The next slide that we’ll see will help
you understand the various structures that
are associated with the lungs in situ. And
those structures will be the lobes, fissures
and then two specific features that we see
associated with the left lung:
the cardiac notch and the lingula.
Here’s your right lung. It has two fissures.
One here: this is called the transverse fissure.
We also have a little bit shown here of the
oblique fissure. These two fissures help divide
the right lung into its three lobes: a superior
lobe, a middle lobe. And then we’re just
seeing a very small portion of a large inferior
lobe to the right lung.
The left lung only has one fissure. It too
is obliquely oriented and we just see kind
of the terminal aspect of that oblique fissure
here. That then means everything above the
oblique fissure belongs to the superior lobe
of the left lung. And then we’re seeing
just a little bit of a much larger inferior
lobe below the fissure.
Two structural features of the superior lobe
of the left lung would be the cardiac notch
that we see here. And you can see it receives
the heart as it projects to the left of the
midline. And then this tongue-like extension
here more inferiorly, but yet still associated
with the superior lobe is referred to as the
Each lung is going to present an apex, base
and surfaces. The apex of the lung, this is
the right lung, three lobes, the apex is shown
here. And then the base is opposite the apex
and is best demonstrated here. And we can
see that the base of the lung is concave because
of its relationship with the respective dome
of the diaphragm. So, the right lung with
its base will be related to the right dome
of the diaphragm. The concave surface of the
base of the left lung will be related to the
left dome of the diaphragm. And then the surfaces
of the lung: there are two. We have a more
extensive costal surface, which is everything
we see here. And then we’ll also be seeing
here more posteriorly.
So, it has relationships to the rib cage.
The mediastinal surface is this area here
and this is the surface of the lung that will
face the mediastinum.
Here we have the right lung in isolation and
we can better appreciate the two fissures
that are associated with the right lung as
well as the fact that the lung has three lobes.
Here is your transverse or horizontal fissure
and then here we can see more clearly the
extent of the oblique fissure. These two fissures
then will separate the right lung into a superior
lobe, a middle lobe and then this extensive
inferior lobe that we see here. And again the
lobes are supplied by secondary bronchi.
Here we’re looking at the left lung. It
only has one fissure: the oblique fissure.
And so, we see the extent of the oblique fissure
here. The area of lung above is the superior
lobe. The area of the lung below our oblique
fissure is going to be the left lobe.
And again, we can see the cardiac notch.
And you can see the lingula associated with that superior lobe.
On the following slide, you’ll be able to
understand the next concept about the lung
and that is the hilum of the lung. The hilum
represents the gateway into and out of the
lung. This gateway provides for the entry
of our respiratory passageways, the entry
of our pulmonary artery and its subsequent
branching pattern and then the exit of the
pulmonary veins that will conduct blood back
to the left atrium.
And so, if we take a look here, we have the
right lung above, its hilum is shown here.
Down below, we have the hilum that’s associated
with the left lung. And we can also see an
outline here of the pleura. And so, here the
pleura is approaching the lung surface itself
and then it’s going to spread out and adhere
to the lung and become the visceral pleura.
And where that reflection is happening below
the hilum, you’ll have this region here
of pleural membranes that constitutes what
is known as the pulmonary ligament.
In the left lung, its hilum will also have
a pulmonary ligament.
Now, within the hilum, we’ll have a relationship
of the airways to the vascular structures.
It’s going to be a bit different between
the right lung and the left lung.
In the hilum of the right lung, your airways
are located here in the posterior superior
aspect of your hilum. If you look anterior
to it, I can see the right pulmonary artery
entering the hilum and it will start to branch.
And then anterior to the artery and inferior
to the artery and airway, you have your two
pulmonary veins that are leaving the lung
to transport blood back to the left atrium.
In the left hilum, here is your airway posteriorly
located, but if you look here, the artery
is immediately above or superior to your airway.
And then your veins lie anterior and inferior
to those particular structures.
There is a mnemonic to help your remember
the anatomic relationship of the pulmonary
artery to the airway in each hilum. That mnemonic
is RALS. RALS stands for Right is Anterior
and Left is Superior. So, in the right hilum,
the artery is anterior to your airway and
in the left the artery is superior to your
The following slide will introduce you to
the concept of bronchopulmonary segments.
Bronchopulmonary segments are their own individual
anatomic unit. Each one is supplied by its
own respiratory passageway. Each one is supplied
by its own artery and also drains by its own
venous system. The bronchopulmonary segments
are also separated
from one another by connective-tissue septum.
As a consequence of these being their own
individual units, it is possible to surgically
resect or remove each one of these pieces
like you would a piece from a jigsaw puzzle.
The slide that you now see shows the various
bronchopulmonary segments in the right lung.
Each coloured region represents a separate
bronchopulmonary segment. Here we see the
numbering in a costal view. And then here
is the mediastinal view of the right lung.
And if you look at the numbering, you will
see that there are 10 bronchopulmonary segments
identified and this is what is normal in the
right lung. The left lung will typically have
two less bronchopulmonary segments. Thus,
we’re at 8. However, it may in some cases
have 9 or even 10.
Here is the left lung in its costal view.
And then, here’s the left lung in its mediastinal
view. And if you count the number of each
coloured segment here, you will see that there
are 9. But, if you look at the numbering system,
you’ll see that 10 is the maximum number
here. And it’s missing one, so this really
only shows 9, but that is within anatomic
variation. And again you can kind of appreciate
how you could surgically resect or remove
each one of these units. And so, if there’s
tumour involvement in two of the segments,
you then remove those surgically and then
you can leave the other bronchopulmonary segments
intact or in place. And each segment is supplied
by a tertiary or segmental bronchus.
The bronchi can be visualized, if necessary,
with bronchoscopy. And so, here we see a bronchoscopic
view. And we’re at the level where we can
actually see the segmental bronchi. So, here’s
a segmental or tertiary bronchus, here’s
another. Here’s one leading off here to
the left. Above at this branching point we see
some additional segmental or tertiary bronchi.
This particular slide is demonstrating an
area within a bronchopulmonary segment. This
region of tissue within the bronchopulmonary
segment is referred to as a pulmonary acinus.
Each pulmonary acinus is going to be fed by
a type of bronchiole called the terminal bronchiole.
Terminal bronchioles will branch from your
primary bronchioles. And so, this bronchiole
that we see here is a terminal bronchiole.
And the area defined within the region here
represents the pulmonary acinus. Within the
pulmonary acinus and even smaller divisions
upstream of this level, what you’ll see
is the pulmonary artery will follow the branching
pattern of the bronchus or the airway. In
this case, we’re at the level of the bronchioles.
Venous blood is going to be drained at
the periphery of this organizational unit, the acinus.