intercalated ducts, 3-6 x size of acinus; striations are due to folds in basal plasma membranes
    • Contains small lymph nodes near or within the gland, which arise from interstitial lymphocytes
    • Resembles pancreatic tissue, but parotid gland had adipocytes and pancreatic tissue has islets and centroacinar cells
  • Submandibular gland:
    • Predominantly serous but also mucinous acini
    • The mucous cells are the most active, and therefore the major product of the submandibular gland is saliva which is mucoid in nature
  • Sublingual gland:
    • Predominantly mucinous but also serous acini
  • The basement membrane protein perlecan/HSPG2 (heparan sulfate proteoglycan 2) triggers differentiation of salivary gland cells into self assembling acini-like structures that express essential biomarkers and secrete alpha amylase (Tissue Eng Part A 2009;15:3309)
  • Serous glands produce thin watery fluid containing alpha amylase, which digests starches
  • Mucinous glands produce viscous mucinous fluid higher in glycoproteins, which provides a lubricating film on oral mucosa
  • Cytomorphologic features of various portions of the salivary system from the secretory end piece to the oral cavity are illustrated
  • From left to right are:
    • The acinus
    • Intercalated duct
    • Striated duct
    • Excretory duct
    • Oral cavity

Micro Images

    Parotid gland:

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    Replacement of serous glands by sebaceous glands

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  • Left:
    • Clusters of large, pale-staining mucous cells (arrows) occasionally are present in the parotid gland, but the acini are overwhelmingly of serous type
    • Each serous acinus is composed of several pyramidal-shaped cells with basal nuclei and basophilic cytoplasmic granules
  • Right: The serous cell granules are PAS+ and resistant to diastase digestion (PAS stain)

  • The cells of the intercalated duct (arrow) are small in comparison to the acinar cells and are cuboidal with pale-stained cytoplasm and central nuclei
  • A small lumen is evident

  • The striated duct is larger than an acinus and much larger than the intercalated duct
  • The ductal cells are eosinophilic columnar cells with central nuclei and vertical cytoplasmic striations due to folds in the basal plasma membranes

  • This small, interlobular excretory duct is lined by pseudostratified columnar epithelium and embedded in dense fibrous connective tissue

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  • Intraglandular adipose tissue in parotid gland
    • The parotid gland from a neonate contains no discernible adipose tissue
    • There is a moderate amount of intralobular adipose tissue in parotid tissue from a middle-aged adult
    • The intraparotid adipose tissue is quite prominent in the gland from an elderly person

  • Sebaceous cells in parotid gland
  • The cells in two foci of sebaceous differentiation (arrows) are large with central nuclei and clear reticulated cytoplasm that is unreactive with mucicarmine stain
  • Small foci of sebaceous cells occur frequently in the parotid gland (Mucicarmine stain)

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  • Facial nerve branches in parotid gland
  • A relatively large nerve lies adjacent to a lobule of parotid glandular tissue (left) while a smaller nerve branch is within a lobule and in contact with serous acini (right)

    Submandibular gland:

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  • Left:
    • In the submandibular gland, mucous acini comprise about 10% of acinar tissue.
    • Serous cells are frequently located at the periphery of mucous acini as crescent-shaped cells (arrow)
    • The striated ducts (arrowheads) are more prominent and the intercalated ducts are shorter than those in the parotid gland
  • Right: The mucous cells are highlighted among the serous acini as rose pink cells (Mucicarmine stain)

    Sublingual gland:

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  • The sublingual gland acini are typically elongated tubules of mucous cells with serous cell demilunes (a demilune is a cap in the shape of a half-moon)

    Minor salivary glands of palate:

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  • Left: The palate contains the largest foci of intraoral salivary gland tissue, which is composed of mucous acini but no striated ducts
  • Right:
    • At high magnification, the mucous acini are round with central lumens
    • The mucous cells are pyramidal with very pale granular cytoplasm and nuclei located next to the basal plasma membranes

    Minor salivary glands of tongue:

  • The minor salivary glands are small aggregates of unencapsulated mucous or serous glands
  • In the tongue they are in intimate contact with the striated muscle tissue

  • Keratin cocktail stains intercalated, striated and interlobular ducts, but acinar and myoepithelial cells are mostly negative

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  • Left: Normal parotid tissue is S100 negative
  • Right: In this parotid tissue adjacent to a mixed tumor, some of the myoepithelial and intercalated duct cells are S100+

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  • Left: The normally indistinct, elongated and flattened myoepithelial cells at the periphery of the acini, intercalated ducts and striated ducts are conspicuous due to their immunostaining for alpha smooth muscle actin
  • Right: The serous acinar cells immunostain for alpha amylase
Positive Stains
Electron Microscopy Description
  • Acinar cells:
    • Numerous cytoplasmic secretory (zymogen) granules in apical portion of cell
    • Extensive rough ER and golgi
    • Numerous mitochondria
    • Numerous folds are present in basal lamina of acinar cells that are not distended with secretory product
    • Mucous acinar cells have larger, more irregular secretory droplets that are more electron lucent than in serous acinar cells
  • Intercalated duct cells:
    • Few special ultrastructural features
    • May have some secretory granules
    • Scant cytoplasm has basal rough ER, apical Golgi and mitochondria
    • Lateral membranes interdigitate with neighboring cells
  • Myoepithelial cells:
    • Between basal plasma membrane of acinar and intercalated duct cells and basal lamina
    • Flattened and elongated with cytoplasmic processes extending around acinar and intercalated duct cells
    • Long / irregular nuclei
    • Desmosomes attach the myoepithelial cells to acinar and ductal cells
  • Striated duct cells:
    • Striations are due to basal vertical folds
    • Numerous mitochondria present
Electron Microscopy Images

  • Variable-sized secretory granules occupy most of the apical portion of the cytoplasmic compartment
  • Parallel arrays of rough endoplasmic reticula lie adjacent to the basally located, round nucleus
  • The intercellular space contains interdigitations of adjacent cells and represents a canaliculus that is connected to the acinar lumen and is actually the beginning of the duct system (X11,300)

  • The myoepithelial cell lies between the basal lamina and the basal plasma membranes of the acinar cells
  • The cell body is flattened and the nucleus is elongated
  • In the cytoplasm are numerous microfilaments with focal dense bodies (arrow) (X13,300)

  • The relatively small cytoplasmic compartment contains a round nucleus, mitochondria, lipid vacuoles and an endoplasmic reticulum
  • There are a few short microvilli on the luminal surface, and intercellular connections are apical junctional complexes with several desmosomes (X6,000)

  • The basal plasma membranes have prominent vertical folds, and there are numerous mitochondria
  • The lateral surfaces have processes that interdigitate with adjacent cells
  • Apical junctional complexes and desmosomes connect adjoining cells (X6,000)