Did you know that your body
has two circulation systems?
One, of course, circulates blood.
But the other - the lymphatic
system - also reaches into all areas
of your body to collect a clear fluid
called lymph, filter it, and circulate
it back into the bloodstream. As
part of the immune system, the
lymphatic system is crucial to
helping your body fight disease
and infection. Here's how it works.
The journey begins
When blood is pumped out of the
heart it enters the aorta, the body's
main artery. Smaller arteries branch
off from the aorta and even smaller
blood vessels branch off from
these, until the outward journey
ends at microscopically small capillaries.
Fluid that contains oxygen,
proteins, minerals, and other nutrients
seeps through the thin walls
of the capillaries into the body's
tissues to nourish them. Excess
fluid (lymph), along with bacteria,
viruses, cancer cells, and worn-out
blood cells, is picked up by nearby
lymphatic vessels for a return trip
through the body. Blood, meanwhile,
returns by way of the veins
of the cardiovascular system.
Lymph makes stops along the
way at lymph nodes, which are
essentially filtering stations that
remove bacteria, viruses, cancer
cells, and other harmful substances
from the fluid. Lymph nodes are
round or kidney-shaped and can
measure up to one inch in diameter.
Most are clustered in areas where
the lymphatic vessels branch off,
such as the neck, armpits, and
groin. However, you can also find
lymph nodes along lymphatic
vessels in the chest and abdomen
and lymphoid tissue in other parts
of the body. In fact, tonsils are actually
lymphoid tissue that helps to filter
out bacteria at the top of the throat.
A well-designed filter
Lymph nodes are well designed
for their filtering task. Each contains
a mesh of tissue in which
infection-fighting white blood
cells are packed. As lymph passes
through the nodes, it is filtered
through the mesh. Foreign substances
are trapped, attacked by
the white blood cells, and disposed
of as waste. This activity can
also trigger the rest of the immune
system to respond.
Once through the lymph
nodes, lymph travels to larger vessels
that ultimately empty the filtered
fluid into veins near the left
and right sides of the neck. From there lymph re-enters the bloodstream and the process
begins again.
What can go wrong?
Swollen or enlarged lymph nodes ("glands") can mean a
number of things, some relatively minor and some far
more serious. For example, if you have a bacterial infection
like strep throat, bacteria can accumulate in the
nearby lymph nodes of the neck faster than the white
blood cells and immune system can deal with them. This
can cause inflammation and swelling. Lymphoid tissue
itself can become infected and swollen, which is the case
with tonsillitis. In both instances, appropriate antibiotics
will almost always take care of the infection and return
things to normal.
However, sometimes an enlarged lymph node can be
of much greater concern. If cells in the lymphatic tissue
itself begin to grow rapidly and erratically, they can form
a mass of extra tissue - a tumor.
Tumors can be either benign or
malignant (cancerous). Cancer
of the lymphatic system is
called "lymphoma," and there
are several different types.
Because lymphatic tissue is
found throughout the body,
lymphoma can start almost
anywhere. As with other cancers,
early detection is the key
to a successful outcome.
A marvel of design
The lymphatic system is a network
of vessels and filters that
protects us against infection and
disease, removes excess fluid from our tissues, and even
alerts us to potentially serious health problems. As with
every other system in the human body, it's a marvel of
design and detail, working in concert with other systems
and organs as a defender of our good health.
