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The Lymphatic System

This week in our organ system section we are going to take a look at the lymphatic system.

The lymphatic system is a system of vessels and organs that return lymph from tissue back to the bloodstream. It regulates the balance of fluids in the body and filters pathogens out of the blood.

Lymph is a fluid that is made from the filtration of plasma, this is the interstitial fluid. Lymph flows dye to the movement of the body as well as the pulsation of arteries and the contraction of muscles. Lymphatic vessels contain valves to prevent the backflow of lymph. Within the lympahtic system, there are different immune cells as well as primary and secondary lymphatic organs.

Lymphatic vessels are located all over the body, especially around the great vessels, groin, and armpit. The average human has 450 lymph nodes, these are secondary lymphoid organs. These nodes contain lymphocytes which are immune cells. If these cells find a foreign microorganism in the lymph the immune cells will begin an immune response to prevent harm from spreading in the body.

Lymphocytes arise from stem cells in the primary lymphoid organs and are a part of the acquired immunity of the immune system. The main cells in this category are B lymphocytes, T lymphocytes, and natural killer cells. They develop a specific immune response to foreign particles.

The primary lymphoid organs are the thymus and the bone marrow. B cells mature in the bone marrow. T cells arise from stem cells in the bone marrow by mature and differentiate in the thymus.

The secondary lymphoid organs include the spleen, tonsils, lymph nodes, and appendix. Once the cells have matured they travel to these secondary organs to prepare for working in immunity.

Fun fact! Lymph nodes contain particles of tattoo ink! If you have a tattoo on your arm, we can determine the colour of your tattoo just by looking at the lymph nodes in your armpit!


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