thereafter to the surface of the nipple, that
that will narrow again.
The arterial supply to the breast is quite
numerous. We'll have branches from the axillary
artery. We'll have branches from the internal
thoracic artery and then we'll have contributions
from the 2nd through the 4th intercostal arteries.
Not all these vessels are shown in this particular
illustration, but let's take a moment to highlight
those for you.
Here, we have our axillary artery. Axillary
artery is divided into three parts. Part 1
lies to the medial aspect of your pec minor.
Part 2 is lying deep to the pec minor and
then the third part will continue lateral
to your pec minor. There is a slender branch
from the first part shown here. This is the
superior thoracic artery and you can see some
branches supplying the breast. Another
branch that is shown here is this one coming
from the second part. This is your lateral
thoracic artery. We see the internal thoracic
artery, in this case, the right one, traveling
along the right lateral margin of the sternum
and you can see branches supplying the breast.
And then intercostal spaces that lie deep
to the breast and the pectoral muscles will
send penetrating branches into the deep tissue
of the breast.
Venous drainage is primarily through these
three veins, the internal thoracic vein,
the lateral thoracic vein and then the intercostal
veins. The internal thoracic vein is shown
here and it accompanies the internal thoracic
artery. And so, you can see some venous blood
draining toward the internal thoracic vein.
We also have our lateral thoracic vein accompanying
the lateral thoracic artery and similarly,
you can see some of the delicate branches
that are draining blood from the lateral margins
of the breast into the lateral thoracic vein.
On the following slide about lymphatic drainage,
there is a key take-home message. That message
is, 75% of the lymph draining from the breast
will drain to the axillary lymph nodes. Those
axillary lymph nodes are located right in
through here and they are clinically said
to reside in three levels.
Level 1 axillary nodes are shown in through
here. They lie lateral to the pectoralis minor.
Level 2 lymph nodes, clinically, are said
to reside underneath the pec minor. And then
level 3 axillary lymph nodes lie medial to
the pectoralis minor. 75% of the lymph is
directed into these axillary nodes. Majority
of the lymph that isn't directed into the
axillary nodes will drain medially into the
lymph nodes that are associated with the internal
thoracic vasculature. And you see some lymph
nodes here, for example. One's right there,
one's right here. These are parasternal lymph
nodes, also known as internal mammary lymph
nodes and then some lymph from the skin of
the breast will drain into the abdominal nodes
and can also drain over into the opposite
Innervation to the breast is supplied by sensory
and sympathetic fibers that travel or are
conveyed in intercostal nerves that travel
in intercostal spaces 2 through 6. In this
particular illustration, we have our spinal
cord, we have a typical spinal nerve and then
we have our typical spinal nerve branching
into an anterior ramus. And when these anterior
rami are associated within the intercostal
spaces, these become intercostal nerves. In
addition, you have a sympathetic structure
and this is a sympathetic trunk. And there
are delicate connections from the sympathetic
trunk into your spinal nerves and their branching
pattern. And this is the way that sympathetic
fibers will get conveyed into these intercostal
A common procedure for women is a mammogram