00:01
So this topic is going to be about
the posterior abdominal wall.
00:06
So let's start by
looking at the boundaries
of the posterior abdominal wall,
and then talk about the diaphragm.
00:12
So here you'll be familiar with
this image from previous slides.
00:16
And you can see that the
posterior abdominal wall
is a highly muscularised structure.
00:22
There's lots of muscles
that are running down
either side of the
vertebral column.
00:27
And these form an
important support network
to help maintain our posture.
00:33
Let's just have a
look at the boundaries
of the posterior abdominal wall.
00:36
And here most posteriorly,
we've got the lumbar vertebrae,
one through to five indicated.
00:42
You can also see we have the 12th
rib highlighted here in green,
and also the iliac crest.
00:48
And these helped to form
part of the boundaries
of that posterior abdominal wall.
00:53
There's some other
important landmarks
like this part of the iliac fossa.
00:58
And we can also see it extends
inferiorly to the pelvic brim.
01:02
We'll talk about that later
on when we look at the pelvis.
01:05
But now we can bring all of
that together and see an outline
of the posterior abdominal wall.
01:12
Posteriorly, now we can clearly
make out the boundaries.
01:16
We can see the green
highlighted vertebral column,
the posterior aspect of the
12th rib, and also the iliac crest.
01:22
And here these lines
indicate the boundaries
of that posterior abdominal wall
from the posterior aspect.
01:29
Here we can see
sitting most superiorly
and extending up into
the thoracic cage,
and really forming the
upper limit of the abdomen.
01:38
We have the diaphragm.
01:39
And again indicates
we've got the 12th rib,
which is an important attachment
site for the diaphragm.
01:45
These together form
the superior border
of the posterior abdominal wall.
01:50
Remembering that the
five lumbar vertebrae
from the posterior abdominal wall,
his posterior border.
01:57
And we can see that inferiorly,
we have that pelvic brim that
we mentioned a moment ago.
02:02
So those structures we spoke about
these helped to form
various boundaries
of the posterior abdominal wall.
02:08
Now we can add on the musculature
that occupies this space.
02:13
We have some important muscles.
02:15
We have psoas major here
and running anterior to psoas
major, we have psoas minor.
02:21
Sitting lateral to psoas minor,
we have quadratus lumborum,
and these are important muscles.
02:27
As we extend down into the pelvis,
we pick up iliacus muscle
that lines the inside
of the pelvic wall.
02:35
So now let's start looking at
these muscles individually.
02:38
Here on the screen we can
see we have psoas major
that sits lateral to
the lumbar vertebrae,
and also the 12th thoracic
vertebrae as well.
02:47
We can see that it originates here
from the transverse processes
of the lumbar vertebrae.
02:52
And here we can see the
bodies of the lumbar vertebrae
and also the 12 thoracic vertebrae
alongside the intervertebral discs.
03:00
It originates from this
location and passes posteriorly
and inferiorly all the way down to
the lesser trochanter of the femur.
03:09
Let's have a look at the nerve
supply to the psoas major muscle.
03:13
And this is coming
from the anterior rami
of the spinal nerves
L1 through to L3.
03:19
And these go on to supply
the psoas major muscle.
03:23
The muscle is important in
helping to flex the trunk
when you're in a sitting position.
03:27
So to bend your trunk forwards and
also it helps to flex the thigh.
03:31
So to bring the thigh
forwards as well.
03:35
Sitting directly anterior to
psaos major is psoas minor
and as its name suggests,
this is a much smaller muscle.
03:43
And it may not always be
present in some people,
but it is quite common.
03:48
Psoas minor, as I said,
is a smaller muscle
that sits directly
anterior to psoas major.
03:54
It originates only from
the bodies of T12 and L1,
and here we can see
the intervertebral disc
between those two vertebrae.
04:02
It runs all the way
down to innovate,
to insert into the
pectineall line of the pelvis.
04:08
The nerve supply to psoas minor
is similar to that of psoas major,
but it's really only
the first rami of L1,
the anterior rami of L1
the first lumbar vertebrae,
and that provides the
innovation to psoas minor.
04:23
Psoas minor which is like I said
consistent but also regularly seen
also helps to flex
the vertebral column
but it's quite a weak flexor
as its size would lead to.
04:34
We can see here if we move
now down into the pelvis,
we're looking at iliacus muscle.
04:39
And this very much sits on the
lateral aspects of the pelvic wall.
04:44
We can see it's coming
from the iliac crest
and it passes all the way down to
the lesser trochanter of the femur.
04:52
The innovation of
the iliacus muscle
is by way of the femoral nerve.
04:57
Iliacus muscle is important
as it helps to flex the thigh.
05:03
Together the iliacus muscle
and the psoas major muscles
combine to have a joint tendon.
05:09
And here we have what's
called iliopsoas,
where these two muscles pass down
and they run towards the
lesser trochanter of the femur.
05:18
The innovation of
the iliopsoas muscle
is the same for both psoas major
and the iliacus muscle individually,
but their tendons
importantly combined.
05:30
Now, let's talk about
quadratus lumborum.
05:32
Quadratus lumborum originates
from the iliac crest on the ilium.
05:37
And it passes
superiorly and medially
to insert into the transverse
processes of the lumbar vertebrae,
and also the inferior
surface of the 12th rib.
05:48
Quadratus lumborum is
an important muscle
and is innovated by the
anterior rami of T12.
05:55
And L1 through to L4,
as you can see here.
06:00
Quadratus lumborum has an
important job working independently
as they help to laterally
flex the vertebral column.
06:07
So if one quadratus lumborum
muscle works independently,
it works on its own,
then it will help to laterally
flex the vertebral column.
06:16
If however, both of these
muscles were to work together,
then it actually helped to
extend the vertebral column.
06:22
So they antagonize the
work of psoas major muscle.