What is Lymph?

Mary McMahon
Mary McMahon

Lymph is a clear to yellowish watery fluid that is found throughout the body. It circulates through body tissues picking up fats, bacteria, and other unwanted materials, and filtering them out through the lymphatic system. It is sometimes possible to see this fluid; cuts sometimes weep it rather than blood, for example. Its circulation through the body is an important part of immune system health.

The lymphatic system, shown in green.
The lymphatic system, shown in green.

This fluid contains white blood cells, known as lymphocytes, along with a small concentration of red blood cells and proteins. It circulates freely through the body, bathing cells in needed nutrients and oxygen while it collects harmful materials for disposal. People can think of it as the milkman of the body, dropping off fresh supplies and picking up discarded bottles for processing elsewhere.

Lymph nodes in the head and neck.
Lymph nodes in the head and neck.

As lymph circulates, it is pulled into the lymphatic system, an extensive network of vessels and capillaries that is linked to lymph nodes, small nodules that act as filters to trap unwanted substances. The nodes also produce more white blood cells, refreshing the fluid before it is pumped back into the body. The fluid may not be as showy as blood, but it is related to an equally complex and ornate system of vessels.

Swollen legs may be a sign of lymphedema.
Swollen legs may be a sign of lymphedema.

Lymph also explains why things like intramuscular shots at the doctor's office work. When a medical professional injects a substance into muscle tissue, it is picked up by the fluid and then slowly filtered into the bloodstream. When people wear tight clothing or their circulation is otherwise impeded, fluids can build up in the tissue, causing edema, a condition that can be both painful and dangerous. Edema happens when lymph cannot circulate to pull these fluids out.

White blood cells called lymphocytes are a major part of the lymphatic system.
White blood cells called lymphocytes are a major part of the lymphatic system.

The lymphatic system can sometimes be used as a diagnostic tool to help doctors understand disease. Lymph nodes can be biopsied, for example, to collect evidence about bacterial agents and toxins in a patient's body. Some types of bodywork are also designed to promote the healthy circulation of lymph to encourage drainage and healthy tissues. Lymphatic massage and other types of bodywork require special training, as a massage therapist can inadvertently cause lymphedema, a collection of fluid in a limb, which can become dangerous and extremely painful.

A message therapist will require special training in order to perform a lymphatic massage on patients.
A message therapist will require special training in order to perform a lymphatic massage on patients.
Elevating the feet may help reduce lymphedema in the legs.
Elevating the feet may help reduce lymphedema in the legs.
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments

anon929707

Is lymph tissue fluid, then?

anon200440

excellent site! found heaps of the information i needed for a school assignment, and even found some cool facts on lymph.

anon180628

The lymphatic system does not have a pump to circulate it, as the circulatory system. Lymph relies on the contraction of surrounding skeletal muscle to move it, and valves to prevent it from backing up.

anon158291

How is the lymph circulated without the use of a pump or contraction?

anon155969

where is the auricle located and what is it?

anon147261

How does it work, though?

anon140472

Wow. That really made me understand the whole lymph system and how everything works. Thanks!

anon101172

informative and helpful.

anon94618

Very good info for medicos like me. Thank you.

anon90977

Amazing article. It helped with my homework!

anon83299

Fine article.

anon70768

found it very helpful.

anon59563

Very informative. Thank you.

anon37660

for a lot of days i was confused about what lymph was but after reading this have well understood. Thank you.

anon28697

Great article very informative and accurate! Thank you! You helped me with my homework!

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