DIP Episode 280 - Branchial Arches : All you need to know

Okay, welcome. My name is Divine. This is episode 280 of the Divine Intervention Podcast. This podcast is going to be focused on a topic that is very high yield for step, the US release step one exam. And this is going to be the podcast on Farring gel Arches. Now I'll try to make it short, sweet and high yield so you can get a lot from it. And again, take away the most important information. And again, my big focus here is not to give you is to just try to integrate many different ways. They love to test this material on step one. And for those of you that I'm interested in the 30-hour step one course, I opened up another course. It's from the 27th to the 30th of January 2021. It's going to be 7 and a half hours each day for four days. And you'll learn the most high yield information that's just classically tested of the US Emily step one from every domain, GI, cardio, respiratory, bio stats, immunology, pathology, pharmacology. Basically, you learn pathology from ecology and physiology, learning to integrate it format using many different clinical vignettes. In fact, I hope to cover about 3,000 concepts across those 30 hours. So that's something you're interested in. Just reach out to me. There's still some space available and I'll be more than happy to have your register. So just hit the contact button on the website and I'll be happy to point you in the right direction. So let's just jump right into it. So, foreign geolarches, they're potentially like a ton.

You can know about them, right? But again, for the most part, let's just some key pieces of information here and there that should help you get most of your questions right on the exam. So the first thing is, what are these foreign geolarches? Basically, there are things that begin to develop around week four of development and it's important to realize that these are things that we find mostly around the lower to thirds of the face, the neck, then some parts of your upper body. I think if you can keep that orientation in mind, it will help you keep many of these facts straight. That's what. So, one other thing that's important to realize is that these things they develop from the back or you know, the dorsal part of you to the front or the ventral part of you, right? And that dorsal ventral orientation and cranial quadrall orientation of things in the body, remember it's controlled by the hox genes, right? Sometimes those things are referred to as home-yubox genes, right? And remember that the red moic acid receptor, vitamin A, has a lot to say about that process. So whenever a person has a problem where they have too much vitamin in development, let's say for example, a person is taking isotret knowing that can cause a lot of foreign geolarch problems. That's why you see many times when people have like a hox gene mutation or something or isotret knowing teratogenicity, they tend to have a lot of like facial problems, right?

It tends to have like cleft, cleft, cleft palate, behalf problems with many derivatives of these brinkial arches. Now the thing is the word brinkial arch right is actually a part of a tripertide structure. So what do I mean by tripertide? Tripertide just means, you know, about three things, right? So you know, there's a common harmonic people use, you can use either the guppnomonic, you can use the cappnomonic. So the guppnomonic, right? G-E-P tells you that you have like grooves, arches and then pouches. Or you can use the cappnomonic that says clefts, arches and pouches, okay? So the grooves or the clefts, you know, grooves clefts seem thin, they derive from etudeur. So they are more lateral in the body. The arches derive from misoder, so they're in the middle. And then the p, the pouches derive from endoder. Although I think one thing that's important to realize is that in this tripertide structure, there are actually points called a far like pharyngeal indentations where the grooves or clefts, you know, I'll just keep calling them clefts, where the clefts and the pouches meet and there's no intervening misoderm between them, okay? These parts are called pharyngeal indentations and they actually have some really unique things that are members of them that again will begin to make, begin to make some sense. Now the stuff in the middle are arches. Well, they don't exist in a vacuum.

They're things, you know, they almost create like a template for others to come and hang out and create some useful stuff, right? So the template they create is inhabited by neurocressels. So neurocressels, they literally migrate to these regions and then they begin to lead down things that ultimately will become like the bones and the cartilage that you get from those arches. The actual misoderm though, you know, the actual template helps us with forming many of the muscles and arteries of these arches, right? So again, remember the grooves or clefts that are right from ectoderm, the arches and that's almost very lateral. The arches that are right from misoderm, right? The misoderm itself gives rise to the muscles and the arteries, but that misoderm is invaded by neurocressels that show up and then help us implant some basically formed bones and cartilage and then the pouches that are right from endoderm, okay? And again, the pouches are, they're most medial, the grooves and clefts, they are most lateral. I think that's one big thing, you just want to really, really, really get down from the from the very beginning. So the so let's kind of bring these thorns up right? So the thing is they actually six arches, but one of them exists very transiently. It doesn't hang around for long. That's arch number five, right? So it doesn't really hang around for long.

So that's no one we're going to talk about, but so that means of the six, we're only really need to care about five, right? There's one, there's two, there's three, there's four, and there's six, we skip number five, because again, it just hangs around for a short while and then it disappears. So for the first arch, right? And the thing is if you're going with these numbers, they actually go in progression from again, that beginning of them lower to thirds of your face, all the way down to like your upper body around your soft August. So if we're going from cranial to caught already, there's like a cranial to caught orientation with these things. So let's go cranial, right? So if you look at the lower to thirds of your face, the first thing you're going to encounter is your maxilla. Second thing you're going to encounter if you go a little bit lower is your mandible. So really, to be honest with you, maxilla and mandible, that should be like the big thing that comes to mind when you think about arch one, right? So for example, if you think about it, what are some things we find around the maxilla mandible? Well, let's let's look at the archies. We said the archies themselves help us give rise to the muscles and arteries, right? So what are the muscles you find around their well? You're going to you true with your mouth, right? So your muscles of mastication actually right from the misoder of arch one, right?

So like your temporalis, your mastidor, your medial lateral terrygoids, your mylohioid muscle is also derived from arch one. And remember, your pallet, one of your palatine muscles actually derived from arch one as well, right? Tenservilae palatine, right? Also, we also have tenser timpani. And then we also have the anterior belly of the digastric. These are all the muscles that come from arch from the misoder of arch one. So again, the muscles of mastication, again, just in your mind, just visualize these are things all around the maxilla and mandible. Okay? So we have the muscles of mastication, the mylohioid muscle, the anterior belly of the digastric, and then we have tenser timpani and tenservilae palatine. Okay? So your two tensor muscles, your muscles of mastication, your mylohioid, and the anterior belly of the digastric. You see a lot of m's, it's a lot of t's, right? So that's a nice way to remember those things and keep them straight. Unfortunately, yes, there's some memorization here. But again, I feel like if you kind of have these things just organized, like really the the antidote for things that are tough to memorize is just organizing them better, then you'll be being very good shape. And like I said, the misoder not just gives muscles, gives rise to muscles also gives rise to arteries. So arch one gives rise to the maxillary artery. Okay? Arch one gives rise to the maxillary artery. And as you will see the nerves for arch one, right?

Again, just think about that generally of the body, maxilla mandible. That's going to be cranial 5 territory, right? In fact, to be more specific is cranial V2, right? That's the maxillary nerve and cranial V3. That's the mandible nerve. Okay? The mandible nerve. And again, like I said, the neurocressels, they show up to the pharyngeal arch is the use of the mesovermitan plate and then they begin to help you make bones, right? So if you think about it, right? Like bones of your face, like bones in your meat face, they all come from neurocressels. Your malios and your incas, not your steppes, your malios and your incas, they ultimately come from the those are actually neurocressels derived. But again, those are the neurocressels that come and populate arch, arch number one. And I mean, there are some problems that can happen when people have issues with this process. And I'm not doing arch one, arch one, probably the one, I'll spend the most time talking about right? Because again, I just want to lay down certain foundations. So if you really think about it, if these neurocressels don't migrate properly, then you're going to have problems mostly with the bones, right? The bones will be all messed up, right? The bones will be all messed up. So those people have like a lot of like phisoma affirmations, right? And this is something that we classically call trigger callin syndrome.

So trigger callin syndrome is where you have problems with arch number one, the neurocressels don't show up and they don't show up. The person who begin to have all these phisoma affirmations, they'll have hypoplasia of the mandible, right? Again, don't forget the pathophase neurocressels did not migrate appropriately. And then another classic one you may see is something called the pure riband sequence, right? So the pure riband sequence, many people are like, oh, divine, how do I know how to differentiate this from trigger callins? Well, the way you differentiate trigger callins from pure band sequences, people that have pure band sequence, they have a lot of tongue problems, right? So just keep that in mind, a lot of tongue problems. In fact, the big buzz word emission you'll examine for this is something called glosobtosis, where basically they are tongue goesposterially, well, if the tongue goesposterially, it's going to block your earway. So those keys, they tend to have a lot of airway problems and they tend to have very small mandible. So again, the five-dollar medical term for that is micro-ganathia. So if you see a present that has a very small mandible, right? Again, you see that mandible area is all arch-one as as I'm giving it that orientation, right? So the mandible area is all arch-one. So if you have a very small mandible, that's micro-ganathia. And then there are tongues of gun backwards and they have any airway problems.

Once you think about the pure, pure riband sequence, once you think about the pure riband sequence. And then there's this thing from that the NBM kind of wants you to understand. Basically, it's more a problem with the with ectoderm of the first arch. But they can give you a question where they tell you about a child and they tell you that, oh, this child has a lot of like scoliosis, right? So it has a lot of spinal problems and especially like around the cervical spine and the tail of this child has like hearing problems, kidney problems. For these children, they actually tend to have like pretty normal intelligence, right? And then they begin to again describe issues with the ears, right? Like, oh, they don't, their ears are almost like nonexistent, right? Sometimes you see that referred to as micro-shia. Right? Crochia means they have very small ears or ears that, you know, just partially form or ears that are completely absent. I mean, sometimes these people have cleft lip and cleft and cleft palate. In fact, the way I remember this condition is that it's a problem that I fix the eyes, it's a problem that fix the ears, a problem that fix the spine. So that I almost think of it as eye ear spine disease. And if that's something you may see referred to as oculo or reculo for tuberous syndrome, okay? This is something called Godinhar, G-O-L-D-E-N, H-A-R syndrome. It's a very high-yield syndrome to know for anbemic exams.

Again, think about it as a problem that arises in the context of the first of the first foreign geo arch, okay? Now, so let me maybe do something here that I think maybe, maybe somewhat helpful. So the thing is the foreign geo grooves, right? The foreign geo clefts for the first arch. Remember, we said those grooves and clefts are very lateral. So it would make sense that the external auditory canal is derived from the grooves of the first foreign geo system, so it's the most lateral. I think if you keep going medium, medium, medium, it's almost like you're going into the ears. You can see the timpanic membrane comes right after the external auditory canal. The timpanic membrane is actually the foreign gillin dintation of that arch one, right? Where the grooves and clefts meet, but without, I mean, sorry, where the clefts and the pouches meet without intervening in a measurder, right? But then if you also begin to go further deeper, that means, oh, you're beginning to get towards like the arch, the measurderum part of this, and we see all the malius and the incas are right in there, right? So I think if you just remember going from lateral to medial, a lot of this will begin to click in your mind, begin to make a lot more sense, right? Because as you'll see, many of the structures that come from the foreign geo pouches, like thymus, parathyroid, all those things, they are all very medial in the body, they are very medial in the body.

So I think those are kind of like the two big, the all the major things I would really like to mention with regards to the first, with regards to the first arch. Now the second arch, again, if we're looking at the muscles of the second arch, again, they all derive from measurder, right? Now the key thing I want to remember here is crinion of seven, right? And there's a lot of S's here, right? Then I'll make many parallels with arch number one. So we said the measurderum of arch one gives rise to the muscles of mastication, mylohioid, the tensors, right? Tensors, timpin, tensor, velipolitini, and in the anterior belly of the digastric, and remember, we said those neurocressels show up and they form the malius and incas. Make some parallels here. Arch two, the muscles of, instead of the muscles of mastication, like you have for arch one is the muscles of facial expression for arch two, right? Instead of the anterior belly of the digastric, like we have for arch one, we have the posterior belly of the digastric for arch two. Unlike the maliohioid that we have for arch one, we have the stylohioid for arch two, right? And like the malios and incas for arch one, we have the steepies for arch two, right? So the muscles of facial expression, posterior belly of the digastric, the stylohioid, and the stipidius, they all come from the muscles of arch two, right? And then you obviously the the bones, right?

We said the bones and cartilage for the most part will come from neurocrest, right? In fact, some times you may see this term, mechus cartilage for for the neurocrest, the rib cartilage for arch one and right shirts, R-E-I-C-H-E-R-T, right shirts cartilage for the cartilage that's neurocrested, the rib for arch two, right? That gives rise to again, a lot of S structure, steepies, right? The styloid process, the stylohioid ligament, right? Those things all come from right shirts cartilage. This is all arch number two. So just something to keep in mind. And remember arch two for the most part is supplied by cranioenerv, by cranioenerv seven, the facial nerve, the facial nerve. So many of the things that are serviced by the facial nerve, like platysma, those things are all arch number two, arch number two, direct, right? And then again, if you go to arch number three, right? Again, the arch is get easier as you go, arch number three, the big the measoldrum again gives rise to a big muscle there. The big muscle there we're worried about is the stylopharyngeous muscle, right? And stylopharyngeous muscle is like integrated by cranioenerv nine. So that should tell you that oh, cranioe three is, I mean cranioe nine is the big nerve of the third of the third arch, right? That's the glossopharyngeonerv, right? Glossopharyngeous stylopharyngeous muscle. And remember, if you take the square of three, you're going to get nine, right?

So that's another way remember that oh, far and geo arch number three has the glossopharyngeonerv as its major as its major nerve, right? And then one thing I guess I forgot to mention with the measoldrum of the second arch. Remember I said the measoldrum gives rise to the muscles and the arteries. So the measoldrum you know gives rise to that you know, the muscles I described but also gives rise to the steveidial and hyoidal arteries. So so the steveidial and hyoidal arteries again as I described they all derive from the other right from the measoldrum of the second arch again third arch big thing to remember stylopharyngeous muscle is the big muscle there, the big nerve there, glossopharyngeonerv, right? And then think of it as your carotid arch, right? So your internal and your common carotid arteries be both come from the measoldrum of arch number three. And again at the end I'll just try to make some quick summaries that I think will really help you here as you study for your exam, right? And again remember every arch the measoldrum is invaded by neurocressels. Again, I'm just repeating the yy repeating yourself over and over again. And just doing these repetitions so that it's easier to remember. So if you hear something over and over again in different contexts it'll very likely stick right? So those neurocressels again they form the bone and cartilage, right?

So the bones they form at the greater and the lower to the greater horn and the lower body of the hyoid bone, the greater horn and the lower body of the hyoid bone. It may be like divine why you emphasize in this. You know friends at the end of the country I'll trick you with some stuff you'll find with arch number four, right? But I'll encourage you it's just remember just remember this and compare with arch two, right? So let's make some comparisons with arch two. In arch two I said the lesser horn and the upper body of the hyoid comes from the neurocressels that invade arch two. But for arch three it's the greater horn and the lower body. So you can just pick one and then take opposites for the other. What you may say an easy way to maybe remember arch two in relation to the hyoid bone is to use this numonic L-hub, like L-h-u-b-l-hub, right? Lower horn, upper body for the hyoid. So if you know that then you just take the opposite of that and you know all the hyoid relationships for the neurocressels for arch number three, right? So we say for arch number two it's L-hub, lower horn, upper body of the hyoid, but for arch three instead of the lower horn you be the greater horn, right? And so being the upper body will be the lower body of the hyoid bone, right? So you can these things are not very terrible to remember, right? They're just fairly straightforward and again like I said I'm going to summarize all the stuff at the end, right?

I'm going to summarize all the stuff at the end. And then arch four, right? So let's go to arch four, basically arch four in six. Just remember them as the vigus nerve arches, right? I remember the numbers four plus six give rise to ten, right? So that's a nice way to remember that. And the big things for arch four, again we say that the muscles are right for a misoder, right? Your craic with thyroid muscle comes from the viso-dom of arch four. And then all your palate muscles, all your palate muscles. I think of this arch to be honest with you as all but one, all but one, I call it the all but one arch, right? Pretty much all your palate muscles come from the fourth arch, but there's one exception. Remember we talked about that exception for arch one, right? We said the tensor of a light palatini, right? And then all the muscles of your firings are also innervaded by arch number four. I mean, they all come from the viso-dom of arch number four, but there's one exception, stylo-firingius, right? So it's like there's an exception from the first arch and an exception from the third arch, okay? So that's a nice way again to keep that stuff straight, to keep that stuff straight. And again, the misoderm like we said, gives rise to not just muscles, also gives rise to arteries, so the arteries here, right? With the right subclavian artery and then the arch of the yoder, yoder, yoder, arch, comes from the misoderm of arch number four, okay? And then those neurocress cells, right?

The neurocress cells, again, remember we said that it gives rise to bones and cartilage, right? So the cartilage is around your larynx, right? Like your thyroid cartilage, your epiglotic cartilage, those things that on neurocress cell derived, okay? They come from the neurocress cells that essentially come, show up and invade, they come, show up and invade arch number, the, the misoderm of arch number four, right? And then the big nerve for arch number four is the superior laryngeonerv, okay? The superior laryngeonerv, as you see for arch number six, it's going to be the recurrent laryngeonerv, right? So remember the superior laryngeonerv is superior, so you should come, remember these things that are arranged from a cranial to quadrilo-orientation, right? So it's superior to arch arch number six, okay? And then again, arch number five just disappears pretty much after a while. Now, arch number six, the big things you want to remember is, again, start with the misoderm, misoderm gives rise to muscles and and arteries, right? So the muscles here, the muscles of your larynx accept crack with thyroid, right?

Remember crack with thyroid is from the arch, is from the misoderm of arch four, but all the muscles of your larynx, they all come from, they all come from a arch number, arch number six, and then your esophagus, remember your esophagus has like striated muscle at the top, mixture in the middle, and then mixture of striated and both muscles in the middle, and then at the bottom has this, what is it called, has purely smoothing muscle, right? That striated muscle that comes at the top of your esophagus, guess what? Is it right from the misoderm of arch number four, of arch number six, sorry, of arch number six, okay? And then the arteries that come from the misoderm of arch six, remember these are your common areas, are your doctor satiriosis, okay? Your common area address doctor satiriosis, remember your doctor's literally connects your common area address to your yoder, right? So it would make sense, right, that maybe your yoder should be in a close by arch like arch number four, right? Because again, remember the doctor satiriosis is literally a conduit between your common area arteries and your yoder, right? So, polar arteries, doctor satiriosis, one part of the connection is arch six, but the yoder, right? Other members, the left yodic arch and the right subclavian, they're right above, right? They're right above. That's arch, that's arch number four.

And you can already see that, oh, since these, since the recurring layer in Joe Nerv, is the big nerve for arch number six, you should already see that, oh, maybe it should have some salient relationships with the closest by pharyngeal arch, right? In this case being pharyngeal arch number four, right? That's why it shouldn't be a big surprise that, oh, the recurring layer in Joe Nerv on the left loops around the yoder arch on the left. And the recurring layer in Joe Nerv on the right loops around the subclavian artery. It so happens that those are the arteries of the fourth arch, right? But again, remember the fourth arch is superior, large, in Joe Nerv, the sixth arch is the recurring layer in Joe Nerv. So hopefully with all these parallels that I'm drawing, some of the stuff will begin to make more sense, make more sense to you, right? Because you definitely want them to make sense to you, right? Because these things are all super, super, super important, right? So again, just to quick, quick summary, right? So again, maybe let me see some things because I feel like I maybe talked about the miserterm a lot and talked about the nerves, talked about the neurocress cells, which give rise to the bone and cartilage. Those things are all important, right? But you know, maybe let's bring in a few more just rapid integrations here. That would, you know, again, mix some of this stuff, click, click on your mind, right? So the thing is, again, the end of the are those pouches.

Those pouches, they ultimately give rise to things that are more medial in the body, right? So if you remember for like arch number one, I said that all the pharyngeal grooves or clefts, those are going to be the external auditory canal, right? That should make sense. And then the miserterm gives rise to the muscles and the neurocress cells invade. And then you have like the malice and incas for arch number one, right? If you go a little more medial in that, so it makes sense that all like your middle ear cavity, right? Should be a ton of, a ton of miserterm, right? So like, I mean, a ton of endotr, right? So like your middle ear, remember you'll start with your external ear first. As you start auditory canal, that's pharyngeal groove. And then we have the tympanic membrane that's around those pharyngeal indentations for arch one, right? And then if you go further inside, right? You should begin to be getting to like the miserterm part of things or the neurocress cells that invade them, miserterm part of things, right? Like malice and incas and if you go even further in, right? Again, like your middle ear cavity, those things are all derived from the pouch for arch one, okay? So like your station tube, your middle ear cavity, your mastoid, your cells, those things all come from pouch one, right? And again, don't forget, you see a lot of M's and T's for your first arch, right?

And then pharyngeal pouch two, again, is like your palatin tonsil, those are kind of like the big things, you don't really test that on them, they're almost certainly very highly unlikely to test that on the exam, right? But pharyngeal pouch number three and four, those are kind of high, you know, right? So pharyngeal pouch number three, you know, three gives rise to the thymus and inferior part of thyrids, right? The thymus and the inferior part of thyrids. And then pouch four gives rise to your superior part of thyrids as something called the ultimate brink your body. I'll talk about that ultimate brink your body in a bit, right? So, so you may say like divine, why those pouch three give rise to the inferior part of thyrids, but pouch four gives rise to the superior part of thyrids. So the thing is in development, the miserterm for pouch, I mean the pouch three endoderm actually migrate quarterly, so it almost like walks it's way down. So that's why pouch three, maybe like wow, why is it from the inferior part of thyrids? It started at the top, but it's headed to walk it's way down to the bottom. That's why it has those things, right? So, and then another thing I think that's important is what's the ultimate brink your body? Well, again, remember the ultimate brink your body is again from pouch four. The big thing about the ultimate brink your body is that it gives rise to the parfolicular cells, those are like the sea cells of the thyroid, the mechaucytony, right?

And the calcium levels, right? In fact, if you really dig deep, although this is a little bit beyond the scope of step one, but if you really dig deep, you would ultimately realize that the MEN two syndrome, I believe it or not, actually brink your pouch syndromes, right? The MEN, especially MEN two e2b, right? I mean, it's not a big surprise that those people have medallary thyroid cancer, right? It's a problem with those, remember medallary thyroid cancer, the tumor marker is calcium toning, right? So, it's a cancer of the sea cells, the sorom, the sorom, the thyroid. So, just maybe something that can help you integrate there, but really MEN two e2b, in fact, maybe let me be a lot more specific, MEN two e, especially, that is for sure a pouch problem, okay? That's for sure a pouch problem. And remember, if the third and fourth pouches don't form properly, then all these things that are derived from them, like your parathyroid, they don't form, your thymus doesn't form, right? So, like your parathyroid, if they don't form, well, you're not going to be making any PTH, you're not making any PTH, you're going to have primary hyperparathy, I mean, you're going to have hypocalcemia, right? You're going to have like a primary hypoprathyroidism, right? So, these people have low PTH, low calcium in return, right? And then your thymus doesn't form, right?

So, your T cells don't match, so the patients are going to have a lot of problems with little viral infections, little fungal infections, right? A lot of viral infections, a lot of fungal infections. That's going to be the George St. John Membrace at 22, Q 11 problem, right? And then, I think those are kind of like the big things I think I want to say, say about say about these things. And then one other thing, if we're maybe going a little lateral, because I want to kind of summarize and tie things together for people at the end, again, every form of repetition helps. But essentially, your, your firing geo like clefts, slash grooves, they actually are supposed to get obliterated, they're supposed to completely disappear. If they don't disappear, then you're going to have something called a brink your cleft zest, right? So, groove, groove slash clefts, two through four should disappear. They don't disappear, they persist, right? You're going to form a brink your cleft zest. Brink your cleft zest, again, because those fragile grooves are clefts, they are lateral, it makes sense that a brink your cleft zest is going to be lateral to the midline, right? It's going to be lateral to the midline, and it doesn't really have any connection to the tongue, right? So, it's not supposed to move with swallowing. I think that's a high-yield thing to remember there. And these brink your cleft zest, right? These should be derived from etch budder, right?

The reason I mentioned in all this point is sometimes your friends at the MBME, they try to see if you can differentiate the stuff from the thyraglossodoxist, remember thyraglossodoxis, right? Like your thyroid is lighter than the refermandoderm, right? And thyraglossodoxis arises lighter because your thyraglossodoxis does not obliterate. But remember the thyroid, it kind of comes from this thing called the fremency coming the back of the tongue. So, the thyraglossodoxis is connected to the tongue, so if you're swallowing, you're moving your tongue, right? So, a thyraglossodoxis should move with swallowing. So, I think those are some very key silly differences between a brink your cleft zest, a thyraglossodoxis. Brink your cleft zest, pathophys, second to your fourth friend Joe Grovesor clefts, don't obliterate because there's a booster. Versus the thyraglossodoxis, your thyraglossodoxis does not obliterate because it's a booster. And then one is derived from enduderm, right? This is going to be a thyraglossodoxis. One is derived from enduderm, that's going to be your your brink your cleft zest, right? So, then you say, give it a cyst and say, oh, it has what kind of derivative? Or you want to remember it again, brink your cleft zest is an ectodermod derivative, a thyraglossodoxis is an endudermod derivative. And then one is in the midline, right? Because again, remember the thyroid is derived from enduderm, right? Like pouch stuff, so you should be in the midline, right?

So, thyraglossodoxis is in the midline, a brink your cleft zest again is from a pouch, which is ectoderm, which is lateral. So, it's lateral to the midline, right? And then again, because the thyraglossodoxis hooked up to the tongue, right? A thyraglossodoxis will move with move with swallowing, but a brink your cleft zest will not move with swallowing, right? Again, just very important, very high yield, very high yield to know. And unfortunately, sometimes people can even have these fistulas, right? Where, like, you're faring, remember I say the brink your cleft zest is where, like, pharyngeal clefts or grooves to through four do not obliterate, right? If pharyngeal cleft, just number two, persists, right? One thing can happen is, unfortunately, you may actually have like a link persistent from the, from your neck, all the way to your tonsils, right? That's something called like a pharyngocutaneous fistula. Some people call it like a pharyngeal fistula, okay? The key thing I want to remember is that is the relationship to the sternoclidomastoid muscle. It's actually anterior to your sternoclidomastoid, right? So, a pharyngocutaneous fistula is where brink your, I mean, brink your cleft or groove, again, same thing. I'm just going to use cleft, going forward, brink your cleft number two does not obliterate, right? So, you form a fistula from there to something inward, right? A pharyngealcutaneous fistula, right?

It's almost like you're from the fistula from an ectoderm-derived structure to an endoderm-derived structure, right? So, let's, let's wrap up on some right song. We have the gap of the capnomonic grooves, arches, pouches, or cap clefts, arches, pouches. I'm going to use clefts going forward. The clefts are derived from ectoderm, so they're lateral arches, misoderm, so they're in the middle, and then pouches endoderm, so they're the most media, right? And then we said we have, originally we have six arches, but five kind of hangs around for a bit and just disappears. So, we really have like one, two, three, four, and six, right? And then we said that the misoderm gives rise to the muscles and arteries of the arches, and then we said that neurocressels envied that misoderm and formed the bones on cartilage of the arches, right? And remember for arches number one, we said a lot of M's, a lot of T's, right? And remember we said that these things are organized from like lower to thirds of your face down to like your upper esophagus, right? So, if you think about it, like arches number one, the muscles, right? Remember we have the myelohioid, we have the muscles of mastigation, we have the anterior belly of the digastric, then we have ten-sutein-penetenservylipalatini, right? So, transdial with arches number two, we're the muscles, right?

Instead of myelohioid, for arches two, we have stylohioid, instead of the muscles of mastigation for arches number one, we have the muscles of facial expression for arches number two, right? We have the posterior belly of the digastric for arches two, instead of the anterior belly of the digastric for arches one, and then remember like we had, there's this parallel othetomic, the malice and incas for arches one, we have the stp for arches two, and remember arches one has the, arches one is cranial v two and v three, right? So, you'll maximally and mandibular nerves, right? And then we talked about trigiricalin syndrome, talked about the pyrroban sequence, we talked about the goodynehar syndrome, for arches one, those are all arches one problems, right? And then arches two, right? There's no real big diseases, I'm going to talk about there, but remember arches two is cranial seven, arches three, remember three squitties, my, that's the arch where you have like stylofyrringious muscle, and you have your, also for angio nerve, they're arch four, remember four plus six is ten, so arches four and six, they are vagus nerve derived, right? So, parallel angio nerve, those arch four, requiring our angio nerve, those arch six, remember that for arch four, the arteries are the right subclavian and the eotic arch, right? But for arch six, for the most part, we have the coronary artery and the doctor's arteriosus, right?

And then we talked about how we have these weird relationships where the, the recoryler angio nerve loops around the subclavian artery on the right, but the eotic arch on the left, we talked about, you know, why that may be the case, because those brinkel arches are very close by, and then we talked about the geor syndrome, right? And then we talked about the difference between a thyragloso docsis that bring your cleft cysts. So, thank you for listening. I hope you've enjoyed those podcasts. I do offer, as we wrap up, you know, I do offer one on one tutoring for step one and step two, you can step three, preclinical med school exams, 30-ish-elf exam, so if you need tutoring for any of those things, feel free to reach out to me. And then I also, and I do all the student values, so just reach out to me for like information and costs and stuff like that, and then please subscribe to the website, subscribe to this podcast, divine intervention podcast, is an Apple Google podcast and Spotify, so please subscribe, and then please subscribe to the You Tube channel as well, divine intervention, USMD podcast and videos.

So, for those of you studying for step one, I've pretty much covered all the farming for state, covered a lot of the biochem that's in first state, basically like if you look at the spreadsheet on my website, you see that I've covered a ton of the information in first state, so if you want to listen to those podcasts, feel free to listen to those, cover the Reno and all those things. So, thank you for listening. I have to rush off to church, so I'll see you in the next podcast. God bless you.

Clefts, Arches, Pouches (or GEP/CAPP).

Ectoderm.

Cranial Nerve VII (Facial Nerve).

Muscles of mastication, Mylohyoid muscle, Anterior belly of the digastric, Tensor tympani, and Tensor veli palatini.

A problem affecting structures derived from the first pharyngeal arch (Arch I), often presenting as eye, ear, and spine defects.

Pouch IV.

They develop from dorsal (back) to ventral (front), controlled by Hox genes.

Arch I.

Branchial cleft cysts do not move with swallowing; Thyroglossal ducts move with swallowing because they connect to the tongue/midline structures.

Arch III.

Recurrent laryngeal nerve (RLN); It loops around the left pulmonary/aortic arch.

MEN I Ib Syndrome (or general pouch defect).

They develop from dorsal (back) to ventral (front), controlled by Hox genes.

Arch I.

Branchial cleft cysts do not move with swallowing; Thyroglossal ducts move with swallowing because they connect to the tongue/midline structures.

Arch III.

Recurrent laryngeal nerve (RLN); It loops around the left pulmonary/aortic arch.

MEN I Ib Syndrome (or general pouch defect).