Hey, what's up everybody? Dr. B here. We're going to take a look next at the sacrum.
The sacrum is going to be basically the centerpiece to our pelvis. If you remember when we did the appendicular skeleton, we had our two os coxa, which were our pelvic girdles. They were going to be joined at the anterior by the pubic symphysis and posteriorly they're going to attach to this guy right here, which is the sacrum. Sacrum is also going to be what sits at the base of the vertebral column. Um, so it kind of serves to bring the upper and lower parts of the axial skeleton.
together. Now, when we take a look at the sacrum, what we're looking at here is the anterior surface of the sacrum, all right? If we flip this around the posterior, you can see what looked to be like little spinous processes, like we talked about on the vertebral column. Those spinous processes that we see right there, that is a structure called the median sacral crest, right? Now, originally, the sacrum is individual segments, all right?
The fusion takes place up of those segments and it turns it into one solid piece of bone. But early in development they are individual segments so they almost resemble a small little vertebra. Now if we look at the top right here we can see an opening here that would be the sacral canal. The spinal cord is going to pass down through all of the vertebra and is going to come in and we're going to have the cauda equina part of the spinal cord pass into the sacral canal. That's the the base right here, we have the sacral hiatus, okay, which is the exit point for some of our coccygeal nerves, which would go down and come out at the coccyx.
Now at each level on anterior and posterior here, you see openings, right? These openings right there are the sacral foramen. Sacral foramen are where the sacral nerves will exit from as the cauda equina passes through the sacral canal. The sacral promontory is this anterior portion right here of the sacrum. This is the base of the sacrum.
We call it the widest point. Down here would be the apex. So your sacral promontory is this part of the sacrum right there. And on either side, we have these two structures here, which are the sacral ala.
All right. So again, you've got sacral ala, sacral promontory, sacral foramen, sacral canal. Median sacral crest, sacral hiatus.