The Lymph System and Lymphoid Organs and Tissues

Overview lymphatic vessels lymph lyphoid cells and tissues lymphoid organs o lymph nodes o spleen o thymus o tonsils o other lymphoid tissue

lymphatic vessels collects excess interstitial fluid returns fluid to blood one way system o flows toward the heart

lymphatic capillaries - cells overlap - collagen filaments anchor ends lymphatic vessels

lacteals - specialized lymph capillaries in lining of small intestine - absorb fats - chyle = fatty lymph that is milky white - moves into lymph vessels lymphatic vessels

lymphatic collecting vessels - similar structure to veins - more valves - reconnect (anastamose) more often lymphatic vessels

lymphatic trunks - formed by union of largest vessels lymphatic vessels

lymphatic ducts - right - thoracic - cisterna chyli - enlarged sac where lumbar trunks meet lymphatic vessels

lyphangitis o when lymph vessel is inflamed, blood vessels that feed them become congested with blood lymphatic vessels

lymph - similar to blood plasma - white blood cells - debris/pathogens

lymph transport no pump skeletal muscles muscles used to breathe o diaphragm o intercostal muscles smooth muscle in lymphatic trunks and thoracic duct valves prevent backflow arterial pumping

lymph transport lymphedema o flow is blocked o lymph vessels removed lymph vessels can regrow!

lymphoid cells lymphocytes o T cells o B cells macrophages dendritic cells reticular cells

lymphoid tissue houses and provides a site for proliferation of lymphocytes surveillance point for lymphocytes and macrophages

lymphoid tissue types diffuse o found in every body organ o scattered lymphoid follicles o solid spherical bodies o germinal center

clusters - inguinal - axillary - cervical functions - filter lymph - help activate the immune system lymph nodes

- average 1" bean shaped - capsule with trabeculae - cortex - medulla lymph nodes

flow through node - afferent lymph vessels - efferent lymph vessels lymph nodes

spleen size of fist largest lymphoid organ site of lymphocyte proliferation site of immune surveillance

spleen cleans the blood o stores and releases breakdown products of RBCs o stores blood platelets o site of RBC production in fetus

spleen

thymus

many thymic lobules cortex o rapidly dividing lymphocytes medulla o thymic corpuscles  development of regulatory T cells prevent autoimmune diseases

tonsils palatine tonsils lingual tonsil pharyngeal tonsil tubal tonsils

tonsils tonsillar crypt

other lymphoid tissue Peyer's patches - aggregated follicles in the far end of the ileum and appendix - immune function of GI tract

other lymphoid tissue MALT - mucosa-associated lymphatic tissue - Peyer's patches - appendix - tonsils - lymphoid follicles in bronchi - lymphoid follicles in genitourinary organs