So here we have got the diagram of the large intestine
which has been removed from the
abdomen. We are looking at in the isolation.
Again we can pick up the ileocecal junction
and then we can see food, the indigestible
parts of food, is going to be running
in this direction. We can see now
the various parts really clearly.
Inferior to the ileocecal junction, we finally
have got the cecum. Attached to the cecum
we find this blind ended pouch, which is the appendix.
And then above the ilocecal junction we
find the ascending colon, remember this is heading
up towards the liver so we have
the right colic flexure also known as the
hepatic flexure which we can see here.
So liver would be positioned around
about in this direction. So there would be
where the liver is. So we have the
hepatic flexure. Then running transversely
from right to left we have
the transverse colon heading towards
the spleen, so here we have the
spleen and so that would be the splenic flexure.
And that's where the transverse colon now
runs down this left side. It descends down this left side
of the abdomen as the descending colon.
Descending colon continues with
the sigmoid colon, so descending colon with the
sigmoid colon which is continuous with the rectum.
The sigmoid colon travels towards
the midline, so starting in this
left inguinal region, the sigmoid colon migrate via
the sigmoid mesocolon, it's a mesentery.
It passes through the midline where that is
in continuous with the rectum.
On here, on this diagram, you can see
there is a whole series of external features.
And that's what we can explore in the next slide.
This is just the small section of
large intestine specifically
the colon really that we have removed.
And we have opened up a window,
and we've reflected these flaps.
Now what we can see on the
large intestine are features that
can distinguishable from
the small intestine. Now you should be able
to notice the small intestine
by it's location. It sometimes
throughout life various things can happen
and the position of organs in the abdomen
can become distorted. But here
we can see there is a series of
distinguishable features that make
the large intestine standout from the small intestine.
We have, what are known as taenia coli. These taenia coli
here are bands of longitudinal muscle.
When we looked at the small intestine
we saw that the longitudinal muscle
that went in the same direction
is the small intestine. When there was the complete band
that went all the way around
be like my sleeve completing covering
the small intestine running in this
longitudinal direction. But
for the large intestine you only
have three bands this is
incomplete sleeve. You just have three
bands that are going around,
going alongside the large intestine
and these are called taenia coli. Now because
these contract, they create these
pouches or haustra. And as
these muscles contract they have to
shuffle the indigestible, the
faeces along the large intestine
and the constriction of these taenia coli,
these three bands of longitudinal muscle
create these pouches which we
known as the haustra. We have three
taenia coli which we will, three different types of
taenia coli which we will explore in the next slide.
And here we can see we also
have some omental appendices or
appendices epiploica. And these are
just fatty tags that are attached
to the colon. You don't find them in
the small intestine. They are just attached
to the large intestine. These
peritoneal sacs that are filled with
fats, these omental appendices.
If we open up the large intestine
we can see that where we have these
kind of pouches, the constriction of
these pouches on the inside leads us
to what we knows as the semilunar folds.
And that gives us the appearance internally of
these regions where the taenia coli
longitudinal bands of muscle have
in-fact shortened the large intestine somewhat.
We can see if we returned to
taenia coli that we have three
types of taenia coli. We have the taenia coli
which is known as the omental taenia.
And this the part that attaches to
the greater omentum. So the greater omentum
hanging down from the transverse colon
will actually be attached to the
omental taenia. The mesocolic taenia is where
the transverse mesocolon attaches
to. So the transverse mesocolon
is coming up from the posterior
abdominal wall in-line with the pancreas.
And it passes up towards the transverse colon
and it attaches to the transverse colon
where this taenia is, where this mesocolic taenia
is located this specific band of
longitudinal muscle. The greater omentum
extends from the omental taenia coli
band. And then the final one
is this free taenia coli
which doesn't have any omental or
mesocolon attached to it.
And here we can see we have got some
details of what I just explained. We have got the
three different bands of taenia
coli: the mesocolic, the omental, the free.
We have got these longitudinal bands of
muscles creating these haustra, the sacculations
and internally creating these semilunar folds.
And also I mentioned the small
fatty tags, these omental appendices.
Another clear way to distinguish
the large intestine from the small intestine
is it's greater diameter. The greater diameter
compared to that of the small intestine
So apart from the obvious position of
the small intestine, you should be out
to work how, where the large intestine
is and due to this inverted "U" shape
around the lateral aspects of
the abdomen. Also via these three
clear distinguishable features.