Parotid Gland

PAROTID  GLAND

• It is the largest of three paired salivary glands
• It is shaped like an inverted pyramid

COVERINGS

• The gland is invested by inner true & outer false capsules.

True  Capsule :-

• It is formed by condensation of fibrous stroma

False  Capsule (Parotid Sheath) :-

• It is formed by the splitting of investing layer of deep cervical fascia.
• It has superficial & deep lamella.

Superficial lamella is strong.

• It is attached to zygomatic arch & blends with masseter muscle to form Parotido-masseteric fascia.

Deep lamella is thin.

• It is attached to the tympanic plate, styloid process.
• It is thickened between tip of styloid process and angle of mandible to form Stylomandibular ligament.

PRESENTING  PARTS

The gland presents -

• Apex
• Base
• 3 Surfaces – Superficial surface, Antero-medial surface, Postero-medial surface
• 3 Borders – Anterior border, Posterior border, Medial border

Apex :-

• It is directed below
• Overlaps the posterior belly of digastric muscle
• Structures passing through the apex-
• Cervical branch of facial nerve
• Anterior division of retro-mandibular vein
• Formation of external jugular vein

Base :-

• It is concave and related to external acoustic meatus, temporo-mandibular joint
• Structures passing through the base-
• Temporal branch of facial nerve
• Superficial temporal vessels
• Auriculotemporal nerve

Superficial  Surface :-

It is covered by –

• Skin
• Superficial fascia
• Posterior fibres of platysma
• Superficial group of parotid lymph nodes
• Great auricular nerve
• Superficial lamella of parotid sheath

Antero-medial  Surface :-

• It is deeply grooved for the ramus of mandible

Relations-

• Masseter
• Ramus of mandible
• Capsule of temporo-mandibular joint
• Medial pterygoid muscle

Pierced by-

• Branches of facial nerve
• Maxillary artery

Postero-medial  Surface :-

Relations-

• Mastoid process with sternocleidomastoid & posterior belly of digastric muscle
• Styloid process & styloid groups of muscles
• Transverse process of atlas
• Internal carotid artery
• Internal jugular vein
• Last four cranial nerves

Pierced by-

• Facial nerve
• External carotid artery

Anterior  Border :-

• It separates superficial surface from antero-medial surface.

Structures radiating deep to the border from above downwards-

• Zygomatic branch of facial nerve
• Transverse facial vessels
• Upper buccal branch of facial nerve
• Accessory parotid gland
• Parotid duct
• Lower buccal branch of facial nerve
• Marginal mandibular branch of facial nerve

Posterior  Border :-

• It separates superficial surface from postero-medial surface.

Relations-

• Sternocleidomastoid muscle
• Posterior auricular branch of facial nerve
• Posterior auricular vessels

Medial  Border :-

• It separates antero-medial surface from postero-medial surface.
• It is also known as pharyngeal border as it comes in contact with the wall of pharynx.

PROCESSES  OF  THE  GLAND

Facial  Process :-

• It is a triangular projection superficial to masseter along the parotid duct.

Pterygoid  Process :-

• It is a triangular process from the deep part of gland.
• Situated between the mandibular ramus & medial pterygoid muscle.

Glenoid  Process :-

• It passes upward between external meatus & capsule of temporomandibular joint.

Pre-styloid  Process :-

• Part of the gland situated in front of the styloid process
• It is related to the internal carotid artery

Post-styloid  Process :-

• Part of the gland situated behind the styloid process
• It is related to the internal jugular vein

STRUCTURES  PASSING  THROUGH  THE  GLAND

From outside inwards –

• Facial nerve & its branches
• Retro-mandibular vein
• External carotid artery

Facial  Nerve  &  Its  Branches :-

Facial nerve pierces the postero-medial surface of parotid gland

Within the gland it runs forward for 1 cm close to superficial surface of the gland

Then it divides into Temporo-facial & Cervico-facial trunks

Temporo-facial Trunk-

• It turns upward within the gland.
• It subdivides into temporal & zygomatic branches.

Cervico-facial Trunk-

• It passes downward within the gland.
• It subdivides into buccal, marginal mandibular, cervical branches.

• The terminal 5 branches radiate like goose’s foot through anterior border of the gland.
• Such branching pattern is known as Pes anserinus.

Retro-mandibular  Vein :-

• It occupies the middle of the gland deep to facial nerve
• It is formed by the union of Superficial temporal & Maxillary veins.
• It divides into anterior & posterior divisions.

External  Carotid  Artery :-

• It occupies the deep zone within the gland
• It ascends & divides into terminal branches- Superficial temporal & Maxillary arteries.

PAROTID  DUCT  (STENSEN’S  DUCT) :-

• It is 5 cm in length
• It is formed within the gland by union of 2 vertical ducts

Parotid duct emerges through anterior border of the gland

Passes forward on the masseter muscle between upper & lower buccal nerves

It abruptly turns medially passes through the buccal pad of fat

Pierces the bucco-pharyngeal fascia & buccinator muscles

It passes obliquely forward between the buccinator & mucous membrane of the cheek

Finally, the duct opens in to vestibule of mouth opposite upper second molar tooth

BLOOD  SUPPLY

Arterial  Supply :-

• From branches of external carotid artery

Venous  Drainage :-

• Tributaries drain into external jugular vein

LYMPHATIC  DRAINAGE

Lymph drains into superficial & deep groups of parotid lymph nodes

Efferent vessels terminate into jugulo-digastric group of deep cervical lymph nodes.

NERVE  SUPPLY

Parasympathetic  Fibres :-

• Secreto-motor fibres cause watery secretion

Preganglionic fibres arise from inferior salivatory nucleus of medulla

Pass through the tympanic branch of glosso-pharyngeal nerve

Tympanic plexus

Lesser petrosal nerve

Relay into otic ganglion

Post ganglionic fibres pass through auriculo-temporal nerve to reach the gland

Sympathetic  Fibres :-

• Secreto-motor fibres cause mucus-rich sticky secretion
• Vaso-motor fibres supply vessels of the gland

Postganglionic fibres derived from superior cervical sympathetic ganglion

Reach the gland through a plexus around the external carotid artery

APPLIED  ANATOMY

Swelling of the Gland :-

• Painful due to the tight capsule
• Due to retrograde bacterial infection may leads to inflammation of the gland

Mumps -

• Viral infection of salivary glands
• Complications– inflammation of testes or pancreas.

Parotid  Abscess :-

• Pus can be drained by a horizontal incision (Hilton’s method)

Mixed  Parotid  Tumour :-

• Slow-growing, benign, painless tumour

Frey’s  Syndrome :-

• It’s a complication during the healing process of penetrating wound of parotid gland.

Penetrating wound of the gland damaging auriculo-temporal & great auricular nerves

During healing process secreto-motor fibres of auriculo-temporal nerve grow out & join the great auricular nerve

So that the fibres intended for salivary secretion reach the sweat glands in the facial skin

When patient eats, beads of perspiration appear on the skin over parotid gland.