hello anatomy colleagues this is dr alsup and in this supplementary dissection video we're going to
focus on the meninges as well as getting an idea of where some of those spaces or meningeal spaces
would be located both actual and potential spaces so we are looking at a spinal cord right here a
portion of the spinal cord and the dura mater has been open so the dura mater is what is being
held by these forceps right here and you can see how thick this dura is in comparison to
some of these other structures right here and see a bit of the dura over here as well
the dura as we know is that outermost covering of the meninges it's that toughest one
and i'm going to skip over the subdural space for just a moment so i can let you have kind
of an idea of the arachnoid mater and usually the arachnoid mater is very closely adhered
to the the dura mater and so you would have no space there but during a during the embalming
process sometimes it can stay adhered to the dura sometimes it becomes kind of collapsed and will
adhere more towards the the pia mater but in this particular dissection you can see kind of this
filmy appearance that is the arachnoid and you can see some of those arachnoid trabeculae that
give the arachnoid its name and that spider-like appearance and the subdural space would be the
space between the arachnoid and the dura mater all right so it'd be somewhere right about here-ish
but keep in mind that the subdural space is a potential space meaning that this there really
should not be a space between these two structures occasionally it can become an actual space or a
real space if something enters the area say like blood if blood entered into that region kind of
creating a space between the dura mater and the arachnoid that would be a subdural hemorrhage so
this is a potential space and we just kind of want you to get an idea of where these would be located
in terms of the dissection the space between the arachnoid mater and the pia mater
would be the subarachnoid space okay so this area right about here-ish which is greatly exaggerated
in terms of its size because the forceps are pulling the dura for us to be able to view these
things but the subarachnoid space is an example of an actual space or a real space that is present
without pathology and during life you'll have cerebrospinal fluid that will be flowing through
there you can have neurovasculature that's also moving through the subarachnoid space
the pia mater is almost completely impossible really to remove from
the central nervous system so from the spinal cord or the brain
is so very closely adhered to that structure it's what kind of gives the that region that shiny
appearance that you can see so the pia mater will be directly on those portions of the cns
this is a different view with the dura modern knot being cut so in this particular dissection
this is a laminectomy was completed so the lamina the spinous processes were removed because we're
looking at a very posterior view so that that portion of the vertebral arch has been removed
and you as well as the epidural fat because that epidural space would be in this region here the
space between the bone and the um in the dura mater and you can see just how robust and thick
the dura mater is and in order to be able to see the spinal cord you would have to make an incision
and reflect open in order to get into those deeper structures
let's talk a specialization of the dura mater called the filum terminale this should be an e
right here my apologies um externum often referred to as the coccygeal ligament and after the dural
sac terminates so the dural sac is around s2 you can see it kind of comes to a point right here
and the rest of this portion of the dura has been reflected in order to see those portions
so right where that the dura mater ends or that dural sac ends you will have a small
extension of the dura mater that will continue all the way to the coccyx and what this does
is it will play a role in terms of anchoring the dural sac to the coccyx and it will also envelop
the phylum terminale interternum which is an extension of the pia mater so it will the internum
will travel through the dural sac and then once it gets to this region at the end of the dural sac
the filum terminale will envelop that and they'll kind of travel together as a coccygeal ligament
there are two ex there are two specializations of the pia mater that we want you to be familiar with
the first is the denticulate ligaments and these are paired extensions of pia mater that will
as it suggests it will extend away from the pia mater
and it will be on either side and these will attach to the dural sac so you'll have the
extensions of the pia extending all the way to the dural sac and they'll appear
kind of this opaque white compared to the rootlets and the roots in this region so you can see it
extending all of this region it will kind of be in between the dorsal and ventral roots
and rootlets of the spinal nerves and usually you have about 20 to 22 pairs of these so you may not
have them at every vertebral level but you have to kind of get really into that deeper portion and be
right at that spinal cord in order to see these denticulate ligaments again similar to what we
had with the filum terminale externum this is going to play an anchoring role
and i mentioned the filum terminale internum when discussing the externum
this is going to be an extension of the pia mater so right here i'm going to draw
a a line around what is referred to as the conus medullaris and we'll talk about that in a bit more
detail in another video but basically this is the tip or the end of the spinal cord which occurs at
around l2 and from there you're going to have extensions or you're going to have roots that
are going to extend from that region called the cauda equina again we'll discuss that in
more detail in another video but you will have a little bit of the pia mater meninge
extending past the conus medullaris and traveling through the dural sac region kind of in the
midline till you get to the the end of the dural sac at about s2 so this is s2 conus medullaris or
the tip of the conus medullaris is about at l2 so you'll have it extending from this space to this
space and then it will be enveloped by that phylum terminally externum or the coccygeal ligament
it will be opaque white you can see a little bit of that right there i think pretty well
in comparison to the surrounding cauda equina all right excellent meninges are always fun
sometimes you can see them really really well in a dissection sometimes not quite as well so it might
it might behoove you to kind of look at as much variation as you can in those regions but at least
conceptually understanding where they're located and getting an idea of those spaces can be helpful
as well all right thank you for your time and attention here and if you have any meninges
questions you can always feel free to reach out to myself or any of my anatomy colleagues
thank you for your time and attention here and have a great rest of your day