Comprehensive Overview of Skull Anatomy and Related Structures

[Music] hello guys uh so now we shall be discussing all the important Concepts

that are related with the head okay so all the important topics in the head so first important topic which we shall be

discussing over here will be the landmarks of your skull okay will be the skeletal landmarks of your skulls

skeletal landmarks of the skull skeletal landmarks of the skull coming to the

skeletal landmarks of the skull first of all in this particular picture which you can see what are the different kinds of

Bones which you can see over here first of all we'll discuss that and then we shall discuss other different landmarks

over here first of all this particular bone which you can see over here is named as your frontal bone all of you

know this this is your frontal bone this bone over here is called as your paral bone paral bone is best visualized from

the top okay next this particular bone over here is called as your temporal bone and you see a bone on the back side

over here this is called as oxital bone oxital bone so how many bones you have got over here you have got the

frontal bone you have got the perial bone you have got the temporal bone and the occipital bone and in the same way

uh you see a bone over here right this particular bone right so this particular bone over here is called as phid

bone okay this bone over here is called as a sphenoid bone so you can also appreciate one very important thing that

the frontal parital temporal and sphenoid Bone all of them are meeting at this point you see so the point where

all the frontal peral temporal occipital and the sphenoid bone the point where all of them are meeting over here right

so this particular point over here is called as terion what is this called as this is called as a terion now if there

is a fracture of teron actually there is a middle menal veins vessels all of them are present behind this okay I will tell

what are the contents of the teron later on right so but you have to remember that this teron is a combination of all

these uh bones frontal peral temporal sphenoid temporal parital and frontal all these bones together form the terion

that is another important question next important anatomical landmark after terion right so it is

terion terion next important anatomical landmark after teron is if you if you look at this right so you know that this

is peral bone this is another peral bone this is your occipital bone the suture which you can see between the the two

peral bones over here this is called as what this is called as your sagital suture sagital suture in the same way

the suture that is present between the occipital bone and the paral bone this suture over here is called as lamboid

suture okay lamboid suture so the where is the place where the seital suture and lamboid suure both of them are joining

that is the area number four over here you see this is the place where both the seital switcher right and two lamboid

switches they're joining here right so this particular area over here is called as

Lambda so what is the area called as Lambda Lambda is nothing but the place where or the junction of lamboid and the

sagital switcher fusing at that region is called as Lambda now if you look at this right so this is your anterior part

this this is your posterior part right you know you know that what is this particular suture over here this

particular suture over here is called as seital suture and this particular suture which

I'm drawing right now with the red is called as coronal suture coronal

suture and what is this sagital suture so the place where sagital suture and coronal suture are fusing exactly at

this Point okay so this point over here is called as bregma what is this called this region is called as

bregma okay so what is bregma bregma is a place where both the sagital and the coronal sutes are fusing that is called

as brigma so so far you have learned what so far you have learned teron what is Lambda and you have learned what is

brigma now look at this what is vertex the next important anatomical landmark is vertex the

highest point of the neurocranium so this entirely is your neurocranium the topmost part the topmost part is exactly

here you see this is the point okay this is the topmost point topmost elevated Point okay so this topmost point over

here is called as vertex so the Superior part Superior part of neurocranium okay that is called vertex

for example if I'm putting all my fingers in this way right if I ask you what is the

topmost area this can be topmost this can be topmost so this is a topmost in this this finger the middle finger over

here is having the topmost point this is called as a Vertex okay so that is a vertex there which we were discussing

right now okay right next important anatomical landmark is that see you you even have you even have got a a swelling

in the frontal region yes right you see an anterior projection of the forehead so this particular anterior projecting

part of the forehead is called as glab this is called glabella so what is your glabella glabella is nothing but

the anterior projecting anterior projecting part of forehead part

of forehead okay anterior projecting part of forehead is called as glaba next important thing is that where is

terion here see this is your teron all of you know that right this is your teron okay now I'm telling you that this

is your frontal bone sphenoid bone temporal bone and what is this parital bone and down here occipital bone now

you see a point you see a point over here this is a point where this is a point where your uh peral bone your

temporal bone and oxital Bone all of them are fusing this point where temporal peral temporal

peral and oxital Bone all of them are fusing this point over here is called as asterion okay

asterion this point over here is called as asterion okay now after this asterion the next important point this is from

behind Okay this is from the posterior side so on the posterior side you see a point over here near the external

occipital protuberance so this Prominent Point of external oxital protuberance is called as Inon okay it is called as Inon

what is Inon Inon is nothing but your prominent part Prominent Point Prominent Point of

external oxital protuberance oxital protuberance okay Prominent Point of external oxital protuberance is

called as in on okay next important thing here uh you see this is the nose this is the nose over here right and I

can tell you that this is the root of the nose the root of the nose is called as Nason what is Nason Nason is nothing

but the root of the nose just above that you have that swelling called as glaba okay that swelling is called as glaba so

this is from outside but if you look at the Bony Landmark where is Nason present first of all you have to know

that this colored part which you can see is called as a nasal bone what is this this is called as a nasal bone now in

between two nasal bones you see a line here you see a line in between two nasal bones like this right so this particular

line in between two nasal bones is called as inter nasal suture what is this this is called as

inter nasal suture this is called as internasal suture okay next important thing what is this particular bone over

here this is your frontal bone okay this is your frontal bone now between the frontal bone and between the nasal bone

and by the way these bones over here what did I tell you these are called as your nasal bones right so this is called

as your nasal bone so between between what between your frontal okay and between your nasal you see a suture over

here right so let me draw that suture here you see this particular suture okay so this suture is separating the frontal

bone from the nasal bone so this suture over here is called as Fronton nasal suture

fronto nasal suture this suture is called as frontonasal suture and this particular

point this particular point over here is what is called as your naon this particular point over here is called as

your naon so this is your naon okay front nasal suture internasal Sut and that point over there is called as your

Nason so these are some of the important bony landmarks which you need to know regarding the skull so now we shall be

discussing after this bony landmarks which the second topic which we shall be discussing is the Fingal arches okay our

topic of discussion would be regarding the Fingal arches so what are the Fingal arches

over Fingal arches are very very important okay so what are these Fingal arches in the sense there are around

five arches okay there are around five arches here so all these arches they develop into the structures that are

related to the head and neck it means some of the Arches they develop into let us say some cartilages some musles right

some of the cartilages develop into the ear inner ear middle ear and so and so forth okay so what are these arches we

will discuss right now now for first important thing is that let us say in the developing embryo this is your head

fold okay this is your head fold and all the way down this is your tail fold this is your head fold and tail fold so this

is a place where you have arches this is a place where you have got these arches over here so if you

look at this if you look at this particular picture as I already told you this part is called as your headfold

okay okay and this part over here is called as your tail fold okay tail fold and this part over here is called as

your mouth mouth is also called as Stadium stadium so attached to the mouth you have got arches so these arches are

nothing but called as your Fingal arches if I remove these Fingal arches outside how many Fingal arches I have got so

I've got one 1 2 3 4 and 5 how many Fingal arches I've got I've got five Fingal arches so

Fingal Arch number one 2 3 4 as well as six okay then where is the fifth Arch over here fifth Arch is

rudimentary okay so where is the fifth Arch yes where is the fifth Arch the fifth Arch is

rudimentary fifth Arch is rudimentary okay now now what I'm telling you is that for example if I cut down these

arches like this okay so all these arches if I'm cutting down in this way okay actually these arches are in this

way I've drawn completely different see the Arches are like this for example if I'm cutting down the Arches like this

and if you're looking in this particular direction how does these look see these arches are not only on one side here I

have got Arch number 1 2 3 4 6 on the left side also I've got 1 2 3 4 6 on both the sides I've got so I this is a

picture which I'm showing from the side right but from the anterior W this is how it looks if I'm cutting down all my

fingers like this right you can see four five arches on the right five arches on the left like this you can see the

Arches here okay so how are these arches looking both on the right and the left we will see now okay first important

thing is that see this particular structure is the first Arch you have got the second Arch third Arch fourth Arch

and sixth Arch second third fourth and sixth Arch so how many arches are there we have got

six arches and we have got six arches on both the sides I told you right on both the sides we have got these arches now

let me number them so this is 1 this is 2 this is three this is 4 and 6 1 2 3 4 and 6 okay now another important thing

is that there is an epithelium that is lining these arches okay let us say the epithelium that is lining the arch from

outside you see there is an epithelium that is lining the arch from outside so this epithelium which is lining the arch

from outside on both the sides this is called as ectom any epithelium outside you call it as what ectom in the same

way there is an epithelium that is lining the inner surface of the arch so if an epithelium is lining the inside of

the inner surface of the arch you call this as endoderm what is this this is called as your

endoderm this is your endoderm and then what is the epithelium that you have in the center of the arch in the center of

the arch theum which you have is misum so there are three different um germ layers right there are three different

layers over here one is called as ectoderm another one is mism yes and the other one is called as your endoderm so

these are the three germ layers that are present over here now important thing is that you can see some depressions right

you see very clearly you can see some depressions on the outside you can see depressions on the inside depressions

which are present on the outside right these are called as clifts what are the depressions that are

present on the outside these are called as Clips then what are the depressions that are present from inside these are

called as pouches okay these are called as pouches so what are the so can I can I tell like

this that clifts are lined by which epithelium clifts are lined by ectom where are pouches are lined by pouches

are lined by endom so this is an important thing you have to know that the clifts are lined by ectom clifts are

lined by ectom pouches are lined by endom pouches are lined by endom okay this is one of the very important thing

you have to keep in your mind okay now next important thing what is the next important thing you have to see is that

what are the structures that are developed out of these clifts as well as pouches okay so first what we'll discuss

is that we shall discuss what are the structures that are developed from clifts then we shall discuss what are

the structures that are developed from pouches then lastly we'll discuss what are the structures that are uh developed

from The Arches okay so let me draw that picture once again so these are your Fingal

arches okay first important thing first important thing you need to know is that you know now you know now that this is

your first Clift this is your second Clift this is your third Clift this is your fourth Clift what are all these

these are all called as clifts inside what do you have you have got pouches now what will happen is that in the

first step what is going to happen is that look at the first Clift the first Clift is already depressed H first Clift

is already depressed but what is going to happen is that this first Clift will undergo invagination in this way you see

the first Clift is undergoing invagination like this on both the sides on both the sides what is going to

happen the first Clift will undergo invagination process in this particular manner so this is how they are

invaginating done now coming to the pouch what are the pouches over here so these are the pouches okay so let us say

this is the first pouch second pouch third pouch and fourth pouch now look at the first pouch what is happening the

first pouch is also undergoing invagination inside okay you see the first pouch is also undergoing

invagination in this way here also the first pouch is undergoing invagination in this way like

this okay now right let us see what is happening with the first Clift over here okay so let us see what is happening

with the first Clift now the first Clift if you look here carefully the first Clift will undergo invagination in this

way you see how it underwent imagination in the same way the first Clift on the opposite side also opposite side also

will undergo invagination this way okay the first Clift on the opposite side also will undergo invagination in this

way like this so there is invagination on both the sides now coming to First pouch as I already told you the the

structures which are present over here are called as pouches right just number wise 1 2 we have got three and four okay

now if you look at this pouches even pouches also invaginate inside like this here also the pouch is invaginating

inside now what is happening the first Clift and the first pouch they touch each other so when the first Clift and

the first pouch when they both are touching each other like this the point where they are touching here this is

forming a specific structure I will tell you what is this now remember here that this particular structure over here

later on you know how does it develop this particular structure this particular structure is like this right

this particular structure is like this isn't it right later on it will develop slowly like this and later on finally it

will take the shape of an ear this is the ear you see this is the ear Pina now you see how the ear p is formed ear p is

formed from the first Clift over here okay now once Earp is formed what did I tell you over here I told you that here

you have got here you have got Earp and what is this particular segment this is called as external auditory canol okay

now you should also have middle ear and internal ear so who is forming this middle ear and internal ear they are

formed with the first P so what is happening the first p will invaginate deep inside and join with the external

arter meatus now after joining this place where they are joining this part will become the tanic membrane and

slowly a septum is developed here now look here what are the structures that are form see this is your external ear

right this is your tanic membrane here you have got this particular part is called as a middle ear and this part

over here is called as a inner ear what is this called this part over here is called as the inner ear so can I

tell you like this that external ear ear Pina right or external arter meatus they are developed from the first Clift and

middle ear inner ear and all these structures are developed from first pouch yes or no so they are developed

from first pole so let us write down what are the structures that are developed from first Clift over here and

what are the structures that are developed from first pouch over here okay so first CL left first left

develops into ear Pina ear Pina and external auditory meatus external

auditory meatus ear pin and external auditus if you look at first pouch first pouch develops into what tanic

membrane develops into tanic membrane it develops into midar right it develops into midar

cavity m dear cavity and remember thing it also develops into usian tube okay it also develops into youasian tube so I

hope now you understood how this first pouch and first Clift are formed so all these are located here okay this thumb

finger is representing the first pouch thumb is exactly touching my ear it means the first pouch and the first CFT

here they are forming what they are forming the ear and all these regions over here okay now next important thing

coming to coming to the second third and the fourth Clift look what is happening with the second third and the fourth CFT

so this second third and the fourth C this will also undergo invagination in a different way so this is how they are

undergoing invagination just look here see they come down all the way like this they come down all the way like

this and they undergo invagination this way second third and fourth okay you see on both the sides

sides on both the sides what is happening the second third and fourth they undergo invagination this

way second third and fourth they undergo invagination in this particular manner second third and

fourth here also second third and fourth This Is How They undergo invagination okay now what is happening

because of this invagination that is very very very important to know okay so what is happening because of this

particular invagination now because of this particular invagination because of this

particular invagination all of you just look here this is your second this is your

third this is your fourth okay this is your second third and fourth now this will later on form what this will later

on form a sinus called as cervical sinus this will later on form sinus called as cervical sinus okay now what

will happen this cervical sinus will later be obliterated obliterated in the sense this cervical sinus will be

disappeared for example if this cervical sinus is not obliterated then what will happen this cical sinus will convert in

this manner 2 3 and four like this 2 3 and 4 this particular structure what it has been converted into is called as

brainalist what is this called this is called as brainal cyst okay so first whatever it is formed is a cervical

sinus cervical sinus will be obliterate it will be disappeared if it is not disappeared that would lead to formation

of a branchial cyst so you can see you can see a small cyst in this child over here in the neck region this is the UN

obliterated I mean the cervical sinus which is not been obliterated so this is your brainal cyst over here okay so this

is the brainal cyst so I hope we are done with all the clips one 2 3 4 all of them are done now let us discuss about

the pouches okay how are these pouches invaginating we will discuss we

discussed already about the first pouch you know the first pouch will develop into tanic membrane middle ear and UST

station tube okay now we will discuss about the second pouch now what is happening over here what is happening

with the uh second pouch over here is that within okay within this second pouch within this second

pouch this second pouch will in imaginate a little deeper not more little deeper like this okay within this

second pouch there is a structure that is formed this structure is called as tonsils okay so tonsils are formed by

which pouch tonsils are formed by your second pouch okay so let me write down over here that the second pouch will

take part second pouch will take part in the formation of tonsils will take part in

the formation of tonsils now once the tonsils are formed by the second pouch look at the third pouch over here look

at the third pouch over here now what will happen with the third pouch is that this third pouch will divide into two

wings like this you see here also I'm drawing this third pouch will divide into one and two it will divide into two

Wings even the fourth pouch is also dividing into two wings so here also it is dividing into one and two here Al it

is dividing into one and two wings like this okay what are these Wings which it is dividing into so it is dividing into

two Wings One Wing is called as a dorsal Wing see this Wing is called as dorsal wing and this Wing over here is called

as ventral Wing one is called as dorsal wing and another one is called as your ventral Wing now what structures are

formed over here what structures are formed over here is that in the dorsal wing

in the in the third pouch in the third pouch in the dorsal Wing a gland is formed over

here now these two glands over here along with that there is another gland also that is formed down over

here okay so this gland which have drawn with the um let us say the this color the pink color over here this gland over

here is called as your thus what is this this is called as your thymus okay and this particular gland

over here is called as parathyroid gland what is this this is your parathyroid gland where is your para where is your

thyroid gland by the way your thyroid GL will be situated in the center let us say look here this is your thyroid gland

like this you see this is your thyroid gland and this is your parathyroid gland over here after that after that uh down

here also in the dorsal wing of the fourth pouch in the dorsal wing of the fourth pouch here also you will see a

Para GL here also you would see a parathyroid GL now tell me which is superior parathyroid gland which is

inferior parathyroid gland now don't get confused the top one is not Superior top one is inferior parathyroid gland

inferior parathyroid gland this bottom one is the superior parathyroid gland so what is going to happen the the inferior

parathyroid gland will travel all the way down inferiorly crisscross in this way you

see it is traveling all the way down inferiorly like this right and and the superior parathyroid land will travel

all the way superiorly in this way crisscross okay clear all of you right so now let us write down all the

structures over here let us write down the structures that are developing from the third

pouch and from the fourth pouch from the fourth fourth pouch now in the third pouch I've discussed that there are two

Wings one is called as a dorsal Wing another one over here is called as your ventral Wing okay so the same thing

you have in the fourth pouch also you have got the dorsal wing and the next one over here is

called as your ventral Wing dorsal Wing as well as your ventral Wing okay now what did I tell you dorsal

Wing over here third power pouch dorsal Wing third pouch dorsal Wing will develop into

inferior parathyroid land inferior parathyroid vental Wing will develop into

thymus and dorsal wing of fourth PCH will develop into Superior par thyroid gland okay so these are the important um

pouches whatever you see pouches or Clips which you can see over here okay now there is one very important clinical

condition what is this clinical condition is that all of you know that let us say that this is a

chromosome okay so this particular chromosome is basically having a long arm like this a long arm as well as a

short arm right now long arm is called as p short arm is called as Q now in this Q at the 11th position 1 2 3 4 5 6

7 8 9 10 and 11 see this this particular position which I'm highlighting with the green is the 11th position so there is a

deletion at this 11th position and this is a chromosome number 22 so how will you write this down you will write this

chromosomal abnormality as 22 there is a problem in the Q exactly which segment 11th position problem in the que exactly

11th position there is a deletion there is a deletion of that particular Gene there okay so this particular uh

condition is called as dorge syndrome what is this condition called as D syndrome so what is happening because of

this D syndrome because of this D syndrome there is a defect in the development of what development will

stop pouch 3 and pouch 4 pouch three and pouch 4 these structures they do not

develop they do not develop okay pouch three and pouch 4 they do not develop over here so when pouch three and pouch

4 do not develop parathyroid glands are not produced thymus is not produced so what will happen in the patient what

will happen in the patient is that there will be absence of parathyroid glands as well as

thymus so this absence of parathyroid gland as well as thymus is called as your Dej syndrome I hope you understood

whatever I'm trying to teach you so in this way uh we have discussed about all the clips we have discussed about all

the pouches right so how many Cliffs four Cliffs how many pouches four pouches so what is coming from the first

Cliff first pouch you know what is coming from the second third and fourth also you know now okay now coming to the

next important thing that we'll discuss about the Arches about each and every Arch first what we shall discuss is that

we shall discuss what are the structures that are derived from these arches okay we shall first discuss what are the

structures that are derived from these arches structures in the sense like what cartilages what muscles does it have

later on from each Arch what artery is supplying here in each Arch what nerve is innervated over here also we'll

discuss okay so first you can see over here that these are all the Arches for example this is the first Arch over here

the blue color one is called as this one is called as your second Arch this yellow one is called as your third Arch

this one over here is called as a fourth Arch and this one over here is called as a sixth Arch how many arches are there

six arches are there now you will tell me first Arch is developed into what all structures what all you can see over

here see first important thing is that you have to know one cartilage called as Mel

cartilage so first cartilage is mels car later on later on this particular mels cartilage will develop into a specific

structure called as mandible okay now all of you know you see this mandible over here this is a

mandible okay after that you will have two important bones what are those two important ear OES over here see what is

this one and this one one is called as malas another one is called as incus one is called as malas and the other one is

called as your incus so all M's okay M for Mel cartilage M for mandible M for malas and I for Inc so majority you have

got the M's all these M's here are derived from what they're derived from the first Arch they derived from the

first Arch after this the next important thing is the second Arch what are the structures that are derived from the

second what is the first letter in second s right so s stands for what what is the remaining bone here

stapes remaining bone here is called a stapes after stapes you see what is this particular process what is this

particular process over here this is called as styloid process this is called as styloid

process okay next after that after styloid process you know what is this ligament that is connecting styloid

process see this is your styloid process right and this is your hyoid bone okay now in this hyid bone also in this hyid

bone also you have got two horns see this horn is called as a greater Horn of hyoid bone this is called as a lesser

Horn of hyoid bone so this uh from the styloid bone you see a ligament that is going and attaching to the Lesser Horn

of hyid bone this is called stylohyoid ligament what ligament is this Stylo hyoid ligament this is called

stylohyoid ligament okay styloid ligament next after styo ligament the muzzles the muzzle that is attached to

the stes is stapedius muszle stapedius muszle clear and finally and finally another important

thing that is your facial musles facial musles so all these are with the S maor majority of them all

almost all of them except one with the s s for second Arch all of them are derived from the second Arch now coming

to this particular part over here uh what is the third Arch derived into third Arch is having what greater horn

second Arch is having lesser horn so this will have greater Horn of hyid what is this greater Horn of hyid bone okay

after greater Horn of H remember only one thing that is styop fingas muscle

styop fanges muscle these are the structures that are derived from the third Arch now coming to the fourth as

well as the sixth these two arches the fourth as well as the sixth these two arches they develop into a specific

structures all the cartilages all the cartilages you can remember by the pneumonic Kate c a okay now with the

help of with C what is a cartilage with the letter c that is your CID okay another C is

uniform C is criid C is uniform next C is corniculate okay after that after that

next you have got what a what does a stands for eroids eroids next uh T stands for your

thyroid and E stands for your epiglottis so all these C ages whether they are paid or unpaid we'll discuss

later so all these cartilages are derived from fourth to sixth Arch over here so these are all the structures

that are derived from these um these arches okay so now we shall discuss that in each Arch what is the artery and what

is the ination okay so what is the artery and innervation in each Arch first let us discuss about the first

arch in the first stge what is the artery that is supplying that is your maxillary artery

maxillary arteries AR that is supplying your first Arch okay next coming to the second Arch let me also write down the

remaining arches also the second Arch and the third Arch okay I'll write the remaining so coming to uh the second

Arch the artery which we have over here is stapedial artery stapedial artery coming to the

third Arch it is common koted artery and and the first part of internal coted artery

first part of internal koted artery okay so these are the nerves over here and by the way from the fourth Arch what is

derived from the fourth Arch you have got arch of Iota what is that you have got arch of Iota so these are some of

the important arteries which are previously asked in from uh I mean in the exams these were the important

Arters which are asked from these respective arches okay so Arch of Iota arch of Iota is derived from your

fourth Arch now when it comes to the nerves okay so what are the nerves which you have over here for example first

Arch if you look at the first Arch you have got the trial nerve that is V3 okay so that is V3 branch of trial nerve okay

coming to the second you have got the seventh cranial nerve and coming to the third you have got the ninth cranial

nerve so these are the branches which you see I mean these are the nerve innervation which you see over here okay

so this completes the Fingal arches so the first Arch is within the first Arch we have got the maxillary artery next

stal artery common carot artery and the first part of internal koted artery now coming to the fourth Arch I mean fourth

to sixth Arch right so together we discuss but here in case we will discuss the fourth Arch separately actually

cartilages are formed together okay from 4 to 6 star cartilages are formed together okay now coming to this coming

to this uh coming to the fourth Arch right in the fourth Arch I mean fourth Arch is derived into what arteries one

is called as your right subclavian artery what is that that is derived into right subclavian artery right subclavian

artery okay another one you have to remember is uh iotic AR the left side of the iotic arch if the arch of Iota is

there that is divided into right and left that is the left iotic Arch left iotic Arch okay when it comes to

the sixth Arch what is sixth Arch developed into okay what is six Arch developed into you know you have got

pulmonary artery dividing into right and left pulmonary artery you know you have got pulmonary trunk like this dividing

into right pulmonary artery as well as left pulmonary artery okay so here this is called as your right pulmonary

artery and this is called as your left pulmonary artery both of them right and

left pulmonary artery and not only that not only that even ductus arteriosis all of you know what is

ductus arteriosis right so even ductus arteriosis also is derived from the sixth Arch when it is coming to the

nerve Supply so already we discussed that trinal nerve for first arch sth for second Arch ninth for third Arch now

coming to the fourth Arch fourth Arch which cranial nerve 10th cranial nerve what is that cranial nerve 10th cranial

then sixth touch again again it is 10th cranial nerve but the branches are different when it is coming to the

fourth Arch the cranial nerve over here is 10th and 10th cranial nerve gives out a branch called as Superior lenial nerve

that is your Superior lenial nerve Superior lenial nerve and remember one thing that this Superior lenial nerve

will will control the muscles that are responsible for swallowing control the muscles that are

responsible for swallowing in the same way coming to this uh particular 10th cranial nerve which is derived from the

sixth Arch over here right so it will uh give off a branch called as a recurrent lingel

nve recurrent lingel nve all of you know recurrent lenal nerve except C thyroid muszle IT inates remaining all musles

right which is responsible for speaking which is responsible for speaking so this is uh one of the very

important thing which you have to understand over here so this completes the complete discussion of your arches

okay so these are uh as as this is a rapid revision session so I've discussed only the important points which you need

to know regarding these arches over here so guys uh now we shall be discussing regarding the development of the tongue

okay development of your tongue so we shall discuss the topic of development of the tongue which is very important

okay so when is the tongue developed the tongue development happens during the fourth week of intrauterine life fourth

week of intrauterine life okay so how is this tongue developed so you already know what are the different kinds of

Fingal arches okay so now what I'm doing is that I will draw this Fingal arches over here and then I will explain you

how the tongue is developed from that so let us say this is your first Fingal Arch over

here second we have got third we have got fourth okay I'm not drawing all the Arches right so these are the arches

over here okay so let us say the Fingal arches are on both the sides I told you right so these are the Fingal arches

that are present on both the sides okay so if this is the midline over here yeah so these are The Arches on

both the sides now if you if you look here if you look here in the first Arch so this is your first this is your

second this is your third and fourth actually six you have to draw but I'm just drawing four okay now uh coming to

the first Arch near the first Arch there are two swellings over here there are two swellings okay these

swellings over here are called as lingual swellings what are these swellings over here these swellings over

here are called as lingual swellings where are these lingual swellings located only one no two laterally they

are located laterally lingual swellings are located laterally okay now in the center of a lingual swelling in the

center of a lingual swelling you have got a body here this is called as a tuberculum okay there's only one

tuberculum so impa right paid or impa impa that is why you called as impar what is the complete name tuberculum

impar so what is the name of this particular tuberculum you call it as tuberculum

impar why are you calling it as impar because there is only one tuberculum over here okay now just beneath this

tubercle just beneath this tuberculum you have got one more structure over here okay so this particular structure

which is located just beneath that particular tuberculum over here you call it as so just beneath the tuberculum you

see a red color structure this structure is called as thyroid primordium what do you call this as you call this a thyroid

thyroid primordium what do you call this you call this as thyroid primodial just beneath the thyroid Prim modium covering

your third second third and fourth Arch like this okay mainly third and fourth Arch covering your primordium you see a

structure over here this structure is called as copula okay well the other name for this is hypobranchial Eminence

so what is this structure called as this structure is called as copula

or hypo branchial Eminence Copa or you can call it as

hypobranchial Eminence so this is one structure over here this is another structure over here and here you have

got a third structure called as copula or hypobranchial Eminence okay Copa or hypobranchial Eminence now how is tongue

developed from these structures so first of all what we will do is that we shall discuss about these things later on but

one very important thing I want to tell you over here is about this thyroid primodial you

know this dense tissue of thyroid Prim modium whatever is there what will happen to this is that this particular

thyroid I will discuss about it later on in much detail okay but for now I just want to tell you here that this thyroid

Prim modium within this thyroid Prim modium you see a small depression okay so this will undergo depression in

this way okay now this depression will elongate down like this you see this depression is elongating down and

forming a duct right this particular duct this particular duct is called as thyroglossal duct what is this this is

called as thyroglossal duct all the way from the thyroid gland to the tongue the there is a duct here this is

thyroglossal duct basically before birth just before birth this will disappear appear okay but sometimes what will

happen is that even after birth also it doesn't disappear that will result in the formation of a cyst that thing I

will discuss when I discuss about the development of your thyroid GL okay but for now for now what I'm telling you is

that you should know what is this thyroid primodial okay right next important thing how is a tongue formed

over here now all of you know that if you look at the tongue like this right so this is a tongue now in this tongue

what are the important regions you have got over here see this part of the tongue is your anterior 2/3 of the

tongue okay this is called as a posterior 1/3 of the tongue okay and finally this part is called as a

posteriormost part of the tongue this is your posteriormost region of the tongue okay

so how these three regions are formed and which region is formed first first important thing is that I just told you

you have got two lateral swellings right these are called as lingual swellings so how many lingual swellings are there two

see there is one lingual swelling over here there is another lingual swelling over here there are two lingual

swellings and down to the lingual swelling you have got a body here what is this body called as I told you this

is called as your thyroid primodial what will happen is that this lingual swelling on the right on the right on

the left okay these lingual spellings they fuse with each other along with with this body this body also fuses with

each other so all these three things together they will fuse with each other now when all these three things together

will fuse with each other all these three things will result in the formation of this particular structure

like this okay what is this particular structure over here this particular structure is nothing but called as your

anterior 2/3 of your tongue okay what it is forming anterior 2/3 of your tongue now if I ask you anterior 23 of the

tongue is formed by you have to tell right lingual swelling left lingual swelling as well as thyroid Eminence

right thyroid primordium okay after that down here what do you have is called as Copa right Copa or you can call as

hypobranchial Eminence so let us bring that thing here so this particular structure over here is called as your

Copa or hypobranchial Eminence now I'm dividing this Copa or hypobranchial Eminence into two structures so this

part which is on the top is called as a cranial part and this part which is on the bottom is called as a codal part

okay how many uh parts do we have over here so this particular part over here is called as a cranial part and this

part is called as the codal part cranial and codal what does cranial part do already anterior 2/3 of the tongue is

done right see this is done 2/3 is finished now leftover is posterior 1/3 so cranial part forms the posterior 1/3

of the tongue posterior 1/3 of the tongue okay and what does this codal part do the codal part will form the

posterior most part of the tongue posteriormost part of your tongue so all of you now understood that anterior 2/3

is formed by uh right and left lateral swelling lingual swelling along with this thyroid um thyroid what is this

Prim modium posterior 1/3 is formed by the cranial part of hypo braal amance and postor most is

formed by the cordal part of the hypo braal Eminence okay now now let us look at the derivatives let us look at the

Arches overall in a summary lingual swellings when I tell lingual swellings tell me from where these lingual

swellings are formed from which arches tell me which arches these lingual swellings are present look at the

picture they are present in the first Arch okay lingual swellings are present in the first Arch okay after

lingual swellings we have got tuberculum impar we have got tuberculum impar so tell me where is this

tuberculum impar exactly located this tuberculum impar is this one right this one so this is located in the first and

second Arch right so somewhere in the first and second Arch so it is located both in the

first and second Arch first and second Arch next where is this hypobranchial Eminence located

hypo branchial Eminence where is this hypobranchial Eminence located that is located all the way in the second Arch

third Arch as well as the fourth Arch okay so second and third we have got the cranial part and fourth we have got the

cordal part we have got the cordal part okay so these are some of the important points which you need to know regarding

the development of the tongue so now we shall be discussing regarding the development of your thyroid gland

development of the thyroid gland now regarding the development of the thyroid gland once if you understood

the development of the tongue development of the thyroid land is easy remember one thing that this development

of the thyroid land is is Right developed from the pouches developed from the pouches so all of you know that

the pouches are lined by what pouches are lined by endoderm so that is why this thyroid land is endodermal

origin endodermal origin thyroid Land is Your endodermal origin okay right next important thing next important thing is

that when does this development of thyroid Land Development start basically it begins on 24 4th

day so it begins on 24th day it begins on 24th day now after when it begins on 24th day from when the thyroid gland

start functioning it starts functioning from the 12th week from the 12th week it starts

functioning it starts functioning from the 12th week okay now another important thing is that you remember that the

picture which I've drawn just before right so what was that uh here I've drawn I'm just drawing it roughly now

here I'm I've drawn some arches like this right I've drawn some arches and I've told you that here you have got two

swellings what are these right and left lingual swelling right below this lingual swelling I have got what this is

called as thy tuberculum impar beneath the tuberculum impar I've have got another body over here what is this

called as this is called as thyroid Prim modium right so this body over here is called as your thyroid

primordium thyroid primordium okay now what is happening with this thyroid primordium all of you

look here this this is your thyroid Prim modium so what will happen is that this

thyroid primordium will invaginate inside right so there is a small depression that is developed within this

thyroid primodial like this okay there is a small depression within this thyroid Prim modium you see the

depression over here now this depression will invaginate more and it will form a duct in this way so this depression will

invaginate more down like this you see and it is forming a duct this depression will invaginate

more like this and it forms a duct in this way okay so this particular duct which is formed actually it starts all

all the way from your tongue and down all the way to the thyroid land so that is why this particular duct over here is

called as your thyro thyroglossal duct okay what is this thyroglossal duct and this thyroglossal duct is having an

opening over here this opening is called as foramen seeum what is this called as foran seeum where is the foran seeum

located on the base of your tongue it is located on the base of your tongue okay on the complete posterior side of your

tongue clear now what is going to happen what is going to happen is that

see all of you just look here uh let me draw just a small picture all of you know that here you

have got your hyoid bone like this this is your hyid and down to the hyid you have got this particular bone what is

this cartilage called as thyroid cartilage and below this you have got your cricoid cartilage and all these are

your tracheal Rings like this so all these are your tracheal rings so in this way I've got tril Rings okay now you

know that here you have got your tongue this is the tongue okay so completely on the back of the tongue

here you have got a small opening called as foramen seeum which I just told you this is called as foramen seeum now what

is happening with this foran seeum is that from this foran seeum you see a duct that is coming all the way down

till the place where the thyroid land used to be there okay so it is having a duct now what is going to happen what is

going to happen is that this is called as a tip of the tip of the duct you see this part is called as a tip of the duct

now this tip of the duct what will happen to this tip of the duct look here this particular tip of

the duct will will bifurcate into two structures see this is forum and this is a duck that tip of the duct is

bifurcating into two structures like this okay so what will happen is that at the end of 7th week at the 7th week end

okay at the end at the end of sth week what will happen is that the cells that are present over uh these bifurcated

part of thyroglossal duct whatever is there these cells they start to multiply so they start to multiply like this they

multiply multiply multiply multiply in this way and now you know they are forming slowly the right lobe of the

thyroid here also they start multiplying like this the cells here multiply and they start forming the left lobe of your

thyroid and here also there are cells even they start multiplying like this they start multiplying like this and

form the esmus of the thyroid land so overall your thyroid land with two loes and the isus third lobe is formed

completely okay so here slowly what is happening that is how the development takes place and finally you see the

thyroid gland that is formed over here now once the thyroid gland is formed just before the birth what will happen

this particular thyro gloal cyst will disappear thyroglossal cyst disappears before

birth before birth for example if the thyroglossal sisters did not disappear before birth what is going to happen

What is going to happen is that sometimes there is a chance that within this uh duct there is a cyst that is

formed like this this particular cyst is called as thyro gloal cyst this particular cyst is

called as thyroglossal cyst okay so when there is thyroglossal cyst you will see a swelling in the anterior part of the

neck usually this is asymptomatic only when it gets infected it becomes symptomatic okay so this particular

thing over here is your thyroid gloal cyst and you know how do you examine this thyroglossal cyst when you

protude the tongue outside this cyst moves okay if the cyst is moving up when you protude the tongue outside right so

that is your thyroglossal cyst over here clear so this is your thyroid gloal syst and this is how the development of your

thyroid gland happens so now we shall be discussing different parts of the skull okay so the first part which we shall be

focusing is the Norma frontalis noral frontalis is the first important part

anyways we shall not be going into detail about each and every part only those parts which are really very

important for your exams we shall be discussing okay the remaining things we shall just superficially touch over

these things okay now when it comes to noral frontalis whatever you can see from the front is called frontalis right

so noral frontalis is first of all formed by how many bones so first bone which you can see over here let let's

discuss in um complete detail with many pictures so this particular bone over here is called as your frontal bone okay

normal frontalis is formed by frontal bone over here and next so if this is your frontal bone over here you can see

what is this particular bone this particular bone over here is your orbital bone okay so what is this this

is your orbital bone okay now after these orbits are done can you if I zoom in if I zoom in can you just see a line

over a suture over here right can you see this particular bone yes or no you see this particular half all the

way yeah you see this right again I'm drawing this on another bone over here see from here all the way from here all

the way you see this bone so this particular bone which I'm drawing right now which is present on

both the sides right these are this is called as Magilla what is this called this particular bone over here is called

as Magill so normal frontalis normal frontalis is formed by frontal bone next we have got two orbits next we have got

two Magill okay along with these two Magilla you even have got one more important thing okay so what is that

another important thing along with this maxil over here see here if if this part over here is called as maile okay okay

so let me I'm just drawing the dotted lenses you see this part over here is called as your maxill

right if this part over here is called as your mailla just side to that mailla you have got another part you

see you see this part this part over here you see this part over here is called as your zygomatic or cheekbone

what is this zygomatic bone or cheekbone okay and next important bone over here is this part over here is called as your

mandible this is your mandible this is your mandible this part over here is called as your zygomatic bone zygomatic

or you call it as cheekbone zygomatic or cheekbone okay next important next important thing is that you can also see

a bone over here actually this is not a single bone there are actually two bones over here okay so what are these two

bones this is called as a right nasal this is called as a left nasal so whatever it is both of them together you

call it as the nasal bones together you call it as the nasal bones okay so if I ask you what are the structures that

form normal frontalis what are the structures that form normal frontalis you have got the frontal bone over here

okay next you have got the two nasal bones two nasal bones third important thing is you have got the

Magilla how many Magilla are there there are two Magill over here next um how many nasal bones we discussed how many

zygomatic right on both the sides you have got the zygomatic bone or cheek bone how many are there two zygomatics

are two and how many mandibles are there one how many mandibles are there one so all these structures together they form

noral frontalis what are they form they form what noral frontalis next important thing after this normal frontalis is

that how many aeres do you have here in the frontal region how many openings can you see so exactly here I

can see three openings see here one two openings for two orbits and next an opening I can see in the nose how many

openings are there three openings are there okay so what you have to write here how many apertures are there here

how many apertures so basically we have got three apertures what are those three apertures two apertures are for orbits

two orbits and one aperture is present in the front this is called as anterior nasal aperture the aperture of the nose

anterior nasal aperture so in this way there are apertures over here next important thing if you first

let us discuss about the orbits okay first we will discuss about the orbits later we'll discuss about the anterior

nasal aperture over here now regarding these orbits what is the important thing you can see is that if I zoom in right

see orbits are having four important walls it is something like a quadrangular not perfectly circular four

important walls see here this particular wall of the orbit is called as supraorbital margin okay this part is

called as infraorbital margin in the same way this part is called as lateral uh orbital margin this is called as

medial orbital margin so how many orbital margins do we have We have basically have got four important

margins see this is called as what supraorbital margin this is called as Supra orbital

margin next this one over here is called as infra orbital margin this one over here

is called as medial orbital margin and this one is called as a lateral orbital margin so how many orbital margins we

have got we have got four orbital margins first let us discuss about supraorbital margin okay if you look at

this supraorbital margin if you look at this Su this entirely is your sua orbital margin now look here carefully

again I'm drawing see this I'm drawing with the dotted lines this entirely is your supera orbital margin now this

entire superorbital margin I'm dividing it into two halves like this okay what are these two halves this is called as

the lateral 2/3 this is called as a lateral 2/3 and this is called as the medial 1/3 okay what are the two halfs

lateral 2/3 and medial 1/3 the junction of lateral 2/3 and medial 1/3 let me use another

color yeah the junction between lateral 2/3 and medial 1/3 you see a a small fosa over here exactly here you see a

small fosa this is called as Supra orbital foramin this is called as what supraorbital foramin okay what are

the structures that are passing in the superorbital foramin superorbital artery superorbital vein and superorbital nerve

so here you have got supraorbital artery supraorbital vein and supraorbital nerve okay these are

the three structures that are passing see here here also you have got and here also youve got Supra orbital Forin where

it is present it is present in the lateral 2/3 Junction between the lateral 2/3 and medial 1/3 of superorbital

margin okay right next important thing next important thing is that if you focus on the infraorbital margin okay if

you focus on the infraorbital margin what are the important things you can see see this entirely is your

infraorbital margin you see from here all the way I'm drawing the dotted lines this entirely

is your infraorbital margin if you if you carefully look at the infraorbital margin here infraorbital margin is

formed by two bones so how am I highlighting see from here all the way till here there is one bone right and

from here all the way till here you have got another bone okay so what are these two bones if you can see here this

particular bone is a this particular bone is B what is a over here a is present

laterally B is present medially yes or no so laterally laterally laterally what is a

bone do you have you have got the zygomatic bone zygomatic bone and medially what do

you have medially what bone do you have you have got the Magilla you have got the mailla right so

both of them together what are they forming both of them together they form the infra orbit margin

infraorbital margin infraorbital margin and in the center of infraorbital margin you see a suture you see there is a

suture in front in in uh I mean in the middle in the center of infraorbital margin so this suture is present between

zygomatic and Magilla I'm calling it as mailo zygomatic suture what is this mailo

zygomatic suture so what is this suture by name this suture is called as mailo zygomatic suture in the same way we are

done with Superior inferior now look at the medial wall if you look at the medial wall where is the medial wall

present see all the way this entirely is your medial wall okay this entirely is your medial

wall now in this medial wall uh this part of the medial wall is the Superior part of the medial wall and this part of

the medial wall is the inferior part of of the medial wall now medial wall is also made up of two important bones what

are those two important bones see here this Superior part of the medial wall this this particular Superior part of

the medial wall is made up of frontal bone yes or no just look at the picture it is made up of frontal bone and what

is this particular one made up of this is made up of Magilla you see this is made up of what maxillary

bone this is made up of Magill right maxilla now this uh frontal and mailla both of them together they form

what they form the medial orbital margin [Music] medial orbital margin they form the

medial orbital margin now in the center can you see a suture over here you can see a suture here yes or no what is this

suture called as this is called as frontomaxillary suture what is the name of the suture this suture is called as

fronto maxillary suture okay what is this suture called as this suture is called as fronto maxillary suture okay

so we are done with Superior inferior medial wall now let us go on to the lateral wall over here now if you

closely look at if you closely look at the lateral wall what are the things you can see so this entire wall over here

let me zoom in again this entire wall over here is called as a lateral wall and this lateral wall is again divided

into see this is the upper part over here and and this part is a lower part okay now now upper part is formed by

which bone over here that is formed by see this part over here is formed by frontal

bone lower part is formed by mailla or zygomatic it is formed by zygomatic bone zygomatic bone so frontal and zygomatic

together they form what they form what is this yeah they form the lateral orbital margin they form the lateral

orbital margin lateral orbital margin in the center of lateral orbital margin in the center of lateral orbital margin you

see a suture here you see a suture this is called as frontozygomatic suture yeah this suture is called as

fronto zygomatic suture this suture over here is called as frontozygomatic suture okay so these are the important sutures

which you need to know over here that are uh associated with the orbit okay next important thing next important

thing is this particular part what is this um exactly above the orbit can you see a small can you see some kind of

swelling over here here and here right what are this swelling called as see this particular swelling over here this

kind of swelling what you can see here is called as super ciliary Arch what is this this is called

as this is called a super ciliary Arch next important thing is that can you also see your nasal bone over here this

is your nose Okay what is this this particular one over here is your nose now this opening over here is called as

nasal aperture what is this this is called as nasal Apert okay this particular opening over here is called