This, then, constitutes the symphyseal surface.
Now, we're looking at a view of an assembled
pelvis where we have the two hipbones, the
sacrum and the coccyx. And our take-home messages
from here would be that the pelvis is divided
into a false or greater pelvis as well as
a true or lesser pelvis. And there is a dividing
line or an anatomic landmark that helps us
to make that regional separation.
We'll get into some of the details of this
landmark here shortly, but for now, this landmark
is referred to as the linea terminalis. And
we see that running from here, along here,
along the sacrum, coming back to the opposite
side to join up in the anterior midline. Anything
above that, so anything spanning between the
ala of the ilia, anything above that superior
to that linea terminalis, that will constitute
the false or greater pelvis. This regionally
is a part of the abdominal cavity.
The area below the linea terminalis, so inferior
to that, this region represents the true or
lesser pelvis. Greater and lesser designations are
being used to describe this overall size.
So, your true pelvic viscera will reside within
the true pelvis.
The true pelvis has two openings, an inlet
and an outlet. The inlet is where you have
your linea terminalis and then the outlet
would be the area located inferior to that.
The next slide helps us to have a better understanding
of the landmarks that describe the pelvic
inlet and specifically, we'll have the sacral
promontory here posteriorly.
And if we go to the left here, we will find
the ala of the sacrum. That will then continue
along the arcuate line, come around anteriorly,
continue as the pectineal line, go to the
pubic tubercle, go across the midline and
come to the opposite pubic tubercle, follow
the opposite pectineal line to the opposite
arcuate line, along the opposite sacral ala
and then back to the midpoint along the sacral
promontory. This area is demonstrating the
The pelvic outlet is shown here and so,
the pelvis is tilted, as you can see in this
view. And here we're looking at the inferior
aspect of the pelvis and the opening that
we see here in this inferior view constitutes
the pelvic outlet. It is somewhat diamond-shaped
in appearance. And the boundaries of the pelvic
outlet anteriorly would be the pubic symphysis
and this is where the two pubic bones will
form their articulation.
We also have the ischial pubic rami. This
would be the joint rami that are formed between
the inferior pubic ramus and the ischial ramus.
So, that would be along here, on this side
and along here, on this side. We will get,
then, to the ischial tuberosities on either
side and then we have some prominent ligaments,
on this side and this side. Those are the
sacrotuberous ligaments and then in the posterior
midline, we have the coccyx.
When we think about the pelvis, the pelvis