Transcript Anatomy of salivary glands

Anatomy of salivary glands
Contributed By :- Dr. Nafisa Parveen
Jawahar Lal Nehru Medical College
Aligarh Muslim University, India
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Embryology
 The parotid glands are the first to develop in the 4th week of
embryogenesis, followed by the submandibular glands at 6th
weeks and finally the sublingual glands at 8th weeks.
 Parenchymal tissue (secretory) of the glands arises from the
proliferation of oral epithelium.
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Embryology
 The stroma (capsule and septae) of the glands originates from
mesenchyme that may be mesodermal or neural crest in
origin.
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Parotid development
 Although the parotid anlagen are the first to develop, they
become encapsulated after the SMG and SLG.
 This delayed encapsulation is critical because after the
encapsulation of the SMG and SLG but bafore encapsulation
of the parotid, the lymphatic system develops.
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Parotid development
 Therefore, there are intraglandular lymph nodes and
lymphatic channels entrapped within the parotid gland (PG).
 PG is also unique because its epithelial buds grow, branch and
extend around the divisions of the facial nerve.
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Embryology
 The epithelial buds of each gland enlarge, elongate and
branch initially forming solid structures.
 Branching of the glandular mass produces arborization.
 Each branch terminates in one or two solid end bulbs.
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Embryology
 Elongation of the end bulb follows and lumina appears in
their centers, transforming the end bulbs into terminal
tubules.
 These tubules join the canalizing ducts to the peripheral
acini.
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Duct Canalization
 Canalization results from mitotic activity of the outer layers
of the cord outpacing that of the inner cell layers
 Canalization is complete by 6th month post conception.
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Acinar cells
 At around the 7-8th month in utero, secretory cells (acini)
begin to develop around the ductal system.
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Acinar cells of Salivary Glands
Classified as :
 Serous cells: containing small granules.
secrete salivary proteins and enzymes.
thin watery secretion.
 Mucous cells: contain larger granules, producing
mucoproteins. more viscous secretion.
 Seromucinous cells: have an intermediate structure.
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Salivary gland secretory unit
 Composed of terminal acini
 Intercalated, striated and excretory ducts
 Myoepithelial cells
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Salivary gland secretory unit
 Basic secretory unit is the acinous.
 Arranged in a sphere surrounding a duct.
 The secretory cells are pyramidal with narrow luminal
apices.
 Their broader bases rest on a basement membrane
surrounded by stellate contractile myoepithelial cells.
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Salivary gland secretory unit
 The acinar ducts coalesce into intercalated ducts
,subsequently striated ducts composed of columnar cells,
then united into the main excretory duct of the gland.
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Salivary gland secretory unit
 The acini in major salivary glands are arranged into lobules
and lobes within the glands.
 Each lobule has a single excretory duct.
 The lobules are linked by dense fibrous tissue containing
excretory ducts, vessels , lymphatics , nerve fibres and
ganglia to form lobes.
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Major glands/Secretions
 Major SG are paired structures and include the parotid,
submandibular and sublingual
 Parotid: serous
 Submandibular: mucous & serous
 Sublingual: mucous
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Parotid gland
 Largest of the salivary glands.
 They resemble a three-sided pyramid.
 Wedge shaped in coronal section.
 Enveloped by the investing layer of deep cervical fascia.
 Each gland has an average weight of 25g.
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Anatomy: Parotid Gland
 Nearly 80% of the parotid gland (PG) is found below the
level of the external auditory canal, between the mandible
anteriorly and the SCM posteriorly.
 Superficial to the posterior aspect of the masseter mm
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Anatomy:Parotid Gland
 Extensions of PG project to mastoid process
 Down the anterior aspect of the SCM for a short distance
 Around the posterior border of the mandible.
 Superiorly to the to inferior margin of the zygomatic arch
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Parotid gland
 The parotid gland is irregularly lobulated.
 The superficial surface is concave.
 Covered by the superficial fascia, the posterior border of
platysma and skin.
 Superficial parotid lymph nodes and facial branches of the
great auricular nerve overlie this surface.
 The great auricular nerve is derived from the cervical plexus
,provides sensory sensation for the lower 2/3rd of the pinna.
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Parotid gland
 The superior surface is concave.
 Lies adjacent to the cartilaginous EAC and the TMJ.
 The auriculotemporal nerve lies in the capsule adjacent to
the neck of the mandible.
 The apex of the gland lies on the posterior belly of the
digastric muscle.
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Parotid gland
 The anteromedial surface lies on the posterior border of the
ascending ramus of the mandible and the medial pterygoid
muscle.
 The facial nerve enters the gland on this surface.
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Parotid gland
 Posteromedial surface is indented by the external carotid
artery before it penetrates this surface of the gland.
 It lies on the mastoid process,the posterior belly of the
digastic,the sternocleidomastoid ms and the styloid process.
 The medial aspect may project as far medially as to be in
contact with the lateral wall of the pharynx.
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Anatomy:Parotid Gland
 CN VII branches roughly divide the PG into superficial
and deep lobes while coursing anteriorly from the
stylomastoid foramen to the muscles of facial expression.
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Anatomy: Deep Lobe
 The remaining 20% extends medially through the
stylomandibular tunnel, which is formed
 ventrally by the posterior edge of the ramus
 dorsally by the anterior border of the SCM & posterior digastric
muscle
 deeply and dorsally by the stylomandibular ligament.
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Anatomy--Salivary gland
Parotid Ductal System was first
described by
Nicolaus Stenonius in 1660.
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Anatomy: Parotid Duct
 Small ducts coalesce at the anterosuperior aspect of the
PG to form Stensen’s duct.
 Lined by low cuboidal epithelium ,surrounded by a
smooth ms and fibrous tissue.
 Runs anteriorly from the gland and lies superficial to the
masseter muscle.
 It lies 



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inferior to the transverse facial artery
Btw the upper and lower buccal branches of the facial nerve.
It is 1-3 mm in diameter
5cm in length
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Anatomy: Parotid Duct
 At the anterior edge of the masseter muscle, Stensen’s duct
turns sharply medial and passes through the buccinator
muscle, buccal mucosa and into the oral cavity opposite the
maxillary second molar.
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Anatomy: Parotid Fascia
 Gland encapsulated by a fascial layer that is continuous with deep
cervical fascia (DCF).
 The fascial envelope is continuous anteriorly with the fascia covering
the masseter ms and posteriorly with fascia enveloping SCM ms.
 Deep to the gland it is attached to the styloid process,tympanic plate
and mandible,forming the stylomandibular ligament
 The stylomandibular ligament (portion of the DCF) separates the
parotid and submandibular gland.
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Parotid fascia
 This fascial layer is largely tough and inelastic.
 The relatively thin fascia covering the apex of the gland can
lead to the spread of sepsis into the parapharyngeal space.
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Parotid Lymphatics
 Lymphatic drainage is to the superficial and deep cervical
nodes
 Preauricular lymph nodes (LN) in the superficial fascia drain
the temporal scalp, upper face, anterior pinna
 LN within the gland drain the parotid gland, nasopharynx,
palate, middle ear and external auditory meatus
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Parotid: Parasympathetic Innervation
 Preganglionic parasympathetic (from CN9) arrives at otic
ganglion via lesser petrosal n.
 Postganglionic parasympathetic leaves the otic ganglion and
distributes to the parotid gland via the auriculotemporal
nerve.
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Parotid: Sympathetic
Innervation
 Postganglionic innervation is provided by the superior
salivary nucleus and carried by the sympathetic plexus
surrounding the carotid vessels.
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Parotid Anatomy: Great Auricular Nerve
(C2,C3)
 Emerges from the posterior border of the SCM at Erb’s
point.
 It crosses the mid-portion of the SCM about 6.5cm beneath the
EAM.
 Passes parallel and superior to the external jugular vein to
supply the ear and pre-auricular region.
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Parotid Anatomy: Auriculotemporal
Nerve
 Branch of V3
 Traverses the upper part of the parotid gland and emerges
from the superior surface with the superficial temporal
vessels.
 It carries sensory fibers from the trigeminal and postganglionic parasympathetic (secretory)fibers.
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Parotid Anatomy: Facial Nerve
 Emerges at the level of the digastric muscle, through the
stylomastoid foramen.
 Main trunk divides at the pes anserinus (intraparotid plexus
of CN7) into the upper temporofacial and lower cervicofacial
divisions.
 Each division further subdivides into five branches: temporal,
zygomatic,buccal,mandibular and cervical,supplying the ms
of facial expression.
 Before it enters gland, gives off 3 branches:
 Posterior auricular, posterior digastric, stylohyoid
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Parotid Anatomy: Vessels
 Retromandibular Vein: located within the substance of the
gland , drain into the external jugular vein.
 Via facial vein drain into the internal jugular vein.
 External carotid : at the inferior level of the gland, the
external carotid divides into the superficial temporal and
internal maxillary artery.
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Parotid Bed: Deep lobe lies on...
 V: internal jugular vein
 A: external and internal carotid arteries
 N: glossopharyngeal N
vagus N
spinal accesory N
hypoglossal N
 S: styloid process
styloglossus mm
stylohyloid mm
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Submandibular gland
 Consist of a larger superficial part and a smaller deep part
wrapped arround the posterior border of mylohyoid.
 Each is irregular in shape.
 About the size of a walnut.
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Submandibular gland
 The superficial part is covered by a fibrous capsule,derived
from the DCF.
 The capsule runs from the greater cornu of the hyoid
bone,splits to enclose the gland before blending with the
periostium of the mandible along the mylohyoid line medially
and the lower border of the body of the mandible laterally.
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Submandibular gland
 The superficial part of the gland lies within the
submandibular triangle.
 It extends from the anterior belly of the digastric anteriorly
to the stylomandibular ligament posteriorly.
 The lower border of the gland overlies the digastric tendon.
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Submandibular gland
 The medial surface lies on the surface of mylohyoid
anteriorly, with the nerve to mylohyoid and submental
vessels.
 Posteriorly is related to the stylohyoid ligament
,styloglossus ,the pharynx and the glossopharyngeal nerve.
 The intermediate part of the medial surface overlies
hyoglossus, the lingual nerve with its submandibular
ganglion,hypoglossal nerve, stylohyoid and posterior belly of
the digastric.
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Submandibular gland
 The lateral surface lies adjacent to the body of the mandible
in the mandibular fossa and the origin of the medial
pterygoid.
 The inferior surface is covered by skin , platysma and deep
cervical fascia.
 It is related to the cervical branch of the facial nerve.
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Deep part -submandibular gland
 The deep part of the gland lies within the floor of the mouth,lying
on the mylohyoid, lateral to the hyoglossus and styloglossus.
 Anteriorly it lies adjacent to the posterior end of the sublingual
gland
 Posteriorly wraps around the posterior free edge of mylohyoid to
join the superficial lobe.
 It lies btw the lingual nerve above and the hypoglossal nerve below.
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Anatomy--Salivary gland
• Submandibular Ductal System was first described by
Thomas Wharton, 1659
• Sublingual Ductal System was described by
Casparus Bartholinus, 1690
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Anatomy: Submandibular Duct
 It is formed by the coalescence of numerous ducts within the
superficial part of the gland before emerging from the
medial surface of the gland.
 Wharton’s duct passes forward along the superior surface of
the mylohyoid adjacent to the lingual nerve.
 The nerve winds around the duct, first being lateral, then
inferior, and finally medial.
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Anatomy: Submandibular duct
 2-4mm in diameter & about 5cm in length.
 It opens into the floor of the mouth thru a punctum adjacent
to the lingual frenulum,after passing btw the sublingual gland
and genioglossus.
 The punctum is a constricted portion of the duct to limit
retrograde flow of bacteria-laden oral fluids.
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Submandibular Lymphatics
 Submandibular gland drains into the deep cervical
group,,particularly the jugulo-omohyoid.
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Nerve supply
 Via submandibular ganglion, which receives autonomic fibres
from the chorda tympani,the lingual nerve and sympathetic
trunk.
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Blood supply
 Arterial supply from the facial and lingual arteries
 Venous drainage into the corresponding veins.
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Anatomy: Sublingual glands
Lie on the superior surface of the mylohyoid muscle and
are separated from the oral cavity by a thin layer of mucosa.
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Sublingual gland
 Smallest paired salivary gland.
 Almond shaped.
 4g weight
 Posteriorly they contact the deep part of the submandibular
gland
 Medially they are separated from the genioglossus by the
lingual nerve and submandibular duct.
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Sublingual glands
 The ducts of the sublingual glands are called Bartholin’s
ducts.
 In most cases, Bartholin’s ducts consists of 8-20 smaller ducts
of Rivinus. These ducts are short and small in diameter.
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Sublingual glands
 The ducts of Rivinis either open…
 individually into the FOM near the punctum of
Wharton’s duct
 on a crest of sublingual mucosa called the plica
sublingualis
 open directly into Wharton’s duct
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Blood supply
 Via the sublingual and submental vessels.
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Nerve supply
 Via submandibular ganglion, which receives autonomic fibres
from the chorda tympani,the lingual nerve and sympathetic
trunk.
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Minor salivary glands

600-1000 in numbers.
the minor salivary glands of mouth include the buccal,
labial,lingual,palatal and palatoglossal glands.
 The buccal and labial glands contains both mucous and
serous elements.
 The palatal, lingual and palatoglossal glands are mucous
glands .
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Physiology
 Physiologic control of the SG is almost entirely by the
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autonomic nervous system; parasympathetic effects
predominate.
If parasympathetic innervation is interrupted, glandular
atrophy occurs.
Normal saliva is 99.5% water
Normal daily production is 0.5L
Salivary flow rates are approximately 0.3ml/min when
unstimulated.
Rising to 1.5-2ml/min when stimulated.
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physiology
 During sleep salivary flow rate is negligible.
 In unstimulated state parotid gland contributes
approximately 20%
 Submandibular gland approximately 65%
 Sublingual and minor salivary glands the remainder.
 When stimulated the parotid contribution rises to 50%
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