This lecture we are going to
look at the Large Intestine.
So like the other lectures, we have
looked at so far, we start off by
looking at the position of the large intestine
within the abdomen and how that projects on to
the surface of the skin. And then we are going
to explore the Gross Anatomy, we will look at the
features like Caecum and Appendix and
the various parts that form the Colon.
We will look at the location and relations
within the abdomen and explore Appendicitis
We will look at the wall structure
of the Colon and then Diverticulosis.
We will also look at the Neurovascular supply.
The large intestine is really
important in the process of digestion
and it is the main site for water reabsorption.
It also plays an important
part in storing the faeces.
As we will see the indigestible remnants
of the chyme that pass through
the stomach and the small intestine.
There it compacts and stores
this material prior to defaecation.
So if we look at the surface anatomy of
the large intestine, then we
can see on our torso,
that we have this inverted "U" shape
You see we have go the ileocecal junction about here,
where the distal portions of the Ileum are
continuous with the large intestine. And then
inferior to that junction we find
we have the cecum and the appendix
attached. This is low in the right
quadrant. So in the right inguinal region
of the abdomen. The colon
then passes upwards as the
ascending colon heads towards the liver.
The liver would be round about in this position
which we can see in this diagram, here is the liver.
And we have got what's known as the
Hepatic flexure or what's called
here the right colic flexure.
Once it's got to the liver, it then takes
a sharp 90 degree turn to the left
and it runs across the abdomen,
it runs towards the spleen.
And here we have what's known as
the splenic flexure or the left colic flexure.
The colon then descends as the
descending colon and it passes towards
the left inguinal region. Whereas in
continuous, we have the sigmoid colon that passes
towards the midline. Here what
is continuous in the rectum and that is where
the majority of these feaces are
stored by the defaecation as it then leave
via the Anal canal, we will explore
that region later on in the separate lecture.
So in this diagram, on the
opposite site, we can see how this
inverted "U" shape large
intestine actually fits within
the large intestine, we can see
we have got this "U" shaped here. And within it
we can see the coils of Jejunum and the coils of Ileum.
These being continuous from the
duodenum which is fed into from the stomach.
So here we can see the basic cartoon outline
of where the large intestine is orientated.
Some key facts in regards the large intestine,
as I have mentioned the couple of
times now that it is the inverted "U"
shape and it has an average length
of about 1 and half to 2 meters.
It's below the level of the stomach and the liver
and it surrounds the small intestine.
It begins in the ileocecal junction
where the terminal Ileum meets
the largest intestine and it ends in the anus
which is in the pelvis. Parts of
the large intestine can be found in all
abdominal regions. So the large intestine
is inverted "U" shape
can be found in the vast
majority of the abdominal regions.
And it consists the large intestine of caecum
and appendix which we mentioned previously
Then it has four parts which constitute
the colon: ascending, transverse,
descending and sigmoid. And then finally
have the rectum which is in continuous
with the anal canal, I will look in
detail at these parts in the subsequent lecture.
The main functions of the large intestine
are like I said, to reabsorb water,
so this dehydrates the stools.
Also it has a role in absorbing vitamins.
And it's vital in the compaction
and storage of faeces. So let's go onto