So let's look at the boundaries
of the perineum. This is a
inferior view of the bony pelvis.
We have anterior up here
and we have posterior here.
We have the pubic symphysis. We have the inferior
pubic ramus. We have the ischiopubic ramus.
We have the ischial tuberosity here.
We have running from the ischial tuberosity
to the sacrum, the sacrotuberous ligament
and here we have the coccyx.
And we can see that creates
this diamond shape.
If we do that again, we can see
this diamond space has been created.
Anteriorly we have the pubic symphysis
Laterally we have ischial tuberosities.
Posteriorly we have the coccyx.
If we connect these four dots up
via the inferior pubic rami
and via the sacrotuberous ligament.
We can see we have this
diamond shape. This diamond shape
can be divided into two
triangles via the transverse line
at the level of the ischial tuberosities.
So if we to draw a transverse line
across the ischial tuberosities,
we have split this diamond into two.
We have split into a more anterior triangle.
This is the anterior aspect,
at more anterior triangle
and we have split into a more posterior
triangle. This is a posterior aspect.
So we now have this
diamond split into two.
This anterior triangle is known
as the urogenital triangle.
And what passes through this triangle.
In the male it's going to be urethra
and in the female, the urethra plus the vagina
the urogenital triangle. This triangle here.
The triangle that's posterior to it,
that just contains one aperture.
Its known as the anal triangle and
this anal triangle allows the anus
to pass through it.
So we are looking at this
as if someone is lying on their back,
this is the posterior aspect.
Anteriorly is up in this direction and we
are looking through into their peritoneum,
with their external genital removed,
we can see the pubic symphysis.
We can see the coccyx
and we can divide this diamond
shape into two triangles
urogenital triangle, anal triangle. Within
these triangles, we will have those apertures
for the urethra/vagina and the anal.
So now I just want to concentrate
on the perineal membrane.
And the perineal membrane is just
associated with the urogenital triangle.
Just associated with the urogenital
triangle and that's what we can see here.
If we look at this view, this
anterior view of the pubic bone
within the pelvis. This is superior
up here. This is inferior at now.
We can see the ischial tuberosities.
We can see the pubic symphysis
and we can see the inferior pubic ramus.
So here if we draw those
transverse line again
we can see we have created this triangle
which is the urogenital triangle.
And we can see that just filling
this urogenital triangle, just
occupying the urogenital trinangle
is a shelf like structure. A shelf like
thin membrane known as
the perineal membrane.
We can that in this perineal
membrane, there is a couple of holes.
And the female is a good one to use as an
example; because, there is two holes.
We can see we have a
hole for the urethra.
We can see we have
a hole for the vagina.
So these structures
are passing through
this perineal membrane at the
level of the urogenital triangle.
We can see surrounding the urethra
is the external urethral sphincter
and we will explore other muscles
in this area as we go on.
But this perineal membrane is
just located within the urogenital
triangle. If we were to
explore some other muscles
then if we can appreciate that we
have got the perineal membrane here.
And that is just the shelf that's
been put in the urogenital triangle.
So if we were to do a
transverse section through
we could see the perineal membrane here. And then
we would have the urethra passing through it.
So we would have the perineal membrane here
attaching to the ischial tuberosities;
attaching to the ischial tuberosities here.
And then we have got this perineal
membrane that is just running across
from ischial tuberosity to
ischial tuberosity. Here
that we could imagine the sections
have been taken along here.
And here we can see the free edge of
the perineal membrane where it stops.
Now associated with this posterior border...
Associated with this posterior border,
there is going to be two muscles -
deep and superficial
transverse perineal muscles.
Along this posterior border
which we can imagine is here.
This posterior border,
there is going to be a deep
and a superficial transverse
perineal muscle layer.
Here we can see the deep
transverse perineal muscle
and here we can see the superficial
transverse perineal muscle.
And these lie along the posterior
border of the perineal membrane
running from ischial tuberosity
to ischial tuberosity.
Now where they converge
in the midline here
we find we have this fibro muscular
structure. This fibrous mass
and that is known as the perineal
body, the perineal body.
And the perineal body lies directly
posterior to the vagina
along the posterior border
of the perineal membrane.
It's in the midline and our
perineal muscles converge into it
is known as the perineal body.
More posteriorly, we then find the anus.
Located posterior to
the vagina or the
bulb of the penis, if we are
in the male, we then would find
the anus and the anal canal. And the
perineal body is positioned between them.