No we're going to spend a moment to understand
the layering of the abdominal wall.
And we're going concentrate away from where we
have our vertically oriented muscle and
focus more on the anterolateral portion
of how the abdominal wall is layered.
First we're going to have the skin and we see
in the illustration here. For example, we see the
skin. We will then have two components that make
up superficial fascia. The more superficial
component of the fascia is this area here shown
in yellow. This is Camper's fascia,
also referred to as the fatty layer. The amount
of adipose tissue is variable. It will depend on
the nutritional status of the individual. The
deepest portion of the superficial fascia
is hard to visualize in this illustration.
But this is going to be Scarpa's fascia,
also referred to as membranous fascia and that
it is this first dark line that we see here
just underneath the yellow layer representing
Camper's. And it will cross over the midline
and continue on to the opposite side over to the
flat muscles that are found on the more lateral
aspects of your abdominal wall. The muscle layers,
and again we're looking at the anterolateral
flat muscles, would include the external
abdominal oblique, the internal abdominal oblique,
and we also have our transversus abdominis. In
this view we can see the external abdominal oblique
with its fibers running down and in. This slide
will demonstrate the other two muscle layers.
Here is the cut edge of the external abdominal
oblique along the rib cage. We also have
the cut edge and reflection here of the internal
abdominal oblique which would lie deep to your external.
And then this demonstrates the deepest flat muscle
layer which would be your transversus abdominis.
Over here on the other side, we can still see
those same components. External abdominal oblique.
This is the internal abdominal oblique being
reflected laterally. And then running deep to that
is the transversus abdominis.
Layers deep to the muscle layers include the
transversalis fascia, the extraperitoneal layer,
as well as the parietal peritoneum. Based on how
this illustration is presented, we are going to
concentrate more underneath the rectus abdominis.
But these three components extend laterally as well.
So what we see here is the transversalis fascia.
This is the fascia that runs on the deep surface
of the transversus abdominis. What we cannot see
here is just deep to the transversalis fascia
we'll have a thin layer called the extraperitoneal
layer. And there is variable amounts of fat
that can be detected here. And immediately deep
to the extraperitoneal layer, you'll have the
parietal peritoneum which is lining the abdominal
cavity. Once you go through the parietal peritoneum
you are then within the peritoneal cavity and
you can see the suspended abdominal viscera
within the peritoneal cavity.
It's also worthwhile to understand the dermatomal
pattern to the anterolateral abdominal wall.
Some key reference points here to help you kind
of understand the levels that are involved
would be the nipple, the umbilicus
and then your inguinal region.
These help you identify where T5 lies. So this
area of skin is going to be innervated by the
anterior ramus of the fifth thoracic spinal nerve.
That will be just inferior to the level of the nipple.
T10. This will lie at the level of the umbilicus.
And then lastly the L1 level will lie immediately
above the inguinal ligament which would run from
your anterior superior iliac spine down to the
pubic tubercle. The inguinal ligament is the
inferior margin of the aponeurosis of the
external abdominal oblique. An example of how
this might be useful clinically would be with
a pregnant women who's undergoing child birth.
She may want to lessen the pain that's associated
with this life event. And when they administer
the epidural, the physician will want to make sure
that the skin is deadened from T10 inferiorly.
And that there is a deadening of the skin bilaterally.
And if there is, the anaesthetic is going
to be effective in alleviating the pain.
The inguinal canal is an area shown deep to the
aponeurosis of the external abdominal oblique here.
It does form the inguinal ligament which would
be running right along here. Coming from the
anterior superior iliac spine down to attach to
the pubic tubercle. This is the
superficial inguinal ring which is an opening then
within the aponeurosis of the external abdominal oblique.
The inguinal canal transmits two major structures.
The spermatic cord in the male, and then it also
transmits a supporting ligament of the uterus
in women referred to as the round ligament.
There are certainly some other structures that
are transmitted but for this overview presentation
this will suffice for now. This now brings us to
the summary slide for we can identify the key
take home messages. First, is the rectus abdominis
defines the linea alba, linea semilunaris,
and the tendinous intersection. The abdomen is
divided into a 4 quadrant and a 9 region
pattern. Referred pain by derivatives of the
foregut, midgut and hindgut is to the epigastric,
umbilical and pubic regions respectively. Inferior
margins of the rib cage, lumbar vertebrae,
superior pelvis structures, and muscles are
major elements that define the abdominal wall.
Layers of the abdominal wall more laterally would
be the skin, the fascia to include Camper's fascia,
Scarpa's fascia. Your three flat muscles, external
abdominal oblique, internal abdominal oblique,
and then your transversus abdominis. The transversalis
fascia, the extraperitoneal layer and then lastly
we would have our parietal peritoneum. Dermatomal
levels T4, T10 and L1 correspond to the nipple,
umbilicus and inguinal regions, respectively.
The inguinal canal transmits the spermatic cord
in the male and the round ligament in the female.
Thank you for joining me on this lecture,
on an overview of the abdominal wall.