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Ch20-21lymphatic&immune system
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- 2. Objectives • Lymphatic System –Lymphoid Organs – Lymphoid Circulation • Immune System – Immune cells – Immune cell function
- 3. The Lymphatic andImmune Systems • Lymphatic system – Main function is to return excess tissue fluid to blood vascular system – Lymphatic vessels collect tissue fluid • Immune system – Protects our bodies from foreign organisms – Confers immunity to disease – Main components • Lymphocytes, lymphoid tissue, and lymphoid organs
- 4. The Lymphatic System •Lymphatic vessels collect tissue fluid from loose connective tissue – Carry fluid to great veins in the neck – Fluid flows only toward the heart – Once tissue fluid is within lymphatic vessels it is termed lymph • Functions of lymphatic vessels – collect excess tissue fluid and blood proteins • Return tissue fluid and blood proteins to bloodstream
- 5. Orders of LymphaticVessels • Lymph capillaries – smallest lymph vessels – First to receive lymph • Lymphatic collecting vessels – collect from lymph capillaries – Lymph nodes are scattered along collection vessels Lymphatic system Lymph duct Lymph trunk Lymph node Lymphatic capillary Blood capillaries Lymphatic collecting vessels, with valves (a) Structural relationship between a capillary bed of the blood vascular system and lymphatic capillaries Heart Arterial systemVenous system
- 6. Orders of LymphaticVessels • Lymph nodes – Scattered along collecting vessels • Lymph trunks – Collect lymph from collecting vessels • Lymph ducts – Empty into veins of the neck
- 7. Lymphatic Capillaries • Locatednear blood capillaries • Receive tissue fluid from CT – Increased volume of tissue fluid • Minivalve flaps open and allow fluid to enter • High permeability allows entrance of – Tissue fluid and protein molecules – Bacteria, viruses, and cancer cells
- 8. Lymphatic Capillaries • Lacteals—specializedlymphatic capillaries – Located in the villi of the small intestines • Receive digested fats • Fatty lymph—chyle
- 9. Distribution and Featuresof Lymphatic Capillaries Figure 21.1 Lymphatic system Lymph duct Lymph trunk Lymph node Lymphatic capillary Blood capillaries Lymphatic collecting vessels, with valves (a) Structural relationship between a capillary bed of the blood vascular system and lymphatic capillaries Heart Arterial systemVenous system Filaments anchored to connective tissue Fibroblast in loose connective tissue Endothelial cell Flaplike minivalve (b) Lymphatic capillaries are blind-ended tubes in which adjacent endothelial cells overlap each other, forming flaplike minivalves. Tissue fluid Tissue cell Blood capillaries Lymphatic capillaries
- 10. Lymphatic Collecting 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 • Lymph propelled by – Skeletal muscles bulging – Nearby arteries pulsing – Tunica media of the lymph vessels • Lymph flow is unaided by heartbeat
- 11. Lymph Nodes • Cleansethe lymph of pathogens • Human body contains around 500 • Superficial lymph nodes located in – Cervical, axillary, and inguinal regions • Deep nodes are – Tracheobronchial, aortic, and iliac lymph nodes
- 12. General Distribution ofLymphatic Collecting Vessels and Regional Lymph Nodes Figure 21.2 Cervical nodes Entrance of right lymphatic duct into vein Internal jugular vein Entrance of thoracic duct into vein Thoracic duct Cisterna chyli Lymphatic collecting vessels Axillary nodes Aorta Inguinal nodes Regional lymph nodes Drained by the right lymphatic duct Drained by the thoracic duct
- 13. Microscopic Anatomy ofa Lymph Node • Fibrous capsule—surrounds lymph nodes • Trabeculae—connective tissue strands • Lymph vessels – Afferent lymphatic vessels – Efferent lymphatic vessels
- 14. Microscopic Anatomy ofa Lymph Node Figure 21.3a Afferent lymphatic vessels Efferent lymphatic vessels Capsule Trabeculae Hilum Cortex Lymphoid follicle Germinal center Subcapsular sinus Medulla Medullary cord Medullary sinus (a) Longitudinal view of the internal structure of a lymph node and associated lymphatics
- 15. Microscopic Anatomy ofa Lymph Node Figure 21.3b Follicles Trabecula Subcapsular sinus Capsule Medullary cords Medullary sinuses (b) Photomicrograph of part of a lymph node (14X)
- 16. Microscopic Anatomy ofa Lymph Node Figure 21.3c (c) Reticular tissue within the medullary sinus (540X) Macrophage Medullary sinus Reticular fiber Lymphocytes Reticular cells on reticular fibers
- 17. Lymph Trunks • Lymphaticcollecting vessels converge • Five major lymph trunks – Lumbar trunks • Receives lymph from lower limbs – Intestinal trunk • Receives chyle from digestive organs – Bronchomediastinal trunks • Collects lymph from thoracic viscera
- 18. Lymph Trunks • Fivemajor lymph trunks (continued) – Subclavian trunks • Receive lymph from upper limbs and thoracic wall – Jugular trunks • Drain lymph from the head and neck
- 19. The Lymphatic Trunks Figure21.4a Left jugular trunk Internal jugular veins Left subclavian trunk Left subclavian vein Esophagus Trachea Ribs Left lumbar trunk Left broncho- mediastinal trunk Entrance of thoracic duct into vein Thoracic duct Hemiazygos vein Intestinal trunk Inferior vena cava Right jugular trunk Right lymphatic duct Right subclavian trunk Right subclavian vein Right broncho- mediastinal trunk Brachiocephalic veins Superior vena cava Azygos vein Cisterna chyli Right lumbar trunk (a) Major lymphatic trunks and ducts in relation to veins and surrounding structures, anterior view
- 20. The Lymphatic Trunks Figure21.4b (b) Thoracic duct (colored green) along the posterior thoracic wall Azygos vein on vertebral bodies Thoracic duct Aorta
- 21. Lymph Ducts • Cisternachyli – 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
- 22. Right Lymphatic Duct •Empties into right internal jugular and subclavian veins Internal jugular veinsRight jugular trunk Right lymphatic duct Right subclavian trunk Right subclavian vein Right broncho- mediastinal trunk Brachiocephalic veins Superior vena cava Azygos vein Cisterna chyli Right lumbar trunk
- 23. The Immune System •Recognizes specific foreign molecules • Destroys pathogens effectively • Key cells—lymphocytes • Also includes lymphoid tissue and lymphoid organs • Lymphoid organs – Lymph nodes, spleen, thymus, tonsils, aggregated lymphoid nodules, and appendix
- 24. Lymphocytes • Infectious organismsattacked by inflammatory response – Macrophages, then lymphocytes • Are effective fighters of infectious organisms – Each lymphocyte recognizes a specific foreign molecule • Antigens are any molecules inducing a response from a lymphocyte
- 25. Lymphocytes • B lymphocytesand T lymphocytes are the two main classes of lymphocytes • Cytotoxic T lymphocytes – Attack foreign cells directly • Binds to antigen-bearing cells • Perforates cell membrane • Signals cell to undergo apoptosis • Destroy virus infected cells and some cancer cells
- 26. Lymphocytes • B lymphocytes –Become plasma cells – Secrete antibodies • Mark cells for destruction by macrophages – Respond primarily to bacteria and bacterial toxins
- 27. Lymphocyte Function Figure 21.5 Tlymphocyte binds to target cell, secretes proteins that lyse the cell’s membrane, and signals the cell to die. B lymphocyte gives rise to plasma cell, which secretes antibodies. Antibodies bind to antigens on bacteria, marking the bacteria for destruction. Antibody-coated bacteria are avidly phagocytized. T lymphocyte detaches from target cell. Target cell dies by apoptosis. T lymphocyte Target cell, bearing antigen Dead target cell Antigen (a) Action of cytotoxic T lymphocyte (b) Differentiation and activity of B lymphocyte B lymphocyte Plasma cell Macrophage Surface antigenAntibodies Bacterium 1 2 3 1 2 3
- 28. Lymphocyte Activation • Lymphocytesoriginate in bone marrow • Some travel to the thymus gland – T lymphocytes • Some stay in bone marrow – B lymphocytes • Able to recognize a unique antigen – Gain immunocompetence • Travels through blood stream – Meets and binds to a specific antigen
- 29. Lymphocyte Activation • Duringactivation – Lymphocyte is presented its antigen by • A macrophage • Or a dendritic cell
- 30. Lymphocyte Activation • BothT 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
- 31. Lymphocyte Activation Figure 21.6 Redbone marrow Bone marrow Immature lymphocytes Red bone marrow: site of lymphocyte origin Secondary lymphoid organs: site of antigen encounter, and activation to become effector and memory B or T cells Primary lymphoid organs: site of development of immuno- competence as 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. Antigen-activated immuno- competent lymphocytes (effector cells and memory cells) circulate continuously in the bloodstream and lymph and throughout the lymphoid organs of the body. 1 2 3 Thymus Lymph nodes, spleen, and other lymphoid tissues
- 32. Lymphoid Tissue • Mostimportant 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)
- 33. Lymphoid Tissue Figure 21.7 Lymphoid follicle Mucous membrane liningsmall intestine LumenMuscle layers Intestine Germinal center Lumen of intestine Lymphoid tissue from mucosa of small intestine (14)
- 34. Lymphoid Organs • Primarylymphoid organs – Bone marrow – Thymus • Secondary lymphoid organs – Lymph nodes, spleen, tonsils – Aggregated lymphoid nodules – Appendix
- 35. Lymphoid Organs • Designedto gather and destroy infectious microorganisms and to store lymphocytes Figure 21.8 Tonsils (in pharyngeal region) Thymus (in thorax; most active during youth) Spleen (curves around left side of stomach) Aggregated lymphoid nodule (in intestine) Appendix
- 36. Thymus • Immature lymphocytesdevelop into T lymphocytes • Secretes thymic hormones • Most active in childhood • Functional tissue atrophies with age • Composed of cortex and medulla – Medulla contains Hassall’s corpuscles (thymic corpuscles) • Differs from other lymphoid organs – Functions strictly in lymphocyte maturation – Arises from epithelial tissue
- 37. Thymus Figure 21.9 Cortex Medulla Thymic corpuscle (b) Micrographof thymic tissue showing part of a lobule Thymus (a)Thymus located in the superior mediastinum
- 38. Lymph Nodes • Function –Lymph percolates through lymph sinuses – Most antigenic challenges occur in lymph nodes – Antigens destroyed and activate B and T lymphocytes
- 39. Spleen • Largest lymphoidorgan • Two main blood-cleansing functions – Removal of blood-borne antigens – Removal and destruction of old or defective blood cells • Site of hematopoiesis in the fetus
- 40. Spleen • Destruction ofantigens • Site of B cell maturation into plasma cells • Phagocytosis of bacteria and worn-out RBCs, WBCs and platelets • Storage of platelets
- 41. Spleen • White pulp –Thick sleeves of lymphoid tissue – Blood-borne antigens are destroyed as they activate the immune response – Provides the immune function of the spleen • Red pulp – Surrounds white pulp – Composed of • Venous sinuses • Splenic cords • Responsible for disposing of worn out RBCs
- 42. Spleen Figure 21.10a, b Splenicartery Splenic vein Hilum (a) Diagram of the spleen, anterior view Arterioles and capillaries Capsule Trabecula Venous sinuses Red pulp Splenic cords White pulp Central artery Splenic artery Splenic vein (b) Diagram of spleen histology
- 43. Spleen Figure 21.10c, d (c)Photograph of the spleen in its normal position in the abdominal cavity, anterior view Diaphragm Spleen Adrenal gland Splenic artery Pancreas Left kidney (d) Photomicrograph of spleen tissue (7). The white pulp, a lymphoid tissue with many lymphocytes, is surrounded by red pulp containing abundant erythrocytes. Capsule White pulp Red pulp
- 44. Tonsils • Simplest lymphoidorgans • 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
- 45. Tonsil Tonsillar crypt Germinal centersin lymphoid follicles Pharyngeal tonsil Palatine tonsil Lingual tonsil Palatine Tonsil Figure 21.11
- 46. Aggregated Lymphoid Nodules& 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
- 47. Smooth muscle in theintestinal wall Aggregated lymphoid nodules (Peyer’s patch) Aggregated Lymphoid Nodule Figure 21.12
- 48. Disorders of theLymphatic 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
- 49. Disorders of theLymphatic and Immune Systems • Hodgkin’s disease – Malignancy of lymph nodes • Non-Hodgkin’s lymphoma – Uncontrolled multiplication and metastasis of undifferentiated lymphocytes
- 50. The Lymphatic and ImmuneSystems 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
- 51. Lymphatic System Video •http://www.youtube.com/watch?v=BX8fBlme 9vQ