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  • This is a tutorial on the bones of the pelvis. So we've got a few bones that make up the

  • pelvic skeleton. You've got these two large hip bones on either side, the sacrum and you've

  • got the coccyx.

  • These two hip bones are actually the os coxae. This comes from Latin. 'Os' means bone and

  • 'coxae' means of the hip, so it's the 'bone of the hip', the hip bone. So we've got two

  • hip bones, a sacrum and a coccyx.

  • So the pelvis is separated into two regions. You've got the upper region, the superior

  • part of the pelvic bone, which is called the false pelvis. It's also called the greater

  • pelvis. And you've got the lower part, the inferior part of the pelvis, which is called

  • the true pelvis or the lesser pelvis.

  • So the upper part of the pelvis is called the 'false pelvis' because it's' often regarded

  • as part of the abdominal cavity rather than the pelvic cavity. So the lower part is the

  • true pelvis because that contains the actual pelvic cavity.

  • So the lesser pelvis begins at the pelvic inlet, which is formed by this rim here. You've

  • got the body of S1 and then this rim, which is formed down here which I'm showing you

  • with the mouse. So this is the pelvic inlet. Below this, you've got the pelvic cavity.

  • This is housed in the lesser pelvis or the true pelvis.

  • So if I just bring in the abdominal organs, you can see that the upper part of the pelvis

  • actually sits with the abdominal organs whereas the lesser pelvis -- so you can see the pelvic

  • inlet here at this rim. You've got the bladder anteriorly, the reproductive tract behind

  • it and most posteriorly, you've got the rectum. These all lie in the pelvic cavity within

  • the true pelvis.

  • So I'll do a separate tutorial on the pelvic cavity and I'll talk about inlet, the outlet,

  • the walls and the floors in that. But this tutorial, I'll just talk you through the features

  • of the pelvic bones.

  • So the hip bone, the os coxae, there's three parts to it. At birth, the three bones which

  • are joined by cartilaginous joints at the acetabula fossa -- this is the acetabula area

  • and this is where the head of the femur articulates with the hip. So this is the hip joint. At

  • birth, you've got three bones. You've got the ilium superiorly, the ischium, posteroinferiorly

  • and the pubis, anteroinferiorly. Just at this region here, they're all joined by cartilaginous

  • joints and these are fused in the adult. It's actually one large bone in the adult.

  • So we're just looking laterally at the hip here. I'll just show you where the ischium

  • lies. This is the ischium posteroinferiorly. This is the ischium. This is posterior, this

  • side here and this is anterior. So anteriorly, you've got the pubis and above, you've got

  • the ilium.

  • So if I just rotate the model around, again, we can look at it medially. So I'll just remove

  • this and we can look at the medial view.

  • So here anteriorly, we've got the pubis. That's this portion here. And then posteriorly, we've

  • got the ischium in this region. And above it, the ilium.

  • So I'll just talk you through some of the features of the ilium, the ischium and the

  • pubis. I'll just remove the femurs. So here, you can see the head of the femur sitting

  • in the acetabulum. This is the acetabulum here. We'll just remove here so we can see

  • the hip bones a bit more clearly and move these as well.

  • So starting superiorly, we've got the iliac crest. This is a flattened crest at the top

  • of the ilium. You've got muscles which attach here. I won't talk about them in this tutorial.

  • That's the iliac crest. This lies at the level of L4.

  • This is the L4 lumbar vertebra and this is also the area where the aorta bifurcates.

  • So if I just bring that in, you can see the bifurcation of the aorta at the level L4.

  • So the iliac crest is a useful landmark to know because it marks the point of L4 and

  • you know that the level of L4 is well below the end of the spinal cord. It's a useful

  • landmark for lumbar punctures.

  • If I just bring in the nervous system, you can see the end of the spinal cord well above

  • the level of the iliac crest. So you've got the iliac crest here and the end of the spinal

  • cord is up here. It's a useful landmark for lumbar punctures.

  • So if we follow the iliac crest forward, it comes to this spine. This is the anterior

  • superior iliac spine. This is also a useful landmark and this can be easily palpated.

  • And attaching to this, we've got the inguinal ligament. This runs from the anterior superior

  • iliac spine, which is known as ACIS because it's a lot easier to say than 'anterior superior

  • iliac spine'. The inguinal ligament runs from ACIS to pubic tubercle.

  • This is another useful landmark. You can feel the pubic tubercle as well. So you can feel

  • both these landmarks, ACIS and the pubic tubercle. So mid-way between these two landmarks, you

  • can palpate the femoral artery. So if I just bring that into view, you can see this artery

  • running halfway between these two points.

  • So just inferior to ACIS, you've got the anterior inferior iliac spine. And if we follow the

  • iliac crest posteriorly, we come to the posterior superior iliac spine and below that, we've

  • got the posterior inferior iliac spine. And then if we follow that around, we've got this

  • notch in the ilium. So this is the greater sciatic notch. And below that, we've got the

  • ischial spine. So this is actually part of the ischium, which I'll come on to talk about.

  • So above the ischial spine, you've got the greater sciatic notch. And below the ischial

  • spine, you've got the lesser sciatic notch.

  • This is a lateral view of the pelvic bone, the hip bone and this is where the gluteal

  • muscles attach. So you can see these large gluteal muscles. You've got the gluteus maximus,

  • medius and minimus. They attach on this lateral surface of the bone.

  • And you've got a few ridges on this bone, which you can't see here, but I'll just mention

  • them. So you've got the posterior gluteal line and anterior gluteal line and an inferior

  • gluteal line, which are roughened ridges where the gluteal muscles attach.

  • So on the medial surface, you've got this slight hollowing in the bone. This is called

  • the iliac fossa. You've got the iliacus muscle which attaches here. So you can see how it

  • sits there. It inserts on the femur. This flexes the hip. It's one of the hip flexors.

  • So another quick thing to mention before moving on is the angle of the pelvis. So if we just

  • imagine a horizontal line running along here, the angle of the pelvis is actually about

  • 50° to 60° to this horizontal line -- the pelvic inlet. So the pelvic inlet is this

  • brim here, this rim. So the pelvic inlet is actually angled at about a 50° to this horizontal

  • line and angled like this.

  • And also about this angle, you can see the pubic tubercle here and the anterior superior

  • iliac spine are in the same plane. So this is the same vertical plane here.

  • So next, we've got the ischium. This lies inferiorly and posteriorly. It's this bit

  • here. I mentioned the ischial spine. So we're looking from a posterior view at the pelvis.

  • So you've got the sacrum here, I showed you the greater sciatic notch and you've got the

  • ischial spine here.

  • You've got two important ligaments to know about here. You've got the sacrospinous ligament

  • and you've got the sacrotuberous ligament. So right at the bottom part of the ischium,

  • you've got this tuberosity. This is the ischial tuberosity. So the sacrospinous ligament runs

  • from the sacrum to the ischial spine and the sacrotuberous ligament runs from the sacrum

  • to the ischial tuberosity.

  • So I've just brought those ligaments in. You can see the sacrotuberous ligament attaching

  • onto the tuberosity and the sacrospinous ligament attaching onto the spine. It's actually a

  • bit further up here. So above this, you've got the greater sciatic foramen and below,

  • you've got the lesser sciatic foramen.

  • So you've got the ischial spine, the ischial tuberosity and if we rotate anteriorly, you've

  • got the ramus of the ischium. This big hole here is the obturator foramen. This is covered

  • by a membrane. There's a little gap above the membrane where the obturator vessels and

  • nerve run.

  • So I've just brought the membrane into view here. You've got this little canal up here,

  • the obturator canal and you've got the obturator vessels, artery and vein and the obturator

  • nerve which comes through this.

  • So going back to the ischium, if you remember the lateral view, the anteroinferior part

  • is the pubis. Half of this bone is part of the pubis and the other half is part of the

  • ischium. So collectively, this is the ischiopubic ramus, but the posterior bit is the ramus

  • of the ischium and the anterior part is the inferior ramus of the pubis. So that's the

  • ischium. It's this posterior inferior bit.

  • So next, we've got the pubis, this is the last bit. This is the anterior and inferior

  • part. The pubis has a body and it's got these two arms, these two branches. So you've got

  • the superior ramus and the inferior ramus. So you've got the superior pubic ramus, the

  • inferior pubic ramus and the body. And where the two pelvic bones meet, this is called

  • the pubic symphysis. And this little protuberance is called the pubic tubercle. This is palpable.

  • Those are the features of the pelvic bones, the hip bones, the ossa coxae. At the back,

  • you've got the sacro-iliac joints. At the front, you've got the pubic symphysis. The

  • sacrum articulates above with the fifth lumbar vertebra and below, this articulates with

  • the coccyx.

  • So next, I'll just do a quick tutorial on the sacrum and the coccyx.

This is a tutorial on the bones of the pelvis. So we've got a few bones that make up the

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