Anatomy, Lymphatic System

Excerpt

The lymphatic system, or lymphoid system, is one of the components of the circulatory system, and it serves a critical role in both immune function and surplus extracellular fluid drainage. Components of the lymphatic system include lymph, lymphatic vessels and plexuses, lymph nodes, lymphatic cells, and a variety of lymphoid organs. The pattern and form of lymphatic channels are more variable and complex but generally parallel those of the peripheral vascular system. The lymphatic system partly functions to convey lymphatic fluid, or lymph, through a network of lymphatic channels, filter lymphatic fluid through lymph nodes and return lymphatic fluid to the bloodstream, where it is eventually eliminated. Nearly all body organs, regions, and systems have lymphatic channels to collect the various byproducts that require elimination. Liver and intestinal lymphatics produce about 80% of the volume of lymph in the body.

Notable territories of the body that do not appear to contain lymphatics include the bone marrow, epidermis, as well as other tissues where blood vessels are absent. The central nervous system was long considered to be absent of lymphatic vessels until they were recently identified in the cranial meninges. Moreover, a vessel appearing to have lymphatic features was also discovered in the eye. The lymphatic system is critical in a clinical context, particularly given that it is a major route for cancer metastasis and that the inflammation of lymphatic vessels and lymph nodes is an indicator of pathology.