00:01
So now let's turn our
attention to the blood supply
and specifically
the arterial supply
of the entire
gastrointestinal tract.
00:11
So previously,
we've looked at the blood supply
to various specific organs.
00:15
And we've touched upon the
distribution of the arteries
to the foregut, the midgut,
and the hindgut.
00:22
Now, let's bring all that together
and look at it as one piece
of information.
00:27
So on the screen at the moment,
we can see at the
bottom of the screen,
the abdominal aorta.
00:32
At the top of the screen,
we can see sitting anteriorly,
to the abdominal aorta,
the entire gastro intestinal tract.
00:41
And what we've done is we've
represented it as one long tube.
00:45
But we can split up this
gastrointestinal tract
into to the foregut,
midgut, and hindgutt.
00:53
Now, each of these areas,
each of these portions of
the gastrointestinal tract
are going to be
supplied by a specific
unpaired branch of
the abdominal aorta.
01:06
That means that each
one of these areas
is supplied by a single branch
coming from the aorta.
01:13
So at the bottom of the screen,
we can see the abdominal aorta
has passed through the diaphragm
through their aortic hiatus
at around about T12.
01:23
We can see that coming off
just as it passes through
the aortic hiatus
within the diaphragm,
it gives rise to the celiac trunk.
01:32
The celiac trunk is going to be
the main unpaired blood vessel
that supplies all of the foregut.
01:39
Coming off the abdominal aorta,
slightly more inferiorly,
at approximately the level of
the first lumbar vertebrae,
we have the
superior mesenteric artery.
01:49
This blood vessel is going to
supply the entirety of the midgut.
01:54
We then finish with the hindguts.
01:56
And coming off the third lumbar
vertebral level of the aorta,
we have the inferior
mesenteric artery.
02:04
So these three
unpaired blood vessels
go and supply the foregut,
the midgut, and hindgut
with the celiac trunk,
the superior mesenteric
and the inferior mesenteric
arteries supplying those regions.
02:18
As we've seen, and what you've
seen in previous lectures,
is there are these things
called anastomosis.
02:23
And this is where interconnecting
branches from two different sources
joined together and how to add some
connectivity to this blood supply.
02:34
They help to rely for some
redundancy in the system.
02:37
So if there's a potential
blockage somewhere,
there's a secondary pathway that
this blood can pass to that location.
02:44
So here we have the
foregut, midgut, and hindgut
with some anastomosis
between those two.
02:50
And we've seen those
anastomoses occur
around the major duodenal papilla,
and around the transverse colon,
2/3 and 1/3.
02:59
They're the separation points
between foregut and midgut,
midgut and hindgut,
and the blood supply to those areas
are therefore coming
from these blood vessels.
03:10
Bridging across those two
different regions we have,
as I said, various anastomosis.
03:17
Let's have a look at this
in some detail.
03:19
Let's have a look at
the actual anatomy
and how it supplies these regions.
03:23
So here we can see we
have the abdominal aorta,
passing through the aortic hiatus
at the level of the
12 thoracic vertebra.
03:31
Here we can see at the
fourth lumbar vertebrae,
and just at the intervertebral
disc between the fourth and fifth,
we have the abdominal aorta,
bifurcating into the
two common ilac arteries.
03:43
They go on to supply the pelvic
organs and the lower limb.
03:47
We'll talk about those later.
03:50
Let's have a look then, at the
celiac trunk supplying the foregut.
03:54
And which structures
reside within the foregut?
We have the abdominal esophagus,
we have the liver,
we have the stomach.
04:02
We also have the spleen, we have the
pancreas, we have the gallbladder,
and we have the first couple
of bits of the duodenum.
04:10
We have the first part
and the first half
of the second part up to
the major duodenal papilla.
04:19
And here we can see that landmark,
the major duodenal papilla,
separating the foregut
from the midgut.
04:27
Now, let's have a
look at the midgut
and what structures reside
within this area.
04:32
So, the midgut is running very much
from that major duodenal papilla.
04:36
But now inferior to it.
04:39
So the second bit
of the second part,
and then the third and
fourth parts of the duodenum.
04:45
They're part of the midgut.
04:47
We also then have all
of the small intestines.
04:50
We've got the jejunum and ileum.
04:52
And then the appendix,
the cecum, ascending colon,
and then up to the first two-thirds
of the transverse colon.
05:01
So that part of the
transverse colon
that's coming from
the hepatic flexure,
and then working all the
way to the splenic flexure,
two-thirds of that distance
is classically the midgut.
05:12
Let's then turn to the hindgut
and which structures
reside within this area.
05:18
So we finished on the midgut
with the first two-thirds
of the transverse mesocolon.
05:25
Now we have the distal third
of the transverse colon.
05:28
And this is the
beginning of the hindgut
and supplied by the
inferior mesenteric artery.
05:34
We then have the descending colon,
we have the sigmoid colon,
and then we have the rectum and
the upper part of the anal canal.