BLD - In yellow we see circular organs that are lymph nodes...

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In yellow we see circular organs that are lymph nodes which line the lympaphatic vessels of the body. So you have a cardiovascular system that takes the blood pumped by your heart and it perfuses your tissues and some of the plasma from the cardiovascular blood vessels, leaks out into your tissues. The lymphatic system then drains that excess fluid and samples it. So the grey lines are the lymphatic vessels that come together at the lymph nodes and they are accumulations of lymphocytes and other immune cells and they filter this fluid searching for pathogenic materials. Eventually, all of these lymph nodes come together into a large lymphatic vessels that drains into the subcleaviane vein and that fluid gets back into the blood stream so you are maintaining homeostasis of fluid pressure in your tissues and in your blood stream. People who are immobilized will become ademitis, they will take on tissue fluid and swell because what moves the lymphatic fluid is your muscle movement. Unlike your blood vessels there is no heart to push that fluid back to the subclavian vein. There are only one way valves that prevent the fluid from moving back in the system. Peripheral infections such as pressure ulcers, with a bacterial infection in them. Your spleen is also a secondary lymphoid tissue, along with the adenoid and tonsil. Lymphoid like tissue that’s imbedded around the intestine and Peyer’s patch (in the small intestinal wall) are also secondary lymphoid tissues. Distinction between a primary and secondy lymphoid tissue is the status of the lymphocytes within them. Primary are where lymphocytes develop. B lympocytes and T lympocytes are being replaced on a daily basis. B lympocytes are completely developed in the bone marrow, primary lymphoid tissue for B lymphocytes. T lymphocytes are educated in the thymus, they leave the bone marrow as immature lymphoid progenitors then they undergo the process of developing their T cell receptors in the thymus, so the thymus is considered the primary lymphoid tissue for T lympocytes. The red tissues are primary lymphoid organs. Everything in yellow is a secondary lymphoid tissue, where B and T cells are activated by the pathogen they are capable of responding to. The vast majority of them present in the lymphnode (secondary) are naïve, one that has never seen its antigen yet. ------------------------------------------------------------------------------------------------------------ The process is that naïve lymphocytes arrive at a lymph node via arterial circulation. So as the arteries break down into capillaries, lymphocytes that are naïve are specifically recruited to crawl into the lymph node. Only lymphocytes can do this! On a daily basis every lymphocyte leaves the the lymphnode tissue it was in, drops into the lymphatics, goes into blood circulation then enters a lymphnode somewhere else in the body. This is important because the first time your body is exposed to any pathogen you have a handful (1 to 10) lymphocytes that are capable of responding to that pathogen. If
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BLD - In yellow we see circular organs that are lymph nodes...

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