When we think about the pelvis, the pelvis
does present pelvic walls and those pelvic
walls have various components. Here, we're
looking at some osseous and
ligamentous components on one of the walls.
We'd have the same components on the opposite
pelvic wall as well. But, the components of
the pelvic wall would be bones, ligaments,
apertures as well as muscles. And we're going
to explore these various components in the
So, again, focusing on the pelvic wall, let's
look at the bones and ligaments that help
form the wall. And again, these are bilateral
structures. So, we would have the coccyx and
sacrum helping to form the wall. We also have
the pelvic bones that would run inferior to
the linea semilunaris, shown in through here.
We have the sacrospinous ligament that is
shown here running from the sacrum to the
ischial spine and then we have a larger, more
substantive ligament that's running from the
sacrum to the ischial tuberosity. This, then,
represents the sacrotuberous ligament.
Apertures are formed within the pelvic wall
and these apertures are openings that allow
the passage of structures. One such opening
is seen here. This is the obturator foramen.
In life, most of this foramen is filled by
an obturator membrane, connective tissue,
and we'll have just a little bit of an opening
here in this general region.
Two other openings are seen here and these
are fairly substantial in size. This is your
greater sciatic foramen and this is your lesser
sciatic foramen. These two foramina are formed
by the sacrospinous and the sacrotuberous
ligaments, which will convert the greater
sciatic notch and the lesser sciatic notch
into their respective foramina. So, your greater
sciatic notch here is converted to the greater
sciatic foramen by the sacrotuberous and the
sacrospinous ligaments. Your lesser sciatic
notch is converted into the lesser sciatic
foramen, again, by the sacrotuberous ligament
here and by the sacrospinous ligament above.
In addition to the bony and ligamentous structures,
the pelvic wall is also partially formed by
the presence of muscles. We have the obturator
internus muscle and the piriformis muscle
contributing to the wall in this particular
Your piriformis muscle is shown here. It is
originating from the anterior pelvic surface
of the sacrum and it'll exit the pelvis by
passing out through the greater sciatic foramen
and we see that occurring right in through
The obturator internus is shown over here.
We do not see it in its entirety because it's
going to disappear on us. The whitish membrane
that we see attached to it is the obturator
fascia, but you see the reddish muscle fibers
just deep to that fascial component, so, again,
obturator internus. And then right in this
area, you see the passageway through the obturator
foramen, that opening that is left just above
where the obturator membrane would be located.