00:02
Now let's look at
the large intestine,
the next major organ
of our digestive tract.
00:09
The large intestine has
three unique features
not seen anywhere else
in the digestive system.
00:15
First we have the teniae coli
which are three bands of
longitudinal smooth muscle
in the muscularis of
the large intestine.
00:25
Also,
we have these pocket like sacs
caused by the tone
of the tinea coli
known as haustria.
00:34
Finally,
we have the epiploic appendages
which are going to be
these fat filled pouches
that are going to hang from
the visceral peritoneum
in the large intestine.
00:49
The cecum is going to be the
first part of the intestine
and where the contents
of the small intestines
are going to empty
into the large intestine.
01:00
Also, just before the cecum.
01:04
We have the appendix.
01:06
This is a mass of
lymphoid tissue
that sits inferior to the cecum
and the opposite direction of
where food will be propelled.
01:16
The appendix is a part
of that mucosal associated
lymphoid tissue or MALT
of the immune system.
01:24
It contains a
bacterial storehouse
that is capable of recolonizing
the gut when necessary.
01:32
We'll talk about this shortly.
01:34
Also because of
its twisted shape
the appendix can be
susceptible to blockages
and this can lead
to the condition known as
appendicitis in some cases.
01:48
The large intestine is also
referred to as the colon
and is divided into
the different regions.
01:57
So we have the ascending colon,
which is going to
travel up the right side
of the abdominal cavity
right at the level
of the right kidney.
02:07
It then ends in a right turn
known as the right colic flexure
and it's sometimes called
the hepatic flexure
because it turns
right at the liver.
02:18
Next we have the
transverse colon.
02:21
This is going to transverse
or travel across
the abdominal cavity
and it will end in
a right angle turn
known as the left kolok flexure
or also, sometimes called
the splenic flexure
because it's going to turn right
at the location of the spleen.
02:39
Finally,
we have the descending colon,
which is going to travel
down the left side
of the abdominal cavity.
02:46
This is followed by
the sigmoid colon,
which is the S shape portion.
02:51
That's now going to
travel toward the pelvis.
02:54
And finally we have the rectum.
02:58
The rectum is going to
contain three rectal valves
that are able to stop feces
from passing when gas passes
through the rectum.
03:08
The rectum is then going to
empty into the anal canal.
03:14
The anal Canal is
the last segment
of the large intestines
and opens the body to
the exterior at the anus.
03:23
The anal canal contains
two sphincters as well.
03:26
It has an internal
anal sphincter
made up of smooth muscles
and under involuntary control
and an external anal sphincter
made up of skeletal muscles
under voluntary control.
03:42
So now let's take
a microscopic view
of our rectum and anus.
03:47
Our large intestines contain
a thicker mucosa made up of
a simple columnar epithelium,
except in the anal canal
where there there's going
to be a stratified
squamous epithelium.
04:02
The differences that anal canal
needs to be able to
withstand abrasion
as feces is moving its
way out of the body
in the large intestines
in the other parts of
the large intestines
we mostly are going to be
specialized for absorption.
04:19
It does not have the
circular folds and the Villi
or the digestive secretions
that we saw in the
small intestine,
but it does contain
abundant deep crypts
that have mucus
producing goblet cells.
04:35
The mucosa of the anal canal
remember the last part
of the large intestine
is actually going to hang
down and long ridges or fold
that we refer to
as anal columns.
04:48
You can see this
here and that image.