So let's have a look at
some examples. The foregut,
The foregut (the stomach), stomach
is an organ within the foregut.
We can see here that in purple.
we have the para-sympathetic input
and we can see we have
that via the vagus nerve.
The anterior and the
posterior vagal trunks.
These enter the abdomen by passing through
the diaphragm alongside the oesophagus
and we can see here that the anterior
vagal trunk is spreading out to supply this
anterior surface of the stomach.
We can see that the posterior vagal
trunk is passing down at the back
and that supplying the posterior
surface of the stomach. So these are
And they will then synapse
with their post-ganglionic
fiber which will then
pass to the organ itself.
But this occurs within the
wall of that target organ.
You can see the poster and anterior
vagal trunks, they're giving
branches that goes over to the
liver and you can see it's
dropping down into the pylorus.
Well you can also see is
this posterior vagal trunk is also
giving a branch into
this mesh, this plexus
that is surrounding the coeliac trunk
and this is the coeliac plexus.
You can see either side of the coeliac
trunk we have got our coeliac ganglia.
And the coeliac ganglia are formed
via the greater splanchnic nerve and
that's we can see coming up here.
So if we look at the para-sympathetic supply
we have got some notes now.
We can see in purple
the anterior trunk is supplying the stomach
and giving branches that go towards
the liver and the duodenum. We can
see the posterior vagal trunk
is giving a branch that goes towards
the coeliac plexus and the posterior
surface of the stomach.
We can see that the sympathetic
supply is coming via
what's known as the
greater splanchnic nerve.
The greater splanchnic
nerve is going to leave
the spinal cord from
segments T5, T6, 7, 8, 9.
Those spinal cord segments
give rise to a sympathetic
greater splanchnic nerve
which passes through the coeliac ganglion.
At the coeliac ganglion it will then
synapse with post-ganglionic fibers
that via the periarterial branches
will pass to the stomach
and there we have the autonomic
supply to the stomach.
Hopefully by the end we will
appreciate by understanding this
where this greater splanchinc nerve comes from
is important, again referred pain.
A similar situation
happens for the midgut.
The midgut being the small intestine
and 2/3rds of the large intestine
and we can see that the small
intestine is going to have
its autonomic supply via
the superior mesenteric plexus.
The superior mesenteric plexus which
is going to be running along side
the superior mesenteric artery.
So what forms, what's
the para-sympathetic input
to this superior mesenteric plexus.
Well for the midgut it's
still the vagus nerve.
The vagus nerve, the parts of the
vagus nerve, of the posterior trunk
that went to the coeliac plexus
then carry on down the aorta,
towards superior mesenteric plexus.
So they just extended down and then
via the periarterial branches
they pass to the midgut.
The sympathetic input, to
the superior mesenteric plexus
is via the superior mesenteric ganglion.
The superior mesenteric ganglion is
formed via the lesser and least
splanchnic nerves. The lesser
and least splanchnic nerves
and these come from T10 - T12.
It's thought that the lesser
is T10 and 11 and the least is T12.
I am not sure it's that
important to remember that.
But it's thought that it comes
from those specific segments.
So pre-ganglionic fibers
pass from those segments
via the lesser and least splanchnic nerves
to the superior mesenteric ganglion.
They synapse with the post-ganglionic
fibers and then they run alongside
the pre-ganglionic fibers
of the vagus nerves
via periarterial branches to
the organs of the midgut.