Anatomy: Face and Parotid

How can the orbicularis oculi function be tested? What cranial nerve is this testing?

-*corneal blink reflex* - a test for CN V *trigeminal nerve* -sensory component is opthalmic division of CN V Motor component is facial nerve

What are some branches of the facial nerve?

-*geniculate ganglion* = SENSORY ganglion that lies at the genu (bend of the nerve*; ganglion contains cell bodies responsible for taste sensation from the anterior 2/3 of the tongue, Still inside the temporal bone at this point. [think you get the BENDS (genu) so you FEEL (sensory) really bad -> twist the muscles of your face in reaction (facial nerve)] -*greater petrosal nerve* = parasympathetic -*chorda tympani* - taste and parasympathetic -nerve passes first through the *internal acoustic meatus* in the temporal bone -> then part of facial nerve exits through the *stylomastoid foramen* [this makes sense because facial innervates stylomastoid muscle -> motor branches to facial muscles

The *parotid duct* aka Stensen's duct extends in which direction? what muscle does it pierce? In what location does it open into the mouth?

-*parotid duct* aka Stensen's duct extends anteriorly -> crosses the masseter muscle -> *pierces the buccinatory muscle* (deep to fat pad in the gross picture. This fat pad is what gives roundness to your cheeks!) -> then oral mucous membrane -> opens into mouth opposite the *second upper molar tooth* [think the parotid is the master gland -> makes the big BUXinator PAIRotid gland -> 2 -> SECOND upper molar]

What's an important parasympathetic function of CN VII related to the eye? What structure is responsible for this function?

-CN VII - tear production! This happens via *lacrimal glands* which receive parasympathetic innervation via CN VII. Lacrimal gland is on upper lateral portion of eye. It's constantly producing tears. Blink -> orbicularis oculi washes tears medially across the eyeball -> orbicularis oculi squeezes the lacrimal sac like the bulb of a pipette! (surrounded by lacrimal portion of orbicularis oculi muscle) -> lacrimal duct -> nasal cavity

where do the suprahyoid skeletal motor branches go?

post belly of digastric stylohyoid

What muscle in the ear does the facial nerve supply?

stapedius muscle in the middle ear [my FACE is beautiful and no one can STAP me]

Facial nerve motor distribution - muscles of facial expression

via To Zanzibar By Motor Car branches [Temporal, Zygomatic, Buccal, Mandibular, Cervical]

What nerve innervates the parotid gland?

CN IX glossopharyngeal! Postganglionic parasympathetic fibers arise in the *otic ganglion* [think OTIC goes to parOTID] amd reaches the gland via the auriculotemporal branch of V3

Why is lagophthalmos (inability to close eye) concerning?

eye tissues get dry and can become red/inflamed -> can lead to *corneal ulceration* aka open sore on cornea. This can result in loss of vision! -to avoid this you'll often tape the eye shut, patch, drops, etc

What are the ways that your eye can be closed via orbicularis oculi?

forcefully or gently!

Facial nerve taste distribution - how does it travel?

internal acoustic meatus -> geniculate ganglion -> chorda tympani -> joins up with lingual nerve (which ultimately distributes the taste fibers) -> taste of anterior 2/3 of tongue

Through what structure does the facial nerve course on its way to the face?

internal acoustic meatus of temporal bone

What are the functions of the following facial munscles: buccinator orbicularis oculi orbicularis oris

*buccinator* - pierced by parotid duct. Presses cheeks against teeth and prevent food from accumulating in that area during mastication. *orbicularis oculi* - closes eye *orbicularis oris* - closes eye [think ORIS -> ORIFICE -> most imp orifice is your mouth!]

Parotid gland completely surrounds main branches of what nerve?

*facial nerve*! -> big surgical challenge!

What are the parts of the orbicularis oculi?

*orbital* - orbits the eye *palpebral* - eyelid (think you PALPate your eyelids) *lacrimal* - near tear duct area, medial aspect, little deeper than where the L is in the pic -Orbital and palpebral portions work to close the eye! This is v imp for protection from light, dust, etc.

Background; What muscle does the gland lie superficial to? What is the gland enclosed in? The gland has superficial and deep portions - what cranial nerve runs between these portions?

-gland lies superficial to masseter muscle [think this is the biggest aka MASSETER gland - it goes on top of the masseter muscle!] -parotid gland is enclosed in tough fascial capsule -between the gland's superficial and deep parts runs the facial nerve.

Which is the largest of the three main salivary glands? Where is it located?

-parotid gland is the largest of the three main salivary glands (parotid, submandibular, and sublingual) -it is located between the ear and the mandible [para = near, otic = ear]

What are the three major functions of the facial nerve?

1) skeletal motor: a) muscles of facial expression b) posterior belly of digastric, stylohyoid, and stapedius 2) taste from anterior 2/3 of tongue 3) parasympathetic: lacrimal gland, salivary glands

What parasympathetic innervation does the facial nerve provide? How?

Parasympathetic innervation of CN VII 1) *greater petrosal nerve* -> *preganglionic parasympathetic axons for innervation of lacrimal gland* [think PETRA makes me CRY!] 2) *chorda tympani* - preganglionic parasymatphetic axons to reach the submandibular (along with the lingual branch of CN V - think CN V has a submandibular component) and salivary glands [think chorda tympani - ear - this nerve travels through the ear and gets down to the mouth - where it does taste and saliva production. Think you have 2 sticks with the tympani - two functions in the mouth. I was the FACE of the percussion section so this goes with facial nerve.]

The facial nerve emerges anteriorly from the parotid gland and goes to the muscles of facial expression. What are its five major branches?

Temporal Zygomatic Buccal Mandibular (marginal mandibular) Cervical [To Zanzibar By Motor Car]

What is sialoadenitis? What might cause it? What is sialolithiasis? What other pathologies are the parotid glands susceptible to?

These are all conditions that can cause an enlarged parotid gland! -Sialoadenitis = infection of salivary gland. Can be caused by *mumps* - a viral infection [mumps is an old term for lumps and bumps within the cheek] -Sialolithiasis = salivary gland stones. *calculi( within the duct system -> can result in sialoadenitis. -gland is also susceptible to benign and malignant tumors. Surgery (parotidectomy) to remove the parotid gland is not trivial since the facial nerve courses through the gland and may be damaged during surg. Facial paralysis is a major risk of parotidectomy.

gross pic of facial nerve entering internal acoustic meatus of temporal bone

[think about it spatially in terms of parotid gland]

what are some clinical tests you can do for facial nerve?

also remember side note - facial nerve innervates posterior belly of gastric and stylohyoid

what would you expect to see if orbicularis oculi is paralyzed (eg damage to a facial nerve)?

can't close eye! = *lagophthalmos* ->