hello anatomy colleagues this is dr. Alsup and I am super excited to discuss these unique
anatomical areas which we refer to as the dural venous sinuses so as its name would suggests we
are talking about regions associated with the cranial dura we have mentioned these in a few
other lecture videos as they play important roles in regards to cerebral spinal fluid drainage as
well as in regards just to the meninges in general but in this video it will be all
dural sinuses all the time they are the star of the show we are going to focus on locations
and where these will eventually drain on their path back to the hearts okay let's start with
a review of what forms the dural venous sinuses these are specifically located between the two
layers of the cranial dura with a few exceptions so the meningeal dura will reflect away from the
periosteal dura and there will be a formation of the dural venous sinuses so say here is the
periosteal dura here the meningeal dura is going to reflect away from it and what you're left with
is this area here which is a dural venous sinus now for our purposes we can think of them as like
veins not veins per se but like them in terms of function they are draining blood from the
brain and internal cranium to return to the heart like a good vein does they are very structurally
sound in terms of not collapsing because of their attachment to the bone with this periosteal dura
most venous sinuses will eventually in one way or another drain into the internal jugular vein
or your ijv which is formed by the coalescence or the joining of the inferior petrosal sinus
with the sigmoid sinus so let's talk about some of the specific dural venous sinuses and we will
start with the two that are associated with the Fox cerebri which is one of those dural
partitions or in foldings specifically that dural partition that's located within the longitudinal
cerebral fissure arguably the longest dural venous sinuses a gentle sinus you can see how
long it is extending it runs in that superior border of the falx cerebri and is very close
to the bones of the calvaria this sinus is also important in terms of CSF drainage as well CSF
will drain into other sinuses this is typically one of the major drainage sites the superior
sagittal sinus will drain into this area here where multiple sinuses will drain as its name
would suggest which is called the confluence of sinuses oops didn't mean to mark through
that confluence of sinuses we'll talk about the other sinuses that drain there in a moment the
inferior sagittal sinus will run in the inferior concave free border of the falx cerebri which I
am outlining right here and it will join with the great cerebral vein which you can see here
it will join together to form the straight sinus which I'm outlining there all right let's return
to the confluence of sinuses and it's just what it sounds like it is an area where many sinuses
come together and drain blood into one region and it's typically load located just lateral to
the internal occipital protuberance of area that portion of the occipital bone and you can often
clearly see where existed on dry bone because it creates a notable divot in the bone next to the
internal occipital protuberance so three dural sinuses venous sinuses will drain here you will
have the superior sagittal sinus as we mentioned before that's straight sinus which is formed by
the coalescence of the inferior sagittal sinus and the great cerebral vein will be the second
and the third sinus is the occipital sinus which is associated with the Falx cerebelli which is one
of the the other dural partitions that's associate that's going to be located between the cerebellum
Hemisphere's the confluence will continue drainage as the pair transfer sinuses so if this is the
confluence where those three sinuses are draining it will continue both right and left excuse me
this would be the right and this would be the left so it will continue into these transverse sinuses
all right let's talk the cavernous sinus this cavern the sinus is so cool that we're going
to talk about this in a whole other session as well and that orbit and cavernous sinus session
and these are the cavernous sinuses the cavernous sinuses are really more of a venous plexus which
is kind of these extremely thin walled veins this is why it's depicted here as more of a complex
and say perhaps this larger sagittal sinus or the transverse sinuses there are a right and
a left cavernous sinus which communicate with one another through venous channels referred to
as the inter cavernous sinus sinuses and these are going to be anterior and posterior to the
infundibulum of the pituitary so you'll have these complex of sinuses on both the right and the left
side I like to think of them on either side of the sella turcica region now many veins of the
brain will drain here such as cerebral veins as well as ophthalmic veins and it's through
these ophthalmic veins that infections often enter into the cavernous sinuses if they're
going to enter into the cavernous sinus the cabinet sinuses will eventually drain into
the superior and inferior petrosal sinuses and this is depicting kind of these generally
and we will discuss this next concept this next point right here in more detail in the
orbit and cavernous sinus session but there is a lot of important neurovasculature which
will either travel directly through the lumen of the cavernous sinus such as the internal carotid
artery or your do since nerves nerve or cranial nerve 6 or through The Associated lateral walls
of the sinus such as the oculomotor or the trochlear nerve or the ophthalmic or first
division of the trigeminal nerve so imagine an infection enters into this region and you have
all that neurovasculature and there it can really greatly affect the structures in there think of
the innervation of the extraocular eye muscles which are innervated by cranial nerves three
four and six so that could have tremendous implications in terms of the movement of the
extraocular eye muscles so like I said we will return to this concept in more detail in that
session ten but I did want to bring it up here because it's it's kind of a cool a cool subject
the last dural venous sinus I want to discuss in greater detail are the sigmoid sinuses of
which there are two a right and a left and so right about at the area of the petrous part of
the temporal bone the transverse sinus will kind of quickly or more directly head inferiorly in a
kind of abrupt curved shape and where this occurs there's a name change to the sigmoid sinus these
sinuses will join with the much smaller inferior petrosal sinuses to form the internal jugular
veins at the level of the jugular foramen ah so say the jugular foramen ax is going to be
like hereis at that point the name changes to the internal jugular vein now here is a
schematic of the dural venous sinuses range the lines indicate where the sinuses are draining
so kind of in this region here so we know that the inferior sagittal sinus joins with the great
cerebral vein to form the straight sinus and we know that straight sinus eventually makes its
way to the confluence of sinuses the confluence of sinuses will have the transverse sinuses that turn
into the sigmoid sinuses and the internal jugular vein so you can kind of get an idea of what we're
meaning in terms of this so not perfect not drawn to scale but I do think it kind of gets the point
as to what sinuses drain into which to eventually make their way to the internal jugular veins I
highly recommend you create your own version of this for your studying and I would love to
see your versions if you if you're proud of them I'd like to see them I would even recommend next
to your boxes or whatever you end up drawing jotting down a few notes as to where you would
find that particular dural venous sinuses I think will be a helpful practice all right as always I
like to finish off with the question question is which of the following does not typically drain
directly into the confluence of sinuses is it a the occipital sinus B the sigmoid sinus C the
straight sinus or D the superior sagittal sinus all right what do you think the correct answer
is it is going to be B the sigmoid sinus these other three do actually drain directly into the
confluence of sinus sinuses most typically whereas the sigmoid sinus is distal to the confluence of
sinuses all right that was a lot of fun please take time to review these concepts and I look
forward to discussing these concepts if you have questions thank you for your time and attention