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presentation on major salivary glands anatomy, overview on histology and apllied aspects, mainly emphasing on surgical aspects.
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SALIVARY GLANDS ANATOMY & APPLIED ASPECTSJoel D’silva
Department of Oral & Maxillofacial Surgery
INTRODUCTIONThe salivary glands are exocrine glands, glands with ducts, that produce saliva and pour their secretion in the oral cavity
Major (Paired) Parotid Submandibular Sublingual
MinorThose in the Tongue, Palatine Tonsil, Palate, Lips and Cheeks
DEVELOPMENT
STAGES OF DEVELOPMENT
STAGE 1
Bud formation: Introduction of the oral epithelium by underlying mesenchyme
STAGE 2
Formation and growth of epithelial cord
STAGE 3Initiation of branching in terminal parts of epithelial cord and continuation of glandular differentiation
STAGE 4
Dichromatous branching of epithelial cord and lobule formation
STAGE 5
Canalization of presumptive ducts
STAGE 6Cytodifferentiation
UNDERSTANDING THE HISTOLOGY
PAROTID GLAND
Largest Average Wt - 25gmIrregular lobulated mass lying mainly below the external acoustic meatus between mandible and sternomastoid.On the surface of the masseter, small detached part lies b/w zygomatic arch and parotid duct-accessory parotid gland or ‘socia parotidis’
Parotid Capsule
• Derived from investing layer of deep cervical fascia.
• Superficial lamina-thick, closely adherent-sends fibrous septa into the gland.
• Deep lamina-thin- attached to styloid process, mandible and tympanic plate.
• Stylomandibular ligament.
External Features
•Resembles an inverted 3 sided pyramid
•Four surfaces• Superior(Base of the Pyramid)• Superficial• Anteromedial• Posteromedial
•Separated by three borders
•Anterior• Posterior•Medial
Relations
• Superior Surface • Concave• Related to
• Cartilaginous part of ext acoustic meatus• Post. Aspect of
temperomandibular joint• Auriculotemporal Nerve• Sup. Temporal vessels
• Apex• Overlaps posterior belly of
digastric and adjoining part of carotid triangle
• Superficial Surface• Covered by • Skin• Superficial fascia containing
facial branches of great auricular N• Superficial parotid lymph
nodes and post fibers of platysma
•Anteromedial Surface•Grooved by posterior border of ramus of mandible
•Related to• Masseter• Lateral Surface of
temperomandibular joint• Medial pterygoid muscles• Emerging branches of Facial
N
• Posteromedial Surface
• Related • to mastoid process with
sternomastoid and posterior belly of digastric.
• Styloid process with structures attached to it.
• External Carotid A. which enters the gland through the surface
• Internal Carotid A. which lies deep to styloid process
BORDERS
•Anterior border
• Separates superficial surface from anteromedial surface.
• Structures which emerge at this border
• Parotid Duct• Terminal Branches of
facial nerve• Transverse facial
vessels
• Posterior Border
• Separates superficial surface from posteromedial surface• Overlaps sternomastoid
•Medial Border
• Separates anteromedial surface from posteromedial surface• Related to lateral wall of pharynx
Structures within the parotid gland
ARTERIES
VEINS
NERVES
• Facial Nerve trunk lies approximately 1 cm inferior and 1 cm medial to tragal cartilage pointer of external acoustic meatus.
Parotid Duct• ductus parotideus;
Stensen’s duct
• 5 cm in length
• Appears in the anterior border of the gland
• Runs anteriorly and downwards on the masseter b/w the upper and lower buccal branches of facial N.
•At the anterior border of masseter it pierces
• Buccal pad of fat• Buccopharyngeal fascia• Buccinator Muscle
• It opens into the vestibule of mouth opposite to the 2nd upper molar
Surface anatomy of Parotid Duct
• Corresponds to middle third of a line drawn from lower border of tragus to a point midway b/w nasal ala and upperlabial margin
Blood supply
• Arterial• Branches of Ext.
Carotid A• Venous
• Into Ext. Jugular Vein
Lymphatic DrainageUpper Deep cervical nodes via Parotid nodes
NERVE SUPPLY
•Parasymapthetic N• Secretomotor via
auriculotemporal N
•Symapathetic N• Vasomotor• Delivered from plexus
around the external carotid artery
•Sensory N• Reach through the Great
auricular and auriculotemporal N
Applied aspects
• Parotid swellings are very painful due to the underlying nature of the parotid fascia.• Mumps is infection of salivary gland caused by paromyxovirus which will cause severe pain
Incision
• Lazy ‘S’ incision• Pre-auricular—mastoid-cervical incision
• During surgical removal of parotid gland for any tumour the facial nerve is preserved by removing the glands in two parts superficial and deep lobe separately.
Superficial parotidectomy
• Hypotensive anaesthesia• Head up position • Infiltration with 1:80,000 LA with adrenaline• Long term paralytic agents should be avoided for C VII monitoring whenever indicated
Facial Nerve injury
• A parotid abscess may be caused by the spread of infection from the oral cavity.• An infection may also spread due to the parotid lymph node draining an infected area
• Parotid abscess is best drained by horizontal incision according to Hiltons method of incision and drainage.
Vertical incision on skin but transverse incision on the parotid fascia to safeguard facial nerve
and branches
• Frey's syndrome
• The lobule of the ear is often pushed up in parotid swelling• For tumours of the parotid gland incision biopsy is not indicated as it will cause the seeding of the tumour
Inflamatory diseases of parotid
Acute suppurative parotitis
Acute parotitis (mumps parotitis)
Recurrent subacute parotitis / chronic parotitis
Neoplasms of the salivary gland
• 75% occur in the parotid glands.• In parotid glands, 80% of tumors are benign.• Of these 80% are Pleomorphic adenomas.
• 15% of salivary tumors occur in submandibular glands.• Of these 50% are benign and 50% and malignant.
• In carcinomas mucoepidermoid ca> adenoid cystic ca > adenocarcinoma
• 10% of salivary tumors occur in sublingual and minor salivary glands• 60-70% of these are malignant
Classification
Epithelial tumors
Connective tissue tumors
Epithilial tumors
• Benign • Pleomorphic adenoma (Mixed tumor)• Oxyphil adenoma• Papillary cystadenoma lymphomatosum (Warthin’s tumor)• Basal cell adenoma
Epithelial tumors
• Malignant • Mucoepidermoid carcinoma• Adenoid cystic carcinoma• Acinic cell ca• Papillary adenocarcinoma• SCC• Undifferentiated ca• Ca arising in pleomorphic adenoma
Connective tissue tumors
• Benign • Hemangioma • Lipoma• Neurilemmoma• Fibroma
• Malignant • Malignant lymphoma• Above mentioned benign tumors may turn malignant.
submandibular salivary gland
Submandibular Glands are….• Irregular in shape
• Large superficial and small deeper part continous with each other around the post. Border of mylohyoid
Superficial Part• Situated in the digastric triangle•Wedged b/w body of mandible and mylohyoid• 3 surfaces
• Inferior, Medial, Lateral
Capsule
• Derived from deep cervical fascia
• Superficial Layer is attached to base of mandible
• Deep layer attached to mylohyoid line of mandible
Relations
• Inferior- covered by • Skin• Superficial fascia containing
platysma and cervical branches of facial N• Deep Fascia• Facial Vein• Submandibular Nodes
• Lateral surface• Related to submandibluar
fossa on the mandible• Madibular attachment of
Medial pterygoid• Facial Artery
• Medial surface
• Anterior part is related to myelohyoid muscle, nerve and vessels
• Middle part - Hyoglossus, styloglossus, lingual nerve, submandibular ganglion, hypoglossal nerve and deep lingual vein.
• Posterior Part - Styloglossus, stylohyoid ligament,9th nerve and wall of pharynx
• 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
Submandibular Duct
• Whartons duct• 5 cm long• Emerges at the anterior end of deep
part of the gland• Runs forwards on hyoglossus b/w
lingual and hypoglossal N• At the ant. Border of hyoglossus it is
crossed by lingual nerve• Opens in the floor of mouth at the side
of frenulum of tongue
Blood supply and lymphatics
• Arteries• Branches of facial and lingual arteries
• Veins• Drains to the corresponding veins
• Lymphatics• Deep Cervical Nodes via submandibular
nodes
Nerve supply
• Parasymapthetic fibers from chorda tympani
• Sensory fibers from lingual branch of mandibular nerve
• Sympathetic fibers from plexus on facial A
Applied aspects
• The formation of calculus is more common in the submandibular gland than in the parotid.• For excision of the submandibular salivary gland( for calculus or tumour), a skin crease incision is as a rule, given more than 1inch( 2.5cm) below the angle of the jaw• A stone in the submandibular duct(wharton’s duct) can be palpated bimanually in the floor of the mouth and can even be seen if sufficiently large.
Tumors of submandibular glands• Tumors in this gland are uncommon• Enlargement is more due to calculus • Of all tumors, mixed tumor is most common• Swelling is hard but not stony hard and should be differentiated from submandibular lymph node
Submandibular gland excision• Indications :• Chronic sialoadenitis• Stone in submandbular gland• Submandibular gland tumors
Incision
• Placed 2-4 cm below the mandible, parallel to it• Preserve : • Marginal mandibular nerve• Lingual nerve• Hypoglossal nerve
Complications
• Hemorrhage• Infection• Injury to mandibular nerve, lingual nerve , hypoglossal nerve
Sublingual Salivary Glands
• smallest of the three glands
• weighs nearly 3-4 gm
• Lies beneath the oral mucosa in contact with the sublingual fossa on lingual aspect of mandible.
Relations
•Above• Mucosa of oral floor, raised as
sublingual fold
•Below • Myelohyoid Infront• Anterior end of its fellow
•Behind• Deep part of Submandibular gland
• Lateral•Mandible above the anterior part of mylohyoid line
•Medial•Genioglossus and separated from it by lingual nerve and submandibular duct
Duct
• Ducts of Rivinus• 8-20 ducts• Most of them open directly into
the floor of mouth• Few of them join the
submandibular duct
•Blood supply• Arterial from sublingual and
submental arteries• Venous drainage corresponds to
the arteries
•Nerve Supply• Similar to that of submandibular
glands( via lingual nerve , chorda tympani and sympathetic fibers)
Sublingual and minor salivary gland diseases
• Mucous cyst (retention cyst) : Ranula, sailoliths • Inflammatory salivary gland diseases • Tumors as described before but it rarely effects sublingual glands
Applied aspects
• The structures at risk during dissection of the gland are the submandibular duct and the lingual nerve.• The duct lies superficially in the floor of the mouth medial to the sublingual fold, and is crossed inferiorly by the nerve which then enters the tongue• The sublingual artery and vein also lie on the medial aspect of the gland close to the submandibular duct and lingual nerve.
Incision
Ann R Coll Surg Engl 1994; 76: 108-109
REFERENCES
• Anatomy – by B.D.Chaurasia• Oral anatomy- by Sicher and DuBruls• Gray’s anatomy• Oral and maxillofacial surgery-by Nilima Malik• Oral and maxillofacial surgery- Kruger• Ann R Coll Surg Engl 1994; 76: 108-109