Welcome to this lecture on an overview on the abdominal wall.
This slide lists the objectives that you should be able to answer
as a learner at the conclusion of this presentation.
First, describe the surface anatomy
of the anterolateral abdominal wall.
Describe the planes and regions of the
four quadrant and nine region pattern.
List the regions where pain is referred by derivatives
of the foregut, midgut, and hindgut.
List the skeletal and muscular elements of the abdominal wall.
List the layers of the abdominal wall from superficial to deep.
List three important anatomic landmarks
with respect to the dermatomes.
And lastly, list the male and female major structures
transmitted through the inguinal canal.
We will then highlight the key messages
from this presentation in a summary
and then provide for attribution of the images
that we'll use throughout this presentation.
Alright here are body map to orient you to the areas
that we're going to be covering today in this lecture.
We will be looking at this area, the anterior abdominal wall.
We will explore orientation to the lateral aspect of the wall.
And then we'll also take a look at the
posterior portion of the abdominal wall.
This slide brings us to surface anatomy or the surface relief
of the anterior abdominal wall.
This is best demonstrated in a young well developed male
with less than ten percent body fat.
The landmarks that we're interested in
are in the area of the rectus abdominis.
The rectus abdominis underlies the skin and rectus sheath
in this area as well as on the left side of the body.
In the midline, we have the belly button or the umbilicus.
And then above and below, but best seen above,
you see this depression or this furrow
and this corresponds to the linea alba.
Additionally, we have an area here
that represents a furrow or depression
and as you proceed inferiorly toward the pubic bone
you'll see that it curves inwards.
Similarly, we have the same thing occuring on the opposite,
rectus abdominis on it's lateral aspect
and again it will curve inwards as you proceed inferiorly.
This team arcades will represents the line
refer to as the linea semilunaris
And lastly, we see some furrows
and they're orientated more transversly
here within the skin overlying the rectus abdominis,
these correspond to tendinous intersections.
When we think about the anterior aspect of the abdominal wall,
we can divide the anterior abdominal wall into quadrants.
This is useful clinically in charting
where a patient may be feedling abdominal pain.
To form these quadrants, we need two lines.
One is a vertical line, one will be a horizontal line.
The vertical line is represented here.
It is running within the linea alba
proceed through the umbilicus inferiorly
toward the pubic symphisis.
The horizontal line will run also through the umbilicus, thereby
intersecting with the vertical line at the perpendicular angle
and then continue to the opposite side as well.
Consequently, we now have a right upper quadrant, a left
upper quadrant, a right lower quadrant, and a left lower quadrant.
Underlying some of these quadrants would be principally
the liver and gall bladder in the right upper quadrant.
The liver does extend over to the left upper quadrant.
We would have the spleen residing within this region.
The portion of the stomach. In the right lower quadrant
for example, we'd have the appendix and the caecum.
And in your left lower quadrant underlying this particular region,
we would have the descending colon and sigmoid colon.
We can also describe the anterior abdominal wall
into a nine region pattern.
This is more complex. There are two vertical planes
that will help define this nine region pattern
and two horizontal planes. Those planes
are shown in this particular illustration.
We have the right mid clavicular plane
being one of the two vertical planes.
And then we'll have the left mid clavicular plane.
The two horizontal planes will intersect the two vertical planes.
The first horizontal plane oriented more superiorly here
is referred to as the subcostal plane
and it is running from the inferior margin the rib cage
to the opposite inferior margin of the rib cage.
The inferior horizontal plane that we see at this level
is running from a bony projection on the iliac crest
refer to as the tubercle and then
will run to the opposite ilium
where it has its associated tubercle.
This is then refer to Apley as the intertubercular plane.
As a result, the overlying the anterior
and even the lateral abdominal wall
of these two vertical and two horizontal planes,
we now have the nine region of pattern.
We have three regions in the upper area, shown here.
We have three regions in the middle region or area.
And we have three regions below. These are named.
This is the right hypochondriac region.
This is the epigastric region.
This then is the left hypochondriac region.
The middle regions, from the right side in the individual
to the left side in the individual
would be right flank or right lumbar,
umbilical where you have the umbilicus
and then you would have your
opposite left flank or lumbar region.
The inferior three regions shown here,
again running from the individuals right to the left,
this would be the right groin or right inguinal region.
This is the pubic or hypogastric region.
And then we have the opposite left groin or left inguinal region.
This nine region pattern is useful
in understanding referred pain.
When we think about the development of the viscera
that would be associated with your abdominal cavity
the primitive gut tube is arranged into
three regions called the foregut, the midgut, and a hindgut.
Adult structures derived from the foregut would include
the oesophagus, the stomach, liver, gall bladder
pancreas, and the proximal portion of your duodenum.
The midgut derives structures would include distal duodenum,
all of the remainder of the small intestinal segments,
the caecum, appendix, ascending colon,
and about the proximal half of your transverse colon.
And then the hindgut would give rise to
the distal portion of your transverse colon,
descending colon, sigmoid colon, rectum,
and a portion of the anal canal.
Pain from those gut-derived structures
is referred to the various regions
based on which part of the primitive gut tube
it was derived from.
So for example, the appendix which would reside
in this particular region,
the appendix is derived from the midgut and so typically then
referred pain will be referred to the umbilical region.
The gall bladder, will typically
refer pain to the epigastric region.
The pancreas can certainly have referred pain
to the epigastric region as well.