Anatomy of facial muscles

Question 1

how can you group the facial muscle?

generally where do they all originate from?

every muscle in the face receives innervation from?

Answer 1

into 3

1. orbital
2. nasal
3. oral

originate from bone

all innervated by the facial nerve

Question 2

how many muscles make up the orbital group?

name them

Answer 2

3

1. occipitofrontalis (frontalis contributes to this functional group)
2. orbicularis oculi
3. corrugator supercilli

Question 3

occipitofrontalis has a digastric structure, which 2 msucles make it up

action

branch of facial nerve that innervates both

arterial supply to frontalis

Answer 3

occipitalis (back of the head) and frontalis (forehead)

action: rasies eyebrows and wrinkles forehead

frontalis- temporal branch of the facial nerve

occipitalis- posterior auricular branch of facial nerve

supraorbital and supratrochlear arteries

Question 4

orbicularis ori is made of 3 muscles, which is the most important?

action

location

innervation

Answer 4

most important orbital orbicularis (+palpebral orbicularis, lacrimal orbicularis)

closes the eye (orbicularis does this under active effort) +controls tear pump

above eyelid

innervation is by the temporal and zygomatic branches of the facial nerve

Question 5

corrugator supercili

action

innervation

location

Answer 5

assists in wrinkling forehead// drawing eybrows downwards+ medially /// helps to guard from high light

Question 6

how many muscles make up the nasal group

what are they

Answer 6

3 muscles make up the nasal group

• nasalis
• procerus
• depressor septi nasi

Question 7

nasalis

action

location

Answer 7

the largest of the nasal muscles

its 2 components have 2 opposing functions: compressing the nares and opening them

they are the actual nostrils

Question 8

depressor septi nasi

action

Answer 8

assists nasalis in opening the nostrils by pulling inferiorly

Question 9

How many muscles make up the oral group

name them

Answer 9

2 muscles make up the oral group

orbicularis ori

buccinator

Question 10

orbicularis ori

action

buccinator

Answer 10

closes the oral cavity entrance pursing lips

buccinator- found between the mandible and maxilla

action- pulls cheeks inwards against the teeth, preventing accumulation of food in them

Question 11

• what are the motor components of the facial nerve
• sensory
• special sensory- which nerve carries this out
• parasympathetic

Answer 11

motor: muscles of facial expression, posterior belly of digastric (oral floor), stylohyoid and stapedius

sensory: small area of cutaneous tissue around the concha of the ear

special sensory: provides taste to the anterior 2/3 of the tongue via the chorda tympani

parasympathetic: many glands of head and neck, submandibular+ sublingual salivary, nsal, palatine and pharyngeal mucous and lacrimal glands

Question 12

which part of the brainstem does it originate?

Answer 12

Pontine-medulla junction

Question 13

the anatomical course of the facial nerve can be divided into an intracranial and extracranial course

describe the intial intracranial course

Answer 13

1. pons
2. internal acoustic meatus (opening in petrous bone)
3. facial canal (motor and sensory root fuse to form facial nerve –>nerve forms geniculate ganglion ///gives rise to 3 branches)
4. facial nerve exits the facial canal via the stylomastoid foramen (posterior to the styloid process of the temporal bone)

Question 14

what are the 3 branches of the facial nerve that arise in the facial canal

Answer 14

greater petrosal (para to mucous and lacrimal glands)

nerve to stapedius (middle ear)

chorda tympani (taste to ant 2/3 and submandicular and sublingual glands)

Question 15

what is the extracranial cours eof the facial nerve

Answer 15

• exits skull via the stylomastoid foramen
• turns superiorly to run anterior to the ear
• gives off 2 branches (post. auricular– motor around ear and motor to digastric and stylohyoid)
• main trunk of the nerve (motor root) continues anteriorly and inferiorly to the parotid gland but doesnt innervate it (the glossopharyngeal does
• terminates by splitting into 5 branches

Question 16

what are the 5 terminal motor branches of the facial nerve (hand and fingers over the face)

what are their functions

Answer 16

1. temporal- orbital muscles of face
2. zygomatic- orbicularis oculi
3. buccal- orbicularis oris, buccinator, corrugator supercili
4. marginal mandibular- depressor labii inferioris, depressor anguli oris, mentalis
5. cervical- platysma

Question 18

how will the motor, sensory and parasympathetic functions of the facial nerve be affected by an intracranial lesion? (proximal to stylomastoid foramen)

Question 19

how will the motor, sensory and parasympathetic functions of the facial nerve be affected by an extracranial lesion? (distal to stylomastoid foramen)

various causes:

Answer 19

only motor function affected

causes:

• parotid gland pathology–> e.g., tumour, parotitis, surgery
• infection of nerve- e.g., herpes
• compression during forceps delivery

Question 20

how does forehead sparing indicate whether Bell’s palsy is an upper or lower motor neurone lesion?

Answer 20

• the main msucle of the forehead is frontalis of occipito-frontalis
• frontalis is innervated by the temporal branch of the facial nerve
• prior to the nucleus of the facial nerve (geniculate ganglion) the nerve has 2 roots, one from either side of the brain

therefore if an UMN lesion occurs- this happens before the fusing of the roots so some motor function is still spared to frontalis via the contralateral input

a LMN would not spare the forehead as at this point both hemisphere’s input has fused into 1

Question 21

layers of the scalp

Answer 21

• S- skin- epidermis+dermis
• C- connective tissue- subcutaneous layer (neurovasculature) + nerves
• A- aponeurois
• L- Loose connective tissue
• P- Pericardium