Health Advice



Wondering what your lymph nodes have done for you lately?

Robert H. Shmerling, M.D., Harvard Health Blog on

Published in Health & Fitness

Here’s a question you may not have been asked lately: what do you know about lymph nodes?

If your answer is “not much,” you’re not alone. But even as our lymph nodes maintain a low profile, they’re working around the clock to deal with potential health problems ranging from common viruses to deadly bacteria and even cancer.

Read on to learn more about these workhorses of the immune system as they stand guard against outside invaders and rogue elements within our bodies.

What are lymph nodes?

Your lymph nodes are one part of the immune system that helps defend the body against health threats. These bean-shaped, pea-sized mounds of tissue form a network of clusters throughout the body. They filter lymphatic fluid (lymph), a white-yellow fluid that originates in the bloodstream.

The human body has hundreds of lymph nodes. They’re most plentiful — and most noticeable — in the neck, armpits, and groin. They’re also abundant in the chest and abdomen, where they’re observable by imaging tests such as CT or MRI scans.


Sometimes, lymph nodes are called glands (as in: “when I had mono, I had swollen glands in my neck”), but that’s not really accurate. Glands such as the thyroid gland produce hormones or other chemicals that have effects elsewhere in the body. That’s not what lymph nodes do.

How does lymph reach our lymph nodes?

Lymph is created when plasma, the liquid part of blood, seeps out of tiny blood vessels and flows into connecting channels that link lymph nodes throughout the body. These connecting channels are known as the lymphatic drainage system.

After lymph passes through lymph nodes, it eventually returns to the bloodstream through lymphatic channels.


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