okay we're going to talk about the ventricular system of the brain and answer the questions what are the ventricles of the brain and what is csf where is it produced and where does it flow hello everyone my name is dr morton and i'm the noted anatomist so the ventricles are can consists of the following lateral two lateral ventricles a third and a fourth ventricle let's talk about each one of those okay so here we're going to do this through a lateral view of the brain and this is the brain and then we've ghosted as if we're superman looking through and we can see those ventricles from a lateral view and then this is the same brain except in a coronal section from an anterior view okay so the lateral ventricles are paired c-shaped chambers in each cerebral hemisphere okay so there's one c-shaped lateral ventricle on the left and there's the other one on the right and then if we look at the chronal view on the right side there in coronal section is the lateral ventricle on the left there's the other lateral ventricle there's two of them which is first and second it doesn't really matter there's just two lateral ventricles which is why we have a third ventricle it's the largest out of all the ventricles so it's far bigger than the third and the fourth ventricle and it's below the corpus callosum so in this coronal section there's our corpus callosum it's right below that large commissure then there's the interventricular foramen of monroe and it's the communication between the lateral ventricles and the third ventricle so there's our lateral ventricle there's the intraventricle interventricular foramen going into the third ventricle so we look on the coronal section there's our two lateral ventricles shing there the paired interventricular foramina going into the third ventricle then the third ventricle is in the midline it's a narrow space between the left diencephalon and the right diencephalon so in the coronal section there's one diencephalon there's the other diencephalon and there is our third ventricle so there is our diencephalon in this lateral view and the thalamus and the hypothalamus are on either side the third ventricle is what is in between the thalamus and hypothalamus on the right and the thalamus and hypothalamus on the left the thalamus and hypothalamus and the epithalamus together are what are called the diencephalon the inner brain then there's the cerebral aquiduct it's also called the mesencephalic aqueduct and it's also called the aqueduct of silvius so i'm going to keep calling a cerebral aqueduct but those other two are used in medicine as well it's located in the midbrain so it connects the third and the fourth ventricles so there's the third ventricle there's the cerebral aqueduct and there's the fourth ventricle so in the coronal section there's the third ventricle there's the cerebral aqueduct and the midbrain all on either side and there's the fourth ventricle and then the fourth ventricle is located between the pons and medulla and the cerebellum so there's the pons and medulla anteriorly and there's the cerebellum posteriorly and outline there is our fourth ventricle and then in the coronal section there's the cerebellum and then outlying there is our fourth ventricle so let's do that again except let's just look at an anterior view those two things that look like ram's horns those are the lateral ventricles there's two of them and they then through the interventricular foramen give rise to the third ventricle between the two diencephalons and then the third ventricle through the cerebral aqueduct go into the fourth ventricle now something i want you to observe is that csf is coming from the two lateral ventricles and the third ventricle and the only way into the fourth ventricle and then into the subarachnoid space is through that cerebral aqueduct and so if you block that cerebral aqueduct all the csf in our two lateral and the third ventricles gets blocked and occluded then the fourth ventricle communicates to the subarachnoid space through these two lateral ventricles okay so now what we're going to do is we're going to go shing and separate this brain in half remove this hemisphere and then look in that view so this is going to be a sagittal section through the brain into a medial view and there's our corpus callosum below the corpus callosum is the lateral ventricle which communicates via the interventricular foramen with the third ventricle and the third ventricle through the cerebral aqueduct communicates with the fourth ventricle now the fourth ventricle communicates with the subarachnoid space so how does that work well before we get into that there's three questions i want us to answer where does csf come from where does csf flow and where does csf drain back into the bloodstream let's go through each one of them so the choroid plexus produces csf by then basically filters blood plasma into the subarachnoid space and so it's got many components of plasma and this is what enables the central nervous system the brain and spinal cord to float so this choroid plexuses are located in each ventricle so there's the choroid plexus in the lateral and the third ventricles and there's the choroid plexus in the fourth ventricle okay and the then the flow goes like this so csf from the choroid plexus and the lateral ventricle flows through the interventricular foramen and joins with the csf from the third ventricle choroid plexuses and they all flow down the cerebral aqueduct and they join with the csf produced by the fourth ventricle choroid plexus and this is how it's flowing so what happens then is the fourth end ventricle has these openings called the median aperture singular and lateral apertures the median aperture of megendi and the lateral apertures of lushka and those apertures were communicating csf from inside the fourth ventricle to the subarachnoid space so there is a singular median aperture and there is one of the lateral apertures on the lateral wall on the right and then you see the csf flowing through that median aperture into the subarachnoid space and then the subarachnoid space flows all around the outside of the brain again flowing up until you come to these things called arachnoid granulations and the arachnoid granulations that are filtering plasma from a filtering csf from the subarachnoid space into the dural venous sinus okay so there's our arachnoid granulations which filter that csf into the superior sagittal sinus which is now back into the bloodstream let's do it again through this coronal section so there's the subarachnoid space there's the arachnoid granulations and that is the superior sagittal sinus in a coronal section now watch csf in the subarachnoid space flows and then flows into the arachnoid granulations and filters through to enter into the superior sagittal sinus and that is how csf gets from the subarachnoid space into the superior sagittal sinus where does csf come from the choroid plexuses where does csf flow from the lateral ventricles through the interventricular foramen third ventricle cerebral aqueduct fourth ventricle and through those apertures into the subarachnoid space not to forget that the subarachnoid space also flows around the spinal cord so when we look at a cross section through the spinal cord the spinal cord is also floating in csf and then where does csf drain into the blood those arachnoid granulations drain csf into the superior sagittal sinus all right now csf's volume in adults is about 150 milliliters so here's a can of coke it's less than half of a can of coke that's how much so not a ton of csf through the subarachnoid space and inside the ventricular system csfs are replaced about every eight hours and we get about a half a liter 500 milliliters of csf is formed each day now csf cushions the brain and spinal cord and gives buoyancy to the brain and spinal cord the brain has a consistency almost like oatmeal like jelly and so the csf gives buoyancy so the brain and spinal cord weigh like almost nothing it reduces the the weight of the brain and spinal cord by like 97 or 98 percent and it cushions it so if we look at just the coronal section and there's the brain and there in blue and inside and outside the brain is the csf and then there's the skull you can see how the how the csf buoys up gives buoyancy to the brain and helps cushions it from hitting the side of the skull and that my friends is the ventricular system of the brain in a nutshell hmm