the dura mater is the outermost layer of the meninges it's like I said before it's the tough
mother I and it's it's incredibly sturdy if you grab ahold of the dura mater if you ever have
the opportunity you can pull on it in almost any direction and it will not tear in this particular
imagery we have an overview of the entire dura here covering the entire surface of the brain
and it has some specializations there are areas where the dura comes up towards the surface and
then it folds together on the midline and that is this structure here which is the falx cerebri
and the falx cerebri separates your two cerebral hemispheres it lies within the superior sagittal
that you we talked about when we were talking about the gross anatomy of the brain so the
Falx cerebri separates the two hemispheres there's a teeny tiny little falx cerebelli that
goes in between the the cerebellar hemispheres but that's really hard to see and then there's
a what's called the tentorium cerebelli and that's this area here where the if you can imagine this
coming out at the screen at you perpendicular to the Falx and tentorium cerebelli means tent
over the cerebellum and that is a tent that lies between the occipital lobe and the cerebellum
below it other specializations that lie within the the dura are the dural sinuses or the venous
sinuses and these are areas where venous blood is collecting on its way back to the heart and we
have two that you can see in this section there's the superior sagittal sinus that runs up here in
the Falx and there's the inferior sagittal sinus that runs along here in the inferior aspect of
the Falx cerebri there's a straight sinus that runs here where the Falx and the tentorium come together
and then just on this outer edge of the tentorium cerebelli is what we call the transverse sinus
because it's going transversely around the back here are some images of the base of the skull
with the top of the skull and the brain removed so you can see these meningeal layers in in situ so
on this image up here we have the fox cerebri at the top with our superior sagittal sinus opened up
and that is dark venous blood up in here so here is again that superior sagittal sinus we have the
falx cerebri up here and then we have the tentorium here you can clearly see the straight sinus right
in here what that's at the intersection of the Falx and the tentorium looking straight down on
the brain we have the tentorium cerebelli in this area and what you can see here again then is that
straight sinus and the see is referring to what's what we call the confluence of the of the sinuses
it's where the transverse and the straight come together with the two from with the superior
sagittal and inferior sagittal so these are areas where blood is returning to the venous system they
don't have any valves and so blood can flow and in your direction depending on whether you're lying
or lying down or standing on your head or standing up they're lined with endothelium so that they're
smooth but they don't have any smooth muscle like the rest of your veins have they are kind of big
caverns into which blood is flowing back all of your dural sinuses eventually are going to drain
toward the base of the skull and they're going to drain into the inferior jugular vein which
are then is going to go back into your heart in the next segment we'll talk about the arachnoid