The inferior mesenteric artery,
this is the third unpaired artery.
This coming off the aorta, the unpaired
visceral branch, this coming up from the aorta.
Comes away at about L3, inferior
mesenteric artery. Comes away L3
and it supplies the distal 1/3rd of the transverse colon,
the distal 1/3rd of the transverse colon.
descending colon, sigmoid colon
and parts of the rectum.
It does this by the left colic,
which we can see passing
towards the left, towards
the descending colon.
It also gives rise to a series may be three four sigmoidal
arteries which go to supply the sigmoidal colon.
And then it gives rise to a superior rectal artery.
And this will be the one that most
continuous with the inferior mesenteric artery.
As the inferior mesenteric artery comes down
the initial left artery gives off to be the left colic.
The subsequent left artery would be the sigmoidal artery.
And the remaining one, would be your
superior rectal which we can see
here. These were your sigmoidal
let me call your left colic
And what we can see is the left colic
and also to some extent the
sigmoidal artery are running towards
the colon where they meet
essentially what is this quite large arcade
similar to what we had with the small intestine.
And that arcade is being fed into via
left colic and the middle colic
coming from the superior mesenteric artery.
So this stretch here
is known as the marginal artery. A stretch of
arterial blood is running parallel
along the inside of the colon
And that helps to supply
this transitional area between the
midgut and the hindgut.
Just before the bifurcation of the aorta
into common iliacs, just superior to that you have
L3 where the inferior mesenteric arteries occurring.
And at this location, it's quite common
for the atherosclerotic plaques to occur.
And this can actually occlude the opening for
the inferior mesenteric artery, the wall can be dissected.
And this means that the inferior
mesenteric artery can become occluded
and the hindgut would have a
reduction in blood supply.
But because of this marginal artery and
we have inputs from the superior mesenteric artery
is actually possible for the blood
to be diverted down in this direction
towards the hindgut which can then receive
blood from the superior mesenteric artery.
So this transition is really important.
And this is just what we have focusing on
towards the end. These two important transitions.
Transitions between the foregut and the midgut,
transitions between the midgut and the hindgut.
And we can see that these can happen in a
number of places, the superior and inferior
And the middle colic and left colic
forming the marginal artery.
And these are really really quite important in
maintaining a sufficient blood supply to the GI tract.