09: Cranio Development V

8/12/2019 09: Cranio Development V

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Transcribed by Erica Manion 3.27.14

Craniofacial Biology Lecture 9

Prenatal Craniofacial Development IV and Vby Dr. Wishe

Slide set: 2014 FACIAL DEVELOPMENT 4 2-23 post.ppt

[Slide 12] L FIG. 18.2 OTIC VESICLE FORMATION 11THED.

Dr. Wishe: Alright I guess we might as well continue. This is where I left off, before

technical difficulties arose. And here we return to our invaginating placode, and what I was

about to say before the problem happened, think of these areas as neural folds. And the two

neural folds come together and when they do, you get the formation of a neural tube. But

here, in terms of the ear, the two folds are coming together and eventually they fuse and

you get a structure reminiscent of the neural tube but this is actually the otic vesicle. Andsome folks throw in an additional term called the otic pit, thats sort of like the opening. In

addition whats not shown on diagrams A and B, see these little yellow structures labeled

statoacoustic ganglion? Think back to the formation of the neural tube, we had neural crest

forming. The neural crest sits on top of the neural tube, and heres your neural tube and

heres your neural crest that are fragments. Well something very similar happens in this

case. The fragmented neural crest that comes off gives rise to the statoacoustic ganglion

which is associated with CN VIII. And CN VIII has dual function, one for hearing, and one for

balance, equilibrium, if you will. The other thing, this is the pharyngeal area (indicated on

Figure B, see image below). And the pharyngeal area seems to be getting larger and larger.

If you use imagination and just follow the sequence of diagrams, youll see that this

pharyngeal region comes smack up to this little indentation (in Figure C, see image below) .And this little indentation is really your first pharyngeal cleft. And all the other clefts

disappear, because the mesenchyme in arch 2 grows inferiorly and all the other clefts or

grooves sort of fuse into a sinus.

Now what do you think this space actually represents? The pouch. So theres your first

pharyngeal pouch. And where the yellow is joining together with the blue, what structure

do you think is going to form over here? Tympanic membrane or ear drum.

This part of development of the ear seems to be far away at the moment (Image C otic

vesicle), but it will come closer to this region (near the first pharyngeal cleft and pouch)

and in essence the ear has an outer ear, a middle ear, and an inner ear. This otic vesicle has

a dorsal and a ventral component.


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[Slide 13] L FIG. 18.3 INNER EAR FORMATION 11TH

ED.And here in essence is your dorsal component (Indicated Image A, Utricular portion of otic

vesicle), and heres your ventral component (Indicated image A, Saccular portion of otic

vesicle). The ventral component gives rise to the sacculus, the dorsal component to the

utriculus. And the utriculus forms the semicircular canals, the sacculus will eventually

form the organ of corti. And the organ of corti is associated with hearing, utriculus with the

formation of the semicircular canals. So starting with the sacculus, it begins to expand and

coil around itself, until finally you get something that looks like this. In essence it looks like

a snail shell and that becomes organ of corti.

[Slide 14] L FIG. 18.4 ORGAN OF CORTI 11THED.Here we have an elaboration of the cochlear duct. And heres the cochlear duct (Image A).

Here we have cells that will form the organ of corti (red cells all along outside of duct) and

there seems to be a darkened area over the top. If we move on to diagram B, you can see

these cells developed further, they are known as hair cells. And they do have little hair like

structures projecting from them. These are in essence your sense organs and the structure

overlying them is your tectorial membrane. You can see this relationship better in the

bottom diagram (Image C). Here are your hair cells and you may or may not be able to see


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it, but there seem to be little projection, those are the hairs, and this is the tectorial

membrane.

In addition to the cochlear duct we are going to get two additional cavities forming. Scala

vestibuli and this as the scala tympani. In addition the cells up in this area (neighboring

scala vestibuli in Image B), which were these cells initially (making up the back part of the

ring in Image A) thin down and become what is known as your vestibular membrane. Nowthese are all epithelial cells and underneath organ of corti theres also a membrane called

the basilar membrane. You can see its just right underneath here (indicated location on

Image C). And connected to this organ of corti youll have your nerve fibers leading into

your ganglion and back into the brain.

[Slide 15] L FIG. 18.5 ORGAN OF CORTI 11THED.

So this is what A that snail shell appearance looks. Here we have something a little bit

more magnified. Whats left out on this diagram is the space on top called the scala vestibuli

and scala tympani. But you have a highly mag view of these special cells (Image B), the

neural epithelial cells which become your hair cells. And here you can see the word hair

cells (Image C), were not distinguishing between outer and inner. Theyre just hair cells.

And you can see little fuzzy structures on top of them.And then youll see that the tectorial membrane seems to be sitting over the hair of the hair

cells. Now what happens in this mechanism is that the outer ear picks up sound waves in

the air, transmits it to middle ear, and again still dealing with vibrations in air, then the

sound waves are transmitted to the inner ear, to the organ of corti. But this whole inner ear

is in a fluid base. So that means the vibrations are transmitted from air to fluid now. And

since everything id in a fluid environment, what happens is that this whole mechanism

rocks up and down, and as it rocks up and down, these little hairs contact tectorial


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membrane. Those vibrations are then eventually transmitted to your nerve fibers, which

takes it back to the brain.

[Slide 16] L FIG. 18.3 INNER EAR FORMATION 11THED.

So that was the sacculus, which gave rise to your hearing mechanism known as the organ ofcorti.

Were looking at the utricular portion now. And it hollows out in three spots (Image A) and

thats what you seeingover here. And as we continue to diagram B, everything is enlarging

and the hollowing out effect is getting more and more. And finally in Diagram C, all the

tissue that existed in these spaces is gone, and youve created canals. So you can look at

this part (drew on Image B, see below). These are all the canals that are going to be

created. And thats essentially your semicircular canals. And there are certain areas like

these little bulges. Each canal has a bulge. Heres one, heres the other, and its hard to see

the third bulge. Those little bulges are called your crus ampluare. Those are receptors

whereas the rest of the canal is your crus nonampullare. What these receptors do is detect

changes in movement. So sometimes if you get up from your bed to quickly all of a suddenyou feel a little dizzy. Thats been picked up by the receptors. And so the way to get out of

bed is really slowly and you wont have an effect on the equilibrium. Thats whats really

being affected. Some people do have this as a normal effect. People with vertigo for

instance. When they are high up they begin to lose their equilibrium. If you happen to have

a tumor in the area, the receptors might be lost as well as equilibrium on one side.

[Slide 17] L FIG. 18.7 MIDDLE EAR 11THED.

So that was the inner ear. Now we are going to bring back to the picture the rest of the

components. So right over here is 1stpharyngeal cleft, and that formed the external

auditory meatus (Image A). Heres your 1stpharyngeal pouch, which really forms your


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eustacian tube, your tubotympanic recess, as well as this area (in B) which is going to be

the primitive middle ear cavity. What this also shows in this particular area, youre getting

a thickening. And theres your thickening, and its referred to as meatal plug. And this is

going to give rise to the eardrum/ Thats the ectodermal component. And heres the

endodermal component (yellow from primitive typmanic cavity). At the same time youre

going to get your little ear bones forming. Your malleus, your incus from Meckles cartilage,1stpharyngeal arch, and your stapes from Reicharts cartilage in the 2ndarch. So this region

which is called your mesenchymal condensation (Image A) will give rise to cartilage, and

then eventually to bone tissue. So the middle ear bones and mandibular symphesis are the

parts of Meckles cartilage which play a role in endochondral bone formation. The rest of

Meckles cartilage disappears and most of the mandible is now formed intramembranously.

These middle ear bones are mostly embedded and held in mesenchyme. Here we see the

representation of the inner ear component. The sacculus, utriculus, and youll notice its

moving closer to the other two parts of the ear.

[Slide 18] L FIG. 18.9 MIDDLE EAR 11THED.So here we have a little bit more detailed picture of the region. 1stpharyngeal cleft,

external aud meatus, this blue part came from meatal plug, the yellow part which is your

endoderm comes from the pharyngeal pouch, the first one, and you see sandwiched

between the two of them the red layer, and thats the mesoderm. So in essence, the

tympanic membrane or eardrum consists of ectoderm, mesoderm, and endoderm. And

now we have mesenchyme that held and positioned these three bones has disappeared.

The bones are now held in position by various ligaments that have formed. And so we

really have a middle ear cavity at this point. And this will then lead downward to eustacian

or auditory tube. These two bones, Meckles cartilage (malleus and incus), this bone

(stapes), Reicharts cartilage. What this picture also shows is the stapes resembles the

stirrup of a saddle that you put on a horse. This is where you put your foot in. And thisstapes seems to be sandwiched against a membranous structure called an oval window. So

the way transmission of sound works, you have sound waves outside the ear, sound waves

inside the ear, and the tympanic membrane is like a drum. So the sound waves hit the ear

drum, and youre literally playing a drum, and those vibrations are then transmitted to

malleus, the incus, and eventually the stapes. Once the stapes get those vibrations, keep in

mind this is all in air, it will push up against the oval window. Complete inner ear filled with

fluid. So it pushes the oval window in.

[Slide 19] L FIG. 18.8 ENTIRE EAR 11THED.

Now the next picture, here again is the stapes, theres the oval window.And what you see in the inner ear, heres your organ of corti, here are your semicircular

canals, and all this blue-purply stuff is the areas where you find your fluid. So fluid

vibrations are created, but where do they then go? Once you push in on a balloon, theres

no place left in a full balloon, so the balloon has to bulge someplace. So if we look down

over here, you see another window, your round window, which also has a membrane. So as

pressure is pushed in, some of this fluid is pushed out. It doesnt leave the system. And


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whats essentially happening is what Im doing with my two hands. In, out. In, out. So you

have equalization of your pressure. And thats how essentially the ear works.

[Slide 20] L FIG. 18.10 EXTERNAL EAR 11THED.

What we are now seeing is the formation of the external ear. #1, 2, and 3 come frompharyngeal arch 1. Numbers 4, 5, and 6 from pharyngeal arch 2. And the space between

them is your external auditory meatus, which came from the 1stpharyngeal cleft. And you

can see on the embryo here these little bulges. These bulges are known as auricular

hillocks. So wherever you see the number, that represents an auricular hillock. And so the

numbers shift around a bit. They still seem to maintain order. Its not that they go out of

sequence, but youre changingthe position of the hillocks and eventually you get the

formation of this external ear.

[Slide 21] L FIG. 18.11 EXTERNAL EAR DEFECTS 11THED.

Now here are some examples of external ear defects. What we are seeing here (Image A) ispointing to the same thing as this and this (B). There are little pits that develop, areas that

dont seal up. And C and D show these structures which are called tags. And theyre sort of

offshoots off the auricular hillocks. And in this particular picture youll see a tag all the way

down here as well (Image D). So thats some of the more common type of defects. You can

have small ears, large ears, in that type of case we use the words micro-otia, macro-otia.

And then you can get all sorts of different notches like we saw in the mandibular facial

syndrome, etc.

I think some of you spend too much time on the phone, some of you spend too much time

playing computer games. And so, a good part of the class doesnt come to class.

Supposedly studying hard. I wonder about that. I think these other activities are moreinductive at this point in time. I have a choice of ending the lecture now, or continuing with

the next lecture. Your choice. You want to go on? Yeah ok.

Slide set: 2014 FACIAL DEVELOPMENT 5 3-3 post.ppt

[Slide 1] MAXILLOFACIAL DEVELOPMENT

Now we used to have a conference in this course, and in the end run I wound up doing all

the conferences. And not that Im that important, but technically no one can replace me in

doing the conferences. No one wanted to replace me in doing the conferences which isprobably more the true story. So we eliminated the conferences from the course. And what

the conferences showed you was actual embryo heads. And you saw a picture yesterday

and Dr. Lai had a section through the embryo head and he made reference that I would do

that.


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[Slide 2] Cartoon of pig snout

So, some of these slides come from pig, some come from rodent, and some are human.

Which is which is totally irrelevant, it doesnt affect our story. But basically we are going to

be looking at sections through various parts of the head. So when you look at a pig, it has a

rather large snout or nose. So here we have the mandible, theres the maxilla, and that

obviously is the tongue. And heres your external nares. Anybody have any idea what theturquoise structures represent? The concha. The inferior, middle, and superior concha of

the nose. So depending on where the cut is made, youre going to see different things. So

youll see the tongue hanging in midair, not attached. Thats just because the cuts been

made over here. And depending on where the cut was made, youre going to see different

concha, different meatus as well.

[Slide 3] L FIG. 18.7 MIDDLE EAR 11THED.

And this just shows you a typical anterior and posterior view in terms of the cut. And heres

the example I just mentioned, where the tongue is in midair (anterior). Here, its attached

(posterior).In addition, you see the little purple structures? Those represent Meckles cartilage. And if

the cut is very anterior, youll find that the two Meckles cartilages are very close to the

midline. Whereas if you go more posterior, Meckles cartilage is moving further apart. And

in essence, this is an anterior cut, this is a posterior cut (back one slide, indicating #1 as

anterior, #3 as posterior). (Back to slide 3) So when two cartilages are close together, part

of those cartilages will form the mandibular symphesis. More posteriorly, these cartilages

will give rise to the malleus and incus. On top is also showing you the formation of nasal

cavity. And these are cartilages up in the nose (Black structure) . This is your nasal septum

(black vertical line), these are your paranasal cartilages (black rounded lines coming off of

the vertical line) which go into the concha. And these little J shaped structures underneath

the nasal septum is your third set of cartilages, your paraseptal cartilage. And Im sure allof this was covered to some extent in anatomy.

[Slide 4] Embryonic Tissues

So this is a rather high power, were going to start off with a low powerbut this is meant to

show you different tissues. All this light type of tissue, cells far apart, really represents

mesenchyme. And the head starts off as mostly mesenchyme. And then the mesenchyme

gives rise to various structures. So structures like this represents developing muscle, and

well go over these muscles that are developing under the tongue a little bit later. Over

here, youre getting some development of salivary glands. And something like this, which

has a big opening, is really a salivary duct. This by the way, is Meckles cartilage. And heresome actually woven bone being layed down, and this will play a role in the formation of

the mandible. And youll notice surrounding bone is periosteum, and the periosteum seems

to become continuous with perichondrium.


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slide, you can barely see something going on over here, and well see a higher power of it,

this is where you get your nasolacrimal duct. And we spoke about the nasolacrimal duct.

You have a nasolacrimal groove which has been formed because a solid cord of cells has

dropped in, and then the skin is supposed to seal up above it and that solid chord of cells

becomes a tube like structure, the nasolacrimal duct which empties into the inferior

meatus.And most of this tissue (white) scattered throughout happens to be mesenchyme. When

you see structures bulging in, like this from the outside, anyone have any idea what they

might be? Whats going to bulge in from the outside? What do we especially, guys, have on

our face? Hair. Those are the beginning of hair follicles. At the same time, you see this, this,

this, and this. Anybody have any idea what those four structures are? Tooth buds.

[Slide 6] Open Palate Stage Dental Lamina

This is a section more posterior. How do I know that, because of the appearance of these

two structures. These are ventricles 1 and 2. So this is the cerebrum in the animal. Inessence you are dealing with the forebrain. And as we look at palatine shelves, we are still

dealing with an open palate stage. The tongue and mandible have not dropped down at all.

We can see the nasal septum, but the concha are sort of jumbled up, we dont get a clear

view. But the space in here is definitely your nasal cavity. Heres Meckles cartilage, and

again a lot of tissue is mesenchyme. And if we look at this structure and this structure, you

wouldnt know what it is but itis the development of the maxillary nerve and vasculatures.

Again, we still have the forerunners here for teeth.


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[Slide 7] - Open Palate Stage Dental Lamina

So here we are still in the post part of pig, and your ventricles are disappearing. Still open

palate, nasal septum, still a little jumbled up in terms of nasal cavity, and now you can see a

lot of little hair follicles developing, and Meckles cartilage,and you begin to see the

appearance of this type of tissue, which happens to be muscle. Good view of your max

nerve and artery. Still, most tissue is mesenchyme. And this is labeled dental lamina, but

its kind of low power. When we do crown development, youll find that theres a

thickening of the oral epithelium which gives rise to a dental lamina which grows into the

underlying connective tissue alias mesenchyme. And that dental lamina will give rise to a

tooth bud, the tooth bud then becomes a cap stage, and a bell stage, and eventually to theproduction of your enamel and dentin.

[Slide 8] Dental Lamina

And heres just a high power. We arent going to concentrate on this much. Oral epithelium,

and theres your dental lamina. Technically this structure here will blossom out like youre


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blowing up a balloon and that will become your tooth bud. But all this tissue is

mesenchyme.

[Slide 9] Closed Palate Stage Tooth Bud

Now we change stages of development. The mandible has dropped, the tongue has pulledout of the nasal cavity, and the two palatine shelves have rotated upward and grown

towards each other. And what you can see here is this line, separating the two palatal

shelves. Now this line is epithelium, and that epithelium should disappear, then you can

have mingling of your mesenchyme in this particular area. What should also happen is that

these shelves should fuse with the nasal septum, it hasnt quite done that yet.

Now this is the first slide that weve seen a clearer picture of the nose. Nice nasal septum.

And these two bulges in here represent your inferior concha. And concha are associated

with meati. Underneath this concha, this space is the inferior meatus. And in this particular

picture, right there seems to be a structure. Thats thenasolacrimal duct that empties into

the inferior concha. You can also see your paranasal cartilage joining up with the nasal

septum, which both are hyaline cartilage. And something is beginning to happen under thenasal septum. You will get two J shaped pieces of hyaline cartilage known as your

paraseptal cartilage, and in the J shape of the cartilage, you will find something called

Jackobsons organ or the vomernasal organ. Meckles cartilage is still pretty close together.

We dont see anybrain so we are not really that far back posteriorly.

[Slide 10] Closed Palate Stage Tooth Bud

A little bit more development occurring, and we certainly have two very nice inferior

concha. And now you can see right there, and right over here is the formation of the

nasolacrimal duct. Youll also see bone forming up in this area. So this is the beginning of

development of the maxilla. And whatever bone forms the first bone is going to be wovenbone.

This type of tissue is the beginning formation of muscle. And heres your nice tongue. Now

you can see two muscles right over here (clubs under tongue) Anybody remember the

name of this particular muscle? What term do we use for tongue? Glossis. Genioglossus

from the tongue into the area. And what about these muscles (triangles). Whats under the

genioglossus anyone remember? Geniohyoid. Then we have what I refer to, I guess most

people do, as the smile muscle. Mylohyoid. So in anatomy you discussed the anatomical

approach to this, and here youre actually seeing embryonic heads showing you the

histology through the head itself.. And what are these two structures? Meckles cartilage.

And down in this neck of the woods youre getting the formation of the mandible. Andagain, heres your formation of dentition, over here, and here as well. And you see

something is happeneing in this region, we dont get a good view of it, but it is the

formation of your salivary glands and salivary ducts.


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[Slide 11] Tooth Bud

And this is just a high power, youll see these pictures again when we do crown

development. Theres your oral epithelium, your oral cavity, your dental lamina, and

heres yourlittle rounded end, thats your tooth bud. Underneath the tooth bud, Ill mention

it now but it doesnt really apply to what were doing,you see this condensation of

mesenchyme. This is going to form your dental papilla. The tooth bud, by the way, gives

rise to enamel. The dental papilla will form the pulp and dentin of the tooth. And then

theres going to be a thinning out of mesenchyme going around and that gives rise to your

dental follicle or dental sac, which will form your alveolar bone, your PDL, and cementum.

But I wouldnt worry about it at this point in time.

[Slide 12] Closed Palate Stage Tooth bud

So again were seeing basically the same thing but in this case everything up here has fused

together. The two palatal shelves with the nasal septum, and we are having continued

expansion of the maxilla. Theres more of a mandible forming. And Meckles cartilage is

moving away from the midline slowly but surely. There are some tooth buds down here.


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[Slide 15] G&H PLATE 13-4 FIG. 2 CAP STAGE 7THED.

This is just a high power to show you that the little balloon shaped structure, the bud,

changes into a cap just like a French beret. And it has different layers and underneath is

the dental papilla. So again, this is going to form the enamel. And we call the wholestructure the enamel organ. And dont worry about the lettering that represents the layers.

And heres the part thats going to give rise to your pulp and dentin (DP). And DS stands for

your mesenchyme outside here. And thats your dental sac or follicle which forms the

alveolar bone, PDL, and cementum. All this other tissue in here is still mesenchyme.

[Slide 16] Nasolacrimal Duct

Now this is a nice high power where we are looking at the inferior concha. This is the nasal

cavity, and heres your inferior meatus which feeds into the nasal cavity. And heres the

structure weve been seeing very tiny up to this point. And thats your nasolacrimal duct

which actually empties into the inferior meatus. This is part of your paraseptal cartilage,which goes all the way around and becomes continuous with the nasal septum. .

[Slide 17] Early Bell Stage

Besides an advancement in the tooth development you can see that the shape here has

changed and once the prongs begin to dip down like this its going to look like a bell, and


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thats where the namecomes from. Here we have a couple of hair follicles. The vestibule is

shown very nicely here and here, and of course the lip.

Now inside paraseptal cartilage you now begin to see the formation of a bony structure.

Thats the development of a vomer. Heres your maxilla, and theres your mandible.

Now way down at the bottom theres a muscle thats forming andthis muscle, look at me,

goes up like this. Anyone remember the name of that muscle? Its pretty thin, close to thesurfaceplatysma.

[Slide 18] Early Bell Stage

Good shot of the lip, the vestibular groove or vestibule. And that was the vestibular lamina.

And this is a nice picture of the bell stage of development.

[Slide 19]

Really a high power focusing on the bottom of the nasal septum. Your paraseptal cartilages

and theres Jacobsons organ. And in between is the vomer thats forming andyou can seepart or the maxilla forming in this area. Nice inferior meatus, and structure here again is

your nasolacrimal duct

[Slide 20]

This picture probably should have come before the other one because this is an earlier

stage in the formation of vomer. Again most of the tissue here is mesenchyme.

[Slide 21] Jacobsons organ aka Vomeronasal Organ

We are just focusing higher and higher. So this tissue is really epithelial in nature(indicated below). The tissue that lines the nasal cavity is epithelial in nature as well.


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[Slide 22] Late Bell StageThis is the maxilla and this area is where the hard palate forming. But notice that this bone

is surrounded by periosteum, and theres another bone that appears on top surrounded by

its own periosteum. Anybody know what that bone might be? The frontal bone. And again,

nasal septum, paranasal cartilage, nasal cavity, and by the way the lining of the nasal cavity

will have glandular elements as well. The tongue means nice anterior cut. This is a nice

bell stage and theres muscle forming here and you can see a little trace of muscle way

down there.

[Slide 23] Late Bell Stage

And this is a higher power of something I showed you before. Really, very nice bell stages.Youre having quite a bit of development of the mandible, Meckles cartilage is still together.

And now the reason the periosteum becomes continuous with the perichondrium, because

this is where you are actually have the mandibular symphesis forming, and thats via

endochondral bone formation. And you can still see certain traces of muscle forming down

here, part of your platysma.


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[Slide 24] Late Bell Stage

And basically whats happening in the upper region, youre getting more development, the

frontal bone is getting larger, the maxilla is getting larger, and we still see your bell stages

of development

[Slide 25] Hair Follicle

This is just a high power to show you the hair follicle. So in essence a hair follicle sort of

develops like a tooth bud. Nerve components. Muscle components, and a lot of

mesenchyme.

[Slide 26]

Now we are changing our location, and we can see a lot more structures in this particular

slide. Heres nasal cavity and your nasal septum would be over here. And you really see 1,

2, 3 bulges. Inferior concha, middle concha, superior concha. Inferior meatus, middle

meatus, superior meatus. And then theres a space up here thats not really shown, we donthave a picture of that, but its called thesupreme meatus. This is stuff you should have

learned in anatomy. Whats forming up in this region? Eye. What youre essentially seeing

here is the formation of retina, and there is some eye musculature developing in this

region. Now this is of the cheek area. SO what muscle do you think is forming right here?

Buccinator. The masseter would come more from this region down. And youre getting

part of a muscle here, thats the upper limit of the platysma.


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[Slide 27]

Another nice picture. Retina and what do you think this structure is? The development of

the lens. And again we see some of the extra-ocular eye muscle. Inferior, middle, superior

conch, inferior, middle, superior meatus.

[Slide 28]

And this one theres been a certain artifactual preparation thats taken place, so the retina

has collapsed on itself. But here we have five structures. Are all five the same? This is the

one thats different. Thats a section through the developing optic nerve. These are your

extra-ocular eye muscles.


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[Slide 29]

And again we have the retina in a smaller position. And by the way this is the anterior 1/5,

then all of this is the posterior 4/5. And here the lens is just ripped apart. What is forming

right over here? The eyelid. And you can see right in this area the two eyelids are joined

together. And when you are born the eyelids separate.

[Slide 30]

This one the retina is missing but you do have the extra-ocular eye muscles and the optic

nerve

[Slide 31]

This gives us a nice shot of the mandibular area with all the muscles. Obviously thats the

tongue. And what was this muscle again? Genioglossus. And this? Geniohyoid. Mylohyoid.

Anyone have any idea what these muscles might be? Its part of the digastric muscles.Anterior belly. And then this thin slivery muscle which goes all the way around and up is

the platysma, and theres your buccinators, once again. And what about this region (under

the tongue). Well it could be the sublingual or the submandibular but it is a developing

salivary gland and here and here you have developing salivary ducts.

[Slide 32]

And this is just another picture showing us essentially the same things. Except here the

mylohyoid you have more muscle slivers than on the previous slide.

That means, next time we get together, Monday, I forget what Im doing first. Itll be skeletal

muscle, embryology, and teratology. And if we should need more time, I think I haveanother period or so afterwards. Have a nice weekend.

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09: Cranio Development V