Chapter 20 (Lymphatics and Immune Systems) PDF

CHAPTER 21 The Lymphatic Human Anatomy Copyright Copyright©©2011 2011Pearson PearsonEducation, Educatio, Inc. Inc. and Immune Systems The Lymphatic and Immune Systems Main structures Lymphatic vessels Main components Lymphocytes Lymphoid tissue Lymphoid organs The Lymphatic System Lymphatic vessels...

CHAPTER 21 The Lymphatic Human Anatomy Copyright Copyright©©2011 2011Pearson PearsonEducation, Educatio, Inc. Inc. and Immune Systems The Lymphatic and Immune Systems Main structures Lymphatic vessels Main components Lymphocytes Lymphoid tissue Lymphoid organs The Lymphatic System Lymphatic vessels collect lymph circulate lymph to great veins in the neck one-way flow to heart Tissue fluid Tissue cell Blood capillaries Lymphatic capillaries Orders of Lymphatic Vessels Lymph capillaries smallest first receive lymph Lymphatic collecting vessels collect from lymph capillaries Lymph nodes scattered along collecting vessels Lymph trunks collect lymph from collecting vessels Lymph ducts empty into veins of the neck Functions of Lymphatic Vessels Located near blood capillaries Collect excess tissue fluid and blood proteins Return tissue fluid and blood proteins to bloodstream Lymph Capillaries High permeability allows: Uptake of tissue fluid Entrance of bacteria, viruses, and cancer cells Lymph Capillaries Lacteals – specialized lymphatic capillaries Located in the villi of the small intestines Receive digested fats Fatty lymph – chyle A villus of the small intestine Lymphatic Collecting Vessels Accompany blood vessels Composed of the same three tunics as blood vessels Contain more valves Helps direct the flow of lymph Lymph propelled by: Bulging of skeletal muscles Pulsing of nearby arteries Tunica media of the lymph vessels Lymph Nodes Cleanse the lymph of pathogens Human body contains approximately 500 Lymph nodes are organized in clusters Lymph Nodes Regional lymph nodes Internal jugular vein Entrance of right lymphatic duct into vein Entrance of thoracic duct into vein Thoracic duct Cisterna chyli Lymphatic collecting vessels Cervical nodes Axillary nodes Aorta Inguinal nodes Drained by the right lymphatic duct Drained by the thoracic duct Microscopic Anatomy of a Lymph Node Macrophage Reticular cells on reticular fibers Lymphocytes Medullary sinus Reticular fiber (c) Reticular tissue within the medullary sinus (540X) Lymph Trunks Lymphatic collecting 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 Subclavian trunks receive lymph from upper limbs and thoracic wall Jugular trunks drain lymph from the head and neck Overview of the Lymph Nodes, Trunks, and Ducts Regional lymph nodes Internal jugular vein Entrance of right lymphatic duct into vein Entrance of thoracic duct into vein Thoracic duct Cisterna chyli Lymphatic collecting vessels Cervical nodes Axillary nodes Aorta Inguinal nodes Drained by the right lymphatic duct Drained by the thoracic duct 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 Right lymphatic duct empties into right internal jugular and subclavian veins The Lymphatic Trunks Right jugular trunk Right lymphatic duct Right subclavian trunk Right subclavian vein Right bronchomediastinal trunk Brachiocephalic veins Superior vena cava Azygos vein Internal jugular veins Esophagus Trachea Left jugular trunk Left subclavian trunk Left subclavian vein Entrance of thoracic duct into vein Left bronchomediastinal trunk Ribs Thoracic duct Cisterna chyli Hemiazygos vein Right lumbar trunk Left lumbar trunk Inferior vena cava Intestinal trunk (a) Major lymphatic trunks and ducts in relation to veins and surrounding structures, anterior view The Lymphatic Trunks Thoracic duct Aorta Azygos vein on vertebral bodies (b) Thoracic duct (colored green) along the posterior thoracic wall The Immune System Recognizes specific foreign molecules Destroys pathogens effectively Key cells lymphocytes Also includes lymphoid tissue lymphoid organs Lymphocytes B lymphocytes and 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 Lymphocytes B lymphocytes Become plasma cells Secrete antibodies Mark cells for destruction by macrophages Respond primarily to bacteria and bacterial toxins Lymphocyte Function Target cell, bearing antigen T lymphocyte Antigen 1 T lymphocyte binds to target cell, secretes proteins that lyse the cell’s membrane, and signals the cell to die. (a) Action of cytotoxic T lymphocyte B lymphocyte Plasma cell Dead target cell 2 T lymphocyte detaches 3 Target from target cell. cell dies by apoptosis. Antibodies Bacterium Surface antigen Macrophage 1 B lymphocyte gives rise to plasma cell, which secretes antibodies. 2 Antibodies bind to antigens on bacteria, marking the bacteria for destruction. (b) Differentiation and activity of B lymphocyte 3 Antibody-coated bacteria are avidly phagocytized. Lymphocyte Activation Lymphocytes originate in bone marrow Some travel to the thymus gland T lymphocytes Some stay in bone marrow B lymphocytes Able to recognize a unique antigen Lymphocyte Activation Activating T or B cells produce Effector lymphocytes – short-lived, attack immediately Memory lymphocytes – wait until body encounters their antigen again Basis of acquired immunity Lymphocyte Activation Immature lymphocytes Red bone marrow Thymus Bone marrow Lymph nodes, spleen, and other lymphoid tissues 1 Lymphocytes destined to become T cells migrate (in blood) to the thymus and develop immunocompetence there. B cells develop immunocompetence in red bone marrow. Red bone marrow: site of lymphocyte origin Primary lymphoid organs: site of development of immunocompetence as B or T cells Secondary lymphoid organs: site of antigen encounter, and activation to become effector and memory B or T cells 2 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. 3 Antigen-activated immunocompetent lymphocytes (effector cells and memory cells) circulate continuously in the bloodstream and lymph and throughout the lymphoid organs of the body. 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 Lymphoid Organs Designed to gather and destroy infectious microorganisms Tonsils (in pharyngeal region) Thymus (in thorax; most active during youth) Spleen (curves around left side of stomach) Aggregated lymphoid nodule (in intestine) Appendix Thymus Immature lymphocytes develop into T lymphocytes Secretes thymic hormones Self-tolerance Thymus (a)Thymus located in the superior mediastinum Lymph Nodes Function Lymph percolates through lymph sinuses Most antigenic challenges occur in lymph nodes Antigens destroyed – and activate B and T lymphocytes Spleen Largest lymphoid organ Two main blood-cleansing functions Removal of blood-borne antigens Removal and destruction of old/defective blood cells Site of hematopoiesis in the fetus Spleen White pulp – thick sleeves of lymphoid tissue Immune response Red pulp – surrounds white pulp Dispose of worn-out blood cells Capsule Trabecula Splenic cords Venous sinuses Arterioles and capillaries Red pulp White pulp Central artery Splenic artery Splenic vein Hilum (a) Diagram of the spleen, anterior view Splenic artery Splenic vein (b) Diagram of spleen histology Tonsils Simplest lymphoid organs Swellings of mucosa Four groups of tonsils Palatine (often the ones to be removed), lingual, pharyngeal, and tubal tonsils Arranged in a ring around pharynx gather and remove pathogens Underlying connective tissue consists of MALT Packed with lymphocytes Aggregated Lymphoid Nodules and the 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