Andrew, Warren Department of Anatomy, School of Medicine, Indiana University, Bloomington, Indiana.
Last reviewed:April 2019
Show previous versions
- Comparative anatomy
- Lymph vessels
- Lymph nodes
- Lymph flow
- Links to Primary Literature
- Additional Readings
A system of vessels in the vertebrate body, beginning in a network of exceedingly thin-walled capillaries in almost all the organs and tissues, except the brain and bones. The lymphatic system is a one-way vascular network in vertebrates that works in parallel with the blood circulation (Fig. 1). It drains interstitial fluid from most of the body's organs, with the exceptions of bone marrow, the retina, the central nervous system, and some avascular tissues (the cornea, cartilage, hair, nails, and epidermis). The interstitial fluid, which is rich in protein, must be removed, or swelling (edema) will occur. When the drainage function of the lymphatics is disturbed, serious swelling can occur; this condition is called lymphedema. When working normally, though, the lymphatic network is drained by larger channels, mostly coursing along the veins and eventually joining to form a large vessel (the thoracic duct), which runs beside the spinal column to enter the left subclavian vein at the base of the neck. The lymph fluid originates in the tissue spaces by filtration from the blood capillaries. While in the lymphatic capillaries, it is clear and watery. However, at intervals along the larger lymphatic vessels, the lymph passes through spongelike lymph nodes, where it receives great numbers of cells—the lymphocytes—and becomes turbid. With the exception of the capillaries, the lymphatic vessels contain numerous valves preventing backflow of the lymph (Fig. 2). In addition to fluid drainage, the functions of the lymphatic system are to remove particulate materials (for example, molecular proteins and bacteria) from tissues, to transport fat from the intestine to the blood, and to supply the blood with lymphocytes (the chief cells of the immune system, including T cells arising from the thymus and B cells produced in the bone marrow). The formation of new lymphatic vessels is termed lymphangiogenesis. See also: Blood vessel; Circulation; Edema; Immunology; Lymphangiogenesis; Vascular disorders
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 9000 highly qualified scientists and 43 Nobel Prize winners.
MORE THAN 8500 articles and Research Reviews covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information