All right, next up, we're going to
talk about the lymphatic system.
It turns out the lymphatic system
is composed of over 400 lymph nodes
scattered throughout the
body in different regions.
I promise you, we're not going to go
through every one of those 400 lymph nodes.
We're going to go through
a couple specific regions.
It turns out that only about 100 of those lymph
nodes are even palpable under normal circumstances.
The majority of them are buried deep
within the thorax or in the abdomen
and can really only be visualized
with radiologic imaging.
The second thing I'll say about the lymphatic
system is that all those lymph nodes are draining
in very predictable ways, draining
back into the venous system ultimately.
So the left side of the body, for the most part,
is going to drain into your left sided subclavian
and internal jugular vein on the left.
And the right side of your body is going to
drain into the equivalent vessels on the right,
with a very important exception
involving the lower half of the body,
which we'll come to later.
But first off, if we're having a patient who
had, let's say, an upper respiratory infection,
we would start off by examining
the head and the neck lymph nodes.
So let's jump into those systems now.
So first place we'll start off with
is looking underneath the mandible.
So we're going to feel the lymph
nodes underneath the mandible here.
Then we'll move on to the
anterior cervical chain.
These lymph nodes are going to be felt just
in front of the sternocleidomastoid muscle
and we'll actually dive deep to
the sternocleidomastoid muscle.
Then we have posterior cervical chain lymph nodes.
These are going to be felt behind
their sternocleidomastoid muscles.
We have preuricular lymph nodes.
We have posterior auricular lymph nodes as well.
And lastly, we have occipital lymph
nodes back here at the occiput.
All those lymph nodes on the left side of the face are
going to drain into the left internal jugular vein.
So now let's move on and take a look at the arms.
So with the upper extremities, there's only really two
significant places you're going to find lymph nodes.
You're going to start off,
if I may have your hand on.
You're going to find what's called
the epitrochlear lymph nodes.
These are located just proximal and
anterior to your medial condyles.
You can feel it.
You could feel the area where they
would be if they were inflamed,
sort of at the base of the biceps muscle
or brachioradialis muscle down here.
You can imagine that if somebody had an acute
paronychia or cellulitis in the forearm,
this is where you might find evidence
of inflammation and infection.
The next place is the axilla.
Now, we'd like to think of the axilla
or the armpit as a box with an anterior,
posterior, a lateral and medial side, and
I'd like to examine each side in order.
So I'm going to start off by first examining the
medial side or the side that's abutting the chest wall,
then the anterior side, which is where
you're going to feel the pectoralis muscles
and you're looking for lymph
nodes buried in that area.
Then the lateral wall underneath
where the humerus is inserting
and then the posterior wall where the
latissimus dorsi muscles are located.
So that's the entirety of the
axilla and the epitrochlear nodes.
Those nodes are also going to drain directly
into your left subclavian on this side
and your right subclavian onto the other side.
Now, let's move off and start
examining the lower extremities.
So a moment ago, we talked about
how the left side of the body
in general is going to drain into your
left IJ and and left subclavian vein as well.
And the right side will drain
into the contralateral side.
The exception starts with the legs.
And so it turns out that both
the left leg and the right leg,
lymphatic system is going to converge
into something called the chyle cistern,
which is just to the right of the aorta.
And then that's going to form
the start of the thoracic ducked.
The thoracic duct is going to march all
the way up in the retroperitoneal space.
Ultimately, it's going to converge in one
place in entering into the left subclavian.
And along the way, it's taking the
lymphatic drainage from the entire abdomen
and most of the lymph lymph
nodes in the chest as well.
So the bottom line is that while everything else
is pretty symmetric with the upper extremities
draining to both sides and the left and right
side of the head draining to both sides,
the legs in the abdomen are exclusively
draining via the thoracic duct
into one place on the left side.
And that has some significance when we
think about different cancers in the abdomen
manifesting with left-sided lymphadenopathy,
particularly in the supraclavicular space.
But let's take a look at the
lymph node regions in the legs.
First, there's really only two spots in
the legs that we look for lymph nodes
and they're both in the inguinal region.
There's a horizontal field and a vertical
field for the inguinal lymph nodes.
So let's take a look.
So the inguinal lymph nodes of the horizontal
plane, if I'm going to just pull this down here,
basically run along the inguinal ligament.
They're going to run from about the anterior
superior iliac spine towards the pubic symphysis.
And in this area, you can palpate
that strand of the inguinal ligament.
As you're going down, you're looking for any
swelling, any swollen lymph nodes in those areas.
Oftentimes in this horizontal
chain, which is draining the groin,
you may find what's called "shotty
lymphadenopathy", which refers to buck shot,
which is the little pellets
that are inside a shotgun shell.
And it's very common and has no really
significant pathology associated with it.
The next part of the lymphatic drainage system
of the leg is actually the vertical chain.
Now, the vertical chain is best demonstrated here.
It actually runs along the saphenous
vein, the greater saphenous vein.
And this is actually what's draining the leg.
The horizontal chain is draining the groin.
The vertical chain is going to drain the leg.
And that would be palpated if it was going to
be present along the greater saphenous vein
in this location here.
So that's the lymphatic drainage for the legs.
And again, they're going to converge form the
thoracic duct with the abdominal and fat lymph nodes
and head all the way up to the insertion of
the thoracic duct in the left subclavian vein.
So having talked about the different
regions where we can find these lymph nodes,
let's talk about some of the things we're
looking for when we find a lymph node.
What are the features that are going to distinguish
between a pathologic concerning lymph node
for something that's more benign or associated
with a transient problem like an infection?
So if I were to find a lymph node here on
Sean's neck in the anterior cervical chain,
I'm going to be looking for a
couple significant properties.
How big is the node?
I know that's less than 1 or 2 centimeters in size.
It's not something I'm going
to be very worried about.
Is it symmetric?
If I'm finding lymph nodes scattered
throughout multiple fields on both sides,
that may be concerning.
If somebody has a breast lump and I find lymph
nodes just in the axillary chain on one side,
that would be concerning as well.
So thinking about sometimes asymmetry is
important, sometimes symmetry is important.
The next feature is whether it's mobile or not.
If I find in his axilla, for example, a
lymph node that is 2-3 centimeters in size
and it's fixed to the deeper
tissues, that is I can feel it,
It's firm, it's rubbery, and
I can't really move it around.
It's as if it's fixed in place.
That is a very significant feature
that may suggest something like cancer,
for example, particularly in
the axilla of breast cancer.
And the last feature is really is it tender or not?
Typically, if somebody has, for example, strep
throat with an acute infectious pharyngitis,
I may find multiple lymph nodes
in these anterior cervical chains.
And the characteristic feature that the patient
would tell me is that they're really painful
and certainly tender to the touch.
So tender lymph nodes more likely
to be infectious in origin,
nontender lymph nodes, I'm more
worried about some indolent process.
And the patient will also tell me in
terms of the timing of these lymph nodes,
if they developed over the span of a few days,
in the setting of a fever in pharyngitis,
I'm not going to be as worried about
them compared with the lymph nodes
that the patient reports have been slowly
growing over the span of weeks to months.
So that really summarizes the key features
we're looking for once we find some lymph nodes
anywhere in the body.