in this lecture we're going to talk about the ventricular system you know already from dr.
Alsup's lectures on the skull that you have holes in your holes in your head basically
holes in your skull I'm going to talk about the holes that are in your brain the ventricles you
have two laterals one on each side one associated with each of your cerebral hemispheres there's a
third ventricle on the midline a fourth ventricle that's underneath the cerebellum and also on the
midline the ventricles are the home of the choroid plexus and the choroid plexus is what makes your
cerebrospinal fluid in this image we can see a cast so we've put a resin into this the ventricle
system and then peel the brain away so you see what's so what is a space shows up is something
positive the lateral ventricle is here on one side and you can see that it has three horns
the midline is the third ventricle a cerebral aqueduct the fourth ventricle is here and you
can see barely shadowed in here is the lateral ventricle from the other hemisphere so how do you
get two lateral ventricles during development your brain starts out or your entire nervous system
starts out as what's called the neural plate and that's this flat kind of section here the neural
plate rolls up and forms the neural tube which we have kind of pictured here the neural tube
then becomes elongated and is starts to kind of look like a long cylinder the front part is going
to be your brain the bottom part is going to be your I'm sorry spinal cord this is then going to
progress and the front part the brain part of the long neural tube is going to grow really really
fast cell division is going to take off and what happens then is you get a big expansion of this
front part of the brain the bottom part or this middle section here stays firmly in place and so
as these cells divide they expand and you end up with two cortical bubbles so this is going to be
your cortex and this is going to be your left hemisphere and your right hemisphere and you
can see then as the bubbles develop that then of course the inside the lumen of those bubbles just
kind of continues on so this again will be your left ventricle and your right ventricle the third
ventricle remains on the midline the cerebral aqueduct is going to be here leading down to the
fourth ventricle and then the lumen still persists into the spinal cord as your central canal and
we'll talk more about the central canal when we talk about the spinal cord in a later series of
lectures so to go back to our lateral ventricles there's one in each of your cerebral hemispheres
and they span the entire range of your cerebral hemispheres so the anterior you have an anterior
horn of the lateral ventricle and this is found you can see this in sections of your frontal lobe
there's an inferior Horn of your lateral ventricle and you can see that in the temporal lobe the
posterior horn of your lateral ventricle is all the way back in your occipital lobe and then your
parietal lobe kind of surrounds this area which we call the body of the lateral ventricle there's
also this area here which is kind of shaped like a triangle if I could draw a triangle and this is
referred to as the trigone it's an area where the body the inferior horn and the posterior horn all
come together what you can see on pictures of embalmed brains is that the lateral ventricle
is seen here and you notice that there's this like a a window across it this is the septum pellucidum
it's a thin layer of tissue and it separates your lateral ventricles one from the other in
this image we've removed the lateral of the septum pellucidum and you can see deep into that lateral
ventricle the ventricles then the two lateral ventricles the cerebrospinal fluid that's in
them flows into that midline third ventricle via a tiny little opening called the interventricular
foramen in the next section of this lecture we'll talk about the midline structures of the third
ventricle the fourth ventricle and then we'll talk more about the flow of cerebrospinal fluid