Welcome to this lecture on arteries and veins
of the thoracic cavity.
This slide lists the objectives that you,
as a learner, should be able to answer at
the conclusion of this lecture.
First, describe the arteries of the thorax,
the parent vessels that issue them and then
List the parts of the aorta found in the thorax.
Describe the normal and variant branching
pattern of the aortic arch.
Describe the veins of the thorax, the vessels
they empty into and the territory that they drain.
And then, we’ll move to the summary slide
and identify the key take-home messages.
And then lastly, we’ll provide attribution
for the images that are used throughout this
This is our body map and we’ll be focused
on the thoracic area and the arteries that
lie within and are distributed to the thorax.
And here’s a posterior view as well as to
the area or region that we’ll be covering.
We’re going to begin with the arteries and
the two arteries of interest will be the pulmonary
trunk, which we see here issuing from the
right ventricle and then we have the aorta
as a very close neighbor.
So, a little bit about the pulmonary trunk;
I don’t have to say a whole lot, it’s not
very complicated. Here, again, is our pulmonary
trunk, receives blood from the right ventricle
so that it can be delivered to the lungs.
The pulmonary trunk will divide into two pulmonary
arteries. This is our left pulmonary artery.
And then, diving underneath the arch of the
aorta is the right pulmonary artery and then,
we can see it reappear just to the right of
the superior vena cava.
Now, we’re going to shift to the aorta, the
systemic circulation. The aorta has three
parts that you should be familiar with. It
has an ascending portion that we see right
here. It’s receiving blood from the left ventricle.
The aorta then will arch superiorly and then
will course posteriorly and to the left of
the midline and as it does so, it becomes
the descending aorta and we see it running
behind or posterior to the heart. The descending
aorta can be subdivided into a thoracic segment
that’s running within the thoracic cavity
and then it’ll pass behind the aortic hiatus
of the diaphragm and then will enter the abdominal
region and become the abdominal segment of
the descending aorta.
When we look at the branching pattern of the
aorta, we’ll look at it in its various parts
and so, we’ll begin with the ascending aorta.
And there are only two arteries that are going
to issue from the ascending aorta and those
are the arteries that supply the heart. Here,
we have the right coronary artery and you
can see where it issues from the aorta. And
there’s a dilatation at this point in the
root of the aorta called the sinus of Valsalva.
Similarly, we have the left coronary artery
issuing from the ascending aorta and there
too, is a dilated portion of the aorta called
the left sinus of Valsalva. The coronary circulation
is described in another lecture and that lecture
is titled “The Heart”.
So, that’ll now bring us to the next part
of the aorta and here, we’re going to focus
on the aortic arch and its normal branching
pattern. And that is demonstrated in the illustration.
Here is your arch running from here to here.
This, then, is the descending aorta. That
continues distally. The first branch of the
aortic arch is the brachiocephalic trunk and
then, it will divide into a right subclavian
artery and a right common carotid artery.
The next branch is the branch that we see
here. This will be the left common carotid
artery. The common carotid arteries will supply
the neck, the head and the brain with the
branches that issue distally from them. And
then the last branch that we have is the left
subclavian artery. The left subclavian and
right subclavian arteries will subserve some
structures in the inferior part of our neck,
will also issue some structures that do supply
the thoracic wall and then will continue and
are the major arterial suppliers of the upper
extremities. The aortic arch is an area of the circulation
that is subject to variations in the branching
pattern. And we see some variations on this
particular slide. Panel B, as we see here,
shows your brachiocephalic trunk and then
here’s your right common carotid artery. And
they are issuing from the same opening within
the aortic arch, so they have a common origin
in this variation. This occurs in about 13%
of the population. Panel C shows yet another
type of variation in the branching pattern.
Here, there’s a common stem and this common
stem will give rise to your right subclavian,
your right common carotid and then this happens
to be your left common carotid. And lastly,
we would have the left subclavian artery branching
off the arch. This occurs in about 9% of the
population. Panel D is a variant pattern that’s
seen in about 3% of the population. Here we
have four branches: brachiocephalic, left
common carotid. This slender branch is the
additional branch, the fourth branch; this
is the left vertebral artery. And then our
last branch is our left subclavian. The most
unique variant is the last image that we see.
Here, we have our right common carotid being
the first branch of the aortic arch. We have,
then, our left common carotid artery. This
is the thyroid ima artery. Here is your left
subclavian artery and if you’re keeping track,
we have not identified the right subclavian artery,
because that is the last branch now
that is coming off the aorta and the right
subclavian is issuing from the aorta on the
left side and it has to make its way to the
right side of the body. And it typically will
do that by passing behind the esophagus, becoming
retroesophageal, or it may run behind the
trachea, thus retrotracheal, in order to assume
its more normal course on the right side of
the body. A very infrequent pattern, but one
I have personally been able to see on some
occasions. It’s an impressive variation.