Transcript Lymph I
Anne and Tresha Thursday, December 2, 2004 Central = Primary lymphoid tissue • Site of maturation of the cells of the immune system • Thymus – encapsulated – T cells • Bone marrow – Bursal equivalent – B cells, monocytes, erythrocytes, granulocytes, and megakaryocytes Peripheral = Secondary lymphoid tissue • Filter blood and lymph • Site of antigen, immune system interaction Peripheral = Secondary lymphoid tissue • Diffuse lymphatic tissue (Unencapsulated) – Found in the lamina propria where pathogens are likely to invade – GI: Tonsils, Peyer’s patches, appendix; Respiratory tract; GU • Lymph nodes – Encapsulated – Interposed btwn lymphatic vessels (only) • Spleen lymphatic tissue – Encapsulated – Interposed btwn lymph and blood circulation Lymph Vessels • Valves • Carries Lymph from tissue lymph nodes blood via thoracic duct – – – – – – – Fluid Proteins Ingested fats Particulate matter Antigen Disease microorganisms Cells (normal and cancerous) Lab 11 Slide 7 Primary follicle - Naïve Lymphocytes - No germinal center Secondary follicle - Germinal Center - Antigen has been encountered - Looks pale! - because of plasmablasts 2 1 Lab 11 Slide 9 • Germinal Center – Dark zone = densely packed lymphocytes separated by reticular cells – Light zone = plasmablasts – T cells at periphery Tonsil • Unencapsulated • Stratified squamous nonkeratinized epithelium • Dense fibrous CT • CT Septum --> lobes • Crypts - invaded by lymphocytes • Numerous Lymphoid nodules – Germinal centers • Lymphocytes invade the epithelium and the connective tissue • GALT (gut associated lymphatic tissue) – – – – In the loose areolar CT of the lamina propria Diffuse lymphatic tissue Solitary lymphatic nodules Aggregates of lymphatic nodules (Peyer’s patches and appendix) Question 1 C. Both D. Neither A B Question 1 C. Both D. Neither Tonsil A • • • • Is encapsulated = B Contains germinal centers = C Peripheral lymphoid tissue = C Central lymphoid tissue = D B Lymph node Question 2 The region at the arrow is: A) Peyer’s Patch B) Germinal Center C) Lymph Node D) Primary lymphoid nodule Question 2 The region at the arrow is: A) Peyer’s Patch B) Germinal Center C) Lymph Node D) Primary lymphoid nodule Lymph Node Function • Filters lymphatic fluid • Enhance antigen presentation • Facilitate B-Cell Activation to generate plasma cells and memory B-cells Lymph Flow w/in Node Afferent Lymphatics Subcapsular sinus trabecular sinuses medullary sinus efferent lymphatics Lymph Node Structural Components • Capsule: Dense, Irregular CT • Trabeculae are extensions of the capsule • Reticular cells- framework (stain black with the Silver stain) • Hilum- efferent lymphs; entry and exit of blood vessels Lymph Node Parenchyma • Cortex – Primary, secondary nodules • • Deep cortex (aka paracortex, juxtamedullary cortex, thymus dependent cortex) – No nodules • Medulla – Cords and sinuses. – Where plasma cells synthesize and release Abs into lymph flowing through the sinuses. Lymphatic Sinuses • Subcapsular sinus – Receive lymph from afferent lymphatic vessels • Trabecular sinuses – • • Drain into medullary sinuses Provide open communication between lymphatic drainage and parenchyma (macrophages monitor lymph as it percolates through; will phagocytose) Macrophages take up India inkstained black. The Germinal Center • Characterizes the 2ndary nodule • Pale staining center: plasmablasts – Large cells, large nucleus, prominent nucleolus – May see mitotic figures • Dark outer zone – Densely packed lymphocytes (sp. B-cells) T-Cell Zone • Comprises Deep Cortex and Paracortex • Where T and B cells enter from the circulation • See post capillary venules with high endothelial cells • B cells migrate, T cells remain Medullary Region • Cords and Sinuses • Cords: reticular cells, lymphocytes, plasmablasts, plasma cells • Antibody secreted into efferent lymph • Macrophages present • Entry/Exit of blood vessels, nerves, efferent lymph Summary of Lymph Node flow Lymph Flow w/in Node Afferent Lymphatics Subcapsular sinus trabecular sinuses medullary sinus efferent lymphatics Question 3 The region inside the box contains which of the following upon antigenic stimulation: A. Plasma Cells A. Macrophages B. T-Cells C. Memory B-Cells D. All of the Above