So if we look at the vasculature
of the large intestine
we can see that the large intestine
is really important. It's what know as
what is known as the watershed organ.
It has a contribution
from two main branches of the abdominal aorta.
So we can see that the arterial supply to
the large intestine comes from the
superior and the inferior
mesenteric arteries. Here we can
see we have the superior mesenteric artery
coming from about L1 from the abdominal aorta.
And here we can see we have the inferior
mesenteric artery coming from about L3.
So LM, superior mesenteric artery
comes from L1 and the
inferior mesenteric artery comes from about L3.
We will explore this in little more detail
in a later session, later lecture.
Essentially coming from these
mesenteric arteries: your superior and
your inferior mesenteric artery.
Our series of colic arteries: ileocolic which
heads towards the ileocecal junction
with right colic, middle colic, left colic.
And these all branch away
ileocolic, right colic and middle colic.
And we see that passing away from their
respective stem, the superior
mesenteric artery in this case or
the left colic artery here from
the inferior mesenteric artery.
We have sigmoid arteries coming down towards
the sigmoid colon. These are spreading out
and fanning out towards
the ascending transverse
sigmoid parts of the large intestine.
We can see here, we have a very
important anastomosis. We have a
continuation of the superior mesenteric artery
and the inferior mesenteric artery.
So blood will be coming in this direction
from the superior mesenteric artery and blood will be coming
in this direction from the inferior mesenteric artery.
So what we have is this
region around here in
this upper left quadrant by the spleen
we have a transition where this region
is supplied by both the superior and the
inferior mesenteric artery.
And this is really important. It forms what's known as
the marginal artery which runs
around this aspect, this upper left
quadrants by the spleen or the
large intestine. And it is important
if the inferior mesenteric artery
was to be occluded. So we can imagine if the
inferior mesenteric artery was
occluded due to atherosclerosis in the region near
the inferior mesenteric artery, then
blood wouldn't be able to pass towards
this descending sigmoid part of the colon. However the
presence of this marginal artery means
the blood can actually root itself around
in this direction via the superior
mesenteric artery, via the
middle colic artery and then being continuous
with branches of the left colic.
So there wouldn't be any serious deficit
if there was a block. We will explore
this in later lectures in a bit more detail.