Connective tissue in red pulp o splenic sinusoids

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connective tissue in red pulp o Splenic sinusoids: very permeable capillaries o Storage site for erythrocytes and platelets 25
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21.4b Spleen Monitoring blood as it flows through the spleen Path of flow: splenic artery, central artery, sinusoids, venules, splenic vein Function of spleen : eat foreign particles; clear defective erythrocytes and platelets; store erythrocytes and platelets The spleen filters and monitors blood (not lymph) White pulp monitors it for foreign materials and bacteria o Macrophages in sinusoids of red pulp remove particles o Phagocytize bacteria, debris, defective erythrocytes and platelets In first 5 months of fetal life, spleen makes blood cells. This function can be reactivated under certain conditions o E.g., some hematologic disorders
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Clinical View: Splenectomy Surgical removal of the spleen May be performed due to Ruptured spleen from abdominal injury (most common) Infection, cyst, or tumor Lymphoma or other cancer Blood disorders (e.g., sickle cell anemia) May be more prone to life-threatening infection
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Tonsils Secondary lymphatic structures Immune surveillance of inhaled and ingested substances Tonsillar crypts o Invaginations that trap material Contain lymphatic nodules o Some with germinal centers 21.4c Tonsils Figure 21.8b, c
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Tonsils ( continued ) Pharyngeal tonsil o In nasopharynx o Called adenoids when enlarged Palatine tonsils o In posterolateral oral cavity Lingual tonsils o Along posterior one-third of tongue 21.4c Tonsils Figure 21.8a
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Clinical View: Tonsillitis and Tonsillectomy Acute tonsillitis: inflammation and infection of tonsils Palatine tonsils most commonly affected Redden and enlarge May partially obstruct pharynx Fever, chills, sore throat, and difficulty swallowing May be infected by viruses or bacteria Persistent recurrent infections, chronic tonsillitis May require tonsillectomy, surgical removal of tonsils 30
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21.4d Lymphatic Nodules and MALT Lymphatic nodules Clusters of lymphatic cells with some extracellular matrix o Not completely surrounded by connective tissue capsule Scattered nodules termed diffuse lymphatic tissue Found in every body organ Help defend against infection In some areas, group together to form larger structures o E.g., MALT
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21.4d Lymphatic Nodules and MALT MALT Mucosa-associated lymphatic tissue Located in gastrointestinal, respiratory, genital, and urinary tracts o Found in lamina propria of the mucosa Help defend against foreign substances Prominent in small intestines , especially ileum o Peyer patches : large collections of lymphatic nodules that form bulges in ileum wall
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Relationship of the Lymphatic System to the Cardiovascular System & the Immune System 33 Figure 21.9a
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