all right ninja nerds in this video we're going to be talking about the development or the embryology of the pharyngeal apparatus before we get started make sure you hit that like button comment down in the comment section and please subscribe also down in the description box with links to our facebook instagram patreon account go check that out get in contact with us we appreciate you and love you and let's get into this all right ninja so when we talk about the pharyngeal apparatus the best thing that i want us to do is start off taking a look at an embryo in a sagittal section so first thing to recognize when you're taking a look here at this little baby embryo this is going to be your cranial end and this down here is going to be the caudal or the tail end right so that's the first thing that you need to know now up in the cranial end you're going to have this kind of like little interesting almost gill-like looking structure within the embryo right about here right and that's called your pharyngeal apparatus you know what's really cool is if we take a slice imagine i take and i make a slice down this pharyngeal apparatus like this and then open it up and take a look at it looky looky what that pharyngeal apparatus is going to look like this is the structure that you'll get so the first thing here is you see where we have this green layer which is your endoderm layer and then this blue layer which is your ectoderm layer you see where they meet right here where they kind of like connect that right there is called your bucco pharyngeal membrane alright so that's going to become the mouth so whenever that kind of busts open it's going to give way to the mouth now there's a couple different components of the pharyngeal apparatus the first one is this kind of blue layer here this like nice little beautiful layer here of blue on the outer parts this right here is called your pharyngeal particularly you see like these little divots in here these little divots in the pharyngeal apparatus right here that is going to be giving way to what's called your pharyngeal clefts or sometimes it's even referred to as your pharyngeal groove so it's called your pharyngeal clefts or the pharyngeal glute groove now the big thing to remember about these pharyngeal clefts is that they are covered with ectoderm and now we're not going to really focus too much on these pharyngeal clefts okay because they don't really give way to anything really special except for the first one i can give away to like some of the tissue that lines the external ear canal but other than that nothing else really specific about it the next one is this inner kind of like red layer this inner red layer is a mesoderm core and this is kind of what gives way to the big structure called the pharyngeal arches okay so these are your pharyngeal arch and this is kind of a core of mesoderm which is a beautiful little like mesenchymal tissue okay the last part of this pharyngeal apparatus is the most inner portion and you see how there's these like these little divots here right here another little divot here another little divot here these little divots here are very specific and very special little structures that give way to a lot of different things and this is called your pharyngeal pouches so these are called your pharyngeal pouches okay so that's really really really important and again what i want you to remember from this is that those good old pharyngeal pouches are made up of endoderm now the next thing i want us to do here is i want us to basically kind of set a a guideline of what we're going to be talking about throughout this video and what we're going to do is we're going to talk about the pharyngeal pouches right what they become pharyngeal arches what they become and the pharyngeal clefts and what they become all right so really quickly i want to give you guys just a basic understanding of what the pharyngeal pouches pharyngeal arches and pharyngeal clefts will become okay tissue wise let's just be very vague here so the pharyngeal clefts is the first one here the pharyngeal clefts remember we said are basically ectoderm right and again we can call them like grooves as well the really the only one that you need to know here is this first one this first little pharyngeal cleft but pretty much what this will become is epithelium so remember it is ectoderm but that ectoderm is going to give way to epithelium and really what it's going to do is it's going to cover a particular area and the first one covers the in the actual lining of the external ear canal so if you really want to remember it the first cleft actually gives way to the lining the external ear canal that's really kind of all i want you to know about the pharyngeal cleft other than that nothing really specific to it the big mama what's going to count for pretty much most of this actual lecture is going to be these good old pharyngeal arches their pain and the noggin and these things are a nice little mesoderm and the reason why it's a tough little thing is that this can give way to connective tissue and we talk about connective tissue that there's a bunch of different things that are related with that but one of the big ones is also going to be cartilage so it can give away a bunch of connective tissue it can give way to a lot of different cartilage especially like laryngeal cartilage it can also give way to muscle okay and to bones as well as nerves sometimes there's going to be some special cranial nerves that are going to be kind of developing from these actual arches as well the last one here is going to be the pharyngeal pouches and really again it kind of goes back to the epithelium from the pharyngeal clefts so the pharyngeal pouches they will give way to some epithelial structures so they will kind of it's endoderm and then endoderm will become epithelium that'll align particular areas particular cavities but also the other thing to remember is that it can also give way to glands some special glands parathyroid it also can give way to uh like the thymus and some other structures as well okay so very important to remember these pharyngeal pouches and again uh what they're going to become so we're going to cover all of each one of these particularly actually the pharyngeal arches and the pharyngeal pouches in more detail so let's move on to that all right so the next thing we have to do is kind of go through particularly what next we kind of really just discussed the basics of differential cleft and again if you really want to remember the first pharyngeal cleft or groove will become the epithelium that lines the external ear canal but other than that nothing else really specific the next one we have to talk about is these pharyngeal arches so again the primary focus here is going to be the pharyngeal arches and again this is going to be that mesoderm core here right so that's what we're really primarily going to focus on now remember what i told you the pharyngeal arch is the mesoderm or that mesenchymal tissue will differentiate into a bunch of different types of tissues what are some of those tissues and that's what we've got to focus on so the first thing that i want you to remember is it gives way to muscles so different types of muscles now we give particular names to the arches right and it's very simple thank the lord it's very simple this is your first arch this is the second this is the third this is the fourth the fifth usually either doesn't form or it digresses and then this last one here is the sixth pharyngeal arch so what we need to know is is what does the mesoderm within that first second third fourth and six pharyngeal arch differentiate into and the first thing is with respect to muscles so the first thing i like to remember is that the first pharyngeal arch is going to be responsible for your chewing muscles it's supplied by the trigeminal nerve so i just like to remember keep it simple right your muscles of mastication that's going to be the first one if you really want to know those that's going to be your pterygoid the medial lateral masseter as well as the temporalis the other muscles that it does also supply is going to be the myelohyoid and the digastric we're going to abbreviate this digastric anterior belly and then the last one is going to be that tensor vely palatini okay so these are the muscles that are supplied by the first pharyngeal arch these are for chewing these are basically going to be super hyoid muscles and then this is also going to play a role within movement of that soft palate during swallowing the second arch remember muscles of facial expression there's a ton of those we're not going to go through all of them but this is going to be your muscles a facial expression okay it also gives way to some other muscles okay such as the stylohyoid as well as the digastric posterior belly and then a tiny little muscle in the actual middle ear called the stapedius so called the stapedius muscle okay the next thing is the third arch the third arch is one muscle thank goodness all right and this muscle is called the stylopharyngeus it's called the stylopharynges and this one is supplied by the glossopharyngeal nerve again a little muscle that helps to be able to play within kind of the deglution or swallowing process and again second arch facial expression stylohyoid digastric posterior belly are super hyoid muscles and stapedius just kind of modulates the movement or bumping of stapedia stapes bone on the inner ear that controls kind of like the sensitivity of hearing the last one is your fourth and sixth arch and these supply your kind of a couple different muscles they supply what's called your pharyngeal constrictor muscles so we're just going to put your pharyngeal muscles right so that's your superior middle inferior fragile constrictors that control kind of the deglution process and it also acts on your laryngeal muscles and you've got a bunch of these little suckers but there's a bunch of these the cricothyroid the arytenoid muscles all those and then the last one is going to be what's called the levator vely palatini and again this is going to be again involved in that deglutition process so you kind of have an idea of what all these muscles that red portion there well all the mesoderm differentiates into muscles respective to their arches and those are these the next thing we've got to do is talk about the next thing that the mesoderm can differentiate into which is bones the bones and connective tissue are cartilage of the first of the pharyngeal arches and again they're corresponding so what is the first second and thankfully nothing really from the third but from the fourth and sixth the first arch okay the first one is going to give way to a lot of the bones um pretty much of your entire skull okay so what are some of these bones it's going to give way to particularly your maxilla okay it's going to give way to the zygomatic bone well bones right and the maxillary bones it's going to give way to the mandible and it's also going to give way to you know this part over here what is this bone here this is that squamous part of the temporal bone so we'll just put temporal bone but again remember we'll put here we'll put squamous part of the temporal bone right so these are going to be some of them you can also have some other bones that come off of that temporal bone like your mastoid process and styloid process and stuff like that right the second arch you see this little bone here this highway bone kind of within the neck right there that's going to be one of them that are derived from the second arch right so the hyoid bone then look what the higher bone is actually connected to you see this ligament here this like bluish ligament this blue ligament here which we're going to kind of represent here there's a ligament that connects the holy bone to the styloid process that is called the stylohyoid ligament pretty original right so stylo hyoid ligament now there is also textbooks that say that the higher bone not only comes from the second arch but a little bit of it comes from the third arch for simplicity's sake we're going to say that most of it's going to be coming from the second arch but if you really want to remember some of it is also they can come from the third arch but the stylohyoid ligament is going to be coming from at least the second arch the next thing here is you have these little bones you see these little bones in your inner ear well actually in your middle ear these little bones here are called your ossicles this little one here which taps on the oval window is called stapes that is found in the that's actually derived from the second pharyngeal arch whereas if we're really being specific the malleus and incus which are the other two little bones in the inner ear those are technically coming from the first french arch so if you really wanted to add on here we can also say the malleus and incus whereas stapes is particularly from the second arch the last one here is going to be the actual cartilage from the larynx so you know the larynx you have a bunch of different types of laryngo cartilage right what are some of them we're not going to do all of them but we're going to mention them at least the first big one here is going to be the thyroid cartilage that's going to be one big one right another one is going to be the arytenoid the arytenoid cartilage and there is other ones there's like the cuny form and then the corniculate and these are pretty much going to give way to the cartilage of the larynx so to finish off with the actual bones that are derived from the mesoderm of the pharyngeal arches first will give way to these bones second to these bones and this ligament and the fourth and six will give way to the laryngeal cartilage thyroid aretenoid cuneiform and cornicule okay we've covered the muscles the bones the connective tissue and cartilage now we're going to do is we're going to move on to the nerves derived from the pharyngeal arches all right so the nerves of the pharyngeal arches so what nerves are going to be supplying the actual particular regions that are going to be derived from the pharyngeal arches so if we look at the nerves that are going to be derived here the first one that is going to be from the first arch is going to be cranial nerve 5. you know cranial nerve 5 is this is the trigeminal nerve so this is the trigeminal nerve the next one here which is going to be supplying the second pharyngeal arch that is going to be cranial nerve seven and cranial nerve seven is going to be the we're just gonna put facial nerve right the next one which is gonna be for the third pharyngeal arch the third pharyngeal arch is going to be cranial nerve nine and cranial nerve nine is going to be which one the glosso pharyngeal nerve and then last but not least the fourth and sixth pharyngeal arches are going to be supplied by cranial nerve ten and that is going to be the vagus nerve so again quick recap of these first pharyngeal arch will be the trigeminal nerve the second pharyngeal arch derivative is going to be the facial nerve third will be the glossopharyngeal and then fourth and sixth particularly if you really want to be specific to superior laryngeal nerve for the fourth and then the recurrent laryngeal nerve for the sixth will be for the vagus nerve so the last one here is going to be the arteries of the fringe arches if you guys watched our video on the development of the vascular system we talked about how from the aortic sac how through the process of angiogenesis blood vessels go from the aortic sac through the pharyngeal arches from the french arches you'll make some blood vessels and then that will sprout to the dorsal aorta and that made what's called the aortic arches so the aortic arches are sometimes even called the pharyngeal arteries right or the pharyngeal arch arteries and they have to become particular structures in the adult what are those structures do you guys remember from that video the first arch we said is what's called the maxillary artery so that'll become the maxillary remember the first is max so the max you can be is number one right so maxillary order for the first one the second one we said it's pretty rare that it actually remains but you said you have what's called the hyoidal artery and that hyoidal artery gives way to what's called the stapedial artery usually this does not actually remain in the adults pretty rare 10 people may keep it but you remember second and s stapedial all right so first is max so maxillary artery second is s stapedial third arch third letter in the alphabet is c so the third arch gives way to what's called the common carotid artery as well as the internal carotid artery but particularly the most proximal portion of the internal carotid artery the fourth arch you actually have the right and left of these arches right so you have technically a right and left first second third fourth and sixth the fifth one again either doesn't develop or digresses the fourth arch technically if we're being really specific here the right one will give way to what the right one gives way to what's called the the subclavian artery so it gives way technically to what's called the subclavian artery whereas the left one will give way to what the aortic arch all right and then the last one here is the sixth arch and again you have a right and you have a left one here the right one will specifically give way to the right pulmonary artery so the right pulmonary artery and then the left sixth arch will give way to what's called what the left pulmonary artery as well as what else the ductus arteriosus which is going to be a little connection between the pulmonary trunk and the aorta so these will be the derivatives of the mesoderm portion of the pharyngeal arches so whenever you kind of see in textbooks here they might have like a couple different like holes here of what's actually going to be coming from this right so you may have like for example there may be like a nerve kind of within that structure that's going to be coming from it there may be a vessel that's coming from that right and then again you're also going to have this portion here kind of transform into muscles into bones and cartilage and connective tissue and all that stuff like that so we're able to see that from these pharyngeal arches what they derive into with respect to muscles bones connective tissue nerves and arteries let's now move into the pharyngeal pouches and talk about what they become all right so we're almost done pharyngeal pouches right so this is the endoderm portion so we talked about the ectoderm like one of them right external acoustic meatus the uh particularly the epithelial lining then we talked about the french arches what all they become the inner part here is the endoderm which is going to be the pharyngeal pouches now there's again a couple different fragile pouches so if you look here the first one is right here this little like little divot in here that is going to be the first pharyngeal pouch this obviously will be the second pharyngeal pouch this will be the third pharyngeal pouch and this will be the fourth pharyngeal pouch now if you noticed the first and second they only have one little divot but then the third one it splits you see how it splits like this this portion here is going to be the third and what's particularly called the dorsal pouch so third dorsal pouch and this one here is called the third ventral pouch okay then over here you have the fourth dorsal pouch and then here you have the fourth ventral pouch what we need to know is is what does each one of these pouches first second third dorsal and ventral fourth dorsal and ventral what do they become all right so the first thing that we should talk about here is the first pharyngeal pouch the first pharyngeal pouch will actually have endoderm that will actually move into the inner i'm sorry the middle ear cavity so you know within the middle ear cavity you have this uh particular area here that we specifically don't call the middle ear cap but we actually call it the tympanic cavity right so it's the middle ear cavity or the tympanic cavity then you have some tissue that's going to be moving and kind of draining the middle ear or the tympanic cavity with actually the uh the nasal the nasal cavity right into the nasal cavity this structure here is called the eustachian tube so what is this one called eustacian tube so technically the first pharyngeal pouch will have epithelial tissue derived from the endoderm move and invade into these areas both the tympanic cavity and the eustachian tube the second pharyngeal pouch will actually become more specifically a type of lymphatic tissue if we're really being specific a type of lymphatic tissue and that kind of lines up in the areas of the actual nasal oral cavity as well and these are called your tonsils your tonsils they're kind of a lymphatic tissue all these green little structures here you're going to have the tonsils these are going to be derived from the second pharyngeal pouch the more particular one here is going to be the on the back of the nasopharynx and that's called your pharyngeal tonsils right but again you do have other tonsils here like your palatine tonsils your tubal tonsils and your lingual tonsils okay all right on to the good stuff which is your third and fourth pharyngeal patch but we actually have to talk about the ventral and we also have to talk about the dorsal components all right so when we talk about the third pharyngeal pouch again you got the ventral and the dorsal the dorsal part of the third pharyngeal pouch the dorsal part will give way to these tiny little very very special glands on the back of the thyroid but you know what's interesting is they're on the bottom part right of the thyroid well they'll eventually go on the bottom part of the thyroid and so these are called your inferior parathyroid glands okay your inferior parathyroid glands which seems odd right you would think that the the actual inferior parathyroid glands would come from like the fourth dorsal but what actually happens is during the development they actually move in a particular way where the uh there's movement of the fourth dorsal pouch upwards where the superior thyroid glands go above but anyway off my soap box the third dorsal pharyngeal pouch will become the inferior parathyroid glands the ventral portion right of that third pharyngeal pouch that is going to give way to a very special kind of lymphatic tissue that will actually start in the neck but then move down into the chest where t cells will actually mature this is called the thymus so this is called your thymus very important to actually understand this stuff the reason why is that sometimes there's a condition called digeorge syndrome they love to ask this stuff especially embryology where the third and fourth pharyngeal pouches don't actually develop and so because of that they lose their thymus and they also lose their parathyroid glands as well and so that becomes a very interesting kind of condition so very important to know this stuff let's go into the last one here the last one here is your fourth fringing pouch and again we got the dorsal and the ventral thankfully science has kept us nice and simple for us the dorsal the fourth dorsal friendship pouch becomes the superior parathyroid glands right so the superior parathyroid glands and then lastly the actual fourth ventral so then you have the fourth ventral pharyngeal pouch what does that become you see these little cells here they actually are particularly it starts off it's weird they start off as what's called these those these little structures here from the fourth ventral fringeal pouch start off what's called the ultimo uh pharyngeal body ultimopharyngeal body or brachial body right so ultimo pharyngeal body and then eventually they give way to what's called parafollicular cells or sometimes noted as c cells which secrete calcitonin so if you think about this let's say that somebody did have digeot syndrome and they didn't develop their parathyroid glands what would that affect their calcium metabolism if they didn't develop their thymus how would that what would that affect that would affect their t cell development so they may develop some immune system issues and also the parafollicular cells the calcitonin release that also is involved in the calcium regulation so you can see how something like this not developing properly could lead to some serious issues but that tells us about our pharyngeal pouches and our pharyngeal apparatus all right ninja nerds in this video we talked about the development of the pharyngeal apparatus i hope it made sense and i hope that you guys did like it and enjoy it as always ninja nerds until next time [Music] you