Anatomy of Submandibular Gland

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Anatomy of Submandibular Gland
Fuad Ridha Mahabot

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Introduction
•a major salivary gland
•situated in the anterior part of digastric triangle in
submandibular region
•about the size of walnut
•roughly ‘J’- shaped - being indented by posterior border
of mylohyoid muscle which divides into
•superficial part
•deep part
•composed of a mixture of serous and mucous acini

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Embryology
•during sixth and seventh weeks of embryonic period
•begins as solid epithelial buds from the primordial oral
cavity
•the club-shaped ends of these epithelial buds grow into
the underlying mesenchyme
•connective tissue - derived from neural crest cells
•all parenchymal (secretory) tissue arises by proliferation
of the oral epithelium

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Development of Submandibular Glands
•appear late in sixth week
•develop from endodermal buds in the floor of
stomodeum
•grow posteriorly, lateral to developing tongue
•later they branch and differentiate
•acini - begin to form at 12 weeks; secretory activity at 16
weeks
•growth continues after birth with formation of mucous
acini
•lateral to the tongue - a linear groove forms  soon
closes over  submandibular duct

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Histology
•branched tubuloacinar glands
•lobes  lobules  adenomeres (secretory unit)
•each adenomere contains one or more acini - small
clusters of cells that secrete their products into a duct
•acini - either serous or mucous cells, with serous
adenomeres predominating (mixed gland)
•mucous adenomeres may also be capped with a serous
demilune, a layer of lysozyme-secreting serous cells
resembling a half moon

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group of
mucous
alveoli
group of
serous
alveoli

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Submandibular gland - histology slide

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Superficial Part
•this part fills the digastric triangle
•extends upwards deep to the mandible up to the
mylohyoid muscle
•has inferior, lateral and medial surfaces
•partially enclosed between two layers of deep cervical
fascia
•superficial layer of fascia covers the inferior surface of
the gland and is attached to the base of mandible
•deep layer covers the medial surface of the gland and is
attached to the mylohyoid line of mandible

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Relations
•inferior surface is covered by
skin
platysma muscle
cervical branch of facial nerve
deep fascia
facial vein
submandibular lymph nodes
•lateral surface is related to
submandibular fossa on the mandible
insertion of pterygoid
facial artery

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•medial surface maybe divided into three parts
anterior part - related to mylohyoid muscles, nerve and vessels
middle part - related to hyoglossus, styloglossus, lingual nerve,
submandibular ganglion and hypoglossal nerve
posterior part - related to styloglossus, stylohyoid ligament, the
ninth nerve, and the wall of pharynx. Inferiorly it overlaps
stylohyoid and posterior belly of digastric

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Deep Part
•small in size
•lies deep to mylohyoid, and superficial to hyoglossus
and styloglossus
•posteriorly continuous with superficial part around the
posterior border of mylohyoid
•anteriorly extends up to posterior end of sublingual
gland

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Submandibular Duct
•a.k.a Wharton’s duct
•thin walled, about 5cm long
•emerges at anterior end of deep part of gland
•runs forwards on the hyoglossus, between lingual and
hypoglossal nerves
•at the anterior border of hyoglossus, the duct is crossed
by lingual nerve
•it opens on the floor of the mouth, on the summit of
subligual papilla, at the side of frenulum of the tongue

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Blood Supply and Lymphatic Drainage
•supplied by facial artery
•veins drain into common facial or lingual vein
•lymph passes to submandibular lymph nodes

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Nerve Supply
•supplied by branches from the submandibular ganglion
•these branches convey:
secretomotor fibres
sensory fibres from lingual nerve
vasomotor fibres from plexus on facial artery
•secretomotor pathway (parasympathetic) - begins in
the superior salivary nucleus
preganglionic fibres pass through sensory root of facial nerve,
geniculate ganglion, facial nerve, chorda tympani, lingual nerve,
to reach submandibular ganglion
post ganglionic fibres emerges from the ganglion and enter
submandibular gland

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•vasomotor function (sympathetic)
regulates submandibular secretions through
vasoconstriction of the arteries that supply it
increased sympathetic activity  reduces glandular
bloodflow  decreasing salivary secretions 
producing an enzyme rich serous saliva.

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Functions of Submandibular Gland
•mainly production of saliva
•contents of saliva
water (98%)
electrolytes:
•2-21 mmol/L sodium (lower than blood plasma)
•10-36 mmol/L potassium (higher than plasma)
•1.2-2.8 mmol/L calcium (similar to plasma)
•0.08-0.5 mmol/L magnesium
•5-40 mmol/L chloride (lower than plasma)
•25 mmol/L bicarbonate (higher than plasma)
•1.4-39 mmol/L phosphate
mucus - mainly consists of mucopoly-saccharides and
glycoproteins

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antibacterial compounds (thiocyanate, hydrogen
peroxide, and secretory immunoglobulin A)
various enzymes:
•α-amylase - starts the digestion of starch and lipase fat
before the food is swallowed. It has a pH optima of 7.4.
•lingual lipase
•antimicrobial enzymes that kill bacteria - lysozyme, salivary
lactoperoxidase, lactoferrin, immunoglobulin A
cells - possibly as much as 8 million human and 500
million bacterial cells per mL.
opiorphin - a newly researched pain-killing substance
found in human saliva.

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Applied Anatomy
1.Excision of the submandibular gland for calculus of tumour is done
by an incision below the angle of jaw. Since the mandibular
branch of facial nerve passes posteroinferior to the angle of jaw
before crossing it, the incision must be placed more then one inch
below the angle to preserve the nerve.
2.In differentiating between an enlarged submandibular gland and a
mass of submandibular lymph nodes, one remembers that the
gland lies not only below the mandible but also extends into the
floor of mouth; it can therefore be palpated bimanually between a
finger in a mouth and a fingerbelow the angle of the jaw. Enlarged
lymph nodes are felt only at latter site.

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3.A stone in Wharton’s duct can be felt bimanually in the floor of
the mouth and can be seen if sufficiently large.
4.Presence of small lymph nodes actually within the substance of
the gland makes removal of the gland an important part of block
dissection of the neck.

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