This view is slightly different. This view
is as if we have cut down sagittally through
the abdomen to have a look at these layers.
So, in this diagram, we have got anterior
here and we have got posterior. And here,
we have got a reminder of those layers above
and below the umbilicus. So, here we see above
the umbilicus and here we see below the umbilicus.
So, here on the diagram, this arrow is pointing
to umbilicus. So, the umbilicus will be about
here. And then we can see above it and we
can see below it. Above the umbilicus,
we had external oblique, okay? So, we had external
oblique. So, we can draw in external oblique.
And that's going to be indicated here in
blue. This blue line here is external oblique.
In orange, we can see the skin of the body.
So, external oblique is anterior to rectus
abdominis. Here, we can see rectus abdominis
muscle. If we look below the umbilicus, external
oblique is still there. So, now, we are below
the umbilicus, external oblique is still present.
It just always lies anteriorly. If we go deep
to external oblique, pick it up in green here,
we can see that we have got internal oblique's
anterior layer because, also in green, above
the umbilicus, we can see internal oblique's
posterior layer. So, here, we have internal
oblique... internal oblique, its anterior
and posterior layers where remember, above
the umbilicus, its divided. What we can
also see, if we keep going posterior, is transversus
abdominis. In purple here, we can see transversus
abdominis and this is above the umbilicus
and then most posteriorly again, we can see
transversalis fascia here in black which is
then the peritoneum. So, importantly, above
the umbilicus, we can see we have got external
oblique, anterior layer of internal oblique,
rectus abdominis. We have got the posterior
layer of internal oblique and then we have got
the transversus abdominis and then transversalis fascia.
Just below the umbilicus, we can see
the rectus abdominis muscle penetrates these
layers. So, we can see rectus abdominis is
penetrating these layers so that it actually
pierces them and lies posterior to these layers.
So, now, that we are below the umbilicus,
you can see we have external oblique, internal
oblique, the anterior and posterior lamina
have merged and we can see we have transversalis
fascia. If we were to look, if we were to
stand in the abdomen and look at the anterior
abdominal wall from the inside, we could see
this transition. We could see this transition
and it's known as the arcuate line.
Here, we can see this arrow is indicating what's
known as the arcuate line and that's where
you have this covering posterior rectus abdominis
which then disappears. And hopefully,
you are gonna appreciate that when we look at posterior
view of the anterolateral abdominal wall.