Next, we will take a moment to understand
the inguinal canal and the features that you
see to your left, the inguinal ligament,
the superficial inguinal ring, lateral crus,
medial crus and inner crura fibers are all
demonstrable on this particular illustration.
The inguinal ligament is the inferior most
aspect of the aponeurosis of the external
abdominal oblique and we see that inferior
margin running along here. It attaches laterally
and superiorly to the anterior superior iliac
spine and then its medial inferior attachment
would be to the pubic tubercle.
In this medial location, along this region,
we see an opening within the aponeurosis.
This happens to be the superficial inguinal
ring, and on the medial side of that, we have
a medial crus, and on the lateral side, we
have a lateral crus and then we have these
interdigitating fibers interconnecting those
two crura and those are the intercrual fibers.
In a man, the major structure that we see
here travelling out through the superficial
inguinal ring is the spermatic cord. The spermatic
cord enters this region by passing internally
through a deep inguinal ring and as it travels
through the inguinal canal, it will pick up
all the layers that we see eventually emerging
through the superficial inguinal ring.
When we think about the inguinal canal, the
inguinal canal will present two walls. It
will also have a roof and it will also have
a floor. So, what we want to do now is to
explore the components that form the anterior
wall, the posterior wall, the roof as well
as the floor.
Using the same image as the previous slide,
our focus here is on the anterior wall and
the anterior wall has been reflected so we
are looking into the inguinal canal itself.
So, let’s take a quick look at some of the landmarks
This is your deep inguinal ring and you see
some vascular structures passing through the
deep inguinal ring. This muscular structure
that we see here, in a man, is the ductus
deferens. So, it passes through the deep inguinal
ring and is now travelling within the inguinal
canal and then it passes through the superficial
inguinal ring at this particular location.
The anterior wall has been reflected, contributing
structure to the anterior wall is the aponeurosis
of the external abdominal oblique which we
see in through here and there is also going
to be a lateral reinforcement from the internal
abdominal oblique muscle.
So, right in through here, and this would
be the lateral most aspect of your canal,
it too has been reflected away from the canal.
The posterior wall is that area that we see
in this general vicinity. The fascial component
that we see that would pass behind the spermatic
cord content that we see at this level is
the fascia of the transversus abdominis. This
is referred to, simply and aptly, as the transversalis
fascia. More medially here along the posterior
wall and not visible at this particular point
in time, is a tendon referred to as the conjoined
tendon. It is formed by the aponeurosis of
the internal abdominal oblique as well as
the transversus abdominis. So, that helps
to reinforce the medial third dorsal at the
The roof of the canal has been opened up.
So, we are looking down into the canal yet
again, but the roof of the canal would be
formed in part by your internal abdominal
oblique which is reflected here and then your
transversus abdominis that we see at this
And then lastly, we will have the floor to
the inguinal canal. A good portion of the
floor will be formed by the inguinal ligament.
As that inguinal ligament approaches its medial
attachment to the pubic tubercle, there will
be an expansion of the inguinal ligament that
will run more posteriorly to attach to the
pectineal line of the superior ramus of the
pubic bone. This expansion of the inguinal
ligament more medially forms what is known
as the lacunar ligament, so it will contribute
to the floor as well.
Again, there is some additional geometry that
we can learn about in the discipline of anatomy
and the inguinal region is no exception to
that. Here, we are looking at the inguinal
triangle also known as the triangle of Hesselbach.
This triangle is bounded inferiorly by the
inguinal ligament which is running right along
here. So, that would actually form the base
of our triangle. Another portion or boundary
to our triangle is the lateral margin of the
rectus abdominis that we see along here. And
then this boundary or border to the triangle
is formed by the inferior epigastric vessels.
So, again, we have a nice geometric triangle
formed by those three structures.
Understanding the inguinal triangle is useful
in one, understanding the difference between
a direct and an indirect inguinal hernia.
Here, we have herniation of intestinal loops
into the scrotum. This is more common in men,
but we can have an inguinal hernia occurring
in women. The difference between a direct
and an indirect is the relationship that the
intestinal loop will take enter the scrotum.
In the profile or image slide here on our
right we have in reference, we have our inferior
epigastric vessels, the artery as well as
the vein. And here, we can see herniation
of an intestinal loop into the scrotum and
it takes a direct route into the scrotum because
it passes medial to your inferior epigastric
The left side of the image shows an indirect
hernia. Here, the intestinal loop is passing
lateral to those inferior epigastric vessels.
Therefore, it will pass into the inguinal
canal and it will have to exit at the level
of the superficial inguinal ring which is
at this general location and then once it
passes through the superficial inguinal ring,
it can then herniate into the scrotum.
That now brings us to the important take-home
messages from this presentation.
First, the muscles of the abdominal wall are
innervated by anterior rami from levels T7
all the way down through L4.
Collectively, attachments are through the
thoracic cage, pelvis and femur.
Anterolateral muscles compress the abdominal
viscera and function in lateral flexion and
The most powerful muscles of the posterior
abdominal wall, psoas major and iliacus, flex
The inguinal canal is a potential point of
weakness allowing for direct or indirect herniation
of intestinal contents.
The inguinal triangle is bounded by the inguinal
ligament, inferior epigastric vessels and
the lateral margin of the rectus abdominis.
And lastly, direct hernias pass medial to
the inferior epigastric vessels whereas indirect
hernias will pass lateral to that vasculature
Thank you for joining me on this lecture on
the muscles of the abdominal wall as well
as its vasculature and innervation.