Lecture 8.2 Parotid gland and Facial nerve

Question 1

Where is the parotid duct (largest salivary gland of variable size) located

Answer 1

Wrapped around the ramus of the mandible on the superficial, posterior and deep side just anterior and below the ear.

Bound superiorly by zygomatic arch, inferiorly by inferior border of mandible

Anteriorly by masseter and Posteriorly external ear and SCM

Question 2

Describe where the parotid duct is found (on surface anatomy) and its course

Answer 2

-the middle third of the line from lower border of tragus to cheilion going 1.5 cm away either side from the line.

It leaves the anterior border of the parotid gland and crosses the face over the masseter muscle, turning 90’ and piercing buccinator muscle where it opens in the oral cavity near the 2nd molar

Question 3

What is the sensory, secretomotory (PS) and sympathetic innervation to the parotid gland

Answer 3

Sensory: Deep fascia of neck enveloping parotid gland: C2
Gland itself: Auriculotemporal nerve (branch of V3)

Secretomotor: (parasympathetic fibres)

preganglionic fibres: CN9 (via lesser petrosal)

post ganglionic V3 (via auricotemporal)

Sympathetic: sup. cervical ganglion via Ext. carotid artery and middle meningeal artery

Question 4

What is the course of the facial nerve into its terminal branches

Answer 4

1. exits skull in stylomastoid foramen
   a) immediately give off posterior auricular nerve -> occipitofrontalis
2. then gives off branch to supply posterior belly of digastric and stylohyoid muscles
3. Facial nerve enters posteromedial surface of parotid gland between deep and superficial part dividing into temporozygomatic branch (sup trunk)
   & cervicofacial branch (inf trunk)
4. Terminal branches of facial nerve exit anterior to the parotid gland: From top to bottom:
   temporal, zygomatic, buccal,
   &
   marginal mandibular and cervical branches

Question 5

What do the first 3 terminal branches of facial nerve supply and what do they cross

(from Temporozygomatic branch on the diagram)

Answer 5

1. Temporal: ant and sup auricularis muscle and frontalis (after crossing zyg arch)
2. Zygomatic: crosses the zyg arch and runs toward the corner of the eye to supply frontalis, orbicularis oculi, and muscles below the eye for blinking
3. Buccal: supplies buccinator and muscles of upper lip

Question 6

What do last 2 terminal branches of the facial nerve of facial nerve supply and what do they cross

(from cervicofacial branch in the diagram)

Answer 6

4. Marginal mandibular: (after travelling along lower border of mandible) supplies muscles of lower lip
5. Cervical branch: supplies platysma

Question 7

What muscle, bone, artery and vein does the facial nerve run superficial to in the parotid

Answer 7

Mandible and Masseter muscle, retromandibular vein and external carotid artery.

Question 8

What structures in the face are superficial and can be damaged in laceration to the face in surgery or trauma

Answer 8

• Parotid duct: both sides need to be sown together within a few hours after cut otherwise cyst formation underneath the skin or secretions over the face due to saliva unchanneled
• Temporal branch of cn7:
• Marginal mandibular: 3cm below or on mandible.

Question 9

What can give to patient to help investigate the parotid duct

Answer 9

lemon or sour will cause it to secrete more

Question 10

What is Bells palsy

Answer 10

Unexplained episode of facial weakness/paralysis on one side that can resolve within weeks-mo/never due to CN7 damage

• difficulty blinking, chewing. drooling, decreased taste, drooping of the face

Question 11

what is a common type of cancer related to the parotid

Answer 11

Neurotrophic cancers from skin cancers. These can invade the face using the facial nerve so the nerve and its branches must be resected, including the dermatomes supplied by this nerve