On the following slide, we will take a look
at the innervation of the diaphragm. And here
I’ll call back that rhyme:
C345 keeps the diaphragm alive.
So, now, let’s take a look at the slide
demonstrating the innervation of the diaphragm.
There are several nerves that innervate the
diaphragm. But, your key take-home point here
is that the phrenic nerve is the only nerve
that provides for motor innervation. So, we
have a right phrenic nerve going to the right
hemidiaphragm, we have a left phrenic nerve
going to your left hemidiaphragm. Here’s
your right phrenic nerve, here’s your left
phrenic nerve and if you follow the
nerves distally, you see these muscular branches
innervating the diaphragm.
These spinal nerve levels that contribute
to the formation of the phrenic nerve are
spinal nerves C3, C4 and C5. So, again, it’s
the phrenic nerve that has sole function of
motor innervation of the diaphragm.
The phrenic nerve also conveys sensory innervation.
And this is a key point because when you look
at the dermatomes that are innervated by C3,
4, 5, again, those same spinal nerves that
provide for innervation of the phrenic nerve,
that’s going to be on the shoulder region
and even up into your neck, here on the left
side and then also on the right side. If there’s
any irritation of the diaphragm, maybe there’s
a liver abscess that’s irritating the inferior
surface of the diaphragm, maybe there’s
accumulation of blood in the peritoneal cavity;
blood is very irritating and if it’s at
the level of the diaphragm, it will irritate
the diaphragm. That will cause pain to be
referred to those dermatomal patterns of C3,
the shoulder into the neck area.
In addition, we have intercostal nerves running
within intercostal spaces 5, 6, 7, 8, 9, 10
and 11 as well as the nerve that travels just
below the twelfth rib called the subcostal
nerve. We can kind of see those dermatomal
patterns along here in this particular figure.
But, again, these nerves are running within
the intercostal spaces or, in the case of
T12, below the twelfth rib, there's a
cutaneous branches that supply the skin from
those intercostal nerves and the subcostal
nerves, but there are also branches from these
intercostal nerves and subcostal nerves that
will provide for sensory innervation of the
That now brings us to our summary, the key
take-home points from this lecture.
The diaphragm is a musculotendinous structure
separating the thoracic cavity from the abdominal
The right hemidiaphragm has a more superior
surface projection than left due to the presence
of the liver on the right.
The sternal, costal and lumbar parts constitute
the muscular diaphragm.
Arterial supply and venous drainage is provided
by vessels with phrenic as a part of their
Motor innervation is via the phrenic nerves
- C345 keeps the diaphragm alive, whereas
sensory is mediated by the phrenic
intercostals T5 through T11 as well as your
subcostal nerves T12.
Potential herniation sites include the oesophageal
hiatus and the sternocostal and lumbocostal
Pain from the diaphragm is referred to the
C3, 4, 5 dermatomes. Again, the neck, shoulder
and lateral arm.
Thank you for joining me on this lecture on