[Music] Hi everyone, welcome to Bodyworks Prime. Today, we're going to be covering the anatomy of the erector spinae muscle group. As you can see here on screen, this is a really big group of muscles, so I'm going to try and keep this video as brief as possible. But, if you would like a longer and more detailed explanation of any of these muscles, I do have videos on them separately, and I'll put links below this video here, so you can go and click on them and watch those videos as well. The erector spinae is a group of three different muscles: we have the spinalis as the most medial of the erector spinae muscles; longissimus, which is in the middle; and then the iliocostalis, which is the most lateral erector spinae muscle. Here we can see each of the sections of the erector spinae muscles. This might be hard to see if you're watching on a small screen, but don't worry, I'll be zooming in on them for you in just a moment. Unfortunately, each of these muscles has three different sections, which can make things a bit tricky to remember. However, I've color-coded each of the sections for you, which should make things a bit easier. The section of each muscle is highlighted in the same color as the corresponding text below it. Let's zoom in on each of these sections to make it a little bit easier to see. We got the spinalis capitis in yellow, cervicis in purple, and the thoracis is colored in green. Next, we got the longissimus muscle with the capitis in yellow, cervicis in purple, and the thoracis in green. Lastly, we have the iliocostalis muscle: cervicis is in yellow, thoracis is in purple, and the lumborum is in green. So here, we can see the origins and the insertions marked out. The origins are in red, and the insertion is in blue, and it's going to be the same color coding throughout this video. So, the spinalis capitis is originating on the spinous processes of C6 all the way down to T2. Spinous processes are these little bony projections coming off the back of the vertebrae. As for the insertion, that's on the occiput, which is a spot on the back of the skull highlighted in green. Now, you can see this ligament which just runs down the back of the neck here, and this is the nuchal ligament. The nuchal ligament is also an origin point of the spinalis capitis section. So now, you can see the origins and insertions of the spinalis cervicis section, and the nuchal ligament is also an origin point for the spinalis cervicis. The rest of the origin and insertions are going to be on the spinous processes again: it's going to be C7 and T1 for the origin and C2 and C3 for the insertion. Next, we can see the attachments for the spinalis thoracis section. The origins are going to be on T11 all the way down to L2, and the insertion is going to be on T2 all the way down to T8. So you might be saying now, "Hang on a second, you've just said that the insertion was on T8, but I can see this label for T9 here." Just take a close look at T8. T8 starts here, and then it continues down, and then we've got the spinous process coming off the back of T8. So that insertion point is on the spinous process of T8; it's not T9. T9 starts here, and then the T9 spinous process comes down here. Moving on to the longissimus muscle, next we're going to start by looking at the capitis section. The origins here are going to be on the transverse processes as opposed to spinous processes. The transverse processes are the projections which come off the side of the vertebrae. So, it's going to be on the transverse processes of T4 all the way up to C4. As for the insertion, that's going to be on the mastoid process. The mastoid process is a bony projection on the temporal bone. Next, we got the attachments for the longissimus cervicis section. All of these are going to be on the transverse processes again. The origins are going to be on T4 all the way up to T1, and the insertion is going to be on C6 all the way up to C2. Let's take a look at the attachments for the longissimus thoracis next. We'll start down at the bottom here, and this attachment point here is going to be on the posterior superior iliac spine. The iliac spine is just this ridge that runs across the top of the hip. We've also got the sacrum, so the sacrum is this big bone. It's going to be on the dorsal aspect of the sacrum, the back of the sacrum. We've also got this bony ridge that runs up here, and this would be the median sacral crest. Moving on to the transverse processes next, we've got the origins on L5 all the way up to L1. We've got our insertions here in blue, again, it's going to be on the transverse processes. We've got T12 all the way up to T1, and it's also inserting onto the ribs. It's inserting onto rib 3 all the way down to rib 12. Moving on to our next muscle, the iliocostalis, you can see the attachments for the cervicis section. That's going to originate on the ribs, from rib six all the way up to rib 3. The insertion is on the transverse processes; it's going to be C6 all the way up to C4. Moving on to the iliocostalis thoracis section, it's going to originate on rib 12 all the way up to rib 7, and it's going to insert on rib 6 all the way up to rib 1. It's also going to insert on the transverse process of C7. Next, we got the iliocostalis lumborum section. The origin is going to begin on the iliac crest, and we've also got this section down here on the lateral crest of the sacrum. The insertion is on the transverse processes, from L4 all the way up to L1. It's also going to insert onto the ribs, from rib 12 all the way up to rib 4. Another insertion point of the iliocostalis lumborum section is the thoracolumbar fascia, a large diamond-shaped connective tissue structure located in the lower back. On the left, I have it without it highlighted, and on the right, you can see it highlighted in green. The innervation for the erector spinae is relatively easy to remember. It's innervated by the posterior rami of each part of the muscle's corresponding spinal nerve. Now, that sounds way more complicated than it actually is, so I'm just going to simplify it and explain it for you now. Here, we can see a cross-section of one of the vertebrae. You can spot the transverse process right here and the spinous process right here. We saw both of these in the origin and insertion section earlier. Based on that, we can determine that this is the back of the body, and then, this right here would be the front of the body. And, you can see, coming off the vertebrae here, a nerve. This nerve splits into two different sections. We've got the ventral ramus right here, which would also be known as the anterior ramus. Then, we've got the dorsal ramus right here, which would also be known as the posterior ramus. So, "posterior" also means "dorsal" in this case, and "anterior" also means "ventral" in this case. The erector spinae muscles are all innervated by this dorsal ramus right here. So, just to give you a visual example of what I mean here: all of these different vertebrae I've got labeled down here, they're all going to have their own individual dorsal ramus. So the part of erector spinae that's next to T6, for example, that's going to be innervated by the dorsal ramus of T6. All of the erector spinae that's across from T7, that's all going to be innervated by the dorsal ramus of T7, and so on and so forth for all of the different parts of the vertebrae and the erector spinae. Let's take a look at the actions next. One thing to bear in mind here is that we're going over the erector spinae muscle group as a whole, but muscles like the spinalis, for example — the spinalis is connecting onto L2, so it's not really covering any of the lumbar vertebrae. So the spinalis won't have any actions on lumbar vertebrae. The iliocostalis, it ends around C4 or just here, so it's only going to have actions at the base of the neck but not at the top of the neck here. So bear that in mind. But, let's take a look at the actions of them all collectively now. Those actions are going to depend on whether just one side contracts or both sides contract together. A contraction of just one side of a muscle is referred to as unilateral contraction. A contraction of both sides of a muscle, that's bilateral contraction. We'll start by going over bilateral contraction first. You can see now, my neck and my trunk are in a flexed position, and as they come backward, like this, that would be extension of the trunk and the extension of the neck. That's going to be our first action of the erector spinae muscle group. And of course, that's bilateral contraction when that happens. But what about unilateral contraction? Let's say just one side of the erector spinae muscle group is contracting. In this case, we're going to use the left-hand side as an example. Well, if the left-hand side contracts, that's going to result in lateral flexion of the trunk and also lateral flexion of the neck as well. So, we've got lateral flexion of the trunk and lateral flexion of the neck as our unilateral action of the erector spinae muscle group. So, if you've enjoyed this video or found it helpful, you know which buttons to press. Press that like, press that subscribe. Let me know what you thought of the video in a comment. I've also got links in the description box below that look at each of the erector spinae muscle group muscles individually. So take a look at them as well if you're interested. Thanks again for watching, everyone. I'll see you all next time!