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The Lymphatic System: Structure and Function

Tap a term to see its role in the lymphatic system.

Lymph

A clear fluid derived from excess fluid that leaks out of blood vessels into surrounding tissue, which the lymphatic system collects and eventually returns to the bloodstream.

Lymphatic Vessels

A network of thin vessels, similar to blood vessels, that transport lymph throughout the body, relying primarily on muscle movement rather than a central pump like the heart to keep fluid flowing.

Lymph Nodes

Small, bean-shaped structures distributed throughout the body that filter lymph fluid, trapping and helping destroy bacteria, viruses, and other harmful substances before the fluid returns to the bloodstream.

Spleen

The largest organ of the lymphatic system, located in the upper left abdomen, which filters blood directly, removes old or damaged red blood cells, and helps the body respond to infection.

Thymus

A gland located behind the breastbone where immune cells called T-cells mature before being released to help defend the body, with the organ generally shrinking in size and activity after childhood.

Role in Fluid Balance

Beyond immune function, the lymphatic system plays an essential role in maintaining proper fluid balance throughout the body, preventing the buildup of excess fluid in tissues that can otherwise cause swelling.

A drainage system working closely alongside the immune system

This page is for general educational information only and is not a substitute for professional medical advice. Unlike the circulatory system, which has the heart as a central pump, the lymphatic system relies on the natural movement of surrounding muscles to circulate fluid, which is part of why regular physical movement is often considered beneficial for lymphatic health.

Frequently Asked Questions

Why do lymph nodes sometimes swell when a person is sick?

Swollen lymph nodes are generally a sign that the lymphatic system is actively working to fight an infection, as immune cells within the nodes multiply in response to the presence of bacteria, viruses, or other threats being filtered out.

Can a person live without a spleen?

Yes β€” while the spleen performs important immune and blood-filtering functions, other organs, primarily the liver, can take over many of its roles if it is removed, though a person without a spleen may have a somewhat higher risk of certain infections.