So let’s have a look at the
vasculature in more detail now.
We say that the jejunum
receives greater supply of
jejunal arteries than
ileal arteries and it's slightly redder
and it becomes pinker as we
pass towards the large intestine.
But let's just have a look and see what
we have if we look at the vasculature.
Now the jejunum and the
ileum receive arterial blood
from branches that comes from
the superior mesenteric artery.
Superior mesenteric artery
originates from the aorta
at approximately the
L1 vertebral level.
Remember the stomach will
supply by arteries that
come from the coeliac trunk
that was at T12. So this
superior mesenteric artery is coming
from the aorta at about the L1
vertebral level. And what is
does it gives rise to a whole
series of blood vessels
called jejunal and the ileal.
The jejunal arteries, as you
would expect, supply the
jejunum. And the ileal
arteries supply the ileum.
Now obviously with there being
a transition from jejunum to
ileum, there is going to be a
transition of jejunal arteries
and ileal arteries. And what these do,
these blood vessels run up
through the mesentery. So the mesentery
that's suspending the small intestine,
these blood vessels run up through
the mesentery. And as they do this,
they form what are known
as anastomotic loops.
And these loops essentially
parallel the small intestine.
So if you imagine the superior mesenteric artery
is running along the base of the mesentery.
And it’s giving rise to the blood vessels that runs
through the mesentery and these fan out
the length of the root of
the mesentery is about 5, 6, 7 cm.
But the actual length of the
small intestine is 6-7 meters.
So these blood vessels fan out,
and they fan out to run towards
the free edge of the mesentery where
the jejunum and ileum are located.
And once they approach the free edge,
they form these loops which run along the
inside of the small intestine
and they run parallel to it.
And these are known as
arterial arcades. We can see
some in the diagram.
They're running up towards
running up towards, then you
have these loops, these
arcades which are running
parallel to the small intestine.
And then now you have got these arcades
running parallel to the jejunum and the ileum.
Small straight arteries come off them
and these are called vase recta
or straight arteries. They leave
the arcade and go and supply
the jejunum or the ileum. And the arcade is running
parallel, these straight arteries then run
towards the jejunum or
the ileum themselves.
So these are really important
and we will go over these
again when we look at the
blood supply to the entire
in a later lecture.
Venous drainage from these
again is relatively
straight forward but we will
go over when we look at
portal system in a later lecture.
But if you are comfortable with the
arterial supply then essentially
the venous drainage is similar.
They're going to drain into
what’s known as the superior
mesenteric vein and that forms
part of the portal system.
and we will look at that as
it passes through the liver.
We will look at the duodenum
and its blood supply
in lecture 9 when we
look at the pancreas.