 Now, just like all of our brain came from the secondary brain vesicles, those swellings in our neural tube from back when you were a little slime, remember that hole I kept drawing down the middle of that tube? Well, there are structures that arise from that hole, from that space in the center of the tube, including the central canal of the spinal cord. So this hole, this central, this hollow place in the neural tube, we're comfortable with it already as running down the middle of the spinal cord, but it also like did some crazy dances, oh, what? And folded and twisted and got covered over in various ways and forms these ventricles in your brain filled with cerebrospinal fluid. Not only are they filled with cerebrospinal fluid, but there's also cerebrospinal fluid outside of the brain floating between, excuse me, yeah, separating the brain from the cranium, the skull, and making it so that your brain actually floats in the skull and doesn't get you a giant headache. Are you ready to learn your ventricles? We know you are. First of all, there's two ways we have to look at this. We have to look at it like this, really, and like this. So take a deep breath because this is like an adventure in three-dimensional thinking. First of all, are your lateral ventricles, lateral ventricles. And how many of them do you have? There's two. They look like sheep horns, like ram horns. And here's the scoop. They are separated in your brain by a structure called the septum palusitum. Septum palusitum, palusitum separates your lateral ventricles. And they really do curve up into your cerebrum. Now, the lateral ventricles are connected to the third ventricle because you have one lateral ventricle and another lateral ventricle, and then you've got the third, third ventricle, which is actually also seen about here, yeah, and which is seen right here, really? That's all your third ventricle. But connecting the lateral ventricle and the third ventricle, connecting two ventricles, is the interventricular foramen. Interventricular foramen. Foramen. All right, so connecting them, we've got the interventricular foramen, and then we're in the third ventricle. The third ventricle is kind of in this thalamus, hypothalamus, epithalamus zone, and it's a space. And then there's another little duct, and it's this thing right here, and that one is the cerebral aqueduct, A-Q-A-D-U-C-T, lateral ventricle, connected to the third ventricle through the interventricular foramen, third ventricle connected to the fourth ventricle from the cerebral aqueduct. So the fifth thing that we're going to look at is the fourth ventricle. I think, yeah, she got to be kidding me. It's not as bad as you think, or maybe it is. Is it as bad as I think? What I say, fourth ventricle. And here's the fourth ventricle. The fourth ventricle is between the cerebellum and the pons, and it's a space that you can stick your little probe in, and here it is, here, that's the fourth, and here it is, here, that's the fourth. Did you follow that? Okay, there's a little hole in the wall around the fourth ventricle, and that hole allows cerebrospinal fluid to drain out of it, and it drains out of that hole and into the surrounding, like, it goes from, there's a hole in here, and it drains into the area surrounding the brain itself. Well, let's see. Once it drains into this space here, I feel like I need to make this bigger. I'm sorry, we're going to just take this, cut it. We're going to go up, find ourselves a blank page. Usually I'm a little more organized than this, yes? Oh, dear. But we're just going to make it bigger so you can see this. I think it will be helpful. So, look, this is our half view. Yeah, yeah, yeah, yeah, yeah, just so we can see it better. And let's just label our meninges while we're here, because you have the meninges are, remember, the structures surrounding your brain and spinal cord, meninges. We have the duramator, which is the tight to the skull. Duramator. And then we have the piamator, remember that guy? Here's piamator tight to the brain. And then between them was the fantastical arachnoid meter. Arachnoid meter. And that was kind of a spiderweb-y stuff in between. Now, here's the scoop, my friends. Here's cerebrospinal fluid actually drains into the subarachnoid space. So it drains into the space between the piamator and the arachnoid meter. And that's what you're seeing right here. Cerebrospinal fluid is this stuff right here, this light blue stuff. But what's the dark blue stuff? You know what that is? Holy bloody hell, it's blood. It's venous blood from your brain. Your brain has taken all the oxygen out of the blood and has dumped it into this sinus right here, this space. And you have little, like, mushroom-shaped structures within that space right here. And these guys basically drain cerebrospinal fluid into the blood. So the cerebrospinal fluid, which started up here in my lateral ventricle and traveled all the way through the gut, will go to these little mushroom-shaped structures and get dumped into the venous blood supply. Old blood is then carried out of the brain through the jugular vein and to the heart and then to the lungs to get re-oxygenated and sent back around to the body again. Your cerebrospinal fluid, because it's being produced in your brain constantly, there's almost like a higher pressure of fluid in there so it's constantly being dumped back into the blood supply, which enables you to constantly be cleaning and renewing that cerebrospinal fluid. If you look down here at the bottom of my brain, boy, you can actually see that the cerebrospinal fluid can travel down through the outside, like, surrounding the spinal cord. Because remember that we had duramator in our spinal cord as well. So that, it can circulate there as well. Oh my gosh, how did you do? That is fantastic and this lecture is done.