So let's start off with
some important definitions
and there is lots of definitions that needs
to be described in relation to this peritoneum.
So let's start off with visceral peritoneum.
This is a portion of the peritoneal
membrane that is tightly adhered to a viscera.
So tightly adhere to say the small intestine.
If you are familiar with the thorax then
this is the same as visceral pleura
that was tightly adhered to the lungs. So we
have visceral peritoneum. And in this diagram
we can see this region around here
would be visceral peritoneum.
This tightly adhered to
the small intestine.
Parietal peritoneum, so visceral
peritoneum, parietal peritoneum
is what is adhered to the inside
of the abdominopelvic wall.
So this is the layer of
peritoneum that lines
the body wall that lines the anterior
abdominal wall, the lateral abdominal wall
and forms a sheet over
the posterior abdominal wall.
So this here is parietal peritoneum
and parietal peritoneum can actually
just run over an organ. It can just run over
an organ like this and we can say this like
is the kidney or the pancreas.
And the parietal peritoneum just runs
over the top of it.
Now visceral peritoneum and
parietal peritoneum. We also have
definitions to define the
relationship of an organ
to the peritoneum.
And these can be even intraperitoneal
organ or retroperitoneal organ.
We mentioned retroperitoneal organs
before when we spoke about the
duodenum that is retroperitoneal
organ; well, the vast majority of it is.
The kidneys are retroperitoneal organ.
The pancreas is a retroperitoneal organ.
And what I mean is
by retroperitoneal organ
is that this organ is positioned between
the body wall and the peritoneum.
Just like in this example
we have the kidneys
Here we have got the
body wall in black
and here is the body wall in black
and red is our parietal peritoneum.
This organ the kidney is
between the body wall
and the peritoneum.
So it's retroperitoneal.
And intraperitoneal organ is an
organ that is completely surrounded
by the peritoneum. And we have a series
of these organs like the stomach,
the spleen, the small
intestine was surrounded
by peritoneum. So here we could have
the stomach, lets say, or the spleen.
And this is where it
is completely surrounded.
Typically it will all be
suspended via the mesentery.
And here we can have mesentery.
Now mesentery is a
double layer of peritoneum.
We can imagine the
coming in this direction. And the parietal
peritoneum coming in this direction.
And where these two converge
they then adhere
and they move upwards
where they can then surround the organ.
So they converge, they move upwards
and then they surround the organs.
And this mesentery is
really, really important
because running through the mesentery
are going to be various blood vessels,
are going to be nerves,
are going to be lymph
allowing that organ to function.
But the advantage of having the mesentery
is it gives the organ mobility.
Allows it to move around within the
abdominal cavity, it's not restricted.
And this is an intraperitoneal
by this mesentery.
So that's a series of
definitions to start off with.
We spoke about retoperitoneal
organs like the kidneys.
But we also have organs which are known
as being secondarily retroperitoneal.
And these organs were initially
intraperitoneal and suspended by a
mesentery, just like we have here.
So if for example we say
this is a piece of colon
then that piece of colon is
suspended from the body
wall via this mesentery
via this mesentery.
And during development,
the small intestine
grow a lot faster and to a greater
extent than the large intestine.
Now we know the position of the small
intestine is right in the middle of the abdomen.
And the large intestine is
being pushed to one side.
Now the consequence of that
massive increase in growth of the
small intestine is that
it actually push
the ascending and descending
colons to their lateral margins.
So what happened is that originally the large
intestine was all suspended by this mesentery.
But as the small intestine
increased in size, so it pushed
and it pushed the large intestine.
Its ascending, descending portion
to one side. It pushed it to
one side so the mesentery
actually collapsed. Which
is what we can see here.
So they actually; an organ like the
ascending or the descending colon
started off having a mesentery.
But this mesentery
actually then blended
with the parietal peritoneum
that was on the body wall.
So originally it was an intraperitoneal
organ suspended with mesentery.
But during development it has assumed
as the retroperitoneal position.
And therefore we call it
It is retroperitoneal due
to a different process
than the kidneys or the pancreas.
Other secondarily retroperitoneal organs
include the duodenum as well.
These organs that are originally started
intraperitoneal but got pushed laterally
due to expansion of the small intestine,
the jejunum and the ileum.
So they then blended, their mesenteries
blended with the posterior
abdominal walls, parietal peritoneum
and become secondarily retroperitoneal.
So that's an another important
definition. Some more definitions...
ligaments and the omenta.
These are double layers of peritoneum that
support and suspend the abdominal viscera.
Let's just look at the mesenteries first. I
mentioned mesenteries in the previous slide.
These are the important conduits for
blood vessels, nerves and lymphatics.
A real good example is the small
intestine mesentery so called the
mesentery. It's very extensive
and runs only about 5 or 6 cm from the upper
left quadrant to the lower right quadrant.
And the mesentery fans out;
it fans out and then attaches, its
free edge attaches to the jejunum and the ileum.
That gives the jejunum and the ileum
great mobility to move freely.
We have an another one which is the
transverse mesocolon but we could have the
sigmoid mesocolon as other example.
The mesentey that was the most extensive and it
allows the branches of the superior mesenteric
artery to run up through it to supply the
small intestine with its blood, its nutrients.
We also have what are known
as the peritoneal ligaments.
And these are double
layers of peritoneum again
and they specifically attach
an organ to another organ
or attach the organ
to the body wall.
For example the liver is attached
to the anterior abdominal wall
via the falciform ligament
and we will come to know more
about the falciform ligament later on.
The stomach is attached to the spleen
via the gastro, stomach, splenic, spleen,
ligament, the gastrosplenic ligament.
So the falciform ligament
is associated with the liver
and then we have the gastrosplenic which
is associated with the stomach.
And the splenic which is
associated with the spleen.
And these two are in communication,
the gastrosplenic ligament.
Again allowing these organs to have their
structure, to have their position retained
within the abdomen. We
also have an omenta.
Now the omenta, a greater omentum and the
lesser omentum are associated with the stomach
and we have seen these before.
We saw the greater omentum where
it was dangling down from the stomach.
And then it attaches to transverse colon;
we will look at that in the next few slides.
And we spoke about the lesser
omentum before as well
connecting the lesser curvature
of the stomach to the liver.