The Lymphatic System, 1652 – Both alarm and defense

Dr David Weissmann praises the defensive power of the body’s lymphatic system when he writes, "Lymph nodes are a combination of a burglar alarm and West Point (the Military Academy)". Like burglar alarms, they are alert to foreign antigens. Like West Point, the nodes train an elite militant group: lymphoid cells that respond to intruders by making antibodies and form a population of B and T cells that will remember the intruder’s signature for years.

The lymphatic system includes a network of vessels, nodes and organs that:

1. Form part of the immune system (to protect the body from invaders such as bacteria);
2. Absorb excess fluid from body tissues and return it to the bloodstream; and
3. Facilitate the absorption of dietary fat in the tiny villi (finger-like projections) of the small intestine.

Lymphatic vessels, through which clear lymph fluid circulates, contain a one-way valve system that helps direct fluid from body tissues to the left and right subclavian veins (blood vessels near the collarbones). Before lymph fluid enters the bloodstream, it passes through small, bean-shaped lymph nodes containing T lymphocytes and B lymphocytes (white blood cells) to help destroy and filter out bacteria. Because the lymphatic system is closely associated with almost all body tissues, it sometimes spreads cancer cells. Lymph nodes can also trap cancer cells, but if they cannot destroy the cells, the nodes may become tumor sites.

The spleen, located in the abdomen, is part of the lymphatic system and is a site of lymphocytes that engulf pathogens. The thymus gland, located in the chest, controls the development and maintenance of T lymphocytes. The lymphatic system also includes the bone marrow, where B cells mature, and the tonsils.

In 1652, Danish physician Thomas Bartholin published a comprehensive description of the human lymphatic system and coined the term lymphatic vessels. At around the same time, Swedish scientist Olaus Rudbeck made similar discoveries.

Description of the article image: Part of the lymphatic system (green), with the spleen at the lower right.

Historical figures mentioned in the article: Thomas Bartholin (1616–1680), Olaus Rudbeck (1630–1702)

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