Salivary glands
INTRODUCTION
There are four main salivary glands, two submandibular glands and
two parotid glands. In addition, there are multiple minor salivary
glands.
MINOR SALIVARY GLANDS
Anatomy
The mucosa of the oral cavity contains approximately 450
minor salivary glands. They are distributed in the mucosa
of the lips, cheeks, palate, floor of the mouth and
retromolar area. These minor salivary glands also appear
in other areas of the upper aerodigestive tract including
the oropharynx, larynx and trachea as well as the sinuses.
They have a histological structure similar to that of
mucous-secreting major salivary glands.
Overall, they contribute to 10 per cent of the total salivary
Volume
Anatomy of salivary glands
_ Two submandibular glands
_ Two parotid glands
_ Two sublingual glands
_ Approximately 450 minor salivary glands
Common disorders of minor salivary glands
Cysts
Extravasation cysts are common and result from trauma to the
overlying mucosa. They usually affect minor salivary glands
within the lower lip, producing a variable swelling that is
painless and usually, but not always, translucent. Some resolve
spontaneously, but most require formal surgical excision that
includes the overlying mucosa and the underlying minor
salivary gland. Recurrence is rare.
Tumours
Tumours of minor salivary glands are histologically
similar to those of major glands;, up to 90 per cent of
minor salivary gland tumours are malignant. Although
tumours of minor salivary gland origin occur anywhere in
the upper aerodigestive tract, common sites for tumour
formation include the upper lip, palate and retromolar
regions. Less common sites for minor salivary gland
tumours include the nasal and pharyngeal cavities. .
Benign minor salivary gland tumours present as painless,
firm, slow-growing swellings. Overlying ulceration is
extremely rare.
Minor salivary gland tumours of the upper lip are
managed by excision to include the overlying mucosa,
with primary closure .
Benign tumours of the palate, less than 1 cm in diameter,
can be managed by excisional biopsy, and the defect is
allowed to heal by secondary intention .
tumours of the palate are greater than 1 cm in diameter,
incisional biopsy is recommended to establish a diagnosis
prior to formal excision.
Malignant minor salivary gland tumours are rare. They
have a firm consistency, and the overlying mucosa may
have a varied discolouration from pink to blue or black .
The tumour may become necrotic with ulceration as a late
presentation.
Malignant minor salivary gland tumours of the palate are
managed by wide excision which may involve partial or
total
maxillectomy.
The
subsequent
defect
can
be
managed by either prosthetic obliteration or immediate
reconstruction. .
THE SUBLINGUAL GLANDS
Anatomy
The sublingual glands are a paired lying in the anterior
part of the floor of mouth between the mucous membrane,
the mylohyoid muscle and the body of the mandible close
to the mental symphysis. Each gland has numerous
excretory ducts that open directly into the oral cavity.
Common disorders of the sublingual glands
Cysts
Minor mucous retention cysts develop in the floor of the
mouth either from an obstructed minor salivary gland or
from the sublingual salivary gland. The term ‘ranula’
should be applied only to a mucous extravasation cyst that
arises from a sublingual gland. It produces a characteristic
translucent swelling that takes on the appearance of a
‘frog’s belly’ (ranula)
A ranula can resolve spontaneously, but many also
require formal surgical excision of the cyst and the
affected sublingual gland. Incision and drainage, however
tempting, usually results in recurrence.
Plunging ranula
Plunging ranula is a rare form of mucous retention cyst
that can arise from both sublingual and submandibular
salivary glands. Mucus collects within the cyst, which
perforates through the mylohyoid muscle diaphragm to
enter the neck. Patients present with a dumb-bell-shaped
swelling that is soft, fluctuant and painless in the
submandibular or submental region of the neck.
Diagnosis is made on ultrasound or magnetic resonance
imaging (MRI) examination.
Excision is usually performed via a cervical approach
removing the cyst and both the submandibular and
sublingual glands.
Smaller plunging ranulas can be treated successfully by
transoral sublingual gland excision, with or without
marsupialisation.
Tumours
Tumours involving the sublingual gland are extremely
rare and are usually (85 per cent) malignant.
They present as a hard or firm painless swelling in the
floor of the mouth.
Treatment requires wide excision involving the overlying
mucosa
and
simultaneous
neck
dissection.
Immediate
reconstruction of the intraoral defect is recommended .
THE SUBMANDIBULAR GLANDS
Anatomy
The submandibular glands are paired salivary glands that
lie below the mandible on either side. They consist of a
larger superficial and a smaller deep lobe that are
continuous around the posterior border of the mylohyoid
muscle.
Important
anatomical
relations
include
the
anterior facial vein running over the surface of the gland
and the facial artery. The deep part of the gland lies on the
hyoglossus muscle closely related to the lingual nerve and
inferior to the hypoglossal nerve.
. The gland is surrounded by a well-defined capsule that is
derived from the deep cervical fascia which splits to
enclose it. The gland is drained by a single submandibular
duct (Wharton’s duct) that emerges from its deep surface
and runs in the space between the hyoglossus and
mylohyoid muscles. It drains into the anterior floor of the
mouth at the sublingual papilla. There are several lymph
nodes immediately adjacent and sometimes within the
superficial part of the gland
Important
anatomical
relationships
of
the submandibular glands
•
_ Lingual nerve
•
_ Hypoglossal nerve
•
_ Anterior facial vein
•
_ Facial artery
*Marginal mandibular branch of the facial nerve
Inflammatory
disorders
of
the
submandibular gland
Inflammation of
the submandibular
gland is
termed
sialadenitis. Submandibular sialadenitis may be acute,
chronic or acute on chronic.
Common causes are:
• Acute submandibular sialadenitis:
– Viral. The paramyxovirus (mumps) is a viral illness of
the salivary glands that usually produces parotitis. The
submandibular glands are occasionally involved, causing
painful tender swollen glands. Other viral infections of
the submandibular gland are extremely rare.
– Bacterial. Bacterial sialadenitis is more common than
viral sialadenitis and occurs secondary to obstruction.
Following
infection
and
despite
control
of
acute
symptoms with antibiotics, the gland frequently becomes
chronically inflamed and requires formal excision.
• Chronic submandibular sialadenitis.
Obstruction and trauma
The most common cause of obstruction within the
submandibular
gland
is
stone
formation
(sialothiasis)
within the gland and its associated duct system.
Eighty per cent of all salivary stones occur in the
submandibular glands because their secretions are highly
viscous and the Secreation of its duct against the gravity
Eighty per cent of submandibular stones are radio-opaque
and can be identified on plain radiography
Clinical symptoms
Patients usually present with acute painful swelling in the
region of the submandibular gland, precipitated by eating
The
swelling
occurs
rapidly
and
often
resolves
spontaneously over 1–2 hours after the meal is completed.
This classical picture occurs when the stone causes
complete obstruction, usually at the opening of the
submandibular duct. More frequently, the stone causes
only partial obstruction when it lies within the hilum of
the gland or within the duct in the floor of the mouth. In
such
circumstances,
symptoms
are
more
infrequent,
producing minimal discomfort and swelling, not confined
to mealtimes. Clinical examination reveals an enlarged
firm
submandibular
gland,
tender
on
bimanual
examination. Pus may be visible, draining from the
sublingual papilla
Management
If the stone is lying within the submandibular duct in the
floor of the mouth anterior to the point at which the duct
crosses the lingual nerve (second molar region), the stone
can be removed by incising longitudinally over the duct.
Once the stone has been delivered, the wall of the duct
should be left open to promote free drainage of saliva.
Suturing the duct will lead to stricture formation and the
recurrence of obstructive symptoms.
Where the stone is proximal to the lingual nerve, i.e. at
the hilum of the gland, stone retrieval via an intraoral
approach should be avoided as there is a high risk of
damage to the lingual nerve during exploration in the
posterior lingual gutter.
Treatment
is
by
simultaneous
submandibular
gland
excision and removal of the stone and ligation of the
submandibular duct under direct vision.
Other causes of submandibular duct obstruction include
external pressure, particularly trauma to the floor of the
mouth from an overextended flange on a lower denture
which
impinges
on
the
sublingual
papilla
causing
inflammation and subsequent stricture
Submandibular gland excision
Submandibular gland excision is indicated for:
1-sialadenitis
2-salivary tumours.
3-stone
Excision
of
the
submandibular
gland
involves
four
distinct phases.
1-Incision and exposure of gland
The incision should be marked at least 3–4 cm below the
lower border of the mandible to avoid damage to the
marginal mandibular branch of the facial nerve
2-Gland mobilisation
In inflammatory conditions, the submandibular gland is
excised by intracapsular dissection,
The superficial lobe of the submandibular gland is first
mobilised
3-Dissection
of
the
deep
lobe
and
identification of the lingual nerve
An important landmark in submandibular gland dissection
is the posterior border of the mylohyoid muscle. Once
identified, it can be retracted forwards to reveal the deep
lobe of the gland.
The hypoglossal nerves lie deep to the submandibular
capsule and should not be damaged during intracapsular
dissection