In front of ear, below zygomatic arch. Mainly parotid gland and masseter muscle.
Arises: lower border zygomatic arch; most fibres slope down and back at 45o ¨
Inserts: whole lateral surface of mandibular ramus.
- posterior-most fibres arise from inferior surface of arch --> upper part of ramus
- upper muscle covered by aponeurosis on which parotid duct and accessory parotid lie
Blood: Branches of facial artery, maxillary, and superficial temporal, particularly transverse facial
Nerve: masseteric branch of mandibular nerve; through mandibular notch ¨ deep surface.
Action:
elevates /
draws jaw forward; deep fibres assist in retracting mandible.
Largest salivary gland; mainly serous (few mucous acini). Irregular & lobulated;
Sited from zygomatic
arch to
upper neck where overlaps post digastric & ant SCM
- anteriorly sits over masseter, and an accessory gland usually lies over the duct there.
- Posteriorly to ext acoustic meatus & on to mastoid
Large in cross-section:
wedge-shape; fills space from ramus mandible -->
mastoid and styloid
processes
- and reaches close to lateral wall of oropharynx (look at fauces when parotid mass)
Lateral surface =
covered by skin and superficial fascia;
- investing layer of deep cervical fascia splits to surround the gland = tough fibrous capsule
- outer capsule reaches to zygomatic arch, inner to base of skull
- great auricular nerve supplies this fascia and its overlying skin (C2)
- acute swelling of this ¨ pain of mumps (viral)
Branches of VII ¨ a superficial
muscular
aponeurotic system (SMAS) on the anterior gland
Anteromedial surface
= grooved by posterior mandibular ramus over masseter &
med pterygoid.
- gland wraps around capsule of TMJ
- anterior edge of surface meets lateral surface over and below masseter
- parotid duct and facial nerve branches emerge from anteromedially
- terminal external carotid artery branches leave this surface further back.
Posteromedial surface
= contact with mastoid, attached SCM and posterior digastric
belly
- medially = styloid (and attached stylohyoid, stylopharyngeus and styloglossus)
- these separate gland from carotid sheath
- ECA enters gland through lower part here
- Facial nerve trunk (or divisions enter b/n mastoid and styloid processes.
Within gland, branches of VII run in different directions.
- communicate ¨ plexiform arrangement on retromandibular vein (formed within parotid)
- retromandibular vein emerges from lower pole ¨ branches as described.
Lymph nodes of parotid group are on or deep to the fascial
capsule and in the gland itself.
5cm long, across masseter ¨ around its anterior border ¨ through buccal fat pad ¨ into buccinator.
- on middle third of line b/n intertragica notch of auricle and midpoint of philtrum.
- Palpable on a clenched masseter.
- Pierces buccinator ¨ beneath mucous membrane to open opposite 2nd upper molar
- With raised intraoral pressure, submucous part compressed ¨ prevents gland inflation.
Accessory Duct:
usually on masseter b/n duct and zygomatic arch; several ducts
from it to
parotid.
- it and duct lie on aponeurotic masseter.
Blood: ECA
branches; veins ¨ retromandibular
Lymph ¨
preauricular nodes in sheath ¨ nodes of
upper group of deep
cervical nodes
Nerves:
secretomotor from otic (via
auriculotemporal nerve)
- passes along mandibular neck, ascends behind TMJ at anteromedial gland surface
- preganglionics from inferior salivary nucleus of medulla via IX, tympanic branch ¨ tympanic plexus ¨ lesser petrosal nerve ¨ otic ganglion
- sympathetics via superior cervical ganglion by way of ECA and middle meningeal branch.
A groove appears in ectoderm of mouth pit ¨ tunnel from blind end cells proliferate ¨ the gland.
Most commonly a conservative approach for pleomorphic adenoma (keeping VII and branches)
- S-incision in front of ear Ð back to mastoid -> down and forward below mandible angle
- Retract gland forward from SCM ¨ expose posterior digastric, stylohyoid and EAM cartilage posteriorly.
- Approach VII along plane in front of anterior cartilage margin; trunk emerges from stylomastoid foramen, deep to jx of cartilaginous and bony EAM, 1cm above / medial to upper end of posterior belly digastric.
- Cartilage here has a slight arrow-head pointing to emerging trunk
- Stylomastoid branch of posterior auricular artery superficial to facial nerve (guides proximity)
- Follow VII into gland, remove tissue while preserving VIIÕs branches
Alternatively find a branch as it leaves gland, follow back to trunk and other branches
- marginal mandibular easy as superficial to retromandibular vein or anterior branch.
- Or a buccal branch.
Emerges through stylomastoid foramen
¨ posterior auricular nerve (to occipitofrontalis)
¨ muscular branch to posterior belly of digastric and stylohyoid
Branches before entering parotid into (1) upper temperozygomatic, and lower (2) cervicofacial.
Further plexiform branching within gland superficial to retromandibular vein and ECA.
(1) Temporal -->
frontalis; emerges 1cm in front of ear, just below zygomatic
arch; behind temporal branch lie the sup. temporal artery and
vein and more posteriorly is the auriculotemporal n.
(2) Zygomatic --> frontalis & orbicularis oculi
(paralysis prevents
blinking;
cornea
ulceration)' emerges 1cm below midpoint of zygomatic arch
(3) Buccal; buccinator, upper lip muscles;
emerges at midpoint of a line between tragus and angle of
mandible
(4) Marginal mandibular --> lower lip muscles. Exits at angle of mandible --> back into face anterior to masseter.
(5) Cervical --> platysma below angle of mandible