00:01
In this video,
we're going to look at the pelvis.
00:04
Its various bony structures
that make up the pelvis,
and the boundaries
of the pelvic cavity.
00:10
So let's start off by looking
at the location of the pelvis,
which is situated inferiorly within
this abdominal pelvic cavity.
00:19
And we can see that on
the screen at the moment,
which is positioned anterior
to the vertebral column.
00:25
So unlike the separation between
the thorax and the abdomen,
which has the diaphragm.
00:30
There isn't a physical structure
that separates out
the abdomen from the pelvis.
It really is a continuous structure.
00:37
We do have some boundaries, though,
that help us to recognize various
regions within this combined space.
00:45
And here we can see
the pelvic inlet.
00:47
The pelvic inlet here really
separates the pelvic cavity
from the abdominal cavity.
00:53
And here we can see parts
of that pelvic cavity
that extends up into the abdomen
is actually part of
that abdominal cavity.
01:01
It's not bound by the
bony structures of the pelvis.
01:05
And this is why we call it the
greater or the false pelvis.
01:08
We can see how the anterior
aspect of it is much open
and it can expand as it does
with pregnancy, for example.
01:15
We can then see
inferior and slightly posterior
to the pelvic inlet.
01:19
We have the lesser
or the true pelvis.
01:22
And this is part of
the pelvic cavity,
and it's completely bound by
those various bony structures.
01:29
So here we can see
the pelvic cavity,
and we can look
at the various boundaries.
01:34
So here again,
we can introduce the pelvic inlet.
01:37
And we can then also
as we have an inlet
have the pelvic outlet.
01:41
So these two regions
are really important,
as we have the continuation
of the gut tube
that passes all the way
down via the transverse,
descending, sigmoid,
parts of the colon.
01:52
All the way down
and through the rectum
to exit the pelvis via the
anus at the pelvic outlet.
01:58
So there needs to be
this continuous space
that allows foodstuffs,
digested foodstuffs,
to leave the body cavity.
02:05
It's also important for
reproductive and urinary function
that we have this
continuation from the abdomen
down through the pelvis
and then to exit the body.
02:15
We can see laterally
within this space.
02:16
We have pelvic walls.
And we can see these
if we have a look at the
superior view of the pelvis.
02:23
Posteriorly, we can see we have S1.
So, the vertebral body of S1.
02:28
Lateral to that on both sides,
we have the Ala of the sacrum,
and that then runs anteriorly
all the way towards the pubic crest
via the pelvic brim,
highlighted here in red.
02:39
Then most anteriorly,
uniting two halves of the pelvis,
we have the pubic symphysis.
02:45
So, from posterior to anterior,
we have the vertebral body of S1,
remember, or the sacral vertebrae
are fused to form the sacrum.
02:53
We have the Ala of the sacrum.
02:54
We have the
pelvic brim, pubic crest,
and then the pubic symphysis.
02:59
If we then have a look
at this in section,
we can see where the
pubic body has been section.
03:04
So, this is where
the pubic symphysis
would attach
each sides of the pelvis.
03:09
Then moving laterally,
we have the superior pubic ramus.
03:13
Moving inferiorly,
we have the inferior pubic ramus.
03:16
And if you've looked at the
lectures on the low limb,
these terms should
be familiar with you.
03:22
We then have the continuation
of the inferior pubic ramus
as it goes all the way around
to form the ishiopubic ramus
And these bony structures
then form the obturator foramen.
03:32
An important foramen
that allows structures
to pass from the pelvis
all the way down into the
lower limb like the obturator nerve.
03:40
If we then continue looking
at these bony structures,
most superiorly we have
the greater sciatic notch,
and then below that we have
the lesser sciatic notch.
03:49
These two notches are important
as they allow structures to pass
between the gluteal region of
the lower limb and the pelvis,
and also of the pelvis
and a structure, a space,
we'll see later on,
the perineum.
04:02
So, these are really spaces that
allow structures to pass between
the pelvis and related areas.
04:08
We have the greater sciatic notch
and the lesser sciatic notch
separated by the ischial spine.
04:13
We then have most inferiorly,
the ischial tuberosity.
04:17
Posteriorly, we have the sacrum,
and then connecting these
bony structures to the sacrum,
we have a series of ligaments.
04:24
So, from the ischial spine
to the sacrum,
we see highlighted here
the sacrospinous ligament.
04:29
And then from the
ischial tuberosity to the sacrum,
we have the sacrotuberous ligament.
04:35
And these are now converting
those notches into foramen.
04:39
So, here we have the
greater sciatic foramen,
and here we have the
lesser sciatic foramen.
04:44
We'll come across these
spaces in more detail
as we progress through
these pelvic videos.
04:50
Now, let's have a look
at the pelvic outlet.
04:52
So this is a space that allows
structures to really exit the pelvis
and either enter into the perineum
or go into the outside world.
04:59
Here we can see the pelvic outlet.
05:01
Anteriorly is demarcated
by the pubic symphysis.
05:04
We then have the
ischiopubic remi on either side.
05:08
We then have
the ischial tuberosity.
05:10
And then that ligament
that connected
the ischial tuberosity
to the sacrum,
we have the sacrotuberous ligament.
05:16
With most posteriorly,
we have the coccyx.
05:18
So here we can see the boundaries
that form the pelvic outlet.
05:23
So, now let's talk about
the pelvic floor.
05:26
We'll talk about this in a lot
more detail in a later lecture.
05:29
But really,
this is a muscular fibrous layer
that sits over the pelvic outlet,
and it serves to hold
the pelvic organs in place.
05:39
We can see here
this thin muscular layer
is stretching from the
lateral aspect of the pelvis
from each side,
and they unite in the midline.
05:48
And later on, we'll hear about
structures like the perineal body,
which is the
central fibrous structure
that helps to unite these two
muscular layers in the midline.
05:58
But importantly, the pelvic floor
has a couple of apertures
that allows various structures
to pass through them
from either the pelvis
into the perineum
or from the pelvis
into the outside world.
06:08
But we'll cover the pelvic floor
in more detail later on.
06:11
For the time being, just remember,
it's a muscular layer
that helps to support
the pelvic structures in place.
06:19
Sitting superior to the
pelvic floor is the pelvic cavity
as we've just demarcated
with its lateral anterior
and posterior boundaries.
06:26
And within the pelvic cavity,
we'll find organs
in relation to digestion,
with the rectum and
the anus with reproduction.
06:34
Be that the uterus,
be that the vagina,
or the prostate in the male,
and also to do with
maturation with the bladder.
06:42
So the pelvis is an
important structure,
which we'll talk through
in the next few slides.
06:48
Sitting underneath
the pelvic cavity
separated by the pelvic floor
is the perineum.
06:54
And the perineum is
an important structure
for allowing
those structures to pass
from the pelvis
to the outside world.
07:01
And as an important function
with both reproduction, micturition
and with the removal
of digested foodstuffs.
07:07
We'll come back to
the perineum later on.