1. Functions of Lymphatic System -Collecting excess interstitial fluid -Filtering lymph -Transporting fats -Produce activated T and B cells

2. Copyright © 2010 Pearson Education, Inc. Cervical nodes Entrance of right lymphatic duct into vein (R sub.) Internal jugular vein Entrance of thoracic duct into vein (L sub.) Thoracic duct Cisterna chyli Lymphatic collecting vessels Axillary nodes Aorta Inguinal nodes Regional lymph nodes: (a) General distribution of lymphatic collecting vessels and regional lymph nodes. Drained by the right lymphatic duct Drained by the thoracic duct 753 Lymph capillaries -skeletal muscles -valves -breathing

3. Copyright © 2010 Pearson Education, Inc. Tonsils (in pharyngeal region) Thymus (in thorax; most active during youth) Spleen (curves around left side of stomach) Peyer’s patches (in intestine) Appendix -Reticular C.T. with lymphocytes, fibroblasts, macrophages and dendritic cells -Some discrete organs, some diffuse lymphatic tissue 756

4. -Mucous membranes -Peyer’s patches -Tonsils -Appendix (follicle)

5. Copyright © 2010 Pearson Education, Inc. Tonsil Tonsillar crypt Germinal centers in lymphoid follicles Pharyngeal tonsil Palatine tonsil Lingual tonsil 759 Clusters of lymph nodules

7. Copyright © 2010 Pearson Education, Inc. Smooth muscle in the intestinal wall Lymphoid nodules (follicles) of Peyer’s patch 760 Within mucous membrane of lower small intestine

8. Copyright © 2010 Pearson Education, Inc. Afferent lymphatic vessels Efferent lymphatic vessels Capsule Trabeculae Hilum Cortex Lymphoid follicle Germinal center Subcapsular sinus Medulla: Medullary cord Medullary sinus (a) Longitudinal view of the internal structure of a lymph node and associated lymphatics 756 Nodules with T&B Lymphocytes & Macrophages B Cells, Plasma Cells and Macrophages Lymph nodes: Filter lymph

9. Copyright © 2010 Pearson Education, Inc. Cortex Medulla Thymic (Hassall’s) corpuscle 758 -T cells become immunocompetent and naïve -In neck and mediastinum -2 lobes -Functional peak during childhood -Max size at puberty -Shrinks and changes to fat Lymphocytes Fewer Lymphocytes SCID

10. Copyright © 2010 Pearson Education, Inc. Figure 20.6a-b The spleen. Arterioles and capillaries Capsule Trabecula Venous sinuses Red pulp Splenic cords White pulp Central artery Splenic artery Splenic vein (b) Diagram of spleen histology Splenic artery Splenic vein Hilum (a) Diagram of the spleen, anterior view 757 -Largest -Thin capsule -Reservoir of blood cells, iron and platelets RBC’s and Macro. (RBC, WBC) Lymphocytes in nodules Lots of macrophages to destroy old and damaged RBC’s Epstein-Barr Virus

11. Copyright © 2010 Pearson Education, Inc. (d) Photomicrograph of spleen tissue (30x). The white pulp, a lymphoid tissue with many lymphocytes, is surrounded by red pulp containing abundant erythrocytes. Capsule White pulp Red pulp 757