What are lymph nodes?

By Dr Ananya Mandal, MD

Lymph is clear or white fluid that travels through vessels, moves within tissues and work to keep all the parts of the body clean.

After passing through the channels of the lymphatic system they drain into the lymph nodes.

The lymph nodes act as filters along the lymphatic system. These nodes trap germs like bacteria, viruses, toxins as well as cancer cells and ensure that these are removed from the body. (1)

Structure of the lymph nodes

The lymph nodes, also known as nodes, are small bean shaped structures that look like tiny bulbs and lie along the lymph vessels.

Lymphocytes

The lymph nodes hold the lymphocytes, a type of white blood cell. These act as fighters against foreign invasion by bacteria, viruses, cancer cells or toxins.

The lymphocytes also help control the immune response.

This function is brought about by bringing the lymphocytes in contact with foreign materials – usually protein on the germs or toxins called antigens. Once in contact with the antigens the lymphocytes are activated. (2)

These lymphocytes originate from stem cells in the bone marrow.

Types of lymphocyte

There are two major classes of lymphocytes - B cells and T cells.

The B cells fully develop in the bone marrow while the T cells are removed from the bone marrow in an immature form when they reach other organs like the thymus where they attain maturity to fight infections and foreign antigens. (2)

What is lymph?

The lymph is a clear or whitish fluid that flows through the lymph channels.

It flows through the tiniest of the blood vessels and lymph channels called capillaries and bathe the cells in the tissues of the body.

Like clean blood that flows in the arteries from the heart lymph also it carries oxygen and other nutrients.

While returning from the tissues the lymph carries away carbon dioxide and other toxins.

If lymph is not drained adequately, it might lead to swelling.

The lymph vessels gather all the lymph and send it towards the chest.

There is a large vessel within the chest that brings the lymph into a large blood vessel near the heart.

The filtered fluid, salts, and proteins that come via the lymph channels are all deposited in the blood.

What do the lymph nodes contain?

The lymph nodes contain immune cells that can attack and destroy the germs that the lymph vessels have gathered.

The node filters fluid and substances picked up by the lymph vessels.

Where are the lymph nodes located?

The lymph nodes are located at specific sites in clusters.

For example, all the lymph channels from the fingers, palm, and hand get filtered through lymph nodes at the elbow, or at the arm pits.

The lymph channels from the toes, legs and feet drain at the nodes behind the knees or at the groin.

The channels from the face, head and scalp get filtered at lymph nodes in the neck.

There are deeper lymph nodes as well located between lungs, around the coils of the intestines etc. (3)

What organs form part of the lymphatic system?

The major organs that are part of the lymphatic system are the spleen, thymus, tonsils and adenoids.

Of these the spleen lies within the abdomen (left side under the ribs), the thymus in the chest and the tonsils and the adenoids within the back of the mouth. (4)

Cancer and the lymphatic system

Another major fact is that the lymph channels serve to spread the cancer cells throughout the body. This is called cancer metastasis and frequently occurs via travelling of the cancer cells through the lymphatic system. (2)

Edited by , BA Hons (Cantab)

Further Reading

Structure and function of lymph nodes
Swollen lymph nodes
Lymph nodes and disease
Lymph node removal

Last Updated: Dec 5, 2013

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Comments
  1. Shirlee Romanz Stern Shirlee Romanz Stern United States says:

    What does a 15mm lymph node mean?

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