1. Lymphatics

2. Lymphatic System Functions 1) Provide alternate pathway for extracellular fluids to return to circulation. 2) Provide pathways for waste materials to be removed from tissues and organs and destroyed. 3) Provide a protective lining along internal organs which are exposed to the environment. 4) Provide places for surveillance, proliferation and maturation of lymphocytes and other immune cells

3. Lymphatic System Two interrelated components: 1) Network of lymphatic vessels 2) Lymphatic organs, such as spleen & lymph nodes Lymphatic tissues such as tonsils Lymphatic cells dispersed through walls of many organs

6. Concentrated in Cervical region Along aorta in thorax & abdomen Axilla Inguinal region

9. Other Lymphatic Organs and Tissues Spleen, Thymus Tonsils, Appendix, Lymphatic tissue lining digestive system trachea, bronchi, bronchioles vagina urethra

10. Spleen Inferior to diaphragm on left side of abdomen Large blood supply through splenic artery (branch of celiac trunk from aorta) Two types of tissue: a) Red pulp produces erythrocytes in fetus & newborn (can resume in adults if necessary) reservoir for eythrocytes & platelets

11. Spleen Inferior to diaphragm on left side of abdomen Large blood supply through splenic artery (branch of celiac trunk from aorta) Two types of tissue: b) White pulp contains lymphocytes & macrophages removes bacteria, viruses, debris from blood removes old & damaged erythrocytes

12. Thymus Superior thorac, anterior to aorta & posterior to sternum Large in children, involutes in adults Secretes hormones which cause undifferentiated lymphocytes to mature into "thymic-derived" lymphocytes

13. Lymphoid tissues (lymphocytes and macrophages) line many hollow organs exposed to bacteria, viruses, etc Clusters, called lymphatic nodules, of closely-packed, proliferating lymphocytes & macrophages. Located just deep to epithelia, easily exposed to antigens Secrete antibodies into and across epithelia into lumen UrethraIntestine EsophagusBronchus

14. Lymphoid tissues (lymphocytes and macrophages) line many hollow organs exposed to bacteria, viruses, etc Some nodules given special names: Tonsils in pharynx Peyer's Patches in small intestine