Welcome to this lecture on “The Diaphragm”.
I want you to keep in mind kind of a silly
rhyme. And that is - C345 keeps the diaphragm
At the end of this lecture, you should be
able to answer the following objectives.
One, describe the general structure of the
diaphragm and its surface projections.
List the causes of an elevated hemidiaphragm.
Describe its muscular parts and attachments.
Describe the apertures of the diaphragm and
the vertebral level of transmitted structures
that is aorta, oesophagus and inferior vena cava.
Describe the location of potential herniation
sites through the diaphragm.
Describe its arterial supply, venous drainage
and innervation of the diaphragm.
And then we’ll take a look at the key take-home
messages with the summary slide and then provide
attribution for the images that are used throughout
I will begin here briefly to take a look at
the body map and we’ll focus first on the
left-hand image and the surface projections
of the diaphragm on the right side of the
The diaphragm would ascend after expiration
to a point just below the nipple. It is higher
on the right side than it would be on the
left side. And we’ll be able to explore
the reason that the right side of the diaphragm
is at a higher level than the left.
This slide depicts the general structure of
the diaphragm. We see the diaphragm right
along here and then extending over to the
left side. It does separate the thoracic and
abdominal cavities from one another yet does
provide for the transmission of structures
between the two cavities, as we’ll explore
a bit later.
It is a musculotendinous structure whereas
we have two domes that are more muscular in
their construction. And then we have a central
area here that is tendinous in its histologic
We can see, as we did in the body map slide,
that the right dome or the right hemidiaphragm
does extend more superiorly than does the
left dome of the diaphragm. And then the central
portion that we see here between the two domes
is depressed. And the reason that this central
location of the diaphragm is depressed is
that the heart is located in this region.
This slide depicts the surface projections
of the diaphragm. This is seen following normal
expiration and certainly, the vigorous nature
of respiratory movements could alter the ascension
of the diaphragm. So, if we had a more forceful
expiration then the diaphragm would be at
yet higher levels that I’m going to depict
here for you.
Here in the anterior view, we see the right
dome of the diaphragm. It typically will rise
following normal expiration to the topography
of the fifth rib, but in this illustration,
it’s actually ascended into the fourth intercostal
If we look at the left view, we’ll see that
the left dome of the diaphragm is located
a bit lower and it’s located in the fifth
intercostal space which we see right in through
there. And the reason that the right dome
of the diaphragm is at a higher level is the
fact that within the abdominal cavity, we
have a very large abdominal organ that projects
upwards and that is the liver.
It has less of a mass effect on the left side
because it‘s much more diminished in size.
So, we don’t have that pushing upwards of
the left diaphragm by any of the abdominal
viscera that we do encounter on the right.