1. © 2014 Pearson Education, Inc. PowerPoint ® Lecture Presentations prepared by Leslie Hendon University of Alabama, Birmingham 21 PART 1 The Lymphatic and Immune Systems

2. © 2014 Pearson Education, Inc. The Lymphatic and Immune Systems Lymphatic system Main function is to return excess tissue fluid to blood vascular system Lymphatic vessels collect tissue fluid Lymph is what was once plasma which has been pushed out of the capillaries and is now infusing tissues. By pressure, it now enters lymphatic capillaries and is called lymph. Lymph has little oxygen and nutrients

3. © 2014 Pearson Education, Inc. Figure 21.1 Distribution and special features of lymphatic capillaries. Lymph duct Lymph trunk Lymph node Collecting lymphatic vessels, with valves Blood capillaries Lymphatic capillary Tissue fluid Tissue cell Blood capillaries Lymphatic capillaries Filaments anchored to connective tissue Endothelial cell Flaplike minivalve Fibroblast in loose connective tissue Structural relationship between a capillary bed of the blood vascular system and lymphatic capillaries Lymphatic capillaries are blind-ended tubes in which adjacent endothelial cells overlap each other, forming flaplike minivalves. Venous system Arterial system Lymphatic system: Heart Lymatic capillaries are blind-ended and originate on the venous side of a capillary bed. Lymphatic vessels are thin and have valves similar to veins. Lymphatic vessels are found throughout the body except the brain and bones. They are found in the loose connective tissues which surround organs. Lymph is formed when plasma leaves capillaries to supply cells surrounding a capillary bed and accumulates to a pressure threshold when it will then enter through minivalves in the lymphatic capillary. Interstitial fluid is defined as the fluid which was first plasma but has left the capillary and is now surrounding cells.

4. © 2014 Pearson Education, Inc. The Lymphatic and Immune Systems Immune system Protects our bodies from foreign organisms Confers immunity to disease Main components: Lymph, lymphocytes, lymphoid tissue, and lymphoid organs Collect excess tissue fluid and blood proteins Return tissue fluid and blood proteins to bloodstream

5. © 2014 Pearson Education, Inc. Orders of Lymphatic Vessels Lymph capillaries Smallest lymph vessels First to receive lymph Are highly permeable vessels Collecting lymphatic vessels Collect from lymph capillaries Lymph nodes are scattered along collection vessels

6. © 2014 Pearson Education, Inc. Orders of Lymphatic Vessels Lymph trunks Collect lymph from collecting vessels Lymph ducts Empty into veins of the neck

7. © 2014 Pearson Education, Inc. Lymphatic Capillaries Located near blood capillaries Receive tissue fluid from CT Increased volume of tissue fluid creates higher pressure Minivalve flaps open and allow fluid to enter High permeability of lymphatic capillaries allows entrance of Tissue fluid and protein molecules Bacteria, viruses, and cancer cells

8. © 2014 Pearson Education, Inc. Lymphatic Capillaries Lacteals Are specialized lymphatic capillaries Are located in the villi of the small intestines Receive digested fats Fatty lymph is termed chyle

9. © 2014 Pearson Education, Inc. Collecting Lymphatic Vessels Accompany blood vessels Composed of the same three tunics as blood vessels Contain more valves than veins do Helps direct the flow of blood

10. © 2014 Pearson Education, Inc. Collecting Lymphatic Vessels Flow of lymph is not aided by the heartbeat Lymph is propelled by three weaker mechanisms Bulging of skeletal muscles Pulsing of nearby arteries Tunica media of the lymph vessels

11. © 2014 Pearson Education, Inc. Figure 21.2 General distribution of collecting lymphatic vessels and regional lymph nodes. Internal jugular vein Entrance of right lymphatic duct into vein Entrance of thoracic duct into vein Thoracic duct Cisterna chyli Collecting lymphatic vessels Aorta Inguinal nodes Axillary nodes Cervical nodes Regional lymph nodes Drained by the right lymphatic duct Drained by the thoracic duct In adults, the thoracic duct is typically 38-45cm in length and an average diameter of about 5mm. The vessel usually starts from the level of the second lumbar vertebra and extends to the root of the neck A drop of lymph will enter a lymphatic capillary and travel the same course as the accompanying vein until it empties into the nearest lymphatic collecting vessel which will travel into a vessel and through one of the regional nodes to be scanned. Once it leaves a node, the vessel will join a lymph trunk (lumbar, intestinal, bronchomediastinal, subclavian or jugular) and then into a lymph duct (the largest vessels) which will be either the thoracic duct or the right lymphatic duct. Those will drain into the L. or R. subclavian veins.

12. © 2014 Pearson Education, Inc. Lymph Nodes Cleanse the lymph of pathogens Human body contains around 500 Superficial lymph nodes located in Cervical region Axillary region Inguinal region Deep lymph nodes are Tracheobronchial lymph nodes Aortic lymph nodes Iliac lymph nodes

13. © 2014 Pearson Education, Inc. Figure 21.3a Structure of a lymph node. Afferent lymphatic vessels Lymphoid follicle Germinal center Subcapsular sinus Efferent lymphatic vessels Hilum Medullary cord Medullary sinus Trabeculae Capsule Cortex Medulla Longitudinal view of the internal structure of a lymph node and associated lymphatics B-cell proliferation Flow of lymph through lymph node Lymph will flow in the sinuses through the node being exposed to B cells, T cells and macrophages B cell proliferation T cells Macrophages

14. © 2014 Pearson Education, Inc. Microscopic Anatomy of a Lymph Node Fibrous capsule Surrounds lymph nodes Trabeculae Connective tissue strands extend inward to divide lymph node into segments

15. © 2014 Pearson Education, Inc. Microscopic Anatomy of a Lymph Node Lymph enters convex aspect of a lymph node through Afferent lymphatic vessels Lymph exits a lymph node at the hilum through Efferent lymphatic vessels

16. © 2014 Pearson Education, Inc. Figure 21.3b Structure of a lymph node. Photomicrograph of part of a lymph node (72  ) Lymphoid follicles Trabecula Subcapsular sinus Capsule Medullary cords Medullary sinuses

17. © 2014 Pearson Education, Inc. Figure 21.3c Structure of a lymph node. Reticular tissue within the medullary sinus (690  ) Macrophage Reticular cells on reticular fibers Lymphocytes Medullary sinus Reticular fiber

18. © 2014 Pearson Education, Inc. Lymph Trunks Collecting lymphatic vessels converge to form lymph trunks Five major lymph trunks Lumbar trunks Receive lymph from lower limbs Intestinal trunk Receives chyle from digestive organs Bronchomediastinal trunks Collects lymph from thoracic viscera

19. © 2014 Pearson Education, Inc. Lymph Trunks Five major lymph trunks (continued) Subclavian trunks Receive lymph from upper limbs and thoracic wall Jugular trunks Drain lymph from the head and neck

20. © 2014 Pearson Education, Inc. Figure 21.4a The lymph trunks and ducts. Right subclavian vein Brachiocephalic veins Superior vena cava Azygos vein Right jugular trunk Right lymphatic duct Right subclavian trunk Right broncho- mediastinal trunk Major lymphatic trunks and ducts in relation to veins and surrounding structures, anterior view Intestinal trunk Left lumbar trunk Cisterna chyli Thoracic duct Left subclavian trunk Left jugular trunk Internal jugular veins Esophagus Trachea Left subclavian vein Entrance of thoracic duct into vein Ribs Hemiazygos vein Inferior vena cava Right lumbar trunk Left broncho- mediastinal trunk

21. © 2014 Pearson Education, Inc. Figure 21.4b The lymph trunks and ducts. Thoracic duct along the posterior thoracic wall Cisterna chyli Thoracic duct Left broncho- mediastinal trunk Esophagus Trachea Aorta Azygos vein Vertebral body Sympathetic trunk Crus of the diaphragm Inferior vena cava

22. © 2014 Pearson Education, Inc. Lymph Ducts Cisterna chyli Located at the union of lumbar and intestinal trunks Thoracic duct Ascends along vertebral bodies Empties into venous circulation Junction of left internal jugular and left subclavian veins Drains three-quarters of the body

23. © 2014 Pearson Education, Inc. Lymph Ducts Right lymphatic duct Empties into right internal jugular and subclavian veins

24. © 2014 Pearson Education, Inc. The Immune System Recognizes specific foreign molecules Destroys pathogens effectively Key cells of the immune system Are termed lymphocytes

25. © 2014 Pearson Education, Inc. The Immune System Includes lymphoid tissue and lymphoid organs Lymphoid organs Lymph nodes Spleen Thymus Tonsils Aggregated lymphoid nodules Appendix

26. © 2014 Pearson Education, Inc. Lymphocytes Infectious organisms trigger an inflammatory response Organisms are attacked by Macrophages, then lymphocytes

27. © 2014 Pearson Education, Inc. Lymphocytes Lymphocytes effectively recognize a specific foreign molecule Antigens are any molecules inducing a response from a lymphocyte

28. © 2014 Pearson Education, Inc. Lymphocytes B lymphocytes and T lymphocytes are the two main classes of lymphocytes Cytotoxic T lymphocytes Attack foreign cells directly Bind to antigen-bearing cells Perforate cell membrane Signal cell to undergo apoptosis Destroy virus-infected cells and some cancer cells

29. © 2014 Pearson Education, Inc. Lymphocytes B lymphocytes Become plasma cells Plasma cells secrete antibodies Mark cells for destruction by macrophages Respond primarily to bacteria and bacterial toxins

30. © 2014 Pearson Education, Inc. Figure 21.5 Lymphocyte function. T lymphocyte Target cell, bearing antigen Antigen Dead target cell B lymphocyte Plasma cellAntibodies Bacterium Surface antigen Macrophage 121233 B lymphocyte gives rise to plasma cell, which secretes antibodies. T lymphocyte binds to target cell, secretes proteins that lyse the cell’s membrane, and signals the cell to die. T lymphocyte detaches from target cell. Target cell dies by apoptosis. Antibodies bind to antigens on bacteria, marking the bacteria for destruction. Antibody-coated bacteria are avidly phagocytized. Action of cytotoxic T lymphocyte Differentiation and activity of B lymphocyte

31. © 2014 Pearson Education, Inc. Lymphocyte Activation Lymphocytes originate in bone marrow Some travel to the thymus gland T lymphocytes Some stay in bone marrow B lymphocytes

32. © 2014 Pearson Education, Inc. Lymphocyte Activation Activated lymphocytes Are able to recognize a unique antigen Gain immunocompetence Travel through bloodstream Meet and bind to a specific antigen Proliferate rapidly

33. © 2014 Pearson Education, Inc. Lymphocyte Activation During activation Lymphocyte is presented its antigen by A macrophage or A dendritic cell

34. © 2014 Pearson Education, Inc. Lymphocyte Activation Both T and B lymphocytes produce clones of Effector lymphocytes Respond immediately, then die Memory cells Wait until the body encounters the antigen again Basis of acquired immunity Prevent subsequent infections of the same illness

35. © 2014 Pearson Education, Inc. Figure 21.6 Differentiation, activation, and recirculation of lymphocytes. Lymphocyte precursors Antigen Lymph node Thymus Red bone marrow Primary lymphoid organs (red bone marrow and thymus) Secondary lymphoid organs (lymph nodes, spleen, etc.) Both B and T lymphocyte precursors originate in red bone marrow. Origin 12345 Maturation Seeding secondary lymphoid organs and circulation Antigen encounter and activation Proliferation and differentiation Lymphocyte precursors destined to become T cells migrate (in blood) to the thymus and mature there. B cells mature in the bone marrow. During maturation, lymphocytes develop immunocompetence and self-tolerance. Immunocompetent but still naïve lymphocytes leave the thymus and bone marrow. They “seed” the secondary lymphoid organs and circulate through blood and lymph. When a lymphocyte’s antigen receptors bind its antigen, that lymphocyte can be activated. Activated lymphocytes proliferate (multiply) and then differentiate into effector cells and memory cells. Memory cells and effector T cells circulate continuously in the blood and lymph and throughout the secondary lymphoid organs.

36. © 2014 Pearson Education, Inc. Lymphoid Tissue Most important tissue of the immune system Two general locations Mucous membranes of Digestive, urinary, respiratory, and reproductive tracts Mucosa associated lymphoid tissue (MALT) Lymphoid organs (except thymus)

37. © 2014 Pearson Education, Inc. Figure 21.7 Mucosa associated lymphoid tissue (MALT). Muscle layers Intestine Lumen Mucous membrane lining small intestine Lymphoid follicle Lumen of intestine Germinal center Mucosa of small intestine (7  )

38. © 2014 Pearson Education, Inc. Lymphoid Organs Primary lymphoid organs Bone marrow Thymus Secondary lymphoid organs Lymph nodes, spleen, tonsils Aggregated lymphoid nodules Appendix Designed to gather and destroy infectious microorganisms and to store lymphocytes

39. © 2014 Pearson Education, Inc. Figure 21.8 Lymphoid organs. Tonsils (in pharynx) Thymus (in thorax; most active during youth) Spleen (curves around left side of stomach) Aggregated lymphoid nodules (in small intestine) Appendix

40. © 2014 Pearson Education, Inc. Thymus Site where immature lymphocytes develop into T lymphocytes Secretes thymic hormones Most active in childhood Functional tissue atrophies with age

41. © 2014 Pearson Education, Inc. Thymus Composed of cortex and medulla Medulla contains thymic corpuscles Differs from other lymphoid organs Functions strictly in lymphocyte maturation Arises from epithelial tissue

42. © 2014 Pearson Education, Inc. Figure 21.9 The thymus. Thymus, located in the superior mediastinum Micrograph of thymic tissue Thymus Capsule Cortex Medulla Thymic corpuscle

43. © 2014 Pearson Education, Inc. Lymph Nodes Function Lymph percolates through lymph sinuses Most antigenic challenges occur in lymph nodes Antigens destroyed and activate B and T lymphocytes

44. © 2014 Pearson Education, Inc. Spleen Largest lymphoid organ Two main blood-cleansing functions Removal of bloodborne antigens Removal and destruction of old or defective blood cells Site of hematopoiesis in the fetus

45. © 2014 Pearson Education, Inc. Spleen Destruction of antigens Site of B cell maturation into plasma cells Phagocytosis of bacteria and worn-out RBCs, WBCs, and platelets Storage of platelets

46. © 2014 Pearson Education, Inc. Spleen White pulp Thick sleeves of lymphoid tissue Bloodborne antigens are destroyed as they activate the immune response Provides the immune function of the spleen

47. © 2014 Pearson Education, Inc. Spleen Red pulp Surrounds white pulp Composed of Venous sinuses Splenic cords Responsible for disposing of worn-out RBCs

48. © 2014 Pearson Education, Inc. Figure 21.10a Structure of the spleen. Splenic artery Splenic vein Hilum Diagram of the spleen, anterior view

49. © 2014 Pearson Education, Inc. Figure 21.10b Structure of the spleen. Diagram of spleen histology Capsule Trabecula Splenic cords Splenic sinusoids Arterioles and capillaries Red pulp White pulp Central artery Splenic artery Splenic vein

50. © 2014 Pearson Education, Inc. Figure 21.10c Structure of the spleen. Photograph of the spleen in its normal position in the abdominal cavity, anterior view Diaphragm Spleen Adrenal gland Left kidney Splenic artery Pancreas

51. © 2014 Pearson Education, Inc. Figure 21.10d Structure of the spleen. Photomicrograph of spleen tissue (30  ). The white pulp, a lymphoid tissue with many lymphocytes, is surrounded by red pulp containing abundant erythrocytes. Capsule Red pulp White pulp

52. © 2014 Pearson Education, Inc. Tonsils Simplest lymphoid organs Four groups of tonsils Palatine, lingual, pharyngeal, and tubal tonsils Arranged in a ring to gather and remove pathogens Underlying lamina propria consists of MALT

53. © 2014 Pearson Education, Inc. Figure 21.11 Histology of the palatine tonsil. Pharyngeal tonsil Palatine tonsil Lingual tonsil Tonsillar crypt Germinal centers in lymphoid follicles

54. © 2014 Pearson Education, Inc. Aggregated Lymphoid Nodules and Appendix MALT—abundant in walls of intestines Fight invading bacteria Generate a wide variety of memory lymphocytes Aggregated lymphoid nodules (Peyer’s patches) Located in the distal part of the small intestine Appendix—tubular offshoot of the cecum

55. © 2014 Pearson Education, Inc. Figure 21.12 Aggregated lymphoid nodules. Aggregated lymphoid nodules (Peyer’s patch) Smooth muscle in the intestinal wall

56. © 2014 Pearson Education, Inc. Disorders of the Lymphatic and Immune Systems Chylothorax Leakage of fatty lymph into the thorax Lymphangitis Inflammation of a lymph vessel Mononucleosis Viral disease caused by Epstein-Barr virus Attacks B lymphocytes

57. © 2014 Pearson Education, Inc. Disorders of the Lymphatic and Immune Systems Hodgkin’s lymphoma Cancer of lymph nodes Non-Hodgkin’s lymphoma Uncontrolled multiplication and metastasis of undifferentiated lymphocytes

58. © 2014 Pearson Education, Inc. The Lymphatic and Immune Systems Throughout Life Lymphatic vessels and lymph nodes Develop from lymphatic sacs Thymus originates as an outgrowth of the endoderm Spleen, lymph nodes, and MALT Arise from mesodermal mesenchyme