Full transcript
0:06I'm engineers in this video we're going
0:09to talk about the external ear in the
0:10middle ear the reason why we want to
0:11talk about this is before we start going
0:13into all the inner ear stuff talking
0:16about the cochlea and the vestibule and
0:18the semicircular canals and how airwaves
0:21or some sorry sound waves can actually
0:22get converted into certain electrical
0:24potentials and then be perceived in
0:25certain ways I want to make sure that we
0:27really have a good understanding of the
0:29external ear and the middle ear because
0:31they're going to play a crucial role
0:32into understanding how these auditory
0:34pathways and these distribute the
0:35pathways occur all right so let's go
0:37ahead and dive into the anatomy of the
0:38external in middle ear so first things
0:41first how are we going to look at lobby
0:42structures so if you real quickly I'm
0:44going to draw here a quick little crude
0:45diagram here imagine here's the skull
0:47okay imagine here I put like the sella
0:50turcica of the sphenoid bone and I can
0:52separate this into an anterior cranial
0:54fossa I'll separate into a middle
0:56cranial fossa and then I have a
0:57posterior cranial fossa so with the
0:59framing magum they're right and if you
1:00want you have your crista galli right
1:02here with the cribriform plate of the
1:03ethmoid bone all that stuff right there
1:05right then if we come over here you'll
1:08have the external acoustic meatus with
1:11the ear right and over here you'll have
1:15a external acoustic meatus with the ear
1:18what I'm going to take a look at is
1:20we're going to look at some of the
1:21structures here off the external ear and
1:22we're going to take a look at this end
1:24external acoustic meatus and then what
1:27we're going to do is there's going to be
1:28this separating structure here that
1:30we're going to take a look at a lot
1:32pretty much most of the videos going to
1:33be about this and it's going to be on
1:35this middle ear we're going to take a
1:37look at it in a box diagram because it's
1:38the easiest way to see the middle ear so
1:40what we're going to start off with is
1:41we're going to start first off talking
1:43about what the external ear not too much
1:46to talk about what we'll discuss some
1:48things but then we're going to spend
1:49most of our time looking at the middle
1:50ear and again we're going to look at it
1:52and what's called a box diagram form
1:54because it's going to make it the
1:55easiest to see okay and easiest for me
1:58to draw here alright so let's go ahead
2:00and start that so first off let's come
2:02over here I know we have a lot of
2:04diagrams here pre John but don't worry
2:05we'll go over everything because just
2:07click on the video don't worry didn't
2:09miss anything
2:09okay so starting off here we're going to
2:11talk about the external ear okay so
2:15external your biggest thing here you see
2:17how you see this big old flap here
2:19coming out this sucker right here that
2:20I'm flicking on right now I'm holding
2:22and moving around you notice how I'm
2:24able to move it around a lot right it's
2:26able to be stretched and go back to its
2:28normal shape right I'm able to move it
2:30around bend it what's the reason for
2:32that
2:32well first off what do we call this part
2:34here not only we call it you know two
2:36things you can call it the Oracle or you
2:40can call it the pin up now what's really
2:43interesting about the Oracle or the pin
2:45up is obviously the outer part of it is
2:47the skin is supplied with what's called
2:49it's actually covered with stratified
2:51squamous epithelia tissue to resist
2:53against friction and abrasion but
2:55underneath that it's primarily made up
2:58of a special cartilage called elastic
3:01cartilage and the reason why I'm
3:02mentioning this because there isn't too
3:04many places in the body that are
3:05actually consisting of elastic cartilage
3:07one is going to be the ear the external
3:10part of the ear the ORAC or the pinna
3:11and the other one is that the glottis
3:12and again the purpose of is lots for it
3:14to be able to be very very able to
3:17stretch but recoil back to its normal
3:18position okay so that's one of the
3:20really really cool things about that all
3:22right sweet nothing much
3:24other than that about the external ear
3:26this outer part here now the next thing
3:28is as we go in to the actual external so
3:33we come from the work or the pinna and
3:34we move into this hole right outside of
3:37it right there's going to be a hole
3:38right side let's go on outside at solo
3:39skull and this is going to be called the
3:41external acoustic meatus so this is
3:45called the external acoustic meatus this
3:47little canal right here that I'm kind of
3:48putting the outlines here in green the
3:53external acoustic meatus is a little
3:55bony canal and inside of this canal
3:58you're going to have some first off the
3:59inner part of it Discoverer would like
4:01some stratified squamous epithelia
4:02tissue right but another thing that's
4:05really important about this is that we
4:07have these things called sera - Glantz
4:09okay we have these things here called
4:12cerumen it's clean and serene - glands
4:14are basically like mat modified apocrine
4:17glands basically they're like modified
4:19apocrine glands and they can produce
4:23a substance called serum on which all of
4:26you probably commonly know as earwax
4:30okay so these guys are producing earwax
4:32serum in which is kind of coating the
4:34inner part of the ear now what is
4:36important about this the importance of
4:39this serum aunt is to be able to deter
4:41insects believe it or not so again what
4:43do these glands here called they're
4:45called sera - clams okay and these
4:50cerumen exclaims are producing serum n
4:52or we know it as earwax and the purpose
4:57of this earwax is to deter certain
5:00insects now some of you might know is
5:02you stick a q-tip in there you pull out
5:03some of that earwax right but you have
5:05to be careful why because you've
5:07probably been told by your mother or
5:08some other person don't ever stick that
5:10q-tip really far down because at the end
5:13of the external acoustic meatus there's
5:16a really really important structure it's
5:20called the tympanic membrane the
5:22tympanic membrane is a very very
5:24important membrane it's a connective
5:26tissue membrane we'll talk about a
5:27little bit more here in just a second we
5:28have the diagram up there to show it but
5:31this pink structure that I'm here is
5:33separating the external ear from the
5:35middle ear this is the tympanic membrane
5:38so that's kind of nice separating
5:39structures so what is this pink thing
5:41they're called it's called the tympanic
5:44membrane and like I said it's actually
5:47made up of two components one component
5:49is called the pars
5:51tensa which is a very very very heavily
5:55dense fibrous irregular connective
5:57tissue we'll talk about that one okay so
5:59this is the dense connective tissue and
6:02particularly it's irregular because it's
6:04in different bundles or arrangements
6:06okay the other one is called the pars
6:10flacid ah don't be thinking about
6:13flaccid other things okay just think
6:14about parse platta what it means is it's
6:16loose okay it's loose and in this case
6:20it's actually made up of a loose
6:21connective tissue particularly areolar
6:24connective tissue the reason why I'm
6:27telling you this that it's actually made
6:28up of two different types is that if you
6:30go and stick the ear q-tip into the ear
6:32and you actually hit the PAR slice of it
6:34too hard you can puncture the tympanic
6:36and that would affect the actual middle
6:38ear pressure as well as a lot of other
6:40structures open up for certain types of
6:42microbes to come in okay all right so
6:45cool so what do we have so far for the
6:47external ear we have the Oracle of the
6:49pinna which is made above elastic
6:51cartilage okay last word to be able to
6:53kind of be stretchable and to be able to
6:55be stretched but always loans to reclone
6:57go back to its normal position right
6:59external ear is also going to consist of
7:01some anise glands which are producing
7:02serum in earwax that are basically
7:05lining encoding the external acoustic
7:06meatus to provide it with a substance
7:09that can deter the insects remember the
7:11sarunas glands are modified African
7:13glance then this bony canal the external
7:17acoustic meatus it gets to this end
7:18point here which separates the external
7:20ear from the middle ear and that pink
7:22membrane is called the tympanic membrane
7:24and the tympanic membrane is a
7:25connective tissue membrane two parts of
7:28it once called the pars tenza which is
7:30made up of a dense irregular connective
7:31tissue that's the inferior part of it
7:33usually if I were to kind of make a
7:34little cut off here usually the actual
7:38part right here that I separate anything
7:40below from this point here to this point
7:42is the pars
7:43tensa usually up here in the top from
7:46this point to this point is the parse
7:48flaccid ax and it's a looser type of
7:50tissue and what kind areolar connective
7:52tissue so now let's imagine that I'm
7:56going to look down the ear okay I'm
7:58going to take on it I want to take it
7:59I'm going to look down this extra
8:01acoustic meatus so I'm going to I'm
8:02going to take and shine a light down
8:04this area so let's pretend I try to draw
8:06a light don't you dare laugh at me I'm
8:08going to take here I'm going to have a
8:09light here and I'm going to shine some
8:13light into this person's eye I'm sorry
8:17none to their eye their ear
8:18okay and I'm going to look down the
8:20external acoustic meatus to the mechanic
8:22membrane when I look at that this is
8:24what I see might not be beautifully as
8:26as as you would normally see it but this
8:29is what you're going to kind of see here
8:30with the tympanic membrane now what we
8:33see here is I see a couple different
8:36things you can actually kind of see an
8:38outline here you see this kind of the
8:39structure here in blue am an outline
8:41right here is actually an obstacle it's
8:43one of the little bones and you can kind
8:46of see a little outlining of it there
8:47what is this bone here call that bone
8:50is called malleus it's actually called
8:54malleus it's one of the ossicles okay
8:56it's one of the three obstacles within
8:57the actual middle ear cavity so you can
8:59kind of see like a little bit of an
9:00outlining of the malleus then you can
9:04kind of see these little folds these
9:05little cold here coming inwards like
9:07this and then another full coming inward
9:09like this okay so this is actually
9:11called since as fold as close to the
9:13malleus it's an anterior mal your fold
9:15and this is the posterior fold we're not
9:17going to actually write these down
9:18they're not significantly important but
9:20again just kind of giving you an idea
9:21here this is the anterior mal your fold
9:23which is come on this side so this would
9:25be the anterior side here there should
9:26be the posterior side of the tympanic
9:28cavity okay
9:29and again it's the answer now your full
9:31posterior malleable and kind of
9:32outlining of the malleus then at the
9:35bottom part this is important here
9:38connecting to the bottom part of the
9:39malleus is a muscle and this muscle is
9:42called the tensor 10 PI tensor tympani
9:49right the tents are campaña we talked
9:50about this muscle if you guys watch the
9:53video on the trigeminal nerve
9:55remember the trigeminal nerve actually
9:56gives off a branch of supplies the
9:58tensor tympani which tenses up to
9:59tympanic membrane we didn't really talk
10:01about the mechanism we will in this
10:03video but we'll say that what happens is
10:05this tensor tympani is innervated by the
10:07trigeminal nerve specifically the
10:09mandibular division okay of the
10:11trigeminal nerve v3 okay and that's
10:14connected to that part then remember we
10:16said we had the parcel acidy and the
10:17pars tensor this right here that's all
10:20in this really really dark shade of
10:21green it's pretty much very very dark it
10:23looked heavily connective tissue lives
10:26right this right here is going to be the
10:28pars
10:30tensa okay that's the pars tense up
10:34which is this really really dark
10:35connective tissue and this is the only
10:37reason we mentioned the malar folds the
10:39anterior malar folds and the posterior
10:41folds are kind of separating the pars
10:43tensa and the parse Placido so all this
10:46loose connective tissues I'm kind of
10:47just drawing like scattered this is the
10:49pars
10:52philosopher okay alright so what have we
10:56covered so far then we've covered
10:57external year with Oracle in the pinna
10:59we covered the external acoustic meatus
11:01the cerumen is glands we covered the
11:03tympanic membrane which is consisting of
11:05the pars flat set up and the pars tenza
11:07are tense as dense connective tissue
11:09irregular parcel acid is areolar we also
11:12said that you can kind of see whenever
11:14you're looking down the ear canal you
11:15can actually see that it's nice of
11:17separation here by the post hearing and
11:19tear mal your folds which are separating
11:21the power sensor from the parcel acid up
11:23and then we also said that you kind of
11:25see like an outline here of the malleus
11:26and you'll see a muscle here connecting
11:28called the tensor campaña which is
11:30innervated by what cranial nerve the
11:33fifth cranial nerve particularly
11:35mandibular division so v3 of cranial
11:38nerve five okay sweet thank and deal so
11:44we covered the external here now let's
11:47go ahead and take a look even deeper now
11:48okay so now we're going to take a look
11:50even deeper and we're going to start
11:51getting into this cavity here we're
11:53going to start looking into the actual
11:54tympanic cavity or the middle ear okay
11:58so I just want to take a little pause
11:59here because I wanted to write down what
12:00we're going to talk about cause we're
12:01gonna talk about a lot of stuff so I
12:03want to make sure that we cover every
12:04single piece of it so just kind of wrote
12:05down a list of what I want to talk about
12:06alright so the first thing we're going
12:08to talk about is ossicles okay so
12:11obstacles there's three little obstacles
12:13located within the actual middle ear or
12:15the tympanic cavity okay what are those
12:19obstacles and what are the Nausicaa
12:20ossicles just tiny little bones so what
12:22we're doing here is we're taking a look
12:24at the middle ear and this is actually
12:26going to be kind of looking at it I'm
12:27removed I removed out the anterior wall
12:31of the middle ear okay so you can't see
12:33the anterior wall of the middle ear I
12:34removed it out and what we're looking at
12:36here is we're looking at a couple
12:37different bones all right this first one
12:39here that I'm kind of like highlighting
12:41already said that remember if I'm
12:42looking here I'm shining a light
12:43remember here was the light I'm shining
12:46a light here okay I'm looking I see the
12:50tympanic membrane what bone that I kind
12:51of see the outline of the malleus so
12:54what would this bone here be this would
12:55be malleus and then for the sake of it
12:59what is that muscle that is connecting
13:01right here to the malleus right here and
13:04it's actually kind of moving
13:05upwards like this it actually is a
13:07really long kind of muscle here it
13:09actually moves all the way up over here
13:11okay this is that muscle right there
13:13this is what muscle is this call this is
13:15called the tensor tympani right because
13:21whenever the crane on our five the
13:22mandibular division innovates this nerve
13:24this muscle contracts and it pulls the
13:26malleus medially okay away from the
13:29tympanic membrane okay and basically
13:31what that does is it tenses up the
13:33tympanic membrane to prevent that
13:35excessive compression and decompression
13:37okay to dampen some of the sound waves
13:40all right sweet so now the malleus is
13:43connected to this next little obstacle
13:45through the next double joint here what
13:46is this muscle I'm sorry what is this
13:48bone here called this obstacle that I'm
13:50highlighting right here so malleus kind
13:53of means like a mallet so imagine here
13:54I'm taking like a mallet and I'm
13:56smacking into like a nice little like
13:58anvil okay they actually disrupt the
14:01thought of look like an anvil so they
14:02just called this incus okay so you have
14:07malleus then you have incus then incus
14:10is connected through a nice little joint
14:12down here to this next bone and this
14:15bone looks like the stirrups like if you
14:17ever get onto a horse it kind of looks
14:19like this imagine here is the actual
14:22state piece this is the stay piece and
14:24they said it kind of look like a stirrup
14:26okay that you can kind of stick your
14:27feet in this right like a nice little
14:30stir up they call this bone here state
14:32these okay this is called state Peas so
14:35what does this bone right here called
14:36this one is called stay peas why am i
14:40mentioning all of these bones the reason
14:43why is it's going to lead right into
14:44when we talk about how sound waves can
14:48actually produce action potentials
14:50within the inner ear and then we can
14:52actually consciously perceive those
14:53sounds so it's amazing we can take sound
14:55waves turn them into action potentials
14:58electrical stimuli and send that
15:00information up to the brain to perceive
15:02so what happens is I'm not going to go
15:05into the whole detail here because we'll
15:06talk about it again later but what
15:07happens is let's say that these are the
15:09sound waves and sound waves are
15:11basically sine waves okay so they're
15:13sine waves they have ups and downs and
15:15ups and downs clefts and troughs right
15:16and what happens is these sine waves are
15:19sound waves are hitting the tympanic
15:20membrane and when that hits the tympanic
15:22membrane it vibrates these little
15:25ossicles and which ones it will valu
15:27vibrate in order it will vibrate malleus
15:30then that will actually hit on the incus
15:32and vibrate incus and then incus will
15:35actually push on stay peas and scabies
15:37is actually anchored on one end actually
15:40it's actually anchored on a posterior
15:41end and the only thing that's hitting it
15:42at the anterior end but just imagine it
15:44tapping on this window right there it's
15:47tapping on the window saying hey I got
15:49some sound waves for you and again past
15:51this point here would be the inner ear
15:53okay like the cochlea alright so what is
15:57this structure right here called
15:59this structure here is called the oval
16:03window okay so from medial side here
16:08this is the medial side and this is the
16:12lateral side I'm sorry I lied this is
16:14the lateral side because it's toward the
16:15external ear and this is the medial side
16:19okay guys this is toward the inner ear
16:23alright now what happens is sound waves
16:26are coming from the external acoustic
16:27meatus they hit on the panick membrane
16:29vibrate the obstacles in order malleus
16:31incus stapes and stabies taps on the
16:34oval window whence tapie's taps on the
16:36oval window he'll take this mechanical
16:39stimuli and it will create fluid filled
16:41vibrations within the actual structure
16:44called the cochlea which will eventually
16:45get converted into action potentials and
16:47sent by the cochlear nerve of the
16:49cochlear branch of the vestibular
16:51cochlear nerve to the brain stem we'll
16:54talk about that when we get to the inner
16:55ear okay so that covers that again
16:57obstacles we got malleus incus state
16:59these the purpose of them is when they
17:00vibrate from the sound waves they tap on
17:03the oval window to create fluid-filled
17:05vibrations within the inner ear
17:06structures okay done with that part
17:10let's move on to the next part next part
17:12here is going to be called the facial
17:14canal so tiny little bony canal within
17:16the middle ear if you guys already
17:17watched our video which we put up for
17:19the actual facial nerve you guys you
17:21guys will know what we're talking about
17:22here okay a lot of these are going to
17:24connect with some of the cranial nerves
17:25that we talked about so if you remember
17:28what was the facial nerve actually
17:29coming from you guys remember here let's
17:31actually kind of show it like this
17:32remember it was actually kind of located
17:34here in this area this was a facial
17:35nerve but had a special nucleus as
17:37remember that nucleus it was called the
17:40superior Salvatori nucleus and if you
17:43remember the superior Salvatori nucleus
17:46comes out through a hole and the school
17:50over here and this hole in the skull is
17:53actually called the internal acoustic
17:54meatus okay it's actually called the
17:57internal acoustic muse
17:58what happens is it actually runs through
18:01the internal acoustic meatus and from
18:04here it actually moves down from the
18:07soup the upper part of the actual what
18:08upper and medial part of the middle ear
18:11and then it works its way backwards to
18:13the posterior wall and then it goes
18:15downwards and comes out through the
18:17stylo mastoid foramen we talked about
18:19that in the facial in our video same
18:22thing is happening here we're just
18:23looking at like this so one nerve will
18:25be coming down through this area this is
18:26cranial nerve what seven facial nerve
18:28right so some of the fibers here are
18:32going to come through this bony canal
18:34and they're going to move through this
18:36bony canal and as they're moving through
18:38this bony canal something really really
18:40important happens right so these are
18:42actually going to be the parasympathetic
18:44fibers but you know the facial nerve
18:45also has motor fibers so it also has
18:48motor fibres let's actually draw these
18:49motor fibres and this nice little blue
18:52color here so here this is our motor
18:54fibers these motor fibers also move with
18:57the facial nerve and they move down
18:58through this canal also so imagine this
19:00guy here is moving through this canal as
19:04it's moving through this canal it gives
19:07off a branch here and this branch comes
19:09in through this tiny little hole within
19:12the posterior part of the actual middle
19:14ear and it supplies this muscle right
19:17here why is this important and first off
19:19what is this muscle this muscle here is
19:22called the stapedius
19:28so if you guys remember this was our
19:30scabies this bone right here was one of
19:31the obstacles it was called stabies and
19:33what was state B is doing was tapping on
19:35the oval window we have a little control
19:37of that what happens is the facial nerve
19:40will innervate the stapedius which will
19:42tense up on that actual state B's what's
19:44the purpose of that if it contracts on
19:46the state DS the state piece isn't going
19:47to tap the oval window as much okay so
19:50it's dampening these actual act the
19:53mechanical events of the state piece is
19:54trying to exert on the inner ear because
19:56again the state piece is tapping on the
19:58oval window to create fluid build
19:59libraries within the cochlea if the
20:02actual stapedius contracts it prevents
20:04the state piece from doing that
20:04excessively okay so it dampens that
20:07activity that's the function of this
20:09part here so again what nerve is
20:11actually running in here this whole
20:13thing right here that we've talked about
20:14so far there's actually one more that
20:16we'll talk about this whole thing that
20:18we've talked about so far is the facial
20:21nerve cranial nerve seven these green
20:23fibers are the parasympathetic fibers
20:25and these baby blue fibers here are
20:27going to be the motor fibers and the
20:29motor fibers are getting supply to the
20:30stapedius and if you remember it'll
20:34continue down through the bony canal and
20:36it will come out through this hole here
20:38called the stylo mastoid foramen and
20:40then if you really wanted to know the
20:42style masked out of the style master
20:44frame it gives two branches one goes to
20:46the stylohyoid and the digastric
20:48posterior belly and the other one
20:50branches out into the temporal it
20:52branches onto the zygomatic the marginal
20:54mandibular and the cervical branches
20:56right if you guys remember that it was
20:57the temporal zygomatic blue cool
21:00marginal mandibular and cervical branch
21:02and then back here gives the taiga
21:04digastric poster belly and it gives it
21:07to the stylohyoid okay but we don't need
21:11to know about that just going to giving
21:12you what's moving through that area okay
21:15now what else is happening remember from
21:18the facial nerve we had some other
21:19fibers here let's do these ones in this
21:20do to brown color here these were
21:23actually sensory fibers these were
21:25sensory fibers and these sensory fibers
21:28are important because they move in the
21:30actual facial canal here too and what
21:32happens is they move down with these
21:34green fibers these parasympathetic
21:36fibers but what happens is they jump out
21:39these sensory fibers they
21:41jump out with these actual green fibers
21:44here look at this these guys jump out of
21:46that facial canal and they move through
21:49a hole within the back of the actual
21:51middle ear so again what's going to
21:53happen here
21:53these parasympathetic fibers these green
21:55fibers are going to jump out and these
21:57brown fibers these sensory fibers are
21:59also going to jump out and then what
22:02happens is they're going to move this is
22:04so frickin cool they move from the
22:07posterior all the way out from the
22:10anterior okay so they move from the
22:13posterior part of the middle ear all the
22:14way to the anterior part of the middle
22:16ear so again what will happen here these
22:17fibers here will come from the posterior
22:19part of the middle ear and they'll come
22:20out through the anterior part of middle
22:22ear these tiny little suckers here this
22:25is just called the posterior it's a
22:27posterior canal Occulus okay this is
22:31just a little post here canaliculus and
22:33this is where these fibers come out here
22:35and they move over in like a cord and
22:38the tympanic cavity which is called the
22:40core doesn't pan on well like that down
22:42in just a second but then they come out
22:44through this tiny little hole in the
22:45anterior side of the middle ear this is
22:47called the anterior canaliculus okay and
22:53again what did we say this whole thing
22:55is called hear this whole thing imagine
22:58this whole thing here that I'm about to
22:59wrap around like this moving from the
23:06posterior wall of the middle ear to the
23:07anterior wall this whole structure here
23:09is called the chorda tympani and if you
23:15guys remember from that video we said
23:17that it eventually would go out and it
23:19will combine with the lingual nerve and
23:22what happens these fibers actually these
23:25do to brown fibers they move with what
23:28nerve they're going to move with cranial
23:31nerve five specifically the lingual
23:33nerve right and they'll go to the tongue
23:35okay the lingual nerve will actually
23:37supply what the lingual nerve the
23:40trigeminal component here will supply
23:42touch pain temperature to the anterior
23:44two-thirds of the tongue and these brown
23:47fibers here provide taste to the
23:49anterior two-thirds of the tongue and if
23:51you remember this comes out to a
23:53ganglion what was that ganglion called
23:55mandibular ganglia and this goes to
23:57glands sublingual salivary gland and the
24:01submandibular salivary gland okay we
24:05already talked about this within that
24:06video right of the facial nerve okay
24:10sweet so so far what we talked about we
24:12talked about the bony canal the facial
24:14canal and then what fibers are moving
24:15through it we're not going to cover
24:16every single fiber because we already
24:18did on the facial nerve but I just want
24:20you to understand that through this
24:21facial canal the facial nerve is moving
24:24through and then out of that certain
24:27fibers are coming out into the middle
24:28ear which ones this blue fiber is the
24:31motor fiber going to the stapedius which
24:33controls the movement of the state piece
24:34we talked about that then we said these
24:36green fibers are parasympathetic fibers
24:38these do to brown fibers are the sensory
24:41fibers are taste fibers right and GVA
24:44fibers if you remember and the green
24:45ones are GBE fibers if you remember they
24:48move down through the facial canal and
24:49then they come out through the posterior
24:52canal lick ulis and move anterior and a
24:54cord called the courtesan pan on and
24:56they come out through the anterior
24:58canaliculus and then again the green
25:00fibers go to the submandibular ganglion
25:02which lots for salivation
25:03and then the brown ones move with the
25:05trigeminal nerve specifically lingual
25:07nerve okay and they go to the anterior
25:102/3 of the tongue
25:11sweet stinking deal all right so what
25:14have we covered so far we did the facial
25:16canal what else did we cover we also
25:18covered in the process we covered
25:20stapedius alright now let's talk about
25:22the next thing which is actually going
25:25to be called the promontory okay so the
25:28promontory what is this promontory so if
25:31you look here we're looking at the
25:32middle ear so looking at the middle ear
25:34here you're going to see here this is
25:37the medial wall this is the medial wall
25:42of the inner ear okay this is the
25:44posterior wall of the middle ear
25:47I took a slice here you can't see the
25:51whole thing so imagine I come this is
25:53the whole anterior wall I cut it okay so
25:56this is the anterior wall but you're
25:59only seeing a small portion of it if I
26:01were to bring this thing all the way up
26:02and all the way up here to the top at me
26:04the whole anterior wall okay and again
26:06down here is just going to be the
26:08more of the middle ear and I removed the
26:11me uh the lateral wall so over here if I
26:15were to imagine coming from this to here
26:16this would be the lateral wall and I
26:18would have the tympanic membrane on I
26:20removed that so that we could see the
26:21court isn't paying on some of these
26:22other structures okay
26:23so post to your wall medial wall and to
26:27your wall and then again I remove the
26:30lateral wall and you can see the floor
26:31of the tympanic cavity sweet on the
26:34medial wall there's a structure that
26:37we're going to talk about eventually
26:38it's called the cochlea right and what
26:41happens is imagine I'm going to kind of
26:42like do it like this here the cochlea
26:44kind of looks like a snail shell right
26:46and what happens it actually kind of
26:48presses okay so the cochlea would
26:50actually be behind this it actually
26:52behind this hole over here so if Majan
26:54here for a second I'll show you what I'm
26:56talking about I'll say here I have
26:58external ear all right external acoustic
27:01meatus let's say here's the tympanic
27:03membrane let's say this is that wall I'm
27:06shading it in here this is actually
27:08going to be the medial wall what will be
27:10right here next to it right here would
27:12be the cochlea okay and then again we'll
27:16talk about eventually good you get to
27:18the vestibule and then the semicircular
27:20canals okay so right here is actually
27:23gonna be the cochlea and the cochlea is
27:24pressing in to this actual medial wall
27:27in causing this little a bump and that
27:30bump is called the promontory why is
27:33that bump important because there's
27:34nerves that run across that it has a
27:38probably going to hate me but if you
27:39guys remember let's do this one in pink
27:42we had a nerve and that was called the
27:45glossopharyngeal nerve right and it came
27:49out from over here remember I'm going to
27:51kind of write it like this
27:52glossopharyngeal nerve it actually moves
27:54out through a hole we're not going to
27:55show here but the jugular foramen and
27:57then if you remember I'm going to bring
27:59it down here I'm going to come from the
28:00bottom okay it's going to come from the
28:03bottom here and it's going to move up
28:06through this hole on the floor you see
28:10that tiny little cavity right there that
28:11tiny little hole that's what's going to
28:13move up through it's going to move up
28:14through that okay so this inner of here
28:16glossopharyngeal nerve is going to come
28:17down down down down
28:20come from the floor and come up through
28:22the tiny little hole within the floor
28:23that's a panic Avenue what is that hole
28:26there called
28:26that hole is called the tympanic
28:29canaliculus okay so what does it call
28:31it's called the tympanic canaliculus and
28:38what happens is the glossopharyngeal
28:40nerve comes up through that then as it
28:43moves up it gives off kind of like these
28:47little branches over here okay it gives
28:50off these little branches okay
28:52so again if you remember this was coming
28:55down these are actually gve fibers so
28:57they're coming from specific area you
29:00guys remember it's coming from the
29:01inferior if you want hair all right it's
29:02coming from the inferior Salvatori
29:04nucleus these fibers are coming up here
29:07through the tympanic canaliculus and
29:09they're giving off these branches here
29:11to the promontory what else is happening
29:13okay they're really going to hate me now
29:15because if you guys remember we have
29:20another structure moving there too
29:21remember we had over here we had the
29:24sympathetic nervous system right and we
29:25had this structure over here this was
29:27called the intermediate lateral gray
29:29horn or the lateral gray horns they come
29:31out here and they go to what's called a
29:33superior cervical ganglion and they give
29:41off these postganglionic fibers that
29:43wrap around the internal carotid artery
29:46remember this was the internal carotid
29:47artery and it forms like a carotid
29:48plexus here and a sympathetic plexus
29:51these fibers come upwards and they give
29:54off branches that move through these two
29:56little holes like this is a superior
29:57hole and that's an inferior hole right
29:59so just a tiny little superior framing
30:01and an inferior framing and what happens
30:03is these actual sympathetic nerves move
30:06through here move through these tiny
30:08little holes and they come out okay so
30:10let's imagine this was coming from the
30:11superior hole and this one over here is
30:13coming from the in fear hole they come
30:15over here and they give off branches
30:17here also why am i mentioning this what
30:20did these fibers here called
30:21these are actually called the karate
30:24coup
30:26tympanic nerves their sympathetic nerves
30:31okay this is our sympathetic nerves that
30:33are coming from the lateral Horn of the
30:35spinal cord coming to the superior
30:37cervical ganglion wrapping around the
30:38internal carotid artery and giving off a
30:40branch that moves to the anterior wall
30:41to the superior and inferior foraminal
30:43right they come off and they give off a
30:46branch there interacts with the
30:49parasympathetic fibers from the
30:50glossopharyngeal nerve what is this form
30:53now it forms a nice little plexus they
30:56call this structure that's on the
30:58promontory they call it the tympanic
31:02plexus and basically all it is is just a
31:06connection from the glossopharyngeal
31:07nerve the parasympathetic fibers and the
31:10karateka tympanic nerves that are coming
31:11from the sympathetic nervous system and
31:13giving off branches that move into the
31:15middle ear okay and if you guys remember
31:17we talked about this one already that it
31:19gives off these parasympathetic fibers
31:21they give off these branches that moves
31:23upwards and as a specific nerve it
31:26actually will come off as the lesser
31:27petrosal nerve and then we said from
31:30here that the lesser petrosal nerve will
31:31move through a hole called the hiatus
31:35for the lesser petrosal nerve and then
31:36it will run through nice little hole in
31:37the skull called the foramen ovale and
31:39then it'll come out to a specific
31:41ganglia on here called the otic ganglion
31:44and this remember goes to a gland
31:48specifically what gland it goes to the
31:50parotid gland right so it goes to a
31:53gland here called the parotid gland
31:54which basically produces the saliva that
31:57goes into the oral cavity all right and
32:00there's so many destinations from the
32:01sympathetic fibers we're not going to go
32:02into all that okay so again that's the
32:05lesser petrosal nerve and that moves
32:06that way and then if you guys do
32:09remember just to be you know it's always
32:11good to have consistency there's another
32:13one that comes off here off the seventh
32:15thing on earth if you guys remember this
32:16was actually called the greater petrosal
32:18nerve and the greater petrosal nerve
32:20actually runs through this area here so
32:23this is called the greater petrosal
32:24nerve it actually runs up through the
32:25hiatus of the great petrosal nerve and
32:27it moves through another hole here
32:28called the foramen lacerum and then it
32:32goes into what's called the pterygoid
32:33canal and it's a terrible Palantine
32:35gangly on
32:36and then eventually goes to the lacrimal
32:38glands and then it goes to the actual
32:39Palatine glands okay
32:41so again that was the greater patrol so
32:43nerve okay and again it moves up through
32:44the hiatus and it goes through the
32:46foramen lacerum
32:46and then it goes down through the
32:48pterygoid canal into the tear go
32:49Palatine ganglia into lacrimal and the
32:51Palatine and the Palatine and nasal
32:53glands all right holy crap we did that
32:56okay so what have we covered so far we
32:58covered the promontory we talked about
33:00the Domanick plexus so we talked a lot
33:02about the nerve supply so we did that so
33:04did the nerve supply with the
33:04glossopharyngeal nerve oh you know we
33:07did not do with the external year we got
33:10to cover one more thing here let's do
33:12this in student purple students purple
33:16here there's actually nerves that supply
33:18if you guys remember we talked about
33:19this in those videos remember we had the
33:22fifth cranial nerve Creon under five it
33:24gave off what's called an auricular
33:25tempora branch so it's a gifts supply
33:28sensory supply to the skin of the
33:30external here and a little bit here to
33:32the external acoustic meatus right that
33:34was the cleaning or five what else did
33:36this to remember cranial nerve 10 and
33:38crater of nine glossopharyngeal nerve so
33:41here I put here cranial nerve nine and
33:46cranial nerve 10 these also supply this
33:51member cranial nerve 10 so gives us uh
33:53supply to the actual tympanic membrane
33:55cranial nerve nine specifically actually
33:57gives supplied like the inner product in
33:58panic membrane and then there was
34:00another one too which is cranial nerve
34:02seven and cranial nerve seven also gives
34:04fibers out here too so we can even put
34:06here one more cranial nerve seven and
34:10cranial nerve seven also gives supply to
34:11the external acoustic meatus and a
34:13little bit of the tympanic membrane so
34:17just reminding you guys that there is a
34:18lot of sensory fibers that are located
34:21within the external acoustic meatus and
34:22on the tympanic membrane external part
34:24of it and internal part of it so just in
34:26general once you guys remember what
34:28nerves are going to be supplying the
34:29external ear and a little bit of
34:31tympanic membrane it will be the ninth
34:33cranial nerve glossopharyngeal tenth
34:35cranial nerve vagus seventh cranial
34:37nerve facial and fifth cranial nerve
34:39trigeminal okay now we cover all the
34:41nerve supply so sweet goodness we did
34:44the nerve supply we did this to PDS we
34:46did the promontory we talked about the
34:47facial canal and we talked
34:49about the obstacles let's now do the
34:50tensor tympani and what is its purpose
34:53and what is basically serving it okay
34:57well we talked a little bit about the
34:59tensor tympani over here right what do
35:01we say that the tensor tempeh and I was
35:02doing it was connecting to the malleus
35:05and it was pulling the malleus medially
35:08okay so towards the medial wall which
35:11tensed up the tympanic membrane because
35:12you know that the mountings is actually
35:14connected to the tympanic membrane here
35:17all right so now let's see how this is
35:20actually effecting so let's come over
35:21here if you guys remember we had another
35:24nerve when we talked about him plenty of
35:26thought we have a huge video on him
35:28cranial nerve 5 right the trigeminal
35:31nerve we have the mandibular division of
35:32it so today gives off member has the
35:34three branches one is the v1 opthalmic
35:37v2 maxillary and v3 is going to be
35:41mandibular well from the v3 division it
35:43gives off a branch that supplies this
35:45muscle right here okay what is this
35:47muscle again here called this muscle is
35:49called the tensor tympani and what does
35:54the tensor 10 pay and i do when the
35:57tensor tympani contracts it pulls so
36:00imagine here it's connected to that bone
36:02obviously the bone with you all the way
36:03over here but I'm just doing it for the
36:05sake of it okay what does this bone here
36:07call this is called malleus it pulls
36:10malleus medially so it pulls the malleus
36:13medially when it pulls on the malleus it
36:16tenses that compan ik membrane when you
36:18tense the tympanic membrane whenever the
36:21compression and decompression of the
36:23titanic' membrane is trying to create
36:24those vibration of the obstacles that'll
36:27be dampened a little bit okay and the
36:29purpose of this is you guys know when
36:31you're chewing food ok muscles of
36:33mastication you know when you're chewing
36:35food right so you have the temporalis
36:36you have the masseter you even have all
36:39the muscles like the medial and lateral
36:40pterygoid a whole bunch of different
36:41muscles that are involved in mastication
36:42right but when you're chewing you can
36:45produce a lot of sounds a lot of a lot
36:47of sounds what happens is the trigeminal
36:49nerve is so kind us and it gives off a
36:51branch of the tensor tip an eye which
36:52tense is the tympanic membrane if it
36:54does that whenever we're chewing food
36:56during the mastication process it
36:58dampens that so whether we don't produce
37:00so much loud sounds
37:02during the eating process or the
37:03mastication process when you're chewing
37:05your food okay so you better Thank You
37:07trigeminal nerve next time you're eating
37:08and it's not super super loud okay and
37:12also thank your facial nerve who gets
37:14apply to this the PDS too because that's
37:15also another one who's really important
37:17because if he gets damaged from Bell's
37:18palsy you could actually cause
37:20hyperacusis where remember it can
37:21actually continue to keep tapping on the
37:23oval window continuously and you can
37:25very very sensitive to sound remember I
37:26told you have to hold the phone out here
37:27for some people because it hurts so much
37:29if people are talking to their ear I
37:31cool covered that now one other thing I
37:35wanted to talk about I didn't write it
37:36up there I'm sorry about that well I
37:37want to talk about this tube right here
37:38this is a very very important tube this
37:43is called the fringe ou can panic tube
37:46there are so many names for they can
37:48call the auditory tube the eustachian
37:49tube or we can call the printer tympanic
37:51- I'm just going to call the fringe into
37:53panic tube you can pick from whatever
37:54three again for injured tympanic tube
37:56eustachian tube or auditory - whichever
37:59one what is the purpose of this soccer
38:01here okay this guy is connecting with
38:04the specific part within our throat let
38:07me actually show you over here because
38:08it's way better because it's perfect
38:09it's perfectly connected over here let's
38:12say again what wall would this one be
38:14this would be the medial wall you can
38:17tell that because it's right next to me
38:18promontory this would be the posterior
38:21wall this would be the anterior wall
38:24okay now what happens is on the anterior
38:27wall there's actually going to be a nice
38:29little tube here a nice little tube and
38:31this tube connects into the pharynx it
38:39connects into the pharynx here and what
38:41happens is what this can do is it can
38:43equalize the pressure between the
38:46atmosphere in the middle ear because
38:48what's normally the pressure outside the
38:49atmosphere atmospheric pressure is
38:51normally 760 millimeters of mercury well
38:55this one you want to equalize these
38:57pressure so that doesn't cause any
38:58problems here developing within the
39:00middle ear because obviously that could
39:01lead to a lot of different situations
39:02that there's pressure accumulation in
39:04here right it might cause abnormal
39:07certain sensations like tinnitus if it's
39:09if it's occurring we don't want that so
39:11what happens here any air and I'll
39:13explain where the air can come from
39:15be moved from the middle ear out into
39:17the external environment or from the
39:19external environment we can bring
39:20something air in here it's the whole
39:22purpose of the fringe of tympanic tube
39:23is to equalize pressures with atmosphere
39:33and middle ear that's the whole purpose
39:39of okay so at the end of the day just
39:41remember that purpose of the furniture
39:43tympanic tube is to equalize the
39:44pressure within the atmosphere Andy
39:45French of tympanic - if for some reason
39:49you need to get the air that is actually
39:52maybe you want to actually have some
39:53more air come into the actual on middle
39:55ear cavity you have this beautiful
39:56structure in the posterior wall a nice
39:59beautiful little structure here this is
40:01called the mastoid sinus so in the
40:06posterior wall you have a little hole
40:08here that connects to the mastoid sinus
40:12so you're going to have a nice little
40:13hole Becker that can actually mastoid
40:15sinus and in certain people not everyone
40:16these people might have mastoid air
40:19cells not every single person is having
40:22mastoid air cells okay but you do have
40:24this mastoid sign is here and the
40:27mastoid sign this is going to have a lot
40:28of mucus right what can happen is some
40:30of the air from this mastoid sinus can
40:34actually be pushed over here into the
40:37middle ear cavity depending upon the
40:38needs okay why am I mention this mastoid
40:41science because in certain situations
40:43when someone might have what's called
40:44mastoid itis or certain types of
40:46infection or inflammation of the mastoid
40:48sinus it doesn't drain into the nasal
40:50cavity so what happens is in certain
40:52people they have really bad infection a
40:53nasty infection of the mastoid sinus
40:55they have to put in little shunts okay
40:57so I have to put in like tiny little
40:58shunts here that can drain the actual
41:01middle ear cavity okay so you actually
41:04have to put shunts in that drains the
41:06middle ear I'm sorry not the middle ear
41:07cavity the mastoid signs that you
41:08actually don't have well you know why
41:10this is important because you don't want
41:11an infection to develop within the
41:12mastoid sinus because then they can
41:14extend work and it actually extent come
41:16here I'll show you the maxillary sinus
41:18can be right over here right so pretend
41:20I actually draw right here I'm going to
41:22raise this out of the way here match
41:23this back here and here's your master
41:24late sinus what can happen is it can
41:26extend
41:27upwards into this area and it can
41:29actually affect the glossopharyngeal
41:30nerve it could affect the tenth cranial
41:33nerve the vagus and it could even affect
41:34the accessory nerve so because of that
41:37if a mastoid sinus infection extends
41:39upwards it can affect a lot of the
41:40cranial nerves moving out through that
41:41area okay
41:42so that's one of the damaging things
41:44about mastoid sinus infections is that
41:46you want to take care of that and make
41:47sure that you put a shunt in there to
41:49drain out any types of substances that
41:52might be in there if it's actually
41:53accumulating a lot of fluid okay
41:55believe me remember another topic here
41:57oh here was in the I didn't talk about
42:01the roof we're talking about the floor
42:03of the middle ear cavity and talk about
42:04the roof and it's probably the most
42:06important thing is a battlekey actual
42:08tympanic cavity so imagine here again if
42:11you remember this was actually I'm going
42:12to shade it in an order this is actually
42:13to be the what wall this is the medial
42:16wall this is going to be the lateral
42:18wall this over here if you imagine I'll
42:21show it like this in green this wall
42:24here is the anterior wall and in the
42:28back here would be the posterior wall
42:30I'm back here would be the maxillary
42:32sinus right
42:32with the air cells on the roof it's
42:36actually made up with a little bone okay
42:38and this bony part here is called the
42:40tag min Tim pan I the reason why I'm
42:45telling you this because it's a very
42:45very thin bone and if someone develops
42:48what's called otitis media middle ear
42:49infection it can actually spread upwards
42:52very easily through the tegmentum pan on
42:54what is separating the middle ear cavity
42:57from the actual cranial cavity not very
43:00much not very much at all if you imagine
43:02here let's say that here's the actual
43:05roof right here okay that's the
43:08tegmentum pan on the only thing that's
43:10really separating it from this point
43:11here is just some dura mater that's all
43:13it is building us really separating the
43:14actual middle ear cavity from the actual
43:16cranial cavity is the tegmentum pan my
43:18instant dura mater that's it so if you
43:20have an infection it can actually easily
43:22spread up through the techniques and
43:23paneling into the actual meninges and
43:24cause severe meningitis okay so very
43:27very dangerous can actually cause
43:28infections within the brain too that
43:30maybe might cause some type of like a
43:32abscess or something okay okay so we did
43:35that part there sweets what have we
43:37covered so far we covered the mastoid
43:38sinus
43:40okay and we covered a little piece in
43:43there the roof of the middle ear cavity
43:45called the tegmentum panel and its
43:47significance that's another thing you
43:49know certain things is actually we'll
43:50talk about later is whenever you have
43:52infections when you give certain types
43:54of antibiotics you have to be careful
43:55about what type of antibiotic you give
43:56because aminoglycosides can actually
43:58cause odor toxicity and actually cause
43:59more damage earlier we'll talk about
44:02that when we get to do that video though
44:03okay next thing that we're going to talk
44:05about is the tensor of Eli Palestine
44:07okay so if you guys remember we said
44:09that we have what's called E some of
44:12them we have the trigeminal nerve
44:14okay the trigeminal nerve or cranial
44:15nerve five you have some muscles here
44:20they're actually a part of the soft
44:22palate let's say that one muscle is
44:24going to be like this so I have one
44:26muscle like this you have a couple
44:27different you have will tell the
44:28laboratory light palette and I you might
44:30even have another one here which is
44:31called the saw Pingo for NGS and you
44:34might even have another one over here
44:35which is called the tensor villi pal
44:37tonight okay so here I'll just write
44:39these here for a second let's say that
44:41this is the Leavitt or villi Palestine
44:44let's say that this is the tensor V live
44:46Powell tonight and let's say that this
44:47was called the South Pingo ferengi Asst
44:52what happens is is if you remember the
44:56trigeminal nerve the fifth cranial nerve
44:58the fifth cranial nerve cranial nerve 5
45:01has the mandibular division that gives
45:04fibers to the tensor villi Palatine and
45:07the tensor reveal I palettes and I what
45:09is it going to do it's actually going to
45:10tense the actual soft palate
45:12another thing is it's not going to be
45:14supplied by the fifth cranial nerve but
45:16if you guys remember we have the tenth
45:19cranial nerves so cranial nerve 10 it
45:21came through the fringe of plexus and it
45:23supplies the saw Pingo Ferengi's and a
45:26supply beat leavitt or villi Powell
45:28tonight the whenever is decree Mueller
45:31ten supplies to South Pingo for in jeus
45:33that actually elevates the soft palate
45:34in the laboratory light palette of my
45:36elevation of soft palate but the cell
45:37Pingo fringes does something else it's
45:39actually connected to the fringe of
45:41tympanic tube a little cartilaginous
45:42lamina and it can pull on that
45:45cartilaginous lamina of the fringe of
45:47tympanic tube to help to equalize the
45:49pressures between what between the
45:51middle ear cavity and the
45:53atmospheric pressure alright so what
45:56have we covered then we've covered also
45:58the tensor villi palate and I and the
46:01other connection which was the South
46:02Pingo Ferengi Asst all right so that
46:04covered that part all right so we cost a
46:07lot about the external here we talked a
46:09lot about the middle ear cavity the de
46:12pano cavity went over a lot of different
46:13things in future videos we'll talk about
46:16something else a little bit later called
46:17a cholesteatoma which can accumulate
46:20within the middle ear and it can become
46:22very very very dangerous okay that will
46:25be a discussion that we will talk about
46:26later when we get to the inner ear
46:27structure and how that can affect the
46:29actual auditory impulses okay so we will
46:32talk about cholesteatoma
46:33but we talked a lot about a lot of
46:35different things about the middle ear
46:37and the external layer I really hope it
46:39made sense I really hope that you guys
46:40enjoyed it and you learned a lot if you
46:42guys did please hit the like button
46:43comment down in the comment section and
46:44please subscribe as always engineers
46:46until next time