Chapter 15

2. Chapter 15 The Lymphatic System

3. Introduction • Transports lymph through lymphatics • Lymphatics: lymph capillaries and vessels • Controls body fluid • Destroys harmful microorganisms

4. Introduction

5. The Functions of the System and the Structure and Functions of the Lymphatic Vessels

6. Introduction • Drain interstitial fluid from tissue spaces • Prevent edema • Transport digested fat to blood • Lacteals: special lymphatics in small intestine • Chyle: milky lymph in lacteals • Develop immunities • Produce lymphocytes

7. Lymphatic Vessels • Lymph capillaries: blind-end tubes • Lymph capillaries are located between cells • Lymph capillaries unite to form lymphatics • Lymphatics converge into two main channels • Thoracic duct and right lymphatic duct

8. Lymphatic Vessels (cont’d.)

9. Lymph Nodes • Found along lengths of lymphatics • Efferent: exit lymph node at the hilum • Afferent: enter lymph node at various locations • Trabeculae: divide the node into compartments • Germinal centers of compartments produce lymphocytes

10. Lymph Nodes

11. Lymph Nodes

12. Lymph Circulation

13. Lymph Circulation (cont’d.) • Interstitial fluid: plasma in interstitial spaces • Lymph: interstitial fluid in lymph capillaries • Passes into lymphatics • Lymphatics join to form lymph trunks

14. Lymph Circulation (cont’d.) • Lymph circulation maintained by • Normal skeletal muscle contractions • Compresses lymph vessels and forces lymph in one direction • Respiratory or breathing movements • Smooth muscle in lymphatic vessels

15. Lymph Circulation (cont’d.) • Lymph trunks • Lumbar: drains lower extremities and pelvis • Intestinal: drains abdominal region • Bronchomediastinal and intercostal: drain thorax • Subclavian: drains upper extremities • Jugular: drains head and neck

16. Lymph Circulation (cont’d.) • Individual trunks drain into two main trunks • Thoracic duct: drains into the left subclavian vein • Right lymphatic duct: drains into the right subclavian vein

17. Lymph Circulation (cont’d.)

18. The Organs of the Lymphatic System

19. The Organs of the Lymphatic System (cont’d.) • Tonsils • Palatine, pharyngeal, and lingual • Protect the nose and oral cavity • Thymus: lymphocyte production and maturation • Peyer’s patches: found in walls of small intestine

20. The Organs of the Lymphatic System (cont’d.) • Spleen • Largest mass of lymphatic tissue • Phagocytizes worn-out RBCs and platelets • Recycles hemoglobin • Produces lymphocytes and plasma cells • Stores blood for release during hemorrhage

21. The Organs of the Lymphatic System (cont’d.) • External view of the Spleen

22. Immunity

23. Immunity (cont’d.) • Ability of body to resist • Infection from pathogens • Damage from foreign substances and harmful chemicals • Humoral immunity • B lymphocytes: produce antibodies • Fight circulating bacteria and viral infections • Become plasma cells when they enter tissues

24. Immunity (cont’d.) • Cellular immunity • T lymphocytes • Come from thymus glands • Fight intracellular viruses, fungi, parasites, cancer

25. Antigens and Antibodies

26. Antigens and Antibodies (cont’d.) • Antigen: foreign protein in our body • B lymphocytes • Produce antibodies in response to antigens • Antibodies bind to specific antigen • Antigens precipitate • Phagocytic WBCs eat the antigens

27. Antigens and Antibodies (cont’d.) • Antibody morphology • Four amino acid chains linked by disulfide bonds • Heavy and light chains • Y-shaped molecule • Binding sites at tips of Y • Stem of the Y is always constant

28. Antigens and Antibodies (cont’d.)

29. Antigens and Antibodies (cont’d.) • Antibody types • IgG: attacks viruses, bacteria, and toxins; activates complement • IgA: found in exocrine gland secretions • IgM: response to bacteria or food antigens • IgD: found on surface of B lymphocytes • IgE: associated with allergic reactions

30. Antigens and Antibodies (cont’d.) • Active immunity: B cells contact antigen and produce antibodies • Natural active: exposure to infection • Artificial active: vaccine • Passive immunity • Natural passive: maternal antibodies to fetus • Artificial passive: gamma globulin

31. Cells of the Immune Response and Other Defenses

32. Cells of the Immune Response and Other Defenses (cont’d.) • B cells: antigen • Antibody binding • Plasma cells: replicated B cells • Helper T cells: stimulate production of • Killer T cells • More B cells

33. Cells of the Immune Response and Other Defenses (cont’d.) • Killer T cells: • Attack virus-invaded body cells • Attack cancer cells • Reject body grafts • Memory cells: descendents of activated T and B cells • Suppressor T cells: slow down activities of B and T cells

34. Cells of the Immune Response and Other Defenses (cont’d.) • Macrophages • Engulf and digest antigen • Present them to T cell for recognition

35. Cells of the Immune Response and Other Defenses (cont’d.) • Lymphokines: chemicals released by sensitized T cells • Monokines: chemicals released by activated macrophages • Skin: mechanical barrier • Acid mantle, sebum • Lysozyme: (tears and saliva) attacks bacteria

36. Cells of the Immune Response and Other Defenses (cont’d.) • Mucous membranes: trap microorganisms and debris • Hydrochloric acid: (stomach) destroys microorganisms

37. Summary • Discussed the functions of the immune system • Described lymph and its flow through the body • Discussed the functions of the spleen and tonsils • Described the different types of immunity • Discussed the immune response