 Hey everybody, Dr. O here. In this video we're going to talk about how the brain is protected and supported so we've talked about how important it is clearly, and now I want to talk about the three physical ways and then I'm going to add the biochemical way that your brain and your spinal cord is protected from the rest of your body. So the three main things we think about when we talk about protecting the brain are going to be the bones of the cranium, the bones of your skull, obviously they protect your brain from the outside world. But then we're going to talk today about the meninges and cerebrospinal fluid because what they basically do is they protect your brain from your skull. You know, think about it, the skull is hard on the inside as well as the outside, so we have to make sure that our brain doesn't hammer the inside of our skull as well. So I won't go through the skull bones here, those have been covered in earlier units, but the bones of the cranium, the bones of the skull, they physically protect the brain from the outside world. Let's go ahead and look then at the meninges and the cerebrospinal fluid here. So the cranial and spinal meninges do have three layers, you can see right here on the screen, the outer layer, the toughest layer is called the dura matter. The middle layer is called the arachnoid matter and you can see why it kind of looks like a spider web there. And then the thinnest, most delicate layer on the innermost layer is called the pia matter. So you have the dura matter, arachnoid matter and pia matter. Those three layers make up the cranial meninges around the brain and the spinal meninges around the spinal cord. So they're going to help protect and stabilize the brain. And then so we have this thick skull, then we have this tough layer on the outside of the brain and spinal cord called the meninges, and then now we have cerebrospinal fluid, which has been covered in other videos, but the cerebrospinal fluid is basically going to protect and hold and support and cushion the brain and spinal cord. So those are going to be the three main physical structures that protect your brain, the bones of the skull, the meninges, the three layers of the meninges and cerebrospinal fluid. But I also want to talk about how the brain is biochemically isolated from the rest of your body by what's known as the blood-brain barrier. So the outside protective layer of the brain and spinal cord has tighter junctions between the cells than other parts of your body. And that forms this blood-brain barrier. It's actually the astrocytes that are the neuroglyl cells that play a big role here. But what it does is it keeps circulating toxins or pathogens that are in your blood from getting into your brain. So the job of the blood-brain barrier is to try to keep the brain and spinal cord sterile, and it does a really good job of that. So that's why things like, you know, brain infections like meningitis and encephalitis are so rare because circulating pathogens and toxins cannot freely enter the brain and spinal cord. So that's great. But at the same time, it can't be an impenetrable barrier. We have to make sure that nutrients get in, waste products get out, and the like. So it's not a perfect barrier, but it does help. And that's what keeps the brain and spinal cord relatively sterile. Now the only bad news here, the downside with this is, yes, it's really hard for things to get into your brain. But that also means it's really hard for medication to get into your brain. So if you look at like treating brain cancer or things like that, so it's hard for medication to get into the brain. And then also if you do get an infection, this is one of the reasons that they're so scary and so deadly, is that it's hard for your immune system to get to the brain and spinal cord as well. So it's kind of a double-edged sword. The blood-brain barrier does a really good job most of the time of keeping your brain and spinal cord extra protected. But if there is an infection or there is a tumor, then it's also really hard for the good guys. The medication and the immune cells to get it in fight as well. Okay. So those are the three physical and one biochemical way that your brain is being protected. I hope this helps. Have a wonderful day. Be blessed.