After reading this post you will know:
- Boundaries of parotid region and location of parotid gland.
- Gross features and relations of parotid gland.
- Structures emerging from the periphery of parotid gland.
- Structures passing through the parotid gland.
- Course, structures pierced by and opening of parotid duct.
- Secretomotor fibers to parotid gland.
- Applied anatomy related to parotid gland.
Q. What are the boundaries of parotid region?
Ans. Parotid region Boundaries:
- Anteriorly: Posterior border of ramus of mandible with masseter and medial pterygoid attached to it.
- Posteriorly: Mastoid process and sternocleidomastoid muscle.
- Superiorly: External acoustic meatus and posterior part of temporomandibular joint.
- Inferiorly: Extends slightly below the posterior belly of digastric and stylohyoid muscle ( into carotid triangle).
- Medially : Styloid process and muscles attached to it.
Location of Parotid Gland
Q. What is the location of Parotid gland?
A. Parotid gland is mainly present in front and below the ear lobule. It fills the gap between the ramus of mandible and the mastoid process.
Superiorly, it extends upto the external acoustic meatus and inferiorly it reaches the upper part of carotid triangle. Posteriorly it overlaps sternocleidomastoid muscle and anteriorly it crosses the masseter.
Gross Features and Relations of Parotid Gland
Q. Describe parotid gland under the following headings.
- Gross features
Ans. Parotid gland : Gross Features
- is the largest of the salivary glands.
- is purely serous in nature.
- Is irregular in shape (roughly 3 sided inverted pyramid) and weighs approx. 25gm. It has:
- An apex
- directed below
- overlaps posterior belly of diagastric muscle and reaches carotid triangle.
- Is concave and directed upwards.
- Is related to external acoustic meatus and posterior part of temporomandibular joint.
- Three surfaces
- Superficial (lateral ) surface
- Anteromedial surface:
- Posteromedial surface
- Three borders
- An apex
2. Parotid gland: Structures emerging from the periphery
- Structures emerging through apex are:
- Cervical branch of facial nerve
- Anterior and posterior divisions of retromandibular vein
- Structures emerging through base are( anterior to posterior):
- Temporal branch of facial nerve
- Superficial temporal vessels
- Auriculotemporal nerve
- Structures emerging along the anterior border ( from above downwards are):
- Zygomatic branch of facial nerve
- Transverse facial artery
- Upper buccal branch of facial nerve
- Parotid duct
- Lower buccal branch of facial nerve
- Marginal mandibular branch of facial nerve
- Structures emerging along the posterior border are:
- Posterior auricular branch of facial nerve
- Posterior auricular vessels
- Medial border: is related to the lateral wall of pharynx.
- Structures emerging through apex are:
3. Parotid Gland Relations
- Superficial (lateral ) surface Is covered from superficial to deep by
- Superficial fascia containing:
- Anterior branch of great auricular nerve
- Pre auricular ( superficial parotid ) lymph nodes
- Platysma muscle fibers
- Superficial lamella of parotid fascia
- Deep parotid lymph nodes
- Structures related to Anteromedial surface:
- Is grooved by ramus of mandible.
- Medial perygoid
- Lateral surface of temporomandibular joint
- Terminal branches of facial nerve
- Structures related to Posteromedial surface:
- Mastoid process
- Sternocleidomastoid muscle
- Posterior belly of diagastric muscle
- Styloid process and muscles attached to it
- Facial nerve enters the gland through this surface
- External carotid artery is lodged in a groove in its lower part
|Styloid process separates the gland from internal carotid artery, internal jugular vein and last four ( IX, X,XI & XII) cranial nerves.|
Capsules of Parotid Gland
Q. Describe capsules of parotid gand.
A. Capsules of parotid gland: Parotid gland is surrounded by two capsules:
- True capsule : form by condensation of the fibrous stroma of the gland.
- False capsule ( parotid fascia) :
- Is formed by splitting of investing layer of deep cervical fascia.
- Its superficial lamina passé superfial to the gland , is thick and attached to inferior border of zygomatic arch.
- Its deep lamina passes deep to the gland, is thin and is attached to styloid process and tympanic plate. It also forms stylomandibular ligament ( from tip of styloid process to angle of mandible) which separates parotid gland from submandibular gland.
|Inflammatory parotid swelling are very painful due to unyielding nature of parotid fascia.|
Structures Passing Through Parotid Gland
Q. Name the structures passing through the parotid gland.
Ans. Structures passing through the parotid gland from superficial to deep are:
- Facial nerve and its branches
- Retromandibular vein
- External carotid artery and its branches
- Facial nerve: Enters the gland through posterior medial surface and divides into five terminal ( temporal, zygomatic, buccal, marginal mandibular & cervical) branches. The terminal branches leave the gland through the anteromedial surface and emerge along the its anterior border.
- Parotid gland is divided into a superficial and deep parts which are connected by isthmus. Branches of facial nerve pass forward though the isthmus ( the plane between the superficial and deep part), this plane helps surgeons to remove parotid tumor without damaging the nerve.
- Parotid abcess is drained by horizontal incision (parallel to the branches of facial nerve ) in the parotid fascia to avoid injury to the branches of facial nerve.
- Is formed within the gland by union of superficial temporal and maxillary veins.
- It divided into anterior and posterior divisions in the the lower part of the gland.
- Anterior dividsion joins facial vein to form the common facial vein.
- Posterior division joins posterior auricular vein to form external jugular vein.
External carotid artery:
- Enters the gland through the posteromedial surface .
- Divides into terminal branches – maxillary and superficial temporal.
Q. Describe briefly:
- Formation, course and opening of parotid duct.
- Nerve supply of parotid gland
Ans. 1. Parotid duct( Stensen’s duct)
- Is thick walled, 5cm. long and 3mm wide.
- Is formed within the gland by joining of smaller ducts, emerges from the gland at the middle of its anterior border on the surface of masseter (a finger breadth below the zygomatic arch)..
- Runs forward and slightly downwards on the masseter.
- At the anterior border of masseter turns medially and pierces:
- Buccal pad of fat
- Buccopharyngeal fascia
- Buccinators muscle
- Buccal mucosa
- It runs obliquely between the buccinators and oral mucosa ( for 1cm.) before piercing the mucosa to open into the vestibule of mouth opposite to the crown of 2nd upper molar tooth.
Nerve Supply of Parotid Gland
2. Nerve supply of parotid gland – Parotid gland is supplied by :
- Parasympathetic fibers – secretomotor
- Sympathetic fibers – mainly vasomotor
- Sensory fibers
- Parasympathetic fibers ( secretomotor fibers); stimulation of parasympathetic fibers produces watery secretion ( rich in enzymes)
Preganglionic fibers arise from inferior salivatory nucleus (in medulla oblongata) -> Glossophryngeal nerve ( leaves through jugular formen)->Tympanic branch of glossopharyngeal nerve -> Tympanic plexus ( in middle ear cavity) -> Lesser petrosal nerve( leaves through foramen ovale) -> Synapse in otic ganglion -> postganglionic fibers pass through auriculotemoral branch of mandibular nerve -> Supply parotid gland
- Sympathetic fibers: mainly vasomotor , and their stimulation also produces thick sticky secretion.
Preganglionic fibers arise from lateral horn of T1 spinal segment -> Synapse in superior cervical ganglion -> Postganglionic fibers form plexus around external carotid artery to reach parotid gland
- Sensory fibers: Carry general sensations . Derived from auriculotemporal nerve.
|Frey’s Syndrome: penetrating wounds of parotid gland may damage the auriculotemporal and greatauricular nerves. During the process of regeneration, secretomotor fibers of auriculotemporal nerve may join the great auricular nerve and supply the sweat glands of the skin covering parotid gland. therefore, when the person eats food , beads os perspiration appear on the skin over parotid gland because the stimulus intended for salivation produces sweat instead.|