hello all it is dr. Alsup and it is my absolute pleasure to get to discuss many
of the general osteological structures that we want you to start becoming familiar with in this
session and some of these will come up again in subsequent sessions and some are actually
review from previous sessions as osteology is my absolute favorite and since we have much to
talk about I can't wait to get started so let's start with some basics of terminology before we
move on to some of the finer scale detail we are looking at a lateral view of the skull here the
term skull means the cranium plus the mandible so here's your mandible as we all know and love
if you did not have the mandible attached this area would be called the cranium the cranium is
composed of the facial region over here or this is often the facial region is often referred to
as the visceral cranium and the rest of the cranium is referred to as the neuro cranium
which makes sense because that is where the brain is going to be housed for what is protecting the
brain the neurocranium is further subdivided into the cranial base or the base of cranium where the
brain sits and the calvaria more commonly called the roof of the cranial vault so that so any area
kind of up in this region so the roof of the cranial vault or more crudely put the skullcap
these are all synonyms for calvaria it is the calvaria that needed to be removed in order to
obtain this superior view of the basic cranium or the cranial base now we have looked at this
particular view before we hopefully know by this point that this is going to be anterior and this
will be posterior back here and here are your frontal bone the sphenoid the temporal bones
and the occipital bone alright so hopefully these things are a review if you're not quite
familiar yet with the bones that are in this particular view make sure that you go back and
review that will add on some additional bones as we move through the course now recall that there
is an irregularly shaped formen that's going to be between the temporal bones and
the occipital bone this is the jugular foramen of the jugular foramen if you're talking about
both of them that the internal jugular vein as well as cranial nerves nine ten and eleven will
Traverse next let's review this anterior view with a focus on the frontal bone and this is
going to be the frontal bone up in this region if you put your hand on your forehead you are that
frontal bone is living underneath there looking at the lateral and inferior most portions of the
frontal bone so here and here you can see these extensions or processes these are your zygomatic
processes and that makes sense because these are the parts of the frontal bone that are going to
head towards or articulate with your zygomatic bone more medially within the supraorbital margin
you will see either a supraorbital notch or a supraorbital foramen we are fortunate enough
with this donor to see both with a notch here on the left and the foramen over here on the right
it doesn't matter if it is a notch or a foramen the same things are going to traverse this region
which is the supraorbital nerve vasculature next let's identify the temporal lines go back to the
zygomatic processes of the frontal bone that we already located and follow this line posteriorly
so it's heading back towards the parietal bones these are the temporal lines so here's the
temporal line over here this line is formed by the attachment of the temporalis muscle to this part
of the bone you may also have temperate umbrellas fascia that is going to attach here as well
looking into the orbit so we're going in excuse me going into the orbital region here you can see a
fairly large orbital part of the frontal bone the frontal bone is actually forming the roof of the
orbit so that roof of the orbit inside that region of the frontal bone is referred to as the orbital
part and lastly let's get an idea where the frontal eminence or imminences are located which
is about here-ish and here-ish these are very slightly rounded eminences or elevations of the
frontal bone these like we have here are typically not very prominent in adult skulls you can have
it a little bit more inferior as well these are generally larger in juvenile skulls let's continue
the discussion of features of the frontal bone but let's look at it from a more anterior lateral view
which we can see here the superciliary arches are ridges which I am outlining right here are
superior to the super orbital margins the size of the arches can vary significantly between
individuals and and then we're lucky enough that they're fairly obvious in this particular
individual the nasal part of the frontal bone is the part of the frontal bone closest to the
nasal bones so these are your nasal bones right here and so these portions of the frontal bone
would be considered part of the nasal part of the frontal bone moving into the orbital region of the
frontal bone again in this superior lateral region right about here --is-- can't see it particularly
well over on this side but it would be here so in the superior lateral region you will have the
fossa for the lacrimal gland which is what's producing tears this is the part of the bone
that though that lacrimal gland will actually sit in is protected by that that particular parts of
the bone the trochlear fovea is on the opposite side so we're heading more medial within the
orbital region so superior medial this is where the trochlea of the superior oblique muscle sits
the superior oblique muscle is an extra ocular eye muscle and we'll talk about that a bit more detail
in the orbit session the last two things I want to identify in this view are the ethmoidal foramina
and i'm going to circle those here these are these tiny holes in the medial portion of the orbit
and the anterior one is going to be the anterior ethmoid 'el parameter or foramen excuse me since
we're just looking at one and the posterior one will of course be the posterior ethmoidal
foramina this allows ethmoidal neurovasculature to exit the skull and you can see that
these foramen are located right where the frontal bone is meeting the ethmoidal part of the orbit
alright let's move on to some of the structures of the parietal bone we are again looking at
a lateral view of the cranium recall that the temporal line of the frontal bone is going to
be about here we saw it from a more anterior view before so right around this region the temporal
line of the frontal bone is going to be there this line will extend into the parietal regions
so sometimes it's difficult to tell the difference between the superior and inferior temporal lines
fortunately on this particular individual I think it's actually a bit more obvious here
is the superior temporal line which is formed by the attachment of temporal fascia and this
one right here will be the inferior temporal line which is formed by the most superior attachment of
the temporalis muscle so one of those muscles of mastication now let's look at the parietal bones
from an internal view so this is that calvaria but we are looking at it we're looking into it
so into the internal portions of it this here is going to be anterior this will be posterior
I can tell this for a few reasons one of the main reads reasons here is you can see how thick the
bone is right here the occipital is going to be a little bit thicker than what you have in the
frontal bone running down this midline region here you will have a distinct groove you can see it a
little bit from this image you're going to have a distinct groove portion of the parietal bones you
can also see it's extending into the frontal bone region as well this groove is formed by
the superior sagittal sinus thus the name groove for superior sagittal sinus near this groove you
will see various holes you see a very distinct one here you see a few around this region these
are referred to as granular foveal a these are formed by arachnoid granulations which we know
are very closely associated with the superior sagittal sinus and the lacunae so how we are
getting that CSF into the venous drainage region all right lastly we see all these
beautiful grooves on the more lateral portions of the internal parietal bones I can see them
particularly well on this anterior portion of the parietal bone on this particular donor you can
see some that are a bit more posterior as well on the parietal bone these are grooves for the
middle meningeal artery this name would actually be more descriptive if it was grooves for branches
of the middle meningeal artery so the middle meningeal artery will send numerous branches
throughout this region because it's a really important supply to the meninges alright movie
back to an external but this time a posterior view of the parietal bones so here are your two
parietal bones here's your occipital here just for review now you see these two prominent eminences
here you see kind of where it looks like the parietal bone is kind of bulging out in this
region these are important ossification centers so where we have the development of bone they
these immanence --is become less prominent with age but on this particular donor they are quite
prominent very close to the sagittal suture that's running right down the midline here you had these
two very small foramina which are referred to as the parietal foramen if you're talking about one
of them or foramina if talking about both this these particular foramen are going to allow for
the parietal emissary veins to traverse so you'll have various areas of the skull where you will
have foramina to allow Emissary veins to traverse they're important in terms of connecting the
venous sinuses inside to the scalp veins outside so these this particular region right here would
be the parietal emissary veins additionally you may not have parietal foramina so they may be
absent some individuals and you'd have them in other areas of the skull all right this next
structure should be a nice review as we covered this in the anterior next session as well so why
don't we use this as a means of reviewing try by yourself to locate or identify where the external
openings for the carotid canal are located so pause the video if you want to take a second to
do that alright so hopefully you took some time to review it and let's see if you got it right
so here and here are going to be the external openings of the carotid canal and this is how
the internal carotid artery is going to enter the skull so hopefully you got that right if
you didn't that's okay you know that this is narrow you to review and it's always nice to
kind of self check there all right now looking at a posterior view the dominant bone you can
see here is the occipital bone and we will focus on two structures we want you to identify in one
part now this whole region here of the flatter portion of the occipital bone is referred to
as the squamous part we will come back to the squamous part in different views so just know
that it's that flat or part of the bone now I want you to take your hand now and feel the back of
your own head until you feel a big bump that bump you feel is the external occipital protuberance
and that is a long name but a pretty descriptive one that bump you can see I've labeled right here
in terms of where it's located on the skull now extending laterally from the external occipital
protuberance is the superior nuchal line which is often considered a superior element of the
neck as this is one of those attachments of the sternocleidomastoid muscle so this can be variably
large in individuals some individuals will not be particularly robust and others it will be
now let's focus on the occipital bone from this superior view of the basic cranium so this view
comes up over and over again so I hope you're getting more and more use to it there are two
main parts of the bone that we can identify here again here is that squamous part of the occipital
bone so that flat or larger part of the occipital bone whereas here is consider the basilar or the
basal or part of the occipital bone sometimes you'll hear this particular area right here
referred to as the clivus of the occipital bone in fact I often kind of prefer that term so you may
hear me say that often all right corresponding closely to the external occipital protuberance
but inside will be the smaller internal occipital protuberance or this bump right here
this is going to be the posterior attachment point for the falx cerebri so one of those
dural partitions now on either side and will follow I believe on this side and either sided
the internal occipital protuberance you will see a groove extending you shouldn't take that
little card there extending laterally this is where the transverse sinus sat during
life these will continue laterally and when they take a turn inferior lis these are going to be
referred to as the groove or the sigmoid sinus so the transverse sinus sat here the sigmoid
sinus set here during life and it formed these grooves in the bone and it makes sense that this
would be the sigmoid sinus because see where it's heading it is heading towards the jugular
foramen which the sigmoid sinus with the inferior petrosal sinus will form the internal jugular vein
so that sigmoid sinus should continue to the jugular foramen fairly obvious here you have
the foramen magnum so that big hole right there in the middle of the occipital bone here again
you have the jugular foramen ah so that sigmoid sinus is leading into the jugular foramen the
portion of the foramen that is of the occipital bone is referred to as the jugular notch of the
occipital there is also a jugular notch of the temporal bone and when you put those together
you have the jugular foramen lastly let's identify the hypoglossal canals and I think you really only
can see it well on this right side here it would be right about here ish on the left I always look
toward the foramen magnum region when trying to identify these and start heading towards the
basilar part or the basilar part and that's where you would have these openings for the hypoglossal
canal which will allow the hypoglossal nerve or cranial nerve 12 to exit the skull lastly
let's look at the occipital bone and its features from an inferior view here again is going to be
the squamous part here is the basilar part and right here in the middle of the basilar basilar
part from this inferior view you're gonna have a bump and this bump is referred to as the pharyngeal
tubercleit is here that that pharyngeal raphe for those pharyngeal constrictor muscles is going
to attach here are two of my favorite features of the occipital bone which are your occipital
condyles here in here these will form a joint with the first cervical vertebrae c1 or the
atlas all synonyms for the same bone this allows for the movement that you make when you shake
your head yes so that joint between c1 and the occipital condyles lastly next to the posterior
extent of the occipital condyles you may or may not see what's referred to as condylar canals
you more often will see them than not so it's more frequent than not these are another means
for emissary veins to traverse specifically the occipital emissary veins alright so that was a lot
of osteology fun and as you work your way through reviewing this material material please do let me
know if you have any questions and I'll be super excited to discuss thank you and have a great day