Lumbar Vertebrae – Vertebral Column

00:00 Next, let’s take a look at the segmental vertebral specification for our lumbar vertebrae.

00:09 And once you get into the lumbar area, a most obvious structural change is that the vertebral bodies get even larger than what we saw above this particular segmental level. And the reason that these vertebral bodies have to become much more massive is that they are supporting a greater weight of the body as gravity pulls those forces inferiorly.

00:36 The vertebral foramen, if we look at it, it tends to be triangular with the base of the triangle oriented here along the vertebral body and then the apex forming at the level of the spinous process. Spinous processes tend to be short and stout. And we can see a spinous process at this particular level. And there are two signature processes that are associated with lumbar vertebrae.

01:11 The first of these are associated with the superior articular processes. And if we look here, we see one of these prominences and we see one on the opposite side. And these are referred to as mammillary processes. Associated with the transverse processes, and we can see one of those here fairly clearly, and we see another one over here as well and we see them here anteriorly. These are accessory processes. And there’s a ligament that will connect a mammillary process to an accessory process with two adjacent vertebrae and mammillary processes also serve as a point of attachment for a muscle that we find in the deep back, the multifidus.

02:05 Our next stop, segmentally, is to understand the specification that’s associated with the sacrum. And here we’re looking at an adult sacrum where the five sacral vertebrae have fused. This is a posterior view that we are looking at. And the first thing that we should note are these superior structures here and here. These are superior articular processes associated with the sacrum. These then will articulate with the inferior articular processes of the fifth lumbar vertebra.

02:45 If we look right here in the posterior midline, we see what is referred to as the median sacral crest. And when we think about the sacral vertebrae fusing together here in this posterior orientation, let’s think about the structures that lie superior to this segment. And in that posterior midline, we had spinous processes. So, what happens here in the sacrum is that spinous processes of adjacent vertebrae will fuse to produce this median sacral crest.

03:21 We also have an intermediate sacral crest that’s less noticeable, but it’s going to be produced by articular processes, superior and inferior sacral articular processes, that are now fused in this adult form.

03:42 And then lastly, we have lateral sacral crests and these are going to represent the point of fusion of transverse processes. And we also then will see here posteriorly, openings four branches of sacral spinal nerves. And we have four that come into view here and we have four that come into view here.

04:19 Right in through here, we have the sacral canal. And so, this results in the individual, sacral foramina will fuse together. And then, down below, we see an area that did not fuse posteriorly and as a result of the laminae of S5 here failed to fuse and as a result, that will form the sacral hiatus.

04:57 Here’s an anterior view of this sacrum. The first thing to note is the superior aspect of the anterior body of S1. This is a very prominent structure referred to as the sacral promontory. And it is readily visible, discernible on radiographs and it helps you identify your vertebral level very, very readily. These lateral extensions at this level are wing-like extensions. In the anatomic terminology that we’ll utilize for wing-like insections is ala.

05:47 We also have these areas here. And these represent the points of fusion between sacral bodies.

05:57 Here is the sacral body at this level, sacral body here and this represents the point of fusion between those sacral bodies. Similarly, this area here is the fusion point between S1 and S2. These are transverse ridges or transverse lines. The inferior aspect, so the inferior most projection of the sacrum is termed the apex. And then we also have foramina that are oriented anteriorly. And these foramina will allow for the transmission of branches of the typical spinal sacral nerves at this level.

06:43 Here’s a lateral view of the sacrum and it has a prominent feature that we see here shaded in blue. Here we have articular cartilage. And so, this is the articular region of the sacrum and this point of articulation is with the ilium. And we would have another articular surface on the opposite side of the sacrum to articulate with the opposite ilium.

07:20 And then our last segment is the coccyx. Generally, it will have four fused coccygeal vertebrae, and that’s exactly what we see in this view. Here is the first, here’s the second, third and then here’s our fourth coccygeal vertebra. But again, there is some anatomic variability.

07:45 We may have three, we may have even up to five. If we focus on the first coccygeal vertebra, it will have these prominent horn-like projections and these are referred to as the cornua. And the cornua will often fuse with the sacrum.