Parotid region Parotid gland - PowerPoint Presentation

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Parotid region

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Parotid gland

G.

para, near + otis, ear) Is the largest salivary gland and it is composed mainly of serous acini.It secretes about 20-30% of total saliva.Large, lobulated and irrgular Wt about 15 g

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PG- Position

(

Nearly 80% of the parotid gland (PG) is found below the level of the external auditory canal, in deep hollow between the mandible and the SCM.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 muscledeeply and dorsally by the stylomandibular ligament.

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PG- Extensions

Project to mastoid process

Down the anterior aspect of the SCM for a short distanceAround the posterior border of the mandible.Superiorly to the to inferior margin of the zygomatic archSuperficial to the posterior aspect of the masseter mm Anterior extension for the facial process of the parotid duct. * Maybe separated from the remainder as the Accessory parotid gland.

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Parotid Capsule

Gland encapsulated by a

fascial layer that is continuous with deep cervical fascia. superficial layer is dense and closely united with gland (parotidomasseteric fascia). the fascia forms the stylomandibular ligament, separate parotid from mandibular gland

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PG- external features

3-sided pyramid

Apex: directed downwardFour surfaces: superior- base, superficial(lateral), anteromedial(anterior) and posteromedial(deep).Three borders: anterior, posterior and medial.

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PG- Relations

Apex(lower pole):

post belly of digastric, Cervical br of facial n and 2 divisions of retromadibular vein.Superior surface(upper pole): cartilagenous of ECM, post part TMJ, suptemporal vessels, and auriculotemporal n

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PG- Relations- surfaces and borders

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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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Structures embedded in the gland

A.External

Carotid (postmedial surface)= *superficial temporal (sup surface)*maxillary art. (anteromed. Surface)*transverse facial art. (ant.border)B. Retromandibular veinFormed within gland by maxillary V. + superficial temporal divides in lower part to its divisions other veins may present:

*common facial and

*external jugular vein

• Branches of facial and

auriculotemporal

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Parotid Duct (

Stensen’s

duct)Formed of small ducts coalesce at the anterosuperior aspect of the PG Arises from middle of anterior borderlies superficial to the masseter muscle 1.5 cm inferior to Zygomatic archIs inferior to the transverse facial arteryBuccal branchs

of facial nerve travel with the duct

It is thick walled: 1-3 mm in diameter+

4-6 cm in length

At the anterior edge of the

masseter

muscle it p

ierces medially through

through

the

buccal

pad of fat,

buccopharyngeal

meebrane

and

Buccinator

at 2

nd

Molar

The oblique course of the duct between the mucous membrane and the

buccinator

act as a valve.

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Parotid Blood supply and

Lymphatics

Blood supply from: Arterial= ECA and branches. Venous= EJVLymphatic drainage is to the superficial and deep cervical nodesPreauricular lymph nodes (LN) in the superficial fascia drain the temporal scalp, upper face, anterior pinnaLN within the gland drain the parotid gland, nasopharynx, palate, middle ear and external auditory meatus

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Innervation

1

. Sympathetic : superior cervical ganglion- superficial temporal artery (Serous watery saliva, amylase decrease)Parasympathetic secretomotor fibers reach the gland by a circuitous route: presynaptic neurons lie in the inferior salivatory nucleus of Glossopharyngeal nerve ( CNIX) thru lesser superficial petrosal nerve

Postsynaptic neurons

secretomotor

fibers leave the

otic

ganglion and the

otic

ganglion and distributed by the

Auriculotemporal

nerve to the parotid gland.

Mucoid

viscosity saliva, amylase increase

3.

Sensory innervation to gland from

Auriculotemporal

and to capsule from

greater auricular nerve

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Facial nerve

Stylomastoid

foramenSuperficial lobe and deep lobe3 Motor branches immediately: stylohoid muscle, posterior auricular muscle, digastric muscle posterior bellyPes Anserinus ((intraparotid plexus of CN7) – 1.3 cm from the

stylomastoid

foramen

Temporofacial

division,

Cervicofacial

division

5 terminal branches

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Facial nerve identification

1.Antigrade dissection

Tympanomastoid sutureTragal pointDigastric muscle posterior bellyStyloid process SCM muscle 2.Retrograde dissection 3.Mastoidectomy

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Clinical application

Frey’s syndrome:

It develops after penetrating wounds of the gland.When the pat. eats beads of perspiration appear on the skin covering the gland.This is duo to damage of GEATER AURICUAL N and AURICULOTEMPORAL N during healing parasympathetic secretomotor fibres from the AURICULOTEMPORAL N grow out and join the GEATER AURICUAL N fibres .Eventually, they reach the sweat glands in the facial skin. * By this means, a stimulus intended for saliva production produces sweat secretion instead Tumors of Parotid gland: Usually arise at the superficial lobe without involvement of the facial nerve. Iatrogenic cause as in surgical injury of facial nerve results to facial paralysis.

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Clinical application

Abscess or cyst of the gland may result in pressure on the Facial nerve.

The weakest part of investing fascia is between Styloid process and spine of sphenoid, therefore, infections breakout parotid fascia drain into the lateral pharyngeal space, which is in direct communication with the retropharyngeal space. That may track inferior along carotid sheath between visceral and prevertebral fascia.

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Clinical application

Parotid Gland Infection:

The gland may be acutely inflamed by retrograde bacterial infection from the mouth via the parotid duct or itself is infected by the bloodstream as in MUMPS. Which is due to PARAMYXOVIRUS. It is an infectious disease.Acute Parotitis: In both cases the gland is swollen, it is painful because of the capsuleSjogren’s syndrome:Xerostomia (dry mouth), keratoconjunctivitis sicca

(dry eyes), rheumatoid arthritis,

hypergammaglobulinemia

Autoimmune disorder that affects not only salivary glands and

lacrimal

glands of

Mikulicz’s

disease, but also minor salivary glands and occasionally lymph nodes, lung, kidney, bone marrow, skeletal muscle, skin, liver

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Nerves related to PG

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.Auriculotemporal NerveBranch of V3Traverses 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 post-ganglionic parasympathetic (secretory)fibers.

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Parotid

Bed

V: internal jugular veinA: external and internal carotid arteriesN: glossopharyngeal N vagus N spinal accesory N hypoglossal NS: styloid process styloglossus mm

stylohyloid

mm

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