Salivary glands
General
Histology


Topic Completed: 1 September 2015

Minor changes: 13 January 2021

Copyright: 2002-2021, PathologyOutlines.com, Inc.

PubMed Search: Salivary glands[TI] histology[TIAB]

Sally Tanakchi, M.D.
F. Zahra Aly, M.D., Ph.D.
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Cite this page: Tanakchi S, Aly FZ. Histology. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/salivaryglandsnormalhistology.html. Accessed January 16th, 2021.
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)
    • Sebaceous type glands are mixed with salivary gland acini in 10 - 40% of normal parotid glands, often in periductal locations in interlobular ducts; either single, isolated sebaceous type cells within serous or mucinous salivary acini or as fully developed sebaceous glands (Arch Pathol Lab Med 2004;128:245)
  • 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 - 6x 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
    • 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
Pathophysiology
  • 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
Diagrams / tables

AFIP images
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Cytomorphologic
features of
various portions of
the salivary system

Microscopic (histologic) images

AFIP images

Parotid gland:
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Acini are
overwhelmingly
of serous type

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Serous cell granules
are PAS+ and resistant
to diastase digestion
(PAS stain)

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Cells of the
intercalated duct are
small in comparison
to the acinar cells

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Duct is lined by
pseudostratified
columnar epithelium

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Striated duct is
larger than an acinus
and much larger than
the intercalated duct


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Facial nerve branches in parotid gland

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Intraglandular adipose tissue in parotid gland

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Sebaceous cells
in parotid gland



Submandibular gland:
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Submandibular
gland: mucous acini
comprise about
10% of acinar tissue

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Mucous cells are
highlighted among
the serous acini
as rose pink cells


Sublingual gland:
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Typically elongated
tubules of mucous
cells with serous
cell demilunes


Minor salivary glands of palate:
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Palate contains
the largest foci of
intraoral salivary
gland tissue

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At high magnification,
the mucous acini
are round with
central lumens



Minor salivary glands of tongue:
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Small aggregates
of unencapsulated
mucous or
serous glands

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Keratin cocktail
stains intercalated,
striated and
interlobular ducts

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Normal parotid tissue is S100 negative

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Some of the
myoepithelial and
intercalated duct
cells are S100+

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Immunostaining
for alpha smooth
muscle actin

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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

AFIP images
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Variable sized
secretory granules

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Myoepithelial cell lies
between the basal lamina
and plasma membranes
of the acinar cells

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Basal plasma
membranes
have prominent
vertical folds

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Relatively small
cytoplasmic
compartment
contents

Videos

Shotgun histology parotid gland

Shotgun histology submandibular gland

Shotgun histology sublingual gland

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