Salivary glands

General

Anatomy & histology



Topic Completed: 1 September 2015

Minor changes: 16 August 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. Anatomy & histology. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/salivaryglandsnormalhistology.html. Accessed October 20th, 2021.
Anatomy
  • Parotid gland:
    • Largest salivary gland (15 - 30 g), 6 x 3 cm
    • It is wrapped around the mandibular ramus, has broad superficial lobe and smaller deeper lobe, with facial nerve usually between both lobes
    • Provides only 25% of the total salivary volume but on stimulation, the parotid secretion rises to 50%
    • Stensen duct (main duct) empties into the oral cavity opposite crown of second maxillary molar
    • 20% have accessory parotid gland and duct, usually overlying the masseter muscle
    • Parotid gland has its own fascia (capsule), which is continuous with superficial layer of deep cervical fascia
    • Contains 3 - 24 lymph nodes (not all with complete structural organization), usually lateral to facial nerve in superficial lobe
    • Blood supply: external carotid artery and its terminal branches
    • Venous return: retromandibular vein
    • Lymphatic drainage: preauricular lymph nodes that drain to the deep cervical chain
    • Nerve supply: mainly autonomic through the glossopharyngeal nerve
    • Vascular bundle (retromandibular vein, external carotid artery, superficial temporal artery and maxillary artery) lies medial to facial nerve

  • Submandibular gland:
    • Divided into superficial and deep lobes, separated by the myelohyoid muscle
    • In submandibular triangle formed by anterior and posterior bellies of digastric muscle and inferior margin of mandible
    • Weighs 50% of parotid gland (7 - 15 g)
    • Provides 60 - 65% of the total salivary volume
    • Wharton duct (submandibular duct) empties into the floor of mouth on both sides of the tongue frenulum at sublingual caruncla
    • Lingual nerve wraps around Wharton duct, CN XII runs inferior and parallel to Wharton duct
    • Has its own capsule, which is continuous with superficial layer of deep cervical fascia
    • No lymph nodes within the capsule but 3 - 6 adjacent lymph nodes in submandibular triangle
    • Blood supply: sublingual and submental arteries
    • Venous return: anterior facial vein
    • Lymphatic drainage: submandibular nodes to upper deep cervical nodes
    • Nerve supply: direct by sympathetic nervous system (facial artery plexus) and indirect by parasympathetic nervous system (chorda tympani)

  • Sublingual gland:
    • Smallest of major salivary glands (2 - 4 g)
    • Lies deep to the floor of oral mucosa between mandible and genioglossus muscle
    • Has no true fascial capsule
    • Has no single dominant duct but is drained by 10 small ducts (ducts of Rivinus)
    • Occasionally, several of more anterior ducts may join to form a common duct (Bartholin duct), which typically empties into Wharton duct
    • Bartholin duct unites with the submandibular duct just prior to its opening into the oral cavity at the sublingual caruncula on both sides of tongue frenulum
    • Blood supply: sublingual and submental arteries
    • Venous return: sublingual vein
    • Lymphatic drainage: submandibular lymph nodes
    • Nerve supply: lingual and chorda tympani nerve (from facial nerve) provides parasympathetic supply

  • Minor salivary glands:
    • Except for the gingiva and anterior hard palate, minor salivary glands (500 - 1000, 1 - 5 mm each) are located throughout the submucosa of the oral cavity
    • More numerous in posterior hard palate
    • Each salivary unit has its own simple duct
    • Most of these minor salivary glands are mucinous with the main exception of Ebner glands, which are serous glands located in the circumvallate papillae of the tongue
Embryology
  • Parotid gland primordia (anlage) arises in weeks 5 - 6 from ectoderm, followed by submandibular gland primordia in week 6 from endoderm, then sublingual gland primordia in weeks 7 - 8 from endoderm
  • Intraoral minor salivary glands (including von Ebner gland) develop during the third month from endoderm
  • Primordia develop from primitive oral cavity (stomodeum) as buds, which proliferate as cords, form terminal bulbs, develop clefts and further proliferate as branches from original cord; then the process is repeated
  • Lumens form in epithelial cords and progress to terminal bulbs; cells differentiate into various ducts and acini
  • Connective tissue diminishes with maturation
  • Parotid buds may penetrate intraparotid lymph nodes; rare with submandibular or sublingual structures
  • Secretion by the parotid glands via the parotid duct begins at about 18 weeks of gestation, while secretion by the submandibular gland begins at 16 weeks of gestation
Histology
  • 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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Drawing of
the oral cavity
of a 9 week
old embryo

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Parotid gland lymph nodes

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Horizontal section
through lateral
portion of pharynx

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Lateral view of
the head shows
anatomic position

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Medial surface
of the mandible
and mylohyoid
muscle

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Cytomorphologic
features of
various portions of
the salivary system

Radiology images

Images hosted on other servers:
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Figures 1a and 3a: normal anatomy

Clinical images

AFIP images
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Right and left submandibular ducts

Microscopic (histologic) images

AFIP images
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Proliferative
epithelial cord
of the developing
parotid gland

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Moderately cellular,
fibrous stroma
in a 25 week old fetus

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At high magnification,
the terminal tubules
are a double layer
of epithelial cells


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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