Now, let’s take a look at the subclavian artery.
And again, we’ll have a right subclavian;
we’ll have a left subclavian. It’s going to
issue some branches that help to supply the
thorax. Those branches are the internal thoracic,
also known as the internal mammary artery.
And there are two trunks that will issue from
each of the subclavian arteries. We have a
costocervical trunk and we have a thyrocervical
trunk. Any time you hear the word “trunk”
being utilized with the circulation, it is
in reference to an arterial structure, so
we never have to designate it as being an artery.
This slide captures the internal thoracic
artery. There’s an internal thoracic artery
that’ll issue from the right subclavian and
there’s a left internal thoracic artery that’s
going to issue from your left subclavian.
If we take a look at the illustration, here
is the right internal thoracic artery, also
known as the internal mammary artery. It is
traveling along the lateral border or margin
of the sternum. The left internal thoracic
artery or mammary artery is doing the same
on the left margin of the sternum. There are
several branches that will issue from the
internal thoracic, but its two terminal branches
are occurring right here, where we have the
musculophrenic and then, the one that courses
more vertically and medial to the musculophrenic
will be the superior epigastric artery. The
internal thoracic artery will help supply
the anterior intercostal spaces with anterior
intercostal arteries. The branches that come
off the internal thoracic will help supply
the first six intercostal spaces anteriorly.
And then the musculophrenic that comes off
the internal thoracic will help supply anterior
intercostal arteries to intercostal spaces
7, 8 and 9. We do not have anterior intercostal
spaces that would correspond to space 10 and
11. Those are fed solely by the posterior
intercostal arteries. In addition, there is
a pericardiacophrenic artery that will help
supply the phrenic nerve, the pericardium,
pleura. Also help to supply the diaphragm.
The superior epigastric artery will assist
in the arterial supply of the anterior abdominal region.
The costocervical trunk, the branch that we’re
interested in as it relates to the thoracic
region, is the supreme or highest intercostal
artery. Here, we can see the costocervical
trunk coming off the subclavian on the right
side. There would also be one on the left.
It will then issue the supreme or highest
intercostal artery and then this will branch
and supply the first two intercostal spaces.
And the branches of the supreme intercostal
artery that do that are referred to as the
first two posterior intercostal arteries.
By traveling within the first two intercostal
spaces, back structures are supplied. The
serratus anterior muscle receives partial
distribution from this vascular system. The
pectoral muscles anteriorly receive some arterial
supply and then the breast region will also
receive some of its arterial distribution
through this branching pattern.
The thyrocervical trunk is the last arterial
component to take a look at as it relates
to the subclavian artery. We see the left
thyrocervical trunk here. The right thyrocervical
trunk is seen here and it has several branches.
But, the branches that we’re interested in
as it relates to thoracic structures will
be the esophageal branches that we see from
the inferior thyroid. Right here: There’s
the esophageal branch on the right one. Here’s
the inferior thyroid from the thyrocervical
trunk on the left giving rise to its esophageal
branch. So, these esophageal branches will
supply the first part of the esophagus and
that is the cervical esophagus.