So we start off by looking at the
surface anatomy of the small intestine
and where exactly it is
positioned within the abdomen.
And then we going to look
at the gross anatomy of it.
So look at the three parts:
Duodenum, Jejunum and Ileum.
And look at the location of these areas.
The relations they have to other organs
within the abdomen. We will look
at the wall structure and then,
like of the stomach, we will look
at its neurovascular supply.
So small intestine is really important.
It’s the main site for chemical digestion
and then absorption. So receives
bile from the liver
And this helps to break
down (emulsify) the fats.
And it also receives digestive
enzymes from the pancreas.
So it's intimately associated,
as we will see, with these organs.
The chyme can then now be absorbed
through the walls of the epithelium
of the small intestine and
then pass into the blood stream.
So the small intestine
finishes off this
digestion and then allows
absorption to occur.
So we start, how we usually start
with these lectures, and we will look
briefly at the surface anatomy,
the position of them as it's been
put on to the torso. So here we can see,
just in this one, we just have the
initial part of the small intestine,
the duodenum this "C" shaped
structure. And this will be
continuous with the "J" shaped
stomach that we saw in the
previous lecture. So we have got
the stomach, we have got the
oesophagus which is coming
down in this direction. And we can see this
"C" shaped duodenum, that's the first part
of the small intestine. And we can't actually see
that part of the small intestine that clearly
on this diagram. Again we
can see the oesophagus nicely
passing down through the thorax entering
the abdomen through the diaphragm
and then being continuous with
the dilated sac of the stomach.
The stomach is then continuous with
the small intestine, initially the duodenum
which is aligned posterior to
what we know as transverse colon
and also it passes the liver.
The duodenum is what’s known as
retroperitoneal. We will come back to this
term later on. But it means
it aligns behind the peritoneum
which as we will see is the membranous
sac that is within the abdominal cavity.
The duodenum is then continuous with the
small intestine. And here we can see the coils
of jejunum and the coils of
ileum that forms the small intestine.
And these are incredibly long; this tube
is passing through the gastrointestinal tract
And it passes really from this upper
left quadrant down in this direction
towards the lower right quadrant where
is then continuous with the large intestine.
And it does this by these coils
of jejunum and ileum as we'll see.
So some key facts with regards
to the small intestine.
About 90% of the ingested nutrients
are absorbed by the small intestine
so it carries out the
majority of the absorption.
It’s fairly long, six to
seven meters in length.
And as it passes from the
stomach to the large intestine
it decreases in diameter from
around about 4cm in the stomach
to about 2cm at the junction
of the large intestine.
It’s a big, long, sprawling
part of the GI tract
and it’s found within 6
of those 9 abdominal regions.
It’s found in 6 of the 9 and it's not found
in the hypochondria, the right and the left
hypochondriac regions and also the
epigastrium. So it’s found in the lower 6.
It's divided, as I have mentioned before, into
three subdivisions and from proximal to distal
so from the stomach to the large
intestine we have the duodenum,
the jejunum and the ileum.
The duodenum is important as
it receives digestive secretions
from both the liver, bile; and
the pancreas, the pancreatic juice
like amylase to aid digestion, to
help break down the ingested food
so it can be absorbed.