Sensory nerves of the face (trigeminal nerve, CN V anatomy)

[Music] [Music] by a thing a little bit busy with models this week because since we've been talking about the face the last couple of weeks and we've been talking about the muscles of facial expression and the facial nerve cranial nerve seven that innovates those muscles of facial expression I thought really before we move on we should talk about the sensory aspects of the face because here we get to talk about cranial nerve five the trigeminal nerve and to do that I need lots of different models because lots of different models show lots of different things [Music] so the plan is to start from the brainstem very briefly and then talk about how the trigeminal nerve gets out of the skull and the trigeminal nerve has three major branches and you can think about those three major branches as then each having another three smaller branches which then have smaller branches that's how branching works right but then they innovate different regions of the face so we'll follow those nerves out we'll see where they go we'll talk about some of the four Aminah and talk about how those nerves get where they're going but the point would we'll get to is we'll be able to talk about branches of the trigeminal nerve innovating different regions of the face and why how you can test for that and then we'll talk about traveling around you all right now trigeminal think about the word right Gemini you know Gemini Gemini refers to the twins that constellation in the sky and it's a Latin word it refers to the Greek twins castor and Pollux so Gemini means twins so trigeminal or trigeminal or tri Gemini means triplets three born at the same time so that's all the trigeminal nerve is it just means three at the same time all right Triton cool see he's my brain model one always falls apart right it's take the blood vessels off his kidneys upside there I always want to turn over so it's the right way around but when I do that it's fine it's absolutely fine someone's left an earring there and right come on you got this the trigeminal nerve then is this large branch here in here on either side so you can see that it's kind of appearing more posterior than some of the other cranial nerves and it's it's quite a big one it's a big nerve now the reason the toy terminal nerve is a big nerve is that it's the major sensory nerve of the face and the scalp and of course your face is very sensitive you've got like really high resolution sensitivity in your lips in your eyes and yeah everywhere right so if you're gonna have a high resolution of sensitivity then you're gonna need a lot of neurons to carry the information from all of those sensory receptors so the the Troy geminal nerve cranial nerve 5 is a big nerve because it has a lot of neurons in there and in fact if we look at where it comes from so if we look within the brainstem so we've got Roo a midbrain pons medulla here it comes from mostly some very long somatic sensory nuclei which which extend through the midbrain sorry extend through the midbrain the pons the medulla and even into the upper parts of the spinal cord so it has a lot of nerve cell bodies in there and it does have a motor component as well it's motor to the muscles of mastication and it kind of live a bit so it has some motor nuclei in there as well but that's where trigeminal nerve 5 comes from that's where the cranial the cranial nerve comes out from if we grab big head big heads cool and big head to show us some of those muscles of mastication and the muscles of facial expression but if we if we turn big head around and we look inside the cranial cavity do you see where we are right this is where the pituitary gland would be there the internal carotid artery so this is the sphenoid bone here and this is this is the this is anterior here right so there that is the trigeminal nerve cranial nerve 5 this lump here is the trigeminal ganglion and from the trigeminal ganglion we then get these three branches of the trigeminal nerve these are the ophthalmic the maxillary and the mandibular branches the ophthalmic and maxillary branches are purely sensory and the mandibular is sensory and motor that's the one carrying the the motor fibers to the muscles of mastication now we can also so we can use some different nomenclature for these branches so we would write in Roman numerals CN v4 cranial nerve five and then for the first branch we might write CN v and then one in subscript and that would refer to the ophthalmic branch of the trigeminal nerve we could then write CN v two and that would be for the maxillary branch and then for the mandibular branch we could write CN v3 so you might see that as well and I refers to these three major branches and these three major branches go into three different regions of the face but they've got to get through the bones of the skull to get out of there now the ophthalmic branch is going to run into the orbit and between the orbit and this cranial fossa we have we have that slit we have the superior orbital fissure and that's where the OP family branch of the trigeminal nerve goes through those through the superior orbital fissure along with a lot of other nerves that are innovating the muscles of the orbit the new VI and so on so the Troy general nerve is the major sensory nerve of the face and by face I kind of mean this region here and it goes well the sensory innervation covers the scalp it doesn't go all the way back it covers the scalp and the top of the head to about there it covers the face on either side as far back as the the auricle the external ear and about the jawline and then it overlaps with the cervical plexus so cutaneous nerves from cervical spinal branches coming out of the spinal cord right spinal nerves the cervical plexus is an innovative skin kind of from the jaw line and down through the neck and then also posterior to the ear and the back of the head we'll talk about the dermatomes later moving but c2 and c3 kind of do that right so there's some overlap between the trigeminal nerve and the cervical plexus or cervical spinal nerves and of course like with most nerves most of these kind of areas overlap a little bit so it's a little bit different yeah the pictures you see might not be the same for everybody right I'm gonna I'm gonna bang into some detail and then pull back out again right now bang into some detail just to just to explain how where the nerves run and then we'll kind of like I'll do an overview now each of these three major branches of the trigeminal nerve they then split again generally described into three so the the ophthalmic nerve has passed into the orbit by going through the superior orbital fissure so it's now in the orbit and then it splits again it's gonna split into the frontal nerve the lacrimal nerve and the nazo ciliary nerve and those are gonna go to different places if we take the frontal nerve first the frontal yeah frontal bone frontal lobe frontal part the frontal nerve then is essentially going to come up here the frontal nerve is going to split into supra trot clear and supraorbital nerves now super orbitals fairly sensible right here's the orbit now up here there's a little groove sometimes it's a foramen sometimes it's a groove and this is where the supraorbital nerve it so it runs right through the orbit and then it gets through the bone here and pops out to run up into this region here it's okay innovate the frontal part of the scalp so that's the that's the super orbital branch of the ophthalmic branch and that's what we're seeing here all right but you can see there's another nerve right next to it that's the Supra trochlear nerve or the Supra trochlea branch of the ophthalmic branches geminal live Joey huh right so then and that's essentially go to the same place and doing the same thing and I'll explain why it's called super trochlear in a moment but then we've got the nazo ciliary nerve so that needs o ciliary branch of the ophthalmic branch of the trigeminal nerve sorry splits into anterior ethmoid 'el and posterior ethmoidal branches and into the infra trochlear nerve now the ethmoid bone is in the middle here right it's the medial wall of the orbit and it's also the upper part of the nasal cavity and the terminal branch of the inter sorry of the anterior ethmoid owner v' is the external nasal branch and what i'm saying is that that branch gets to the skin here in the middle of the nose right running the length of the nose so the nasal axillary nerve carries some sensory innervation from here now those other branches they go to the conjunctiva of the eye you know the the covering of the eye you know this yeah the like the lining the sensitive bit and they also some of those branches going to go into the nasal cavity and carry sensory innervation from the nasal mucosa now the reason that we have the super trochlea branch and the infra trochlea branch is we're in the eye right there is more anatomy per cubic centimeter in the orbit than anywhere else in the body so it's not my fault it is complicated now the eye we have a number of muscles the movie.i within the orbit these are the extra ocular muscles and most of them are straightforward own if you've looked at these before but that this muscle here so we have a muscle so this is the midline here this is lateral in the nose here but we have the superior oblique muscle and it does a bunch of things one of the things he does it kind of rotates the eye but anyway the superior oblique muscle is running this way and then it's passing through a pulley and then running back to the I the pulley is the drop clear that's that's what chocolate means is a pulling right so this trochlea is here in this part of the bone of the orbit so the super trochlear nerve runs superior to the trochlea the infra trochlear nerve is running inferior to the trochlea all right that's why they're named that way I'm sure so it makes a little bit more sense it's not completely mad we'll come back to the I in the future this hasn't got a lacrimal gland but you know the oh he has so the lacrimal glands up here right the lacrimal gland is up in the the superior lateral part of the orbit is what makes the tears then there the the third branch of the ophthalmic branch of the trigeminal nerve is the lacrimal nerve and the lacrimal nerve just runs across the orbit kind of ryan the orbit to get out to the lacrimal nerve here so it's going to carry sensory innervation from the lacrimal gland itself but it's also going to carry sensory innervation from you know the upper eyelid and the skin in this region over here now the other thing that the lacrimal nerve does is it carries postganglionic parasympathetic neurons to the lacrimal gland so those are the neurons that are motor to the lacrimal gland other words that switch it on and made the tears flow but they're not from cranial nerve five they're not from the trigeminal nerve they're from the facial nerve cranial nerve seven and those postganglionic parasympathetic neurons they're just running with the lacrimal gland to get over here because that nerves already go in that way right so don't get confused the sensory stuff from here is in Quay number five but the the nerve that makes you cry is the facial nerve I so in summary the ophthalmic branch of the trigeminal nerve gives off three branches which run up here to the upper eyelid to the conjunctiva reveai to the strip of skin on the nose here and to some of the nasal mucosa that's v1 all right okay now what about the maxillary branch of the trigeminal nerve II the second branch I forgot about bighead that's Fiat family branch of the trigeminal nerve that then is the maxillary branch here and you can see it dropping out through another bone in the skull so if that's the superior orbital fissure they're running through there then the hole next to it the nice round hole that's foramen rotundum and that's where the maxillary branch of the trigeminal nerve runs it gets out of the skull by passing through or rather gets out of the cranial cavity by passing through foramen rotundum and that pops out in kind of just a better see in there deep deep within the face in the maxillary level which is what you'd expect because that this bone is the maxilla this is the maxillary branch of the trigeminal nerve that's where it's supposed to go that's where it's supposed to do and this nerve the maxillary branch of the trigeminal nerve again splits into three branches we can see a couple of clues there's another right there's another forum in there if I put a pipe cleaner through you can see that it it actually pops out within the orbit and what happens here is there are three branches of the maxillary nerve and those are the zygomatic au facial the zygomatic o temporal and the infraorbital nerve we've got a super orbital nerve you can have an infraorbital nerve right this is then the infraorbital foramen and what happens is is that the these branches get back into the orbit by passing through the inferior orbital fissure and then they have to get out of the orbit again so the the infraorbital nerve pops out there so it gets into the maxillary region and innovates the skin of you know the lateral nose to magolor the upper teeth the upper lip that sort of region there and there's like a matakohe facial zygomatic a temple where this is the zygomatic bone here and the zygomatic au facial nerve there is there is a small zygomatic a facial foramen I can just see a little tiny eye indentation on this plastic skull here but pops out here and then the zygomatic Oh temple goes up here and there's a little there's a little again a little kind of firm suggestion of a foramen here so I go back to Cove temple no then get up into the temporal region so there's like a mask Oh Murali so there's I go matakohe facial should I feel where my face is so we go they have done still on the same side shouldn't I so there's the orbit there's the orbit right there's my zygomatic bone out here right the infraorbital nerve runs inferior to the orbit and innovates this region here the zygomatic own facial nerve kind of stays close to the orbit but over the zygomatic bone and the zygomatic Oh temporal actually gets into the temporal fossa so it stays quite deep here and then pops out and then innovates the skin over the kind of the anterior part of the temporal region here so zygomatic own facial zygomatic the temple so those are the three branches of the migratory branch of the trigeminal nerve and they innovate this space here right okay good really there's another bit so the maxillary branch of the trigeminal nerve actually has a short desire matic nerve and that runs across the orbit and then splits into the zygomatic au facial and zygomatic o temporal branches but is that helpful to remember there's a sinus under here right I'm caught on my corn skeleton they go ah let go what why oh right back off man [Applause] what was I talking about there's a sinus under the bone here and the maxillary sinus which is lying to the mucosa so the the second branch of the trigeminal nerve the maxillary nerve is also carrying sensory innervation from the magazine Reese is in that region as well it's it's common sense right okay so the third branch then of the trigeminal nerve is the mandibular branch and the mandibular branch is dropping down in fear it's going to drop down here to get to these guys so in the skull we see we see the oval foramen right so the oval foramen that's how the mandibular branch of the trigeminal nerve gets out you can see where it's popping over there so it's pretty deep in the face and again this is going to give off three branches as well kind of mm-hmm do this so it's like we're both on the same side the auricular temporal nerve so we're already deep to the mandible so the auricular temporal nerve is a nerve it's a branch of the mandibular branch of the trigeminal nerve that's deep to the ramus of the mandible it's deep to the parotid gland but it's going to find its way out to get up to this region here so the auricular temporal nerve is going to innervate the skin kind of around around here right so anterior to the external ear anterior theorical and kind of the posterior part of the temporal region but not on the top just kind of as far as that safley auricular temporal nerve and then we've got the buccal nerve and the buccal nerve is going to find this way out of the cheek in fact the other way we were talking about the branches of the facial nerve and there's a buccal branch of the facial nerve there isn't there now the buccal branch of the mandibular branch of the trigeminal nerve is sensory to the skin of the cheek and the oral mucosa on the other side and it will actually often join with the buccal branch of the facial nerve just because again these nerves are going to the same place so during development they just followed the same cues when they're together right wanna get mixed nurse so that's the buccal branch down there and then we have the mental nerve now the mental nerve well first of all we have the inferior alveolar nerve in the mandible down here there's this canal here right is this a real canal in this plastic no of course not so this is this is mandible this is the mandibular canal the inferior alveolar of alveolar nerve runs into here it's gonna carry all the sensory innervation back from the teeth and then the mental nerve is gonna pop out through this forum and here the mental foramen and innovate the the skin of the chain and the lower-left on what have you that's a lot of wiring that's probably way more information than most people need to know but what it boils down to is that the the first branch of the trigeminal nerve the a family branch innovates the skin of the scalp at the top of the head and the front here then the eyelids like that and also the conjunctiva of the unnies the second branch of the trigeminal nerve the maxillary nerve innervates the skin covering the maxilla the medial nose the upper lip and the skin beside the eye the lower eyelid part of the conjunctiva and the skin of the anterior temporal region and then the third branch of the trigeminal nerve the mandibular branch innovates the skin over the mandible and as far back as the the auricle the external ear and what's remaining of the temporal region and then if you remember that distribution then you can add on the teeth and the oral mucosa natural thing all right that's what it boils down to and that means that you can test the function in a patient by testing the different regions you can test the opthalmic so it's going on your skin but Mazdas got a skin by using some light cotton wool or maybe you want to test for ten what have you so you can test the first branch of the trigeminal nerve by testing sensation up here you can then test the the second branch of the trigeminal nerve by testing sensation around here and you can test the third branch by testing sensation down here and that's very that's very useful just as with the other nerves of the face these nerves are susceptible to trauma you know to lacerations to fractures of the bone and that sort of thing to also susceptible to tumor and what-have-you as well there is a there is a condition of somewhat peculiar to the trigeminal nerve which is 20 mm long year round year and in trigeminal neuralgia a patient might get like a sudden excruciating pain if either one region of the face innovated by one branch of the trigeminal nerve or more than one and it can be random or they might have realized that there's a trigger point if if something touches that part of their face it kicks off this this inappropriate pain response from that region of the face and this trigeminal neuralgia is usually caused by either one of those three main branches or maybe a little bit early but often one of those three main branches has been damaged either by a tumor or a blood vessel and then we get this spontaneous switching on of that branch of the trigeminal nerve completely inappropriately by something we're saying causes a lot of pain it can be treated somewhat pharmacologically but it can be very difficult to treat and surgical options are difficult somewhat extreme but there are some you know a lot of very skilled surgeons out there who know far more about this than only do I want my thinking about dermatomes then there aren't you know there aren't dermatomes in the traditional sense where we have the dermatome pattern are they so nerves from a certain spinal level running pretty peripherally from the spinal cord out of different regions of the body we'll know that um different patches of skin are innervated by nerves from different spinal levels right we can use that dermatome map to diagnose what we think might be going on on a patient and that's a little bit different in the head because most of this is innovated by cranial nerves not a spinal nerves but essentially then if you have a dermatome map this would be v1 and then this would be v2 and then this would be v3 and as we get back to the ear then the skin around here is innovated by c2 nerves and then further down the next III and c4 there isn't a dermatome fur for the c1 spinal level and the one final thing to consider when we're talking about the trigeminal nerve is of course the corneal reflex so we saw that these nerves are innovating the the conjunctiva the the covering sensitive covering of the eyeball so with with touch or pressure or temperature or you know the trigeminal nerve then is carrying the sensory afferent lymph that reflex is carrying the sensory information back to the brain stem and then the reflex relay then triggers the facial nerve cranial nerve seven which we were looking at in recent weeks to cause orbicularis oculi to close and protect the eye so that's the reflex there Craig another five sensory cranial nerve seven motor but uh-oh blimey that was that was a lot of information if I'm if I'm clever I'll edit that down into something here concise and useful but hey there's just there's just a lot of anatomy in the head and neck so I mean I thought it was used for the read we finished that off because we've talked about the muscles of facial expression we've talked about the muscles of mastication in the past we talked about the tongue we'll talk about all sorts of bits of the face and we've probably mentioned that the trigeminal nerve is sensory to the faces having their detail on top let's you work out so much like the important things are the three main branches but there's other little nerves and the spaces they run through it's not just interesting and it's important because you know the orbit affects so much right if you've got my information in the back of your head even if you don't remember it all then you might be able to draw without pull it back when you need it when you're trying to work out what the heck is going on in this person's head right Oh see you guys next week [Music]

Channel: Sam Webster

Views: 98,130

Keywords: human anatomy, anatomy, trigeminal nerve, CN V, face, mandibular nerve, maxillary nerve, ophthalmic nerve, opthalmic, zygomaticofacial, zygomaticotemporal, supratrochlear, infratrochlear, infra orbital, supra orbital, mental, CN V1, CN V2, CN V3, Sam Webster, dontbeasalmon, Swansea

Id: Di-Qej7-w04

Length: 27min 32sec (1652 seconds)

Published: Tue Apr 24 2018