2Lymphatic System • Lymphatic Vessels • Lymphoid Organs and Tissues – Functioning in returning interstitial fluid to thevascular system.• Lymphoid Organs and Tissues– House phagocytes and lymphocytes– Activate the immune response
16What feature of lymphatic vessels is visible here? What do they prevent? Why are they necessary?
17• Receive lymph from lymphatic collecting • Types: Lymphatic Trunks• Receive lymph from lymphatic collectingvessels.• Types:–JugularSubclavianBronchomediastinalIntestinalLumbar
18Lymphatic Ducts • Receive lymph from lymphatic trunks. • Right lymphatic duct– Receives lymph from the right jugular, right subclavian,and right bronchomediastinal trunks– Empties into the right internal jugular vein• Thoracic duct– Receives lymph from the left jugular, left subclavian,left bronchomediastinal, intestinal, and lumbar trunks– Empties into the left internal jugular vein
21Lymphatic Vessels Lymphatic Trunks Lymphatic Ducts Where’s pressure high andwhere’s pressure low?Lymphatic TrunksWhat makes lymph flow?Lymphatic DuctsBloodstream
22Lymph Flow • Lymph flow will be similar to… • 3 main factors promote lymph flow:– Skeletal muscle pump– Respiratory pump– Lymphatic smooth muscle
231. How does elevating an injured limb affect lymph flow? 2. How would exercise affect lymph flow?3. How could massage affect lymph flow?4. In some surgeries for breast cancer, thelymph nodes along thearm are removed inorder to assess the spread of the disease.What would be a result of this?
24What happens when lymph cannot flow? What could prevent lymph from flowing?Filaria
25Lymphoid Cells • Lymphocytes • Phagocytes • Dendritic cells – T lymphocytes• Kill virus-infected and cancerous cells• Coordinate/control immune response– B lymphocytes• Become plasma cells which secrete antibodies• Phagocytes– Eat and kill and activate the rest of the immune system• Dendritic cells– Activate the immune system• Reticular cells– Make reticular fibers that support lymphatic tissues andorgans
26Reticularconnectivetissue forms theframework ofmost lymphoidtissues andorgans.
27Lymphoid Tissue • Aggregations of lymphoid cells Storage/proliferation site for lymphoid cellsSurveillance site2 main types– Diffuse lymphatic tissue– Lymphoid follicles
28Diffuse Lymphatic Tissue • What does “diffuse” mean?• Found in lymph nodes and spleen.• Especially prominent in the mucousmembranes lining the digestive, respiratory,urinary, and reproductive tracts.– Hence the term MALT.
29Mucosa Associated Lymphatic Tissue • Where are themucosae?• Why is lymphoidtissue needed there?• 2 main types:– GALT– BALT
30Lymphoid Follicles • A.k.a. lymphoid nodules • Solid, packed spherical clusters of lymphoidcells and reticular tissues• Often found as parts of larger lymphoidorgans (e.g., lymph nodes)• Found in the mucosae• Large number in the distal ileum andappendix
39Lymph Nodes • Receive lymph from an afferent lymphatic vessel • Drain lymph into an efferent lymphatic vessel• Surrounded by dense CT capsule– Inward extensions (trabeculae) divide it intocompartments• Reticular fibers support the resident macrophagesand lymphocytes• Divided into a cortex and a medulla
48Spleen • Major function is blood cleansing – Removal of aged, broken, or malformed RBCs.• Who does this?– Removal and destruction of pathogens and foreignmatter.
49Spleen • Surrounded by a CT capsule w/ inward extending trabeculae• Internal framework is provide by reticular fibers.
50Spleen • Splenic arterioles are surrounded by sheathes of lymphocytes.– This is known as the white pulp of the spleen.– What will happen here?• The arterioles terminate in splenic capillaries –which are twisty, sinusoidal, and incomplete.– The capillaries and the surrounding splenic tissueis referred to as the red pulp of the spleen.– Macrophages line the capillary surface.– Why?
55Thymus • Largest and most active • Involved in T in fetus and infancy• Involved in Tlymphocyte maturationand selection– Also, the removal ofthose T cells that attackself tissue• Growth ceases duringadolescence• No direct fighting.