18: The Lymphatic System
- Describe the structure of the lymphatic tissue (lymph fluid, vessels, ducts, and organs)
- Describe the structure of the primary and secondary lymphatic organs
The lymphatic system is the system of vessels, cells, and organs that carries excess fluids to the bloodstream and filters pathogens from the blood. The swelling of lymph nodes during an infection and the transport of lymphocytes via the lymphatic vessels are but two examples of the many connections between these critical organ systems.
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- 18.1: Structure of the Lymphatic System
- This page discusses the lymphatic system, highlighting its structure of capillaries that collect interstitial fluid, forming lymph, and larger vessels that transport it to the bloodstream. The system includes right lymphatic duct and thoracic duct for asymmetrical drainage into the subclavian veins. Superficial lymphatics follow veins while deep ones follow arteries.
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- 18.2: Lymphoid Organs
- This page discusses key components of the lymphatic system and immune response, including the thymus, lymph nodes, spleen, and tonsils. The thymus is situated between the sternum and aorta, with distinct layers of thymocytes. Lymph nodes filter lymph to eliminate pathogens and activate T and B cells. The spleen filters blood to remove bacteria and aging red blood cells while supporting immune responses.
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- 18.3: Spleen
- This page discusses the spleen, a secondary lymphoid organ approximately 12 cm in length, which filters blood and clears microbes and dying red blood cells. It is comprised of red pulp for blood filtration and white pulp for immune responses, housing germinal centers for B cells and T cells. Additionally, the marginal zone aids in presenting antigens to lymphocytes, supporting both nonspecific and adaptive immunity.
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- 18.4: Lymphoid Nodules
- This page discusses tonsils, lymphoid structures in the pharynx that aid immunity against oral pathogens. It highlights the pharyngeal tonsil, or adenoid, which can swell from infections. Tonsils, lacking a complete capsule and featuring crypts, trap pathogens to trigger immune responses. They are crucial for children's immunity development. Tonsil removal may be necessary for children with frequent throat infections, especially when palatine tonsils swell and obstruct breathing or swallowing.
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- 18.5: Exercises
- This page presents laboratory exercises focused on lymphatic structures and tissues, including matching activities, diagram labeling, and identification of components like the thoracic duct and lymph nodes. Students observe slides and draw samples while noting their structure, epithelium type, source, and function. The aim is to deepen understanding of the lymphatic system and its components.
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- 18.6: MODELS- Torsos and Mid-Sagittal Head
- This page details the lymphatic system's components, highlighting the major lymph node clusters (cervical, inguinal, thoracic, axillary) and key structures like the thoracic and right lymphatic ducts, cisterna chyli, spleen, and tonsils (pharyngeal, palatine, lingual, tubal). It also reviews the histological features of lymph nodes (medulla, cortex, hilus, vessels) and spleen (white and red pulp), along with Peyer’s patches as part of mucosal-associated lymphatic tissue (MALT).