Chapter 22 - Lymph Tissues and Organs Lecture 5 PDF

Part 1: Lymphatic Tissues - the MALT System and Histology AND Issues Related to the Immune Sys. Part 2: Lymphatic Organs and Their Histology Cervical nodes Axillary nodes Inguinal nodes    Lymphoid nodules = areas of densely packed, unencapsulated lymphocytes w/in areolar CT. Each nodule contains...

Part 1: Lymphatic Tissues - the MALT System and Histology AND Issues Related to the Immune Sys. Part 2: Lymphatic Organs and Their Histology Cervical nodes Axillary nodes Inguinal nodes    Lymphoid nodules = areas of densely packed, unencapsulated lymphocytes w/in areolar CT. Each nodule contains a germinal center which lymphocyte division occurs. The collection of LT protecting mucous membrane epithelia of digestive, respiratory, urinary, and reproductive systems (exposed to environ.) is known as MALT. ◦ Mucosa-associated lymphoid tissue. ◦ Ex: tonsils, Peyer patchs, and appendix.  MP: No clear line of separation from surrounding tissue (although easy to see).   Mucosa-associated lymphoid tissue Tonsils guard entrances to digestive + respiratory tracts. ◦ 5 total tonsils   Peyer patches are aggregated (clustered) nodules in intestinal lining protecting digestive tract. Appendix near junction of small + large intestines further protecting digestive system.  Images are related to the Mucosa-associated lymphoid tissues!  1) Autoimmune disorders – immune system attacks “normal” (self-) antigens. Autoantibodies? ◦ Abs that attack one’s self. Examples of disease? ◦ May be result of reduction in suppressor T-cells. ◦ Ex: thyroiditis (thyroid), rheumatoid arthritis (synovial membranes), Type 1 Diabetes (beta cells), myasthenia gravis (Ach receptors), and multiple sclerosis (myelin sheath).  2) Immunodeficiency disease results from? ◦ Failure to develop immune system = severe combined immunodeficiency disease (SCID) ◦ Viral infection from HIV leading to acquired immunodeficiency syndrome (AIDS). ◦ Immunosuppressive drugs = lead to immunological failure; however, important for transplants.    excessive immune response caused by allergens – antigens that trigger allergic reaction. Anaphylaxis? Circulating antigen activates mast cells throughout body, which can lead to death. ◦ Increases capillary permeability causes hives on skin and edema in dermis. ◦ Breathing difficult due to contraction of smooth muscle of respiratory tract. ◦ Peripheral vasodilation can causes circulatory collapse (anaphylactic shock) due to drop in BP.  Antihistamines block histamine release by mast cells; may relieve mild symptoms. 1. 2. 3. 4. 5. 6. How do lymph tissues differ from lymph organs, & what is a lymphoid nodule? What are the 3 MALT tissues discussed, where are they located, and how can you distinguish them histologically? How do autoimmune diseases differ from immunodeficiency, and provide examples of each and explain why they are “autoimmune” vs “immunodeficiency? What are allergies + anaphylaxis? What are lymph nodes, efferent vs afferent lymphatics, & what’s the order lymph flows through the node + the cells it encounters? What’s the role of the thymus, and how does the cortex differ from medulla? What’s the function of the spleen and how does the red pulp differ from white pulp? Part 1: Lymphatic Tissues - the MALT System and Histology AND Issues Related to the Immune Sys. Part 2: Lymphatic Organs and Their Histology Cervical nodes Axillary nodes Inguinal nodes     Encapsulated tissues that form organs separate from other tissues/organs. Which 3? ◦ 1) Lymph nodes, 2) Thymus, 3) Spleen Function to monitor peripheral tissues for infection + contain it if infection occurs. 1) Clustered along lymph vessels. Functions: 1) filter lymph before reaching veins Cervical nodes Axillary nodes ◦ Macrophages destroy microorganisms + debris.  2) Early immune response – lymphocytes are activated + mount attack on foreign antigens. Inguinal nodes     Remove 99% of antigens + filter lymph, scattered throughout the body. (anatomy described below) Trabeculae – bundles of college fibers extending into interior. Hilum – indentation where blood + nerves enter. Afferent lymphatics = vessels that bring lymph to nodes from peripheral tissue (several).  Efferent lymphatics = vessels that carry filtered lymph onward to return to venous system (singular).       Lymph flows through a series of sinuses passing different regions containing diff. cells w/in organ. 1) Subcapular space = macrophages + dendritic cells (first set of cells). 2) Outer cortex = B cells in germinal centers 3) Deep cortex = T cells (leaving blood) 4) Medulla = B cells + plasma cells 5) Finally through hilum + efferent vessels.   Site of T-cell maturation via thymosin stimulation. ◦ Located w/in mediastinum. Develops to max size @ puberty, but gradually atrophies as we age.  Each lobe (2) divided by septa to form lobules.  Cortex = site of T-cell division + maturation.  Medulla = site where T cells enter/leave via capillaries + site of thymic corpuscles whose function is unknown.      Filters blood (instead of lymph; similar to nodes). ◦ Located b/n stomach, left kidney, + diaphragm. 3 Main Functions: 1) Remove abnormal blood cells + blood components via phagocytosis. 2) Store recycled iron from RBCs. 3) Initiate immune response of B- + T-cells in response to antigens circulating in blood.     A capsule of collagen + elastic fibers surrounds the largest collection of lymphoid tissue. Splenic veins, arteries, and lymph vessels enter via hilum. Red pulp = lots of RBCs; white pulp = resembles lymph nodules.  Phagocytes + lymphocytes of spleen identify + attack damaged and/or infected cells in the blood, purifying it.  Histology of: Thymus, Spleen, and Lymph Node