hello anatomy friends this is dr alsup and in this dissection video we will focus on
the osteology that is pertinent to session 12 the pelvic cavity
so we discussed the pelvic girdle in the learning objectives but let's do a
nice review here because this is certainly an area that we all need to be on the same page
the pelvic girdle is officially formed by the paired coxal bones so this whole area right here
is considered part of the coxal bones as well as the sacrum or that distal portion of the spinal
column i always think the sacrum is pretty darn distinguishable because of the very
obvious sacral foramina that you can see on either side you can also see a bit of the coccyx which
i'm outlining right here the coccyx is always pretty variable in terms of what it looks like
but generally you have a larger portion that kind of tapers down to a smaller portion
and the coccyx is important in terms of muscle and ligament attachment for um
for things associated with the pelvic cavity as well as the pelvic diaphragm
the coxal bones are going to articulate anteriorly at the pubic symphysis so where the two pubic
bones or pubis bones are going to articulate and a symphysis is a type of cartilaginous joint so
you have a little block of cartilage right here which is very prominent in the anterior portion
and not on your list of structures but we did talk about in the learning objective
videos are the paired sacroiliac or SI joints which i am outlining right here
so this is where those coxal bones are going to articulate with the sacrum
all right now let's focus on this lateral view and um because it's very i know i'm
looking at a lateral view because of the very obvious acetabulum which is right here this is
where the head of the femur will articulate with the coxal bone to form the hip joint so
anytime that you can see a really nice view of the acetabulum you're looking at a lateral view
it also affords a nicer view of the ischium which is in this region right here it'll
extend a little bit in this issue of pubic ramus and you can't see the ischium quite as
well when you're looking at an anterior view so this lateral view or a posterior view will
show the ischium better and the most prominent portion of the ischium is the ischial tuberosity
and this looks like a very rigorous bump sometimes this landmark is referred to as the sit bone and
you would think based on the size of this bump that a lot of things attach here in your right
your hamstrings have a proximal attachment here so those large muscles of the posterior thigh
and there are also some very robust ligaments attaching at the ischial tuberosity some we'll
talk about here and some will talk about more in the musculoskeletal portion of the curriculum
now i want to go a little out of order here in terms of what i have on the list of structures
and i want to focus on this region right here and this is referred to as the greater sciatic notch
and this is uh this is a notch that's actually part of both the ischium and the ilium the ilium
is going to be this larger fan shaped portion of the issue of the coxal bone so the ilium as
well as the ischium are going to form the greater sciatic notch and this notch is so
large because lots of things traverse this region region including its namesake the sciatic nerve
which is the largest nerve in the body so it makes sense that you're gonna have a fairly large notch
but not only does the sciatic nerve move through here the piriformis muscle actually traverses this
region as well in addition to quite a few more neurovascular structures the greater sciatic
notch ends inferiorly at a region that i'm going to put a little arrow at called the ischial spine
the ischial spine is an important pelvic landmark and you can actually see these pretty clearly
when we look over here at the superior view of the pelvic girdle so this right here is initial spine
this right here is initial spine and you can see how far they project medially so towards that
pelvic viscera specifically these spines these ischial spines can be palpated through the vagina
which can be important in a pedental nerve block so you can see that you can see it not
only in this lateral view but you can see it fairly clearly in this superior view as well
the potential nerve will actually exit the pelvis through the greater sciatic notch
but then it will almost immediately head back into the pelvic region or the perineal region
through the lesser sciatic notch and this lesser sciatic notch is going to
be between the ischial spine and the ischial tuberosity so i'm outlining it right here
so you can see how the greater sciatic notch is quite a bit larger than the lesser sciatic notch
so again that lesser sciatic notch is between the ischial spine and the ischial tuberosity so
that pudendal nerve which is going to enter the pelvic region again through the lesser
siding notch is the primary innervation of the perineum so much more to come on that nerve
so keep that ischial spine initial tuberosity in your mind as these
are important attachment sites for two of the most prominent ligaments of the pelvis
the sacrotuberous ligament is going to attach from the sacrum and coccyx
down to the ischial tuberosity so i'm outlining the sacral tuberous ligament here
and you can see it is projecting this is the ischial tuberosity right here it's projecting
quite posteriorly as we know about the ischium you can actually see the femur
right here so we're looking at a side view of the hip joint so the ischial tuberous or
ligament is going to be between the sacrum and coccyx to the ischial tuberosity
whereas the sacrospinous ligament is going to attach from the sacrum and coccyx
to the ischial spine so this is going to be the sacral spinous ligament you can
see the sacrotuberous ligament is a bit more posteriorly placed and it's going to be longer
and if you're looking at a straight posterior view it often includes the view of the sacral spinous
now when these ligaments are present they transform those greater and lesser sciatic notches
into the greater and lesser foramina all right so right here is where that greater sciatic notch
would be but with the ligaments it's going to form the greater sciatic foramen and here between the
ischial spine and the ischial tuberosity is where that lesser sciatic notch would be and when you
combine the ligaments that would make the greater sciatic foramen so more complete circles or ovals
for that neurovasculature that we just discussed to actually travel so providing additional
protection along with the bone of course for that neurovasculature excellent you know i love to talk
through the osteology of a session in particular why we are having you know these structures
so please take time to review you always have those blue link atlas images that have the labels
directly drawn in already so you can review those as well please reach out if you have any questions
to myself or any of my anatomy colleagues and i thank you for your time and attention