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

© 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

© 2014 Pearson Education, Inc. The Lymphatic and Immune Systems Immune system Protects our bodies from foreign organisms Confers immunity to disease Main components Lymphocytes, lymphoid tissue, and lymphoid organs

© 2014 Pearson Education, Inc. The Lymphatic System Lymphatic vessels collect tissue fluid from loose connective tissue Carry fluid to great veins in the neck Once tissue fluid is within lymphatic vessels it is termed lymph Lymph flows only toward the heart

© 2014 Pearson Education, Inc. Orders of Lymphatic Vessels 1. Lymph capillaries Smallest lymph vessels First to receive lymph Are highly permeable vessels 2. Collecting lymphatic vessels Collect from lymph capillaries Lymph nodes are scattered along collection vessels

© 2014 Pearson Education, Inc. Orders of Lymphatic Vessels 3. Lymph trunks Collect lymph from collecting vessels 4. Lymph ducts Empty into veins of the neck High permeability of lymphatic capillaries allows entrance of Tissue fluid and protein molecules Bacteria, viruses, and cancer cells

© 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

© 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

© 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

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

© 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

© 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 Afferent lymphatic vessels Efferent lymphatic vessels Hilum Capsule Cortex Medulla

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

© 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

© 2014 Pearson Education, Inc. Right subclavian vein Right jugular trunk Right lymphatic duct Right subclavian trunk Right broncho- mediastinal trunk Intestinal trunk Left lumbar trunk Cisterna chyli Thoracic duct Left subclavian trunk Left jugular trunk Entrance of thoracic duct into vein Ribs Hemiazygos vein Right lumbar trunk Left broncho- mediastinal trunk Cisterna chyli –Located between lumbar and intestinal trunks Thoracic duct –Ascends along vertebral bodies –Empties into venous circulation Right lymphatic duct –Empties into right internal jugular and subclavian veins

© 2014 Pearson Education, Inc.

The Immune System Includes lymphoid tissue and lymphoid organs Lymphoid organs Lymph nodes Spleen Thymus Tonsils Aggregated lymphoid nodules Appendix

© 2014 Pearson Education, Inc. The Immune System Recognizes specific foreign molecules Destroys pathogens effectively Key cells of the immune system Are termed lymphocytes *Infectious organisms trigger an inflammatory response Organisms are attacked by Macrophages, then lymphocytes

© 2014 Pearson Education, Inc. Lymphocytes Lymphocytes effectively recognize a specific antigen (foreign protein on a foreign molecule) Antigens are any molecules inducing a response from a lymphocyte Two main Lymphocytes 1.B Lymphocytes 2.T Lymphocytes

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

© 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 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

© 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

© 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)

© 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  )

© 2014 Pearson Education, Inc. Lymphoid Organs Primary lymphoid organs Bone marrow Thymus Secondary lymphoid organs Lymph nodes, spleen, tonsils Aggregated lymphoid nodules Appendix

© 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

© 2014 Pearson Education, Inc. Thymus Site where immature lymphocytes develop into T lymphocytes Secretes thymic hormones Differs from other lymphoid organs Functions strictly in lymphocyte maturation

© 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

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

© 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