2. Draining excess interstitial fluid Transporting dietary lipids

3. Lymphatic vessels: In spaces between cells Closed at one end, converge to form larger vessels (like veins) to trunks to right and left duct to venous blood Contain valves to ensure one way movement Flow through lymph nodes (masses of B and T cells) Lymphatic capillaries: Anchored by elastic filaments Open and close with pressure differences

5. Lymphatic Organs & Tissues Divided into 2 groups –Primary lymphatic organs Sites where stem cells divide & become immunocompetent Red bone marrow, thymus –Secondary lymphatic organs Sites where immune response occurs Lymph nodes, spleen, lymphatic nodules, etc.

6. Thymus: Located between sternum and aorta (mediastinum) Two lobes divided into lobules Cortex (outer layer) of immature cells -T cells: antigenic activity: -dendritic cells: assist maturation -epithelial cells: “educate” pre-T cells by positive selection -macrophages: clear debris and dead cells Medulla (inner layer) of mature T cells, epithelial cells, dendritic cells, and macrophages

7. Lymph nodes: Lymph flows in through afferent vessels and out through efferent vessels Made up of nodules -Primary nodules: B cells -Secondary nodules: plasma cell and memory B cell formation

8. Spleen: Located between stomach and diaphragm Contains white and red pulp -White pulp: lymphocytes and macrophages around central arteries -Red pulp: red blood cells, macrophages, lymphocytes, plasma cells, and granulocytes Removes worn out or defective RBCs Stores platelet Produces blood cells in fetus

9. Lymphatic nodules: no capsule Throughout mucus membranes (MALT= mucosa-associated lymphatic tissue) Tonsils

10. Figure 12.6

11. Nonspecific Resistance/ Innate Defenses: born with and offer immediate protection First line of defense- skin and mucous membranes Physical and chemical barrier

15. Figure 12.7

16. © 2012 Pearson Education, Inc. Adaptive Defense System: Third Line of Defense Three aspects of adaptive defense Antigen specific—recognizes and acts against particular foreign substances Systemic—not restricted to the initial infection site Memory—recognizes and mounts a stronger attack on previously encountered pathogens

17. © 2012 Pearson Education, Inc. Adaptive Defense System: Third Line of Defense Cells of the adaptive defense system Lymphocytes respond to specific antigens B lymphocytes (B cells) T lymphocytes (T cells) Macrophages help lymphocytes

18. © 2012 Pearson Education, Inc. Adaptive Defense System: Third Line of Defense Immunocompetent—cell becomes capable of responding to a specific antigen by binding to it Cells of the adaptive defense system Lymphocytes Originate from hemocytoblasts in the red bone marrow B lymphocytes become immunocompetent in the bone marrow (remember B for Bone marrow) T lymphocytes become immunocompetent in the thymus (remember T for Thymus)

20. Figure 12.11, step 1a Red bone marrow: site of lymphocyte origin Primary lymphoid organs: site of development of immunocompetence as B or T cells Secondary lymphoid organs: site of antigen encounter, and activation to become effector and memory B or T cells Immature (naive) lymphocytes Red bone marrow KEY:

21. Figure 12.11, step 1b Red bone marrow: site of lymphocyte origin Primary lymphoid organs: site of development of immunocompetence as B or T cells Secondary lymphoid organs: site of antigen encounter, and activation to become effector and memory B or T cells Lymphocytes destined to become T cells migrate (in blood) to the thymus and develop immunocompetence there. B cells develop immunocompetence in red bone marrow. Bone marrow Thymus Immature (naive) lymphocytes Red bone marrow 1 KEY:

22. Figure 12.11, step 2 Red bone marrow: site of lymphocyte origin Primary lymphoid organs: site of development of immunocompetence as B or T cells Secondary lymphoid organs: site of antigen encounter, and activation to become effector and memory B or T cells Lymphocytes destined to become T cells migrate (in blood) to the thymus and develop immunocompetence there. B cells develop immunocompetence in red bone marrow. Immunocompetent but still naive lymphocytes leave the thymus and bone marrow. They “seed” the lymph nodes, spleen, and other lymphoid tissues, where they encounter their antigen and become activated. Lymph nodes, spleen, and other lymphoid tissues Bone marrow Thymus Immature (naive) lymphocytes Red bone marrow 1 2 KEY:

23. Figure 12.11, step 3 Red bone marrow: site of lymphocyte origin Primary lymphoid organs: site of development of immunocompetence as B or T cells Secondary lymphoid organs: site of antigen encounter, and activation to become effector and memory B or T cells Lymphocytes destined to become T cells migrate (in blood) to the thymus and develop immunocompetence there. B cells develop immunocompetence in red bone marrow. Immunocompetent but still naive lymphocytes leave the thymus and bone marrow. They “seed” the lymph nodes, spleen, and other lymphoid tissues, where they encounter their antigen and become activated. Antigen-activated (mature) immunocompetent lymphocytes (effector cells and memory cells) circulate continuously in the bloodstream and lymph and throughout the lymphoid organs of the body. Lymph nodes, spleen, and other lymphoid tissues Bone marrow Thymus Immature (naive) lymphocytes Red bone marrow 1 2 3 KEY:

32. Active immunity