hello all this is dr. Alsup again and I'm very excited to get to talk about the meninges and some
of the special specializations of the dura mater specifically the dural partition so we have quite
a bit to go through so let's get started so as we know from the the lecture videos meninges are
those membranous coverings of the brain and the spinal cord there are three types of meninges and
the most external layer is the dura mater which is the toughest and the thickest layer so it's often
looking this kind of pearly white color or silver color now when the calve area or the skull cap is
removed the first thing that you should see is not the brain but the dura mater which you can
see very clearly here so we are looking directly at dura when we're looking at this image you can
see a bit of the dural venous sinus that's going to be deep to this region and we're going to talk
a little bit more about the dural venous sinuses in another video but the rest of what you can
see here is the dura mater and you can see in this particular image over here that the dura
is when it's reflected superiorly you can really see how thick and opaque the dura is and it will
be pretty distinguishable from the thinner and more translucent arachnoid and Pia mutters the
dura mater associated with the brain is different from the dura mater of the spinal cord that we've
already talked about as it has two separate layers the layer that you can see when you're looking at
the superior view without the dura being opened is the periosteum which we have here sometimes
you hear referred to as the end osteo layer the meninges typically very closely adhered to both
the periosteal dura and the arachnoid mater but in certain areas there are elongations of the
meningeal layer of the dura mater that help to protect the brain and create compartments in the
cranial cavity and these are the dura partitions also in certain areas the peri still excuse me
the meningeal dura will kind of reflect away from the periosteum dura to allow for the dural
venous sinuses to flow so you can see right about here so closely adhere to the bone would be the
periosteal dura and then you can see a reflection occurring right about here this would this part
of the dura is going to be the meningeal and you can see it's heading this way and reflecting off
so that's going to be a partition and you can see this dark area right here is where a dural being
a sinus we're slow so you can see how it's nicely reflecting off and anything that is reflecting off
will be part of that meningeal dura now moving to the deeper meninges let's try to understand
where the arachnoid and Pia mater are going to be located the arachnoid is a little thicker and can
actually be dissected away from the brain so this is going to be part of the arachnoid right here
whereas the Pia mater is so closely adhered to the brain it cannot easily be dissected away so
the Pia is what's really giving the brain and the spinal cord that shiny appearance so the Pia mater
would be directly on the brain now looking at the spinal cord which I know isn't in this particular
session but I want to review a few things really quickly sometimes it's easier to see these deeper
meninges now the Pia mater again is very closely adhered to the spinal cord you can see it how it's
really making this on a cord look shiny here what the forceps are holding on to is the dura mater
with the arachnoid mater very closely adhered to the dura you can see a little bit of it kind of
right around this region now what is really nicely visible in this image are the arachnoid trabeculae
you can see these kind of all over the place here it is these are right enoyed trabeculae that give
the spider web-like appearance associated with the arachnoid and thus why they right no mater
has its name the trabeculae are located within the Sudbury we'd space that separates the arachnoid
and the PIA mater which also has vessels in CSF or cerebrospinal fluid during life all
right let's move back to the discussion of the dural partitions and stop for a second and try
to think of what these partitions are composed of so we reviewed it towards the beginning but
think about what our dual partitions made of I bet you got it right it's going to be that meningeal
dura perfect okay so let's get into those four dural partitions and we'll try to look at them
in some different views here we are looking at a superior lateral view with only half of the
calvarium removed so you can see the other half is over here and obviously the brains been removed we
can see two of the four dural partitions pretty well here and we'll start with the falx cerebri
this is the largest of the dural partitions and is very distinctly sickle-shaped and when the brain
is president it's going to run right down the middle of the longitudinal fissure between the
cerebral hemispheres the partition is going to attach to the crista galli of the ethmoid bone
all the way back towards the internal occipital protuberance of the occipital bone so obviously my
squiggly line isn't exactly as nice and anatomical as I would like it but I want you to understand
that it has a fairly large expanse from the most anterior portions of the skull back to some of the
most posterior portions of the skull it will also house both the superior what you can see here and
you can't see as well but the inferior sagittal sinus is and we'll have a video specific to the
venous sinuses in another session you can also see in this image the tentorium cerebelli so
you can see a little bit of it here you can see a bit of it over here this is the second largest
oral partition it's going to sit a bit more turns transversely separating the cerebrum specifically
the occipital lobes from the cerebellum so an since the forebrain is going to sit above
the tentorium cerebelli and the hindbrain will be inferior now we are looking at a straight superior
view here also importantly the falx cerebri has been removed but now we have a really nice view
of the tentorium cerebelli and how expansive it is so here is the tentorium cerebelli on either
side you can see a bit where that falx cerebri did sit so you can see a little bit of a remnant
of it here now one thing I want you to note is you can see this distinct curved much associated
with the tentorium cerebelli excuse me and this is the tentorial notch this not just where the
mid brain sits during life and it also separates the tentorium cerebelli from the diaphragmatic
cell a which you can see a little bit of in this region here alright so what is the diaphragmatic
cell a it's going to cover the sella turcica of the sphenoid bone and forms a roof over
the hypophyseal fossa so it will have during life an aperture for the infundibulum or the
pituitary stalk because we know that posterior pituitary is going to be in this region here now
this partition is the smallest and the least dense so a good amount of it has been removed
in this dissection but as long as you get an understanding of where the diaphragmatic cell
a would be located conceptually we were happy with that because often in dissections it's not
very visible now last but not least we're going to have the falx cerebelli so not the fox cerebri
the falx cerebelli so we know it probably has something to do with the cerebellum or
have a close relationship there and you can see just a little bit of it right about here so the
fox cerebri would have stopped a little bit more superiorly we are looking at a superior view again
but not only has a fox cerebri been removed but also the tentorium cerebelli and that's
an important distinction that or iam cerebelli has to be removed or reflected in order to see
any of the Falx cerebelli the Falx cerebelli is located between the cerebellar hemispheres when
the brain is present and when the brain is not present you can see it inferior - excuse
me inferior to where the tentorium cerebelli would be located and heading kind of towards
but not quite to the foramen magnum all right so that is our review of the cranial meninges
as well as the dural partitions as always after you you've reviewed these and if you have any
outstanding questions please make sure that you reach out to me and have a wonderful day