In this lecture we are going to look at
the arterial supply to the gastrointestinal tract.
So we are going to look at
the numerous arteries that supply
nutrient rich, oxygen rich blood
to the gastrointestinal tract,
the duodenum, the stomach, the colon, parts
of the small intestine and also to the
accessory organs of digestion
like the pancreas and the liver.
What we need to do is first of all
imagine the gastrointestinal tract as one long
continuous tube and we can divide
it into foregut, midgut and hindgut.
And what we are going to do, is we are going
to look at the organs that make up the foregut
and explain how they are
supplied by the coeliac trunk.
We will then look at the division
between the foregut and the midgut
detail the midgut organs and how they're supplied by
branches of the superior mesenteric artery
And then look at the organs that constitute
the hindgut and how they're supplied by
the inferior mesenteric artery.
And then we will look at some
important transitions that occur between
forgut-midgut and the midgut-hindgut.
So if we just look at the schematic first of all.
Then what I want to do, is try and explain
the aorta running parallel
to the gastrointestinal tract.
So this is the gastrointestinal tract all
the way along here. This is the anterior aspect
and this is the posterior aspect,
anterior aspect and the posterior aspect.
So this view really is as if you are lying
on your back and someone is looking at you
from the side. What we can see is
the diaphragm indicated here in green.
The aorta passes through the diaphragm
and at various points along the course,
the coeliac trunk is given off; the superior
mesenteric artery is given off
and the inferior mesenteric
artery is given off.
So at T12, L1 and L3, these vertebral levels,
we have the coeliac trunk, or the superior
mesenteric artery or the inferior mesenteric artery.
If we then look to
the gastrointestinal tract, we can see
that the GI tract is split
into foregut, midgut and hidgut.
Now, the separation between the foregut
and the midgut, this occurs at the duodenum;
specifically the major duodenal papilla.
That separates the foregut from the midgut.
And remember the major duodenal papilla was
half way down the descending part of the duodenum.
The midgut becomes the hindgut
2/3rd of the way along the transverse colon.
So 2/3rd of the transverse colon is midgut
and then the remaining 3rd is hindgut.
And that's important when we look at which
artery supply which parts of the GI tract.
So simply here in this diagram, we can see that
the coeliac trunk is going to give rise to the branches
that supply the foregut. We can see
the superior mesenteric artery
is going to give rise to
branches that supply the midgut.
And finally we can see the branches from the
inferior mesenteric artery are going to supply the hindgut.
These dotted lines here
represent the transitions between
the blood supply to the foregut and midgut.
We saw this, when we looked at the superior
and inferior pancreaticoduodenal arteries
at the head of the pancreas and the duodenum.
Between the midgut and the hindgut, we had the
transition that formed the marginal artery
inputs primarily from the middle
colic and left colic artery.
With the middle colic coming from the superior
mesenteric and the left colic coming from the
inferior mesenteric artery.
So these foregut, midgut and hindgut
regions have specific blood supply.
But there is also a transitional area between them.
So we are going to look at the specific branches from
the coeliac trunk, superior mesenteric artery
inferior mesenteric artery and
also consider those transitions.
So here we can see a general,
more anatomical drawing of
the blood supply to the GI tract. We can see
we have got the abdominal aorta up here.
We can see it's passing
down through the diaphragm.
Remember, the aorta passes through the
diaphragm through the aortic hiatus
at about T12, oesophagus T10 and
the inferior vena cava T8.
So the aorta passes down and then
really we can pick it up again
around about here. Where we have the coeliac trunk
pretty much immediately being given off.
So the coeliac trunk would be given
off really at the lower border of T12.
We can see that the coeliac trunk has a number of branches.
We can see a branch goes in this direction
in this direction, in this direction. Three branches
that are going to go and supply the foregut.
We can see we have the hepatic artery that is
going towards the liver. We have got a gastric artery
that is running up towards the stomach. And we can see
we have got a splenic artery that running towards the spleen.
Coming off these blood vessels, we have smaller
vessels that are going towards the pancreas.
We can see the hepatic artery going towards
the duodenum, going towards the head of the pancreas.
All coming off the coeliac trunk.
If we were to look at the superior mesenteric artery here,
superior mesenteric artery
comes off at about L1.
And we can see, this is giving blood
really that is passing to
the jejunum into the ileum
It also gives rise to a blood vessel
that passes up to the pancreas and the duodenum,
the inferior pancreaticoduodenal arteries.
And we can see it also giving rise to
the blood vessels that go to the caecum,
ascending colon and also
to the transverse colon.
We can see we have the inferior mesenteric artery.
This originates from about L3
And this supplies blood to the hindgut.
So we can see we have left colic arteries,
sigmoidal arteries and the superior rectal artery
that passes through the rectum.
We can then see these black circles
which are indicating the important transition.
The transitions between the foregut and
the midgut, the pancreaticoduodenal arteries.
And the transition between
the midgut and hindgut at the
marginal artery here, from the middle colic
and the left colic. So this is the general scheme
of how the gastrointestinal tract
receives its arterial blood
to carry out its vitally important function
of providing oxygen to the tissues to work
and nutrients to provide
them with sufficient energy.