Face LO - Muscles of Facial Expression

hi let's talk about the muscles of facial  expression in this video we'll discuss the  

various groups of facial muscles how they're  distributed about the face their functions and  

their innovations so the superficial muscles  of the head are divided into two groups the  

epicranial muscles are those muscles which are  upon the cranium and the cranial facial muscles  

are those muscles of the cranium but associated  with the face the cranial facial muscles can  

be grouped according to the orifice that they  control so for instance surrounding the orbit  

and palpebral fissures are the circum orbital and  palpebral muscles surrounding the nares and nose  

are the nasal muscles and surrounding the oral fissure so the the labia and the buccal or cheek  

regions are the bucco labial muscles so let's take  this group by group so the epic cranial muscles  

are more diverse than what will be discussed here but the major epic cranial muscle is the occipitofrontalis

muscle so occipital occipital frontalis frontal so those are the two bones that  

these muscles are going to attach to so we can  conceptualize the occipital frontalis muscle  

as one large muscle with two bellies a frontal  belly and an occipital belly with a large epi

cranial aponeurosis between the two or we can  conceptualize them as two separate muscles the  

frontalis and the occipital for the purposes of  this video we'll treat them as the same muscle  

with different innervations so when active the  occipitofrontalis muscle is going to elevate  

the brow so it gives this look of surprise perhaps  slight condescension depending on how you want to  

mix and match this so the the greatest amount of  movement in expression here is generated by that  

frontal belly that frontal belly is innervated  by temporal branches of the facial nerve and  

posterior to that frontal belly we have a very  large and robust epicranial aponeurosis which  

we can also see here as well this can be very  very extensive the occipital belly is usually  

smaller than the frontal belly and we can see  that here and typically on cadaveric specimens  

it might be very hard to see it tends to atrophy  and go through a process of fibrosis with age so  

if you don't see a very well-developed occipital  belly of occipitofrontalis it's not the end  

of the world it's probably quite typical the  interesting thing is that that occipital belly  

is innervated by a different set of branches  versus the frontal belly so that occipital  

belly is innervated by an occipital branch of the  posterior auricular nerve of the facial nerve so  

that's that nerve that comes out of the stylomastoid foramen heading back that way so  

it's going to innervate the occipital belly it's  also going to innervate the posterior auricular  

and sometimes even the superior auricular nerve  but oftentimes that is dual innervation between  

the occipital branch and those temporal branches  moving on to the craniofacial group let's start  

superiorly and work our way down orbicularis oculi  so orbicularis oculi let's let's break that down  

muscles can be named a variety of ways sometimes  they're named for their attachments or the regions  

that they over lie sometimes they're named for  the direction of the they're muscle fibers or  

they're fascicles and in this case it's it's a  little bit of that and a little bit of regional  

so orbicularis means that the muscle fibers are  arranged in a circular fashion like so and oculi  

refers to the eye so this is the muscle with  circularly arranged fibers that overlies the  

eye and there are three parts to it there's the  orbital part the orbital part is the largest part  

of orbicularis oculi that would be everything  between these two circles that i've drawn that  

orbital part is what voluntarily and forcefully  closes the palpebral fissure the palpebral part  

that would be everything within that almond shape  area that I've prescribed overlies the palpebrae  

so that was very well named in the palpebral part  is voluntarily controllable but typically is under  

involuntary control so blinking is a function  of the palpebral part you don't spend most of  

your day thinking time to lubricate the eyes so we  have that going for us there's also a third part  

of this muscle which lies deep here in the medial  area by the medial angle of the eye called the  

lacrimal part and this is overlying the lacrimal  apparatus so as to squeeze it to create pressure  

to draw tears across the eye now all parts of  this muscle are innervated by both temporal and  

zygomatic branches of the facial nerve so one of  the landmarks that I use is that lateral canthus  

so we'll have temporal branches above and somatic  branches below now deep to orbicularis oculi and  

also deep to the frontal belly of occipital  frontal assess a small strip of muscle called  

the corrugator supercilii corrugator supersilii so this is the superciliary region and  

corrugator to make corrugated this is a furrow  of the brow so when this muscle contracts  

like so it pulls the brow together this is an  action that people will take involuntarily when  

they are confronted with a bright light so this  this can be paired with squinting so along with  

orbicularis oculi you can contract the corrugator  supercilii so as to provide your eyes a  

little bit more shade this is also something  that sometimes involuntarily gets gets paired  

with a disdainful feeling that you might have for  a foreign individual considering this photograph  

was taken indoors obviously this this person is  acting but this this kind of looks like perhaps  

the recipient of the gaze is in a little bit of  trouble corrugator supercilii is innervated  

by temporal branches of the facial nerve so  everything above there would head that way

next up the buccolabial muscles so we're going to  skip over the the nasal muscles ever so briefly to  

to turn our attention to those muscles that  are associated with the the oral fissure so  

there are several here and one of them is going  to be in that nasal group and we'll come back to  

this one this is one of my favorite muscles the  Levator labii superioris alaeque nasi

but let's begin with this muscle here levator labii superioris levator labii superioris is just  

inferior to orbicularis oculi and it's going to  the the superior lip or the upper lip and when  

levator labii superioris muscles in tandem so let's  say we had both of these firing at the same time  

that is going to elevate the upper lip hence the  name we also have moving lateral zygomaticus minor  

zygomaticus minor is over the zygomatic bone and  there are two of these and so the smaller of the  

two gets the name minor zygomaticus minor when  it fires is going to pull the lip superiorly and  

laterally so we have kind of a an oblique vector  there and it is going to uncover the teeth to  

about the canine so there is let's see central  incisor lateral incisor canine it just barely  

bares the canine sometimes the zygomaticus minor  is present sometimes it's absent sometimes it  

can be indistinguishable from zygomaticus major so  those two muscles can can go together nevertheless  

you know if it's they're wonderful if it's not  it's not the end of the world moving laterally  

we have the zygomaticus major zygomaticus major is  overlying the zygoma or the zygomatic bone and is  

larger than the minor we can see here that both  of these muscles are coming down to participate  

in the modeolus that's that inner digitation  of fibro muscular tissues that is controlling the  

angle of the mouth so what we have are a series  of muscles that are going to contribute to an  

for a widening smile so levator labii superioris  elevates the lip zygomaticus minor is going to  

expose to the canine zygomaticus major is going to  go beyond the canine as we can see there so when  

used in sequence we have an ever widening smile  so how wonderful they're all compliments of what  

these muscles do to the upper lip and that modeolus controlled the modeolus and you control  

the mouth these three muscles are all innervated  by both zygomatic and a buccal branches of the  

facial nerve so zygomatic and buccal branches  of the facial nerve deep to these muscles along  

with leveator labii superioris alaeque nasi  is that in for orbital or canine facial space

the muscle of oral fisher facial expression is  going to be orbicularis Oris this this is the  

money muscle in terms of social media photography  so orbicularis those circularly shaped fibers

oris of the oral Fisher would be this muscle  here so this will be deep too and surrounding deep to the skin of and surrounding the superior and  inferior lips and when contracted this purses the  

lips so if you think about that that full lipped  ducky face that people make when they they take  

selfies that's that's compliments of orbicularis  Oris and orbicularis Oris is innervated by buccal  

branches so we've got buccal branches coming  across and marginal mandibular branch of the  

facial nerve next up the Buccinator muscle  the Buccinator muscle is the deepest of all  

of the facial muscles here so it's originating or  attaching to that pterygomandibular raphe and  

it comes and it is going to attach to the alveolar  surfaces or ridges surrounding both the maxillary  

and mandibular teeth so this is really forming the  the muscular wall of the cheek when contracted the  

Buccinator muscle is going to push anything in  the oral vestibule and deep so that's going to  

bring food into the occlusal surfaces or between  the occlusal surfaces of maxillary and mandibular  

teeth for for eating which is a nice thing to do  right it's it's helping the muscles of mastication  

by bringing the items to be masticated between  the teeth the buccinator muscle is interesting  

in that it is pierced by the parotid duct and  superficial to it we have a very robust and  

nice buccal fat pad so we can see that buccal  fat pad here in the cadaveric you mentioned we  

can see the parotid duct moving across and then  diving deep into what would be the buccal facial  

space so that buccofacial space is traversed by  Stetsons duct or the parotid duct coming through this  

space is the buccal branch of v3 so the maxillary  division of the tripe I'm sorry the mandibular  

division of the trigeminal nerve sends the buccal  nerve anteriorly through this space - apparently  

serve the the skin of the cheek and also some of  the the gingiva surrounding the the molars very  

frequently this this buccal nerve is referred to  as the long buccal nerve by clinicians now we also  

have a couple of other muscles controlling the  the oral fissure life can't be all smiles and so  

well in this case we're not done smiling deep  to the labii superioris is the so here we  

have that limit or labii superioris is the levator anguli oris so here coming from the modeolus

up to the maxilla deep to levator labii superioris  is a levator anguli horas it's an elevator of  

the angle of the mouth so it's enabling a smile  this muscle is innervated by buccal branches of  

the facial nerve as it should be for that region  we also have a highly variable muscle the risorius muscle risorius muscle may be present it  may not be present it goes from the Modeolus

out laterally superficial to that buccofacial  space and when it's activated it pulls the sides  

of or the angles of the mouth laterally so as to  produce a smirk and like levator anguli oris

risorius is also innervated by buccal branches  of the facial nerve now some of the the frowny  

muscles let's start with depressor anguli oris  depressor anguli oris is originating from that or  

I should say attaching to the Modi olace and going  down to the mandible there depressor depresses  

the angle of the mouth so it pulls the angle of  the mouth inferior laterally and this muscle is  

innervated by both buccal branches of the facial  nerve as well as the marginal mandibular branch  

of the facial nerve we also have depressor  labia inferioris depressor labia inferioris muscle tends to be deep to depressor anguli  oris and this muscle when working in concert with  

its counterpart is going to depress the lower  lip so to pull it downwards we also have the  

mentalis muscle the mentalis muscle is in the  mental or that shin region and when active the  

mentalis muscle is going to produce a pelt by both  elevating and protruding the skin of the chin so  

by pulling this chin skin upwards it displaces  the lower lip to produce the pout and mentalis  

is innervated much the same way depressor late  valium for yours is by the marginal mandibular  

branch of facial now the the nasal muscles  starting with one of my favorite facial muscles  

the levator labii superioris alaeque nasi so let  me trace this muscle for you this is going to blow  

your mind so levator labii superioris it's  going to elevate the superior lip which it does  

and there's also this little slip of muscle that  goes to the ala or the wing of the nose that's  

the area above the nostril so elevates the upper  lip and also the wing of the nose so Levator

labii superioris alaeque nasi is  going to dilate the nostril and elevate the upper  

lip so I kind of think of this as kind of like  the the Elvis snarl if you're familiar with the  

King of Pop and this muscle is the longest named  muscle of any human muscle so if you're ever at  

trivia night and you're asked what the longest  name of any muscle is in the human body it's  

levator labii superioris alaeque nasi which is  innervated by both zygomatic and buccal branches  

of the facial nerve next up we have the nasalis muscle the nasalis or just the nasal  

muscle has two parts to it sometimes these  parts are given their own muscle name so we  

have one part the transverse part that is over  the body of the nose here so running along the  

bridge of the nose down laterally now when that  contracts it actually constricts the Naris and  

so that transverse part when given its own name is  called the compressor Naris there's also another  

part from the alar region that when it contracts  it pulls the alar region outwards that's the  

alar part also known as dilator naris so compressor  narrows and dilator naris are antagonistic to one  

another and both are innervated by zygomatic and  buccal branches of seven which makes sense and  

this leads us to our assessment question and  that would be which muscle may both elevate  

the upper lip and dilate the Naris so elevate the  upper lip and dilate the Naris let's see levator

angularis oris that's going to pull the modeolus superolaterally so that's a smiley muscle it's  

not really an elevator of the upper lip though so  Levator superiois that definitely  

elevates the upper lip but it doesn't touch the  Narus levator labii superioris aleque nasi

yeah we've got it zygomaticus major and minor  are both smile muscles so they're pulling the Modeolus

superior laterally they're not the correct  answer so the muscle with the longest name Levator

labii superioris alaeque nasi is the  correct answer thank you very much for your time