 I have an opportunity today to show you an example of a spinal cord that has just been removed from an autopsy case. This is a normal spinal cord. Let's review for a moment the spinal column on this model, which is a little bit twisted, but that's okay. Here is the posterior or dorsal surface with the spinous processes. So let me move this out of the way and show you the spinal cord. The main thing I want to stress to you is how small and how delicate the spinal cord is. Notice it's diameter. It's smaller than the diameter of my little finger. And if I come down here and make a cross section at the cervical region right here at the top of the cord, I can show you that this tissue is totally soft. It's as soft as a piece of gelatin. And so you can imagine if there was a subluxation. The subluxation is when the spinal column suddenly with trauma goes one way or another. And the disc or the bone can temporarily compress the green spinal cord that is within it. It just takes a moment to cause, you can imagine, a jerk on the cord and to leave a patient with paralysis. This is very, very soft tissue and very vulnerable. So let's examine the cord now. Let's look up close. I'm looking now at the posterior or dorsal surface. And I can see, and I hope you can, between the forceps are the dorsal or posterior columns with branches of the posterior spinal arteries running along the surface. And if I turn it over, I can see the anterior surface with its single spinal artery. This spinal artery is very important because it provides blood to the grey matter of the anterior horn to the cortical spinal tract as it descends in the cord and to the pain and temperature pathway. Whereas the posterior spinal artery, as you might imagine, supplies one or the other of the two dorsal columns carrying propriocepture. So damage to the anterior spinal artery are nothing more than hypoxia during a surgical intervention, let's say to replace a section of aorta, can leave this anterior spinal artery without enough oxygen or blood to supply the cord and the patient will remain without control of motor function below that level and with loss of pain and temperature traveling in the lateral regions. So now I'm going to open the dura for you. The arachnoid is adherent to the dura. So we're going to look down, as we have been, on to the pia or the peal surface. Down here, near the cauda equina, we can see the dorsal and the ventral roots. And I'll open the dural sac in just a moment. Here is a dorsal root ganglion on this side. Here is the stub of one on this side. Here is another one on this side. The dorsal and ventral roots are emerging here. Now we're looking at the cauda equina and the tip of the spinal cord. Here is the conus medularis. And here are the elongated dorsal and ventral roots. And you can see that they are running to emerge. Here would be at one spinal level, probably a lumbar. And here is another one here. If you zoom in close, you can see the roots. Here's one group of roots emerging. Up here is another group of roots emerging. And in between, you can see a thin membrane here, the denticulate ligament that anchors the cord laterally and separates anterior or ventral from posterior, which you can't see from this side of the spinal cord. It's good to point out that the cauda equina, these represent both dorsal and ventral roots. Therefore they are sensory and motor. They have emerged from the spinal cord and therefore are ensheathed in Schwann cells. These are peripheral nerves, so to speak. That is to say, if they were compressed or damaged, but not separated between proximal and distal end, they could regenerate. So damage to the cauda equina roots gives you the option or the possibility or the potential that these axons can regenerate down through the Schwann cell tubes that are left behind, whereas damage to the cord at this point with our knowledge is basically irreversible, but sometimes some of the pain and temperature fibers are spared along the edges.