 Hey everybody, Dr. O here. In this section of videos, we're going to introduce the spinal cord. So the brain gets all the credit for all the conscious and subconscious activities that occur in our body. But without the spinal cord, it wouldn't receive the information it needs to process that information and it wouldn't be able to send signals away. So the spinal cord, critically important. And then we have, then we'll talk about reflexes, which are rapid automatic responses that occur in your body that are controlled by just the spinal cord. So don't sleep on the spinal cord, very, very important. So we'll start by looking at just the gross anatomy of the spinal cord here. The adult spinal cord is about 18 inches long and around a half inch wide. First key thing to note is where it ends. The adult spinal cord ends between L1 and L2 in the lumbar spine. The reason that's significant is because if here, if you're going to do a lumbar puncture or a spinal tap, or if you're going to go into the vertebral canal there, then you're going to want to make sure you miss the spinal cord. So they always do lumbar punctures below the levels of L1 and L2. So we won't talk about the clinical significance of this really, but this is a way to go in and extract cerebral spinal fluid, which should be sterile. So it's a way to tell what's going on in the brain and the spinal cord, but by going in here in a really safe area. So it's used to diagnose diseases of the central nervous system. You can find evidence of meningitis, subarachnoid hemorrhage, those types of things here. But that's the first really important thing to know. The spinal cord ends between L1 and L2, and that's why you do lumbar punctures below that level. Okay. So here, when you look at the spinal cord, generally it starts big and then tapers down. And that's because all the sensory information from the entire body has to travel through the top. Only the sensory information from the lower half has to travel through the bottom. Same thing with motor commands. So generally speaking, the spinal cord is biggest at the top and gets smaller. But the amount of gray matter that you'd see at any individual level depends on how many cell bodies there are, what area is it controlling. So you will see those two swellings, the cervical and lumbar enlargement. So the cervical enlargement is going to be where you have all the extra gray matter to control the upper extremities, the shoulder and the upper limbs. The lumbar enlargement is going to be to control the pelvis and the lower limbs. So that's why you see it. It generally tapers down, but you have those two swellings, the cervical and lumbar enlargement. So I've already said the spinal cord ends between L1 and L2. The end of the spinal cord is called the conus medullaris. Then a few more terms below that. The conus medullaris is actually going to be connected to a little piece of fibrous tissue called phylum terminale, which actually goes down and attaches to the coccidio ligaments. That's going to stabilize the spinal cord there. So it ends between L1 and L2 at the conus medullaris. Then you have this little phylum terminale that stabilizes it to the coccidio ligament there at the bottom. Last term there would be cauda equina or horses tail. That's going to be that big long collection of spinal nerves that travel below the spinal cord. It looks like a horses tail. That's where the name comes from. The spinal cord. So we'll look at sectional anatomy of the spinal cord in a separate video, but there are 31 individual spinal segments, each named for the vertebrae where that spinal nerve originates. So there are 31 because you have, there are eight cervical and then 12 thoracic and then the five lumbar, but then you also have the sacral and coccidio nerves as well. So the relationship, so where they were named, that relationship is going to change as you get bigger. That's why there are 31 segments and they're named after the cervical, thoracic, lumbar, sacral and coccidio nerves. As far as naming a cervical nerve is going to be named from the, named after the vertebrae underneath it and all other nerves will be named after the vertebrae above it, but not a big deal. Okay. So that is the basics of the gross anatomy of the spinal cord. I'll come back in the next video and we'll look at a cross section. We'll look at sexual anatomy of the spinal cord. I hope this helps. Have a wonderful day. Be blessed.