Lymphatic System

Lymphatic System

Dr. Kozeka Lymphatic System Copyright © 2010 Pearson Education, Inc. Lymphatic System: (General) Functions Returns interstitial fluid and leaked plasma proteins back to the blood Specialized lymph capillaries (called lacteals) present in intestinal mucosa absorb digested fat and deliver fatty lymph (chyle) to the blood Filter lymph (once interstitial fluid enters lymphatics, it is called lymph) Together with lymphoid organs and tissues, provide the structural basis of the immune system Produces T lymphocytes, B lymphocytes, and plasma cells T cells and B cells and macrophages protect against antigens Anything the body perceives as foreign Attack and destroy bacteria and their toxins, foreign cells, cancer cells, viruses, debri, Mismatched RBCs or cancer cells plasma cells (made by B cells) secrete antibodies Copyright © 2010 Pearson Education, Inc. Lymphatic System: (General) Functions Summarized: • Filter (clean) and return tissue fluid and blood plasma that leaked out back to the circulatory system • Immunity against all antigen and pathogens • Transport digested fat from intestine to circulatory system Copyright © 2010 Pearson Education, Inc. Lymphatic System (general structure/organs & tissues) Consists of 1. A network of lymphatic vessels (lymphatics) 2. Lymph 3. Lymph nodes 4. Spleen 5. Thymus 6. Tonsils 7. Lymphoid follicles (similar to tonsils) Copyright © 2010 Pearson Education, Inc. Lymphatic System (general structure/organs & tissues) Summarized: Microscopic network of vessels (sewer system) Filters (cotton balls) with lymphocytes living in them (police stations) The “filters” or “cotton balls” or “police stations” come in different sizes and shapes as lymph nodes, tonsils, spleen, thymus, and lymphoid follicles ( similar to tonsils) Copyright © 2010 Pearson Education, Inc. Venous system Arterial system Heart Lymphatic system: Lymph duct Lymph trunk Lymph node Lymphatic collecting vessels, with valves Tissue fluid Blood Lymphatic Tissue cell capillaries capillary Blood Lymphatic capillaries capillaries (a) Structural relationship between a capillary bed of the blood vascular system and lymphatic capillaries. Filaments anchored to connective tissue Endothelial cell Flaplike minivalve Fibroblast in loose connective tissue (b) Lymphatic capillaries are blind-ended tubes in which adjacent endothelial cells overlap each other, forming flaplike minivalves. Copyright © 2010 Pearson Education, Inc. Figure 20.1 Dr. Kozeka Anatomy of the Lymphatic Vessels Copyright © 2010 Pearson Education, Inc. Regional Internal jugular vein lymph nodes: Cervical nodes Entrance of right lymphatic duct into vein Entrance of thoracic duct into vein Axillary nodes Thoracic duct Cisterna chyli Aorta Inguinal nodes Lymphatic collecting vessels Drained by the right lymphatic duct Drained by the thoracic duct (a) General distribution of lymphatic collecting vessels and regional lymph nodes. Copyright © 2010 Pearson Education, Inc. Figure 20.2a Right jugular trunk Internal jugular veins Right lymphatic duct Esophagus Right subclavian trunk Trachea Right subclavian vein Left subclavian trunk Right broncho- Left jugular trunk mediastinal trunk Left subclavian vein Brachiocephalic veins Entrance of thoracic Superior vena cava duct into vein Left bronchomediastinal Azygos vein trunk Ribs Thoracic duct Hemiazygos vein Cisterna chyli Right lumbar trunk Left lumbar trunk Inferior vena cava Intestinal trunk (b) Major lymphatic trunks and ducts in relation to veins and surrounding structures. Anterior view of thoracic and abdominal wall. Copyright © 2010 Pearson Education, Inc. Figure 20.2b Lymphatic Vessels • One-way system, lymph flows toward the heart • Lymph vessels (lymphatics) include: • Lymphatic capillaries • Lymphatic collecting vessels • Lymphatic trunks and ducts Copyright © 2010 Pearson Education, Inc. Lymphatic Collecting Vessels • Similar to veins, except have thinner walls, with more internal valves • Travel with veins and arteries Copyright © 2010 Pearson Education, Inc. Lymphatic Ducts • Lymph is delivered into one of two large ducts • Right lymphatic duct (drains the right upper arm and the right side of the head and thorax) • Thoracic duct drains the rest of the body • Each empties lymph into venous circulation at the junction of the internal jugular and subclavian veins on its own side of the body Copyright © 2010 Pearson Education, Inc. Dr. Kozeka How Does Lymph (fluid) Move Around From The Tissues To The Heart? Copyright © 2010 Pearson Education, Inc. Lymph Transport The lymphatic system does not have a pump (heart) and so for its propulsion it relies on force generated indirectly such as • Pulsations of nearby arteries • Pulsations of Skeletal muscle when moving limbs • Pressure changes in the Thorax and Abdomen To a lesser extent, contractions of smooth muscle in the walls of the lymphatics can help to propel lymph fluid Copyright © 2010 Pearson Education, Inc. Lymph Transport If lymph fluid is propelled by “milking” action (like squeezing a tube of toothpaste in the middle of the tube), what keeps lymph from flowing backward (i.e., in both directions)? Copyright © 2010 Pearson Education, Inc. Lymph Transport If lymph fluid is propelled by “milking” action (like squeezing a tube of toothpaste in the middle of the tube), what keeps lymph from flowing backward (i.e., in both directions)? Many valves along the lymph vessels and ducts and also at the openings and exits of lymph nodes! (See later image of lymph node) Copyright © 2010 Pearson Education, Inc. Dr. Kozeka Lymphocytes and Macrophages Copyright © 2010 Pearson Education, Inc. Lymphoid Cells • Lymphocytes the main warriors of the immune system • Two main varieties: T cells (T lymphocytes) and B cells (B lymphocytes) • T cells and B cells protect against antigens (anything the body perceives as foreign) • Bacteria and their toxins; viruses • Mismatched RBCs or cancer cells Copyright © 2010 Pearson Education, Inc. Lymphocytes • T cells • Manage the immune response • Attack and destroy foreign cells • B cells • Produce plasma cells, which secrete antibodies Copyright © 2010 Pearson Education, Inc. Macrophages • Macrophages phagocytize foreign substances and help activate T cells Copyright © 2010 Pearson Education, Inc. Plasma cells • Plasma cells (made by B cells) produce antibodies Copyright © 2010 Pearson Education, Inc. Dr. Kozeka Other Lymphoid Cells Copyright © 2010 Pearson Education, Inc. Other Lymphoid Cells • Dendritic cells capture antigens and deliver them to lymph nodes • Reticular cells produce stroma that supports other cells in lymphoid organs Copyright © 2010 Pearson Education, Inc. Macrophage Reticular cells on reticular fibers Lymphocytes Medullary sinus Reticular fiber Copyright © 2010 Pearson Education, Inc. Figure 20.3 Dr. Kozeka Lymphoid Tissues Copyright © 2010 Pearson Education, Inc. Lymphoid Tissue • Houses and provides a proliferation site for lymphocytes • Furnishes a surveillance vantage point • Two main types • Diffuse lymphatic tissue - scattered reticular tissue elements in every body organ • Lymphatic follicles - Lymphatic follicles (nodules) are solid, spherical bodies of tightly packed reticular elements and cells; have germinal center composed of dendritic and B cells; may form part of larger lymphoid organs Copyright © 2010 Pearson Education, Inc. Lymphoid Tissue • Lymphatic follicles (nodules) are solid, spherical bodies of tightly packed reticular elements and cells • Germinal center composed of dendritic and B cells • May form part of larger lymphoid organs Copyright © 2010 Pearson Education, Inc. Dr. Kozeka Lymphoid Nodes Copyright © 2010 Pearson Education, Inc. Lymph Nodes • Principal lymphoid organs of the body • Embedded in connective tissue, in clusters along lymphatic vessels • Near the body surface in inguinal, axillary, deltoid, pectoral, cubitaland cervical regions of the body Copyright © 2010 Pearson Education, Inc. Regional Internal jugular vein lymph nodes: Cervical nodes Entrance of right lymphatic duct into vein Entrance of thoracic duct into vein Axillary nodes Thoracic duct Cisterna chyli Aorta Inguinal nodes Lymphatic collecting vessels Drained by the right lymphatic duct Drained by the thoracic duct (a) General distribution of lymphatic collecting vessels and regional lymph nodes. Copyright © 2010 Pearson Education, Inc. Figure 20.2a Lymph Nodes • Functions 1. Filter lymph—macrophages destroy microorganisms and debris 2. Immune system—lymphocytes are activated and mount an attack against antigens Copyright © 2010 Pearson Education, Inc. Structure of a Lymph Node • Bean shaped • External fibrous capsule • contain B cells, T cells, plasma cells, and macrophages • Trabeculae extend inward and divide the node into compartments • Two histologically distinct regions • Cortex • Medulla Copyright © 2010 Pearson Education, Inc. Cortex • Lymphoid follicle Afferent lymphatic • Germinal center vessels • Subcapsular sinus With valves Efferent lymphatic vessels With valves Hilum Medulla: • Medullary cord • Medullary sinus Trabeculae Capsule (a) Longitudinal view of the internal structure of a lymph node and associated lymphatics Copyright © 2010 Pearson Education, Inc. Figure 20.4a Dr. Kozeka Spleen Copyright © 2010 Pearson Education, Inc. Diaphragm Spleen Adrenal gland Left kidney Splenic artery Pancreas (c) Photograph of the spleen in its normal position in the abdominal cavity, anterior view. Copyright © 2010 Pearson Education, Inc. Figure 20.6c Capsule Trabecula Splenic cords Venous sinuses Arterioles and Splenic capillaries artery

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