>>Dr. Ketchum: In this lecture video, we will learn about the lymphatic system. The lymphatic
system is really cool, but we do not get to spend a lot of time on this system. So I have
included a video link here if you want to learn more about this system. I know that
some of you have heard about lymphoma, right? If so, you will definitely want to watch this
video. This video is not required; it’s just an FYI. To understand the lymphatic system,
you need to know the players in this organ system. Several of these players include the
immune cells. This little guy here is called a lymphocyte. This is a type of white blood
cell that aids in a immune response. So when you think about your tonsils, for example,
you have a lot of lymphocytes stored in your tonsils, and they remain there until you have
an infection. At that point, these lymphocytes are released and enter into circulation to
do their job. What is their job, you ask? They will kill or assist in killing invaders
that have, for a lack of a better term, invaded your body. Let’s say, for example, that
you were bit by a mosquito, and during its blood meal it injected the virus that causes
West Nile virus into your body. You see, most people think of mosquitos as bloodsuckers.
That’s true; but in order to do that, they also have to spit anticoagulants and antihistamines
into your body. Thus, the virus is injected into your body. Your body has been invaded;
now the lymphocytes have a job to do. Their goal in life is to kill or assist in killing
that invader. You will learn more about how these lymphocytes do their job when we discuss
the immune system.
The other immune cell that serves as a player in the lymphatic system is this cell here,
called a macrophage. Macrophages, like lymphocytes, are also white blood cells. Macrophages are
housed in the lymph nodes, as well as other places throughout the body.
But in this video, we will only focus on their role in the lymph nodes. All cells have a
job, right? Macrophages are phagocytes; so their job is to engulf invaders of the body
and kill them. So the two immune cells important in the lymphatic system are lymphocytes and
macrophages. The next players in the system are the vessels.
In this diagram, the green structures represent the lymphatic system. The lymph nodes are
connected to lymphatic vessels, and the lymphatic capillaries are an example of a lymphatic
vessel. There are many other vessels, but we are not going to worry about their names.
Here is the lymphatic vessel, a lymphatic capillary, and a lymph node.
The last player in the lymphatic system is the fluid called lymph. Simply stated, the
lymph is the fluid that is within the lymphatic system. The diagram I showed you before was
a simplified version of the lymphatic system, but this is what is really looks like. The
most obvious part of the lymphatic system are your lymph nodes. When you are sick, you
can squeeze your neck right below the jawline to feel your cervical lymph nodes. That’s
what doctors are doing when they squeeze your neck; they are checking for swollen lymph
nodes, which may indicate infection. But we have lymph nodes in other places as well.
We have them in our axillaries (our armpits), all up and down the abdominal cavity, and the
inguinal area. So all of these little things here that look like swellings—these are
all lymph nodes. Check them all out, they are really important. Lymph nodes are not just
important in bacterial and viral infections. Cancer can spread to lymph nodes. The lymph
nodes in the axillaries is one of the first places breast cancer is likely to spread.
Let me tell you a true story. I had a 20 year-old student that came to me one day and said,
“Dr. Ketchum, I don’t know what to do. One of my testicles hurts REALLY bad.” I
immediately told him to see a doctor. He did, and he was diagnosed with testicular cancer.
They believe the cancer was confined to one of the testicles, so they removed that testicle.
Several months later, doctors were concerned that the cancer had spread to his lymph nodes.
So my student went in for surgery, and they removed his lymph nodes throughout his thoracic
and his abdominal cavity—just scraped them out of there in hopes that if the cancer had
spread to his lymphatic system, they would get all of the cancer. My student is doing
fine now, and has four children. [laughs] A story with a happy ending.