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- 1. © 2012 Pearson Education, Inc. 23 The Lymphoid System PowerPoint® Lecture Presentations prepared by Steven Bassett Southeast Community College Lincoln, Nebraska
- 2. © 2012 Pearson Education, Inc. Introduction The lymphoid system Lymphatic vessels Lymph (fluid connective tissue) Lymphoid tissues Diffuse lymphoid tissues Lymph nodule Lymphoid organs Lymph node Thymus: most active during infancy and youth. Spleen (the largest organ of the lymphatic system) Plays central role in body’s defenses against viruses, bacteria, and other microorganisms Lymphatic vessels originate in peripheral tissues and deliver lymph to the venous system.
- 3. © 2012 Pearson Education, Inc. An Overview of the Lymphoid System Lymph consists of: Interstitial fluid, which resembles blood plasma, but with a lower concentration of proteins Lymphocytes, cells responsible for the immune response Macrophages of various types
- 4. © 2012 Pearson Education, Inc. Functions of the lymphatic system Primary functions of the lymphoid system: Produce, maintain, and distribute lymphocytes Maintain normal blood volume and eliminate local variations in the chemical composition of the interstitial fluid Provide an alternative route for the transport of hormones, nutrients, and waste products
- 5. © 2012 Pearson Education, Inc. Figure 23.2a Lymphatic Capillaries A three-dimensional view of the association of blood capillaries and lymphatic capillaries. Arrows show the direction of blood, interstitial fluid, and lymph movement. Loose connective tissue Endothelial cells Lymph flow Interstitial fluid Venule Smooth muscle Blood capillaries Arteriole Lymphatic capillary
- 6. © 2012 Pearson Education, Inc. Structure of Lymphatic Vessels Lymphatic capillaries (or terminal lymphatics) form a complex network within peripheral tissues. Lymphatics contain internal valves that prevent backflow of lymph. Lymphatic vessels (or lymphatics) carry lymph from peripheral tissues to the venous system. The right lymphatic duct receives lymph from the right side of the thorax. The rest of the body’s lymph (most of the lymph) returns to the venous system through thoracic duct. Thoracic duct joins the left subclavian vein at the junction of left internal jugular vein. Large lymphatic trunks are located in the posterior thoracic and abdominal wall.
- 7. © 2012 Pearson Education, Inc. Figure 23.2b Lymphatic Capillaries Sectional view through a cluster of lymphatic capillaries Incomplete basal lamina Lymph flow Loose connective tissue Lymphocyte To larger lymphatics Interstitial fluid Interstitial fluid Blood capillary Lymphatic capillary
- 8. © 2012 Pearson Education, Inc. Figure 23.3ac Lymphatic Vessels and Valves The cross-sectional view emphasizes the structural differences between blood vessels and lymphatic vessels. Lymphatic vessel Vein Artery Toward venous system Lymphatic valve Lymphatic vessel From lymphatic capillaries Artery Vein A diagrammatic view of loose connective tissue showing small blood vessels and a lymphatic vessel. Arrows indicate the direction of lymph flow.
- 9. © 2012 Pearson Education, Inc. Structure of Lymphatic Vessels Two sets of lymphatic vessels: Superficial lymphatic vessels travel with superficial veins The subcutaneous layer next to the skin The loose connective tissues of the mucous membranes The loose connective tissues of the serous membranes Deep lymphatic vessels are large lymphatic vessels that accompany the deep arteries and veins. Collect lymph from skeletal muscles and other organs of the neck, limbs, and trunk, as well as visceral organs in the thoracic and abdominopelvic cavities
- 10. © 2012 Pearson Education, Inc. Figure 23.1 Lymphoid System Tonsil Cervical lymph nodes Right lymphatic duct Thymus Thoracic duct Cisterna chyli Lumbar lymph nodes Lymphatics of lower limb Lymphatics of upper limb Axillary lymph nodes Thoracic (left lymphatic) duct Lymphatics of mammary gland Spleen Mucosa-associated lymphoid tissue (MALT) Pelvic lymph nodes Inguinal lymph nodes
- 11. © 2012 Pearson Education, Inc. Figure 23.4a Lymphatic Ducts and Lymphatic Drainage The collecting system of lymph vessels, lymph nodes, and major lymphatic collecting ducts and their relationship to the brachiocephalic veins Right lumbar trunk Inferior vena cava (cut) Azygos vein Rib (cut) Superior vena cava (cut) Right bronchomediastinal trunk Right subclavian vein Right internal jugular vein Right jugular trunk Right lymphatic duct Right subclavian trunk Brachiocephalic veins Left internal jugular vein Left jugular trunk Thoracic duct Left subclavian trunk Left bronchomediastinal trunk Left subclavian vein First rib (cut) Highest intercostal vein Thoracic duct Thoracic lymph nodes Hemiazygos vein Parietal pleura (cut) Diaphragm Cisterna chyli Intestinal trunk Left lumbar trunk
- 12. © 2012 Pearson Education, Inc. Figure 23.4b Lymphatic Ducts and Lymphatic Drainage The thoracic duct collects lymph from tissues inferior to the diaphragm and from the left side of the upper body. The right lymphatic duct drains the right half of the body superior to the diaphragm. Drainage of thoracic duct Drainage of right lymphatic duct
- 13. © 2012 Pearson Education, Inc. Lymphocytes Lymphocytes are the primary cells of the Lymphoid system, and they are responsible for specific immunity. They respond to the presence of Invading organisms, such as bacteria and viruses Abnormal body cells, such as virus-infected cells or cancer cells Foreign proteins, such as the toxins released by some bacteria
- 14. © 2012 Pearson Education, Inc. Lynphocytes Three different classes of lymphocytes in the blood: T cells (thymus dependent) Cytotoxic T cells Helper T cells Suppressor T cells Memory T cells B cells (bone marrow derived) Plasma cells (providing humoral immunity) Memory B cells (stay in the body to fight off the second time infection easier) NK cells (natural killer)
- 15. © 2012 Pearson Education, Inc. Figure 23.6a Lymphocytes and the Immune Response BACTERIA Macrophage activation Antigen presentation Activation of cytotoxic T cells Activation of helper T cells Activation of B cells Destruction of bacteria by cell lysis Antibody production by plasmocytes Defenses against bacterial pathogens are usually initiated by active macrophages.
- 16. © 2012 Pearson Education, Inc. Figure 23.7 Derivation and Distribution of Lymphocytes The second group of stem cells migrates to the thymus, where subsequent divisions produce daughter cells that mature into T cells. One group remains in the bone marrow, producing daughter cells that mature into B cells and NK cells that enter peripheral tissues. Mature T cells leave the circulation to take temporary residence in peripheral tissues. All three types of lymphocytes circulate throughout the body in the bloodstream. Cell-mediated immunity Antibody-mediated immunity Immunological surveillance Peripheral Tissues Red Bone MarrowThymus Lymphoid stem cells Mature T cell Thymic hormones Production and differentiation of T cells Migrate to thymus Transported by circulatory system Lymphoid stem cells Mature T cell B cells NK cells Lymphoid stem cells Pluripotential stem cell Interleukin-7 As they mature, B cells and NK cells enter the bloodstream and migrate to peripheral tissues.
- 17. © 2012 Pearson Education, Inc. Lymphoid Tissues Any tissue containing an abundance of lymphocytes Diffuse lymphoid tissues—loosely packed lymphocytes within connective tissue Lymphoid nodules—densely packed lymphocytes within loose connective tissue Tonsils Pharyngeal tonsils(Adenoid) Lingual tonsils (at the base of the tongue) Palatine tonsils(at the entrance to oropharynx) Aggregated lymphoid nodules (Peyer’s patches)
- 18. © 2012 Pearson Education, Inc. Figure 23.8c Histology of Lymphoid Tissues The location of the tonsils and the histological organization of a single tonsil Pharyngeal tonsil Pharyngeal epithelium Germinal centers within nodules LM × 50 Pharyngeal tonsil Palatine tonsil Lingual tonsil Palate
- 19. © 2012 Pearson Education, Inc. Lymphoid Organs Lymphoid tissues that are separated from surrounding tissues by a capsule Lymph nodes Receive the lymph through afferent vessels and the cleanest lymph will leave the node through efferent vessels. Thymus Spleen
- 20. © 2012 Pearson Education, Inc. Figure 23.1 Lymphoid System Tonsil Cervical lymph nodes Right lymphatic duct Thymus Thoracic duct Cisterna chyli Lumbar lymph nodes Lymphatics of lower limb Lymphatics of upper limb Axillary lymph nodes Thoracic (left lymphatic) duct Lymphatics of mammary gland Spleen Mucosa-associated lymphoid tissue (MALT) Pelvic lymph nodes Inguinal lymph nodes
- 21. © 2012 Pearson Education, Inc. Figure 23.9 Structure of a Lymph Node Lymph node artery and vein Hilum Lymph nodes Lymph nodes Lymph vessel Efferent vessel Trabeculae Medulla Cortex Subcapsular space Deep cortex (T cells) Capsule Medullary cord (B cells and plasmocytes) Afferent vessel Medullary sinus Outer cortex (B cells) Dividing B cell Germinal center Subcapsular space Outer cortex Capsule Dendritic cells Nuclei of B cells Capillary
- 22. © 2012 Pearson Education, Inc. Figure 23.10 Lymphatic Drainage of the Head and Neck Periauricular lymph node Retroauricular lymph node Occipital lymph node Parotid lymph node Superficial cervical lymph node Deep cervical lymph node Sternocleidomastoid muscle Orbicularis oculi muscle Infraorbital lymph node Submandicular lymph node Buccal lymph node Mandibular lymph node Submental lymph node Parotid salivary gland
- 23. © 2012 Pearson Education, Inc. Figure 23.11a Lymphatic Drainage of the Upper Limb Superficial lymphatic vessels and nodes that drain the upper limb and chest of a male Deltopectoral lymph node Deltoid muscle Pectoralis major muscle Cephalic vein Basilic vein Axillary lymph nodes Supratrochlear lymph node
- 24. © 2012 Pearson Education, Inc. Figure 23.11b Lymphatic Drainage of the Upper Limb Superficial and deeper lymphatic vessels and nodes of the upper limb and chest of a female Subclavian lymph node Axillary lymph nodes Pectoralis major muscle (cut) Axillary vein Subscapular lymph node Pectoral lymph node Mammary gland Central lymph node Parasternal lymph node
- 25. © 2012 Pearson Education, Inc. Figure 23.12 Lymphatic Drainage of the Lower Limb Superficial inguinal lymph nodes Deep inguinal lymph nodes Popliteal lymph nodes Great saphenous vein
- 26. © 2012 Pearson Education, Inc. Figure 23.14b Lymphatic Drainage of the Inguinal Region A superficial and deeper view of the inguinal region of a male showing the distribution of lymph nodes and lymphatics Deep Inguinal and Iliac Lymph Nodes Superficial Inguinal Lymph Nodes Superficial inguinal lymph nodes Lymphatic vessels Fascia Anterior superior iliac spine External iliac artery External iliac vein Inguinal ligament Femoral artery Deep inguinal lymph nodes Femoral vein Great saphenous vein
- 27. © 2012 Pearson Education, Inc. Figure 23.15 Lymph Nodes in the Large Intestine and Associated Mesenteries Inferior mesenteric lymph nodes Inferior mesenteric artery Distal portion of duodenum Superior mesenteric artery Descending colon Sigmoid colon Rectum Appendix Appendicular lymph nodes Transverse mesocolic lymph nodes Cecum Ileum Ascending colon Transverse colon Superior mesenteric lymph nodes Ileocolic lymph nodes
- 28. © 2012 Pearson Education, Inc. Figure 23.16a Anatomy and Histological Organization of the Thymus The location of the thymus on gross dissection; note the relationship to other organs in the chest Right lobe Diaphragm Trachea Thyroid gland Right lung Left lung Left lobe THYMUS Heart
- 29. © 2012 Pearson Education, Inc. Figure 23.16bc Anatomy and Histological Organization of the Thymus Anatomical landmarks on the thymus Histology of the thymus. Note the fibrous septa that divide the thymic tissue into lobules resembling interconnected lymphoid nodules. Left lobe Right lobe Septa Lobule SeptaMedulla Cortex Lobule Lobule The thymus gland LM × 50
- 30. © 2012 Pearson Education, Inc. Figure 23.16cd Anatomy and Histological Organization of the Thymus Histology of the thymus. Note the fibrous septa that divide the thymic tissue into lobules resembling interconnected lymphoid nodules. Histology of the unusual structure of thymic corpuscles. The small cells in view are lymphocytes in various stages of development. A thymic corpuscle LM × 550 Lymphocytes Thymic corpuscle Reticular cells SeptaMedulla Cortex Lobule Lobule The thymus gland LM × 50
- 31. © 2012 Pearson Education, Inc. Figure 23.17a Anatomy and Histological Organization of the Spleen The shape of the spleen roughly conforms to the shapes of adjacent organs. This transverse section through the trunk shows the typical position of the spleen within the abdominopelvic cavity (inferior view). Spleen Aorta Rib Pancreas Liver Parietal peritoneum Visceral peritoneum Stomach Diaphragm Kidneys Gastrosplenic ligament Gastric area Diaphragmatic surface SPLEEN Hilum Renal area
- 32. © 2012 Pearson Education, Inc. Figure 23.17b Anatomy and Histological Organization of the Spleen External appearance of the visceral surface of the intact spleen showing major anatomical landmarks. This view should be compared with that of part (a). SUPERIOR INFERIOR Splenic lymphatic vessel Splenic artery Splenic vein Hilum Renal area Gastric area
- 33. © 2012 Pearson Education, Inc. Aging and the Lymphoid System With advancing age, the lymphoid system becomes less effective at combating disease. T cells become less responsive to antigens. The number of helper T cells is reduced. B cells are less responsive. Antibody levels do not rise as quickly after antigen exposure. The net result is an increased susceptibility to viral and bacterial infection, and cancer.