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March 12, 2010 at 9:45 PMComments: 37 Faves: 2

What Organs Make Up Your Immune System?

By Smarty More Blogs by This Author

You probably know that your heart pumps blood. You may even know that the kidneys filter the blood and create urine. But do you know what your spleen does? Did you know you have an organ called a thymus? These last two organs, along with lymph nodes, bone marrow, and other tissues are all important parts of the immune system.

Bone Marrow

While bone marrow isn't considered an organ, it is vital to the immune system and shouldn't go unmentioned. Bone marrow is a tissue that lies inside most of your bones. It creates hematopoietic stem cells through the process of hematopoiesis. These stem cells differentiate into all sorts of blood and lymphatic cells - such as red blood cells, white blood cells, platelets, immature thymocytes, B cells, etc. - in response to hormones released by cells which make up the bone marrow. Some cells of the immune system mature in the bone marrow, and some travel to other areas of the body to complete their maturation.


The thymus is a small, butterfly-shaped organ that lies between your breastplate and your heart. You probably haven't heard of it because, after adolescence, it doesn't do much. It is fully developed at birth and grows until puberty, after which it becomes fatty and shrinks to about 15% of its maximum size. During its most active time, the thymus is responsible for directing the maturation of immature thymocytes into T cells. T cells are the managers of the immune system, instructing other cells how to react to foreign substances. During this maturation in the thymus, T cells learn to differentiate between "self" (the body's own cells) and "nonself" (foreign objects, organisms, or diseased cells). If a T cell thinks a self cell is foreign, it is destroyed, as it could cause the effects of an autoimmune disease if allowed to leave the thymus.


The spleen performs several functions; it filters the blood, destroying old or damaged blood vessels. It also contains many specialized cells (e.g. T cells) of the immune system that look for foreign particles as blood circulates. T cells also receive information from migratory dendritic cells and macrophages, which ingest foreign microorganisms and present their pieces to T cells. If a T cell recognizes a presented particle as foreign, it instructs a B cell (which also recognizes the particle) to create antibodies against it.

Lymph Nodes

Lymph nodes are a bit like the spleen, but instead of filtering blood, they filter lymph. Lymph is composed of fluids which drain from tissues. It is collected at various locations throughout the body and circulates through a series of lymph nodes, eventually returning to the blood for circulation. Unwelcome microorganisms enter the lymph nodes either by circulating with lymph or by ingestion by a cell that then travels to the lymph node. Lymph nodes contain the same specialized cells found in the spleen, which sample the incoming particles and respond accordingly. These important organs make up the framework of the immune system, providing meeting locations for specialized cells to communicate.


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  • very good

  • I know people can live without their spleen, does it make you more prone to impaired immune function?

  • this freakin sucks!!! :) BIG TIME! Only nerds can understand this crap.

  • Immune system is a movie n T helper cell is the director with co director B cell while T killer cell and macrophages are the heros to kill the vilon(forghn particl)


  • :)

  • sup dog

  • thank you! really helps my science home work :D

  • I need to find simple organs in the immune system

  • How You Doin!!!!?????

  • thats all the organs they have ??

  • i love science

  • Wow, from the response you would think that people are no longer worried about autoimmune diseases. Great blog! I always wondered what my spleen does. This gave me a very concise picture. Thanks Hellolife

  • Who sponsors this website?

  • @Meagan - the company HelloLife LLC does - check out the "about" link in the footer.

  • This was sooo sxux braah best info out

  • That was beautiful. absolutely potato egg sandwich in my pants. :3

  • im happy they have sites with this sort of info or i would have failed pe theory already :)

  • this stuff is in the lymphatic system

  • if thymus is not most important in adolesence then what about "T cells" in thymus and their function?

  • Really good, but i was wondering if there are multiple systems with the same parts. For example the reproductive and urinary systems have a lot of the same parts.





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  • Hi Kara

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  • hey rex do u know that song called wiggle its the best

  • I had an appointment with a oncologist this morning as the cardiologist sent me to him to make sure the lymph nodes in my neck that showed up a little swollen in my ultrasound were no danger to me he turns out I'm alright but they will keep a close watch ,they especially watch for signs of cancer so far I'm a happy camper I love the information on this site: thank you

  • Great read, about the immune system.

  • Sup dawgs

  • Our environment can be toxic also.

  • hi people

  • hi joel hannimen

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