 Hello everyone, welcome back to another session in dentistry and more. So we are moving on to human anatomy osteology and embryology lecture series today's topic is pharyngeal or visceral arches, which is also known as Brankiel or Gil arches. Why it is known as Brankiel or Gil arches? Because this is humans vertebra is similar to fish vertebra. So the fish arches known as Gil arches or Brankiel arches. So this is interchangeable You also in exams the question might come as pharyngeal arch or Brankiel arch So it is interchangeable because both has both vertebrates has six pairs of arch but in humans the fifth arch is failed to develop and the sixth arch is rudimentary So let's see the details of very interesting very important pharyngeal or Brankiel arches pharyngeal arches or Brankiel arches We'll start with this picture So this is a primitive embryonic cavity a longitudinal section picture So you can see a primitive embryonic cavity around two to three weeks just true to three weeks So the total gestational period we know it is around 40 weeks So you can imagine how primitive how early it is So in the earliest stage if we take a longitudinal section, okay? This is a side view. So if we turn this 90 degree we get a embryonic cavity like this or embryo like this So if you take a longitudinal section, we get at this type of Primitive pharynx with three germ layers that is endoderm, mesoderm and ectoderm So endoderm, mesoderm, ectoderm are the three distinctive germ layers where the endoderm is covering the inner cavity So the primitive pharynx is lined by endoderm, which is the most innermost one Ectoderm is outermost covering of the embryonic cavity and the tissues or the Portion which is between the endoderm and ectoderm is known as mesoderm. So this is the earliest cavity This is the buccal pharyngeal membrane, which is a future mouth So just imagine you will be having head here The cranial cavity and this is esophagus will be having the other portions here Okay, so this is the very earliest primitive stage So this is around two to three weeks So so you need to visualize it in a three-dimensional view. This is side view. This is a friend view This is a cross-sectional. Sorry the longitudinal section of this embryo So around fourth week of intrauterine life or the fourth week embryo There will be a mesodermal out thickening. So mesodermal Thickening will be there which will be projected outward. Okay, so out pouching of mesoderm on both sides of developing pharynx So there will be out pouching. Okay, so it happens around fourth week So this is a mesoderm this green one. So this will grow outward Okay This will grow outward So this cavity will be like this at around fourth week of Intrauterine life. So fourth week embryo will be like this. So this Mesoderm is out pouching. So we have pouches like this One two three four pouches on either side. Okay, so it is bilateral So don't get confused when I say pouches So we have two pouches basically that is Mesodermal pouch, which is actually known as Arches that is brankill arches or pharyngeal arches. Okay, that is mesodermal thickening or mesodermal pouches. Okay The next thing is endodermal pouches. Okay, that is this one The endodermal pouches, which is known as The real pharyngeal pouches. Okay The origin is what matters. Okay, whether it origins from mesoderm Whether it is origin from endoderm Is what matters. So if it is Endodermal origin, which is known as pharyngeal pouches And if it is a mesodermal thickening or mesodermal pouches, which is known as Brankill arches or pharyngeal arches. Don't get confused. The origin is important Mesoderm endoderm and ectoderm and the most outer covering that is a ectodermal Origin, which is known as Brankill or pharyngeal clefs or grooves So the out pouching happening from the mesoderm. So the mesoderm is growing outward. Okay on both sides at around fourth week of embryo Which is known as pharyngeal arches or brankill arches. So which is a mesodermal thickening. Okay So this is a mesodermal thickening. Hope you clear this idea So That is a mesodermal Thickening which is known as arches. Okay arches so whereas the This is It both the both sides on the pharyngeal cavity. So this blue is the violet is the pharynx the developing pharynx So these pharyngeal pouches Okay Is present between The arches. Okay And now we have pharyngeal pouches Which form on the endodermal side. Okay. So the endoderm, you know inner cavity So endodermal side we will be having pharyngeal pouches. This is a mesodermal thickening. Okay This is the outermost covering is the ectoderm the innermost layer is the endoderm. So there will be pharyngeal pouches form on the endodermal side between the arches And there will be pharyngeal grooves or pharyngeal clefs. Okay. So I interchangely Use pharyngeal and branquil is both the same. So branquil cleft or branquil arches branquil pouches or pharyngeal pouches pharyngeal arches pharyngeal clefs And this pouches is the pockets of endoderm. Okay And there will be clefs pharyngeal clefs forms From the lateral ectodermal surface of the neck region to separate the arches. Okay. So The arches develops from mesoderm The pouches develops from endoderm and the clefs Is developing from ectoderm. Okay. So the mesodermal thickening and there will be pharyngeal pouches between between the arches and there will be the pharyngeal clefs which is forming from the ectodermal surface of the neck region to separate the arches. Okay. So these arches are formed from mesoderm whereas the pouches which is present between the arches are from endoderm and the clefs is forming from ectoderm which is separating these two arches. Okay. So the same picture I have drawn here. Okay. So we have six pairs of arches in general but the problem is this is similar to fish that is why it has got this name gill arches but the problem is we don't have two pairs active. So we have in turn four pairs and one is rudimentary. So we have first arch, second arch, third arch, fourth arch and the sixth arch. The fifth arch is failed to develop and sixth arch also it is very rudimentary. So actively we have four arches. Okay. So this is the pharyngeal arches which is developed from mesodermal thickening. Okay. So this mesoderm out pouching and become pharyngeal arches and the endoderm pouches is formed between these two arches which is known as pharyngeal pouches and the pharyngeal clefs or brachial clefs which separates these arches. Fine. So the same picture I am drawn here with more detail description. So there will be a buck of pharyngeal membrane just like here. Okay. So this goes here then this goes here. So buck of pharyngeal membrane will be here. We have one, two, three, four pouches pharyngeal pouches. Okay. So here the number might not be true. Here this is a clear picture. I just wanted to differentiate between mesoderm, ectoderm and endoderm. So now we are in this picture. We have clearly one, two, three, four and fifth one that is a sixth arch, fifth is missing. Missing in the sense it is failed to develop. So we have four pouches. Similarly, we have four clefs. Why? Because we have five arches. So there will be four spaces between these. Okay. Four mesodermal spaces that is known as pharyngeal pouches and four outermost covering that is clefs or pharyngeal or brachial clefs. Okay. So that is the space between these. So ectoderm will be the outermost covering. So this is the ectoderm which is known as pharyngeal cleft. The inner layer is known as endoderm which is the pharyngeal pouch. Hope you are clear with this. So you need to visualize from the very beginning of embryogenesis where the one cell, two cell, four cell, morula, blastolite is becoming. It is changing into three layer cells that is endoderm, ectoderm and mesoderm. After that around two to three weeks this type is formed with primitive pharynx. So around four weeks we have thickening on the either side of pharynx that is mesodermal thickening. One, two, three, four, five arches. One, two, three, four pouches and four clefs. Okay. So these are the arches which later give rise to various structures in the head and neck regions. Hope you are clear with this picture. This is a human face on a lateral aspect. This is a nose. This is a lips. This is a chin and this is a neck portion. Okay. So we are talking about pharyngeal arches which ultimately give rise to mandible, maxilla, hyoid bone and all the muscles, various arteries, nerve elements, the ligaments in the head and neck region that is important of brachial arches or pharyngeal arches. Okay. So till now I hope you are clear with this, this picture, this picture and this picture. Okay. Now we are moving on to the details of each arch. So each arch will consist of a cartilaginous element, a cranial nerve, an aortic arch and a myoblast which are basically neurochleous cells. So cartilage will give rise to various elements, various bones and cranial nerve which is associated with each arch which supplies those muscles and other parts and aortic arch which is the arterial supply or the vascular supply of that particular arch and its other related structures and myoblast are the primitive cells which later give rise to various muscles associated with each arch. Now we are moving on to the derivatives of each arch which is very, very important. It is commonly as Christian, the pharyngeal arch, derivative of first arch, second arch, third, fourth and sixth and its muscles and its nerve supply and its arterial supply, the ligaments associated, the bones associated. So you need to remember this picture. Okay. So the first arch is known as mantibular arch. Okay. So the first pharyngeal arch is known as mantibular arch and which is the first of sixth pharyngeal arch that develops during the fourth week of development and it is located between the stomodium and the first pharyngeal groove. Okay. So this is the first pharyngeal groove and this is the stomodium and it forms between these two. Okay. That is the first pharyngeal arch which is formed between the stomodium that is the stomodium is a future oral cavity and this bucko pharyngeal membrane which lines the stomodium. So the first pharyngeal arch which is also known as mantibular arch. Okay. So this is the first one is a mantibular arch. Okay. So this is a lateral side. This is just one arch, not the just both arch. So the expanded version of this arch is this elongated black. This one. Okay. So this is known as mantibular arch. Okay. So as we mentioned, it has one cartilage, it has one cranial nerve and it has supple, aortic supple that is a vascular supple and muscles attached. So every arch will give rise to bones, certain ligaments, certain muscles and there will be a nerve associated with it. So let's see one by one. The first one is mantibular arch. So the cartilage which later gives rise to various bones is known as the mechels cartilage. That is the cartilage of first arch or the mandibular arch is known as mechels cartilage which is very, very important. It's commonly asked as question mechels cartilage and its derivatives. So mechels cartilage which give rise to. Okay. So this is mechels cartilage, this red dotted line which is present within the mandibular arch. Okay. So mechels cartilage which forms the mesoderm of mandibular process and eventually regresses to form the incus and malleus of middle ear, the anterior ligament of malleus and the sphenomantibular ligament. Okay. So the mandible. So you can see that it looks like a mandible. Right. So the mandible or lovojo forms by the pedicontral ossification using this mechels cartilage as a template. Okay. So this is malleus bone. This is incus bone. So we have three bones present in our ear. Okay. So hope you can imagine a future ear at this place. Okay. So this is a mandible. So this is the ear cavity. So future three bones, but the two bones are developed here. That is within the first pharyngeal arch, the malleus, incus and the mandible. Okay. So there lots of bones are formed within the mandibular arch. Let's see one by one. So the malleus, incus, then the premaxilla, then the maxilla, zygomatic bone, mandible and part of temporal bone because temporal bone is formed here. So part of temporal bone will be the first arch. Okay. So we have malleus, incus, the first two bones. Okay. The first two upper bones of ear cavity. Then we have the premaxilla, maxilla, zygoma, mandible and part of temporal bone. So most of the facial bones are formed from the first arch. Okay. So from this arch, from this arch, most of the facial bones are formed. So that is a skeletal part bone. Now the ligament is sphenomantibular ligament. Okay. So we have sphenoid bone here and disjoint mandible. So sphenomantibular ligament is formed from the first arch. And other structures are this squamous part of temporal bone exactly and the anterior ligament of malleus and the palatine bones, all are formed from first arch. Now we have muscles of mastication which is formed from first arch because it is, since it is a masticatory muscles, most of the muscles are attached to mandible. Okay. So what are the muscles of mastication? We have four muscles that is masseter muscle, medial and lateral teregoid muscle and temporalis muscle. So all are associated with mandible. So it is very easy to understand if there is mandible and if there is mandible or arch, there will be muscles of mastication because mandible is the bone which is associated with mastication. So always connect muscles of mastication with mandible. So it is easy to remember the arch one give rise to muscles of mastication because why I am telling you this because mandible instead of mandible or arch, the second arch giving rise to muscles of facial expression that is a different one. Okay. So you always get confused. So the mandible is associated with muscles of mastication. So the first arch giving these muscles of mastication, those are masseter, medial and lateral teregoid and temporalis. Along with that, we have mylohyoid muscle, the anterior belly of digastric muscle, tensor valley palatine muscle and tensor timpani muscle. Okay. So all these are derived from first arch and also along with that, we have the tongue develops from anterior to third of tongue because oral cavity is here. So we also have tongue here. So we are not going very detail about this. So anyway the tongue, the anterior to third of the tongue is developed from the first arch. Okay. Now we have nerve supple that is the first arch is known as mandible or arch and nerve supple is basically from trigeminal nerve. The nerve supple of first arch is trigeminal nerve. So we have three branches basically of thalamic maxillary and mandibular branches. So maxillary branch and mandibular branch and also corda timpani branch which is a branch of facial nerve is supplying the first arch. Now let us move on to the second pharyngeal arch. Okay. So this is second pharyngeal arch, second pharyngeal arch. So second pharyngeal arch you can see the second pharyngeal arch which is the this line. Okay. So it is very easy to study second pharyngeal arch. The most upper part we have one bone which is steps. Okay. So the third bone of your carotomyllis incus and steps. So the bony parts are steps then the styloid process, styloid process then we have this is the hyoid bone. So hyoid bone has basically body and the conva. The body and conva is there. So body has superior surface and inferior surface and conva has smaller part and smaller conva and greater conva. So the second arch and third arch are involved in the formation of hyoid bone. So the bones are lesser conva of hyoid bone whereas the greater conva is developed from the third arch. Hope you are getting the getting the idea of it. Okay. So it is not very easy to depict here. So this is a hyoid bone this black one it has two parts basically that is conva and the body conva has smaller and greater part smaller is this one that is formed from the second arch whereas the greater conva is developed from the third arch and the superior surface of the body is developed from the second arch whereas the inferior surface or the lower part is developed from the third arch. Okay. And we have the ligaments in first arch we have seen sphenomandibular ligament in the second arch it is stylohyoid ligament. Okay. First arch it was sphenomandibular ligament and second arch it is stylohyoid ligament. One thing I forgot to mention that is the arterial supply that is a blood supply of first arch which is from maxillary artery which I forgot to mention so the nerve was trigeminal nerve whereas the maxillary nerve mandibular nerve and a part of facial nerve that is corda timpani nerve is involved the arterial supply is maxillary artery. Okay. Now we are into second and third arches the second arch I told you it all basically starts from S the stabes styloid process all are bony processes or the bone we are talking about smaller corner of hyoid superior surface of body of hyoid and again the ligament is stylohyoid ligament. Okay. And the first arch the cartilage was known as mechels cartilage the second arch which is known as raches cartilage. Okay. So the mechels cartilage and raches cartilage are important question. So this arch is giving rise to all these structures and muscles are like I mentioned muscles of facial expression then platysma muscle stylohyoid muscle and the posterior belly of digastric in the first arch it was anterior belly of digastric and this is posterior belly of digastric. Okay. Second arch is giving posterior belly of digastric, stapedius muscle, auricular muscles, occipitofrentalis muscle all are from the second arch and the nerve supply of second arch is facial now and the blood supply is basically from stapedial artery. Okay. So stapedial artery is the blood supply the first arch was maxillary artery and second arch is stapedial artery whereas the nerve supply is facial now and the muscles derived I mentioned now we are into the third arch third arch only two bones basically that is greater conva greater conva and the lower surface of body of hyoid the other parts the remaining parts of hyoid bone which is derived from third arch okay there's no ligament from third fourth and six arches and the third arch is giving rise to only one muscle which is stylofaryngeus and the nerve supply is glosopharyngeal nerve and fourth and sixth is conveniently give laryngeal cartilage such as thyroid, crickard, erythnoid and other laryngeal cartilages and this is hope you can see this is a thyroid cartilage this is a frackle rings and crickard cartilage so all are derived from fourth and sixth arches so the nerve of first arch is basically mandibular and maxillary nerve but part of facial nerve that is caudative panizer second arch the nerve is facial nerve the third arch is glosopharyngeal nerve so the fourth arch is superior laryngeal branch of vegas whereas the sixth arch is recurrent laryngeal branch of vegas okay so the fourth and sixth arch combined lingering cricothyroid, levator, pylate, constrictors of pharynx and intrinsic muscles of larynx so that was about the pharyngeal arches regarding the blood supply that is a maxillary artery the first arch is applied by maxillary artery then the stepedial artery third arch is by common carotid and internal carotid artery fourth arch by the subclavian artery and aortic artery sixth arch is basically by pulmonary artery and doctor's arteriosis so this is all about brankill arches it is a very important question so question might be brankill arches pharyngeal pouches its derivatives mechels cartilage reaches cartilage so the first cartilage is known as mandibular sorry the first arch is known as mandibular arch the second arch is known as hyoid arch because it is mostly associated with hyoid bone the stylohyoid ligament and the small cone of hyoid superior surface of body of hyoid and the styloid process so we need to learn the bones formed from it the muscles attached to it and the ligament and the blood supply and the nerve supply okay so the muscles I repeat the first arch is giving mastigatory muscles and the myelohyd muscle anterior belly of digastric tensor timpani and tensor palatine whereas the second arch giving muscles of facial expression posterior belly of digastric stylohyoid stepedius muscle third arch is giving stylofaryngeus fourth and sixth arch is giving muscles of larynx that is thyroid crickard and other muscles and the nerve supply the mandibular maxillary and corda timpani in the first arch the facial nerve in the second arch and the glosopharyngeal in third arch and the vagus superior laryngeal for the fourth arch and the recurrent laryngeal for the sixth arch okay and the bones formed from first arch myelous incus maxilla zygoma mandible and the a part of temporal bone the second arch stape styloid process and the corner smaller corner and superior surface third arch is greater corner and inferior surface of hyoid and this other bones so it was bones and this is muscles so that's all about brankill arches laryngeal arches I took a lot of time because it is very very important primitive or the embryogenic the pouches are very important so the rest of the anatomy chapters will be based on this one so you need to understand what is ectoderm and endodermisoderm what is the first second third fourth and sixth arches and its derivative so you can study very easily just like how we study tooth formation the basic steps should be very thorough so you can easily build up the remaining chapters over it so it is a very very important chapter not just for your exam purpose it is important to learn the other chapters as well okay thank you I'll come up with another topic in anatomy