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

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