Understanding the Lymphatic System: Functions and Circulation

1. Chapter 15 The Lymphatic System

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

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

4. 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

5. 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

6. 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

7. Lymph Nodes (cont’d.) • Germinal centers of compartments produce lymphocytes

8. Lymph Circulation

9. 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

10. 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

11. 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

12. 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

13. The Organs of the Lymphatic System

14. 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

15. 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

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

17. Immunity

18. Immunity (cont’d.) • Ability of body to resist • Infection from pathogens • Damage from foreign substances and harmful chemicals

19. Immunity (cont’d.) • Humoral immunity • B lymphocytes: produce antibodies • Fight circulating bacteria and viral infections • Become plasma cells when they enter tissues

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

21. Antigens and Antibodies

22. 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

23. 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

24. 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

25. 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

26. Cells of the Immune Response and Other Defenses

27. 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

28. 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: descendants of activated T and B cells

29. Cells of the Immune Response and Other Defenses (cont’d.) • Suppressor T cells: slow down activities of B and T cells • Macrophages • Engulf and digest antigen • Present then to T cell for recognition • Lymphokines: chemicals released by sensitized T cells

30. Cells of the Immune Response and Other Defenses (cont’d.) • Monokines: chemicals released by activated macrophages • Skin: mechanical barrier • Acid mantle, sebum • Lysozyme: (tears and saliva) attacks bacteria

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

32. Animation – Lymphatic System Click Here to Play Lymphatic System Animation

33. Summary • Discussed the functions of the immune system • Described lymph and its flow through the body • Discussed the functions of the spleen and tonsils

34. Summary (cont’d.) • Described the different types of immunity • Discussed the immune response