Unit D

Module 8 ~ Lesson 1

The Lymphatic System

The lymphatic circulatory system is a network of vessels with associated glands or nodes that extends throughout the body.

The lymphatic system works with the body's white blood cells to protect against pathogens. Swollen lymph nodes under the jaw or armpits can be painful and indicate that the body is fighting an intruder. This system plays a critical role in the maintenance of the body's fluid and osmotic balance. The lymphatic system is much like the venous portion of the circulatory system. It is a network of one-way vessels that collects the fluid that "leaks" from the capillaries into the interstitial (or extracellular) space between cells. It does not have a central 'pump' to circulate this fluid, so relies on skeletal muscles in the body to transport this fluid. 

Blausen.com staff (2014). "Medical gallery of Blausen Medical 2014". WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. / CC BY (https://creativecommons.org/licenses/by/3.0)


Lymph vessels are closely associated with the capillaries of the cardiovascular system. Fluid that escapes from the cardiovascular capillaries forms part of the interstitial fluid. Some of this fluid is collected in the lymphatic capillaries and is eventually returned to the blood.
The lymphatic system also works with the white blood cells to protect the body against infection. White blood cells, called lymphocytes, mature in the lymph nodes, which are the glands found throughout the lymphatic system. The lymph nodes also contain macrophages, which trap and destroy bacteria that are circulating within the body.


Read the information on the lymphatic system on pages 292 and 293 of your textbook.