Massage Therapy Journal Winter 2024

Winter 2024 • 37

vascular system provides the transportation network for tissue fluids, proteins, fats and cells. This system is further subdivided into primary and secondary organs , each of which have their own role in immunity. The primary lymphatic organs are bone marrow and the thymus. The secondary lymphatic organs are the spleen, mucosa associated lymphatic tissue (MALT), and the lymph nodes. Understanding the Primary Lymphatic Organs Bone marrow is found in the short flat bones of the body, such as the vertebrae, sternum and pelvis. This is where lymphocytes (lymphatic cells) are produced from stem cells. T lymphocytes (T cells) leave the bone marrow early, moving to the thymus, where they further develop a capability to respond to foreign antigens (a foreign substance that enters the body and initiates the immune response). This is known as cell-mediated immunity. Upon activation, these T cells leave the thymus and take on the role required for a specific cell mediated immune response. There are various types of T lymphocytes, each with a specific function: • Cytoxic T cells destroy cells directly by releasing cytokines • Helper T cells activate B cells to secrete antibodies, and also activate cytoxic cells • Suppressor T cells decrease the activity of the immune response • Memory T cells remember a previous antigen and initiates a response when the antigen presents itself again The B-lymphocytes (B cells) leave the bone marrow at different stages, migrating to secondary lymphatic organs after encountering antigens. B cells have surface receptors that bind with a specific type of antigen that stimulates them to produce antibodies (a protein produced by a B cell that triggers an immune response when the antigen presents itself again). This type of immune response is known as humoral immunity. A third type of lymphocyte—natural killer (NK) cells—can be found in lymph nodes, blood and bone marrow. They secrete a protein that

Putting the Lymphatic System Into Historical Context A desir e to understand the workings of the lymphatic system and its anatomy and physiology goes back to early scientists in ancient times.

Hippocrates (460–377 B.C.) first described the lymphatic vessel as “white blood” and coined the word “chyle.” Chyle is a white milky fluid that contains fats and fat-soluble vitamins following the absorption of fats in the digestive tract. Jean Pecquet (1622–1674) , a French scientist, was famous for his discovery of the lacteals, the major lymph collectors responsible for the absorption of fats and fat soluble vitamins in the small intestine. He was also known for discovering that the thoracic duct, the largest lymph vessel in the body, leads into the left subclavian vein. Olaus Rudbeck (1630–1702) , a Swedish scientist, also known for his pioneering work in the study of the lymphatic system, discovered the pathway of lymph fluid leading from the tissues into the lymph vessels then back to the thoracic duct into the cardiovascular system.

can destroy the membranes of tumors and virus cells. The thymus is located in the upper thorax in the mediastinum between the lungs and behind the sternum. It’s a fairly large organ during the embryonic stages of life, but begins to atrophy at an early age and is very small by the end of puberty. Here, T prolymphocytes settle into the cortex after the third embryonic month, where they differentiate to become mature immune fighting T lymphocytes, eventually becoming a part of the cell mediated immune response. The thymus is also recognized as a gland because it produces and secretes hormones called thymosins. Understanding the Secondary Lymphatic Organs The largest lymphatic organ is the spleen, located in the left epigastric region of the thorax and surrounded by a capsule of connective tissue.

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