Unit III: Homeostasis Defense Against Invasion Chapter 19

Functions of Lymphatic System Immunity Lymph nodes Lipid absorption Lacteals Fluid recovery 2 to 4 L/day interference leads to severe edema

Lymphatic Vessels Lymph Lymphatic capillaries Bud from veins Tunica interna, tunica media, tunica externa valves LM x 65 Lymphatic vessel valve

Route of Lymph Flow Tissue fluid  Lymphatic capillaries  Collecting vessels (lymph nodes)  6 Lymphatic trunks  2 Collecting ducts : right lymphatic duct  R subclavian vein thoracic duct - begins as a prominent sac in abdomen called the cisterna chyli;  empties into L subclavian vein

The Fluid Cycle Lymphedema in a foot Drainage of thoracic duct Drainage of right lymphatic duct Lymphedema in a foot

Lymphatic Cells Classes of Lymphocytes T Cells B Cells NK Cells 80% Mature in thymus Attack foreign cells by direct contact Stimulate the activation and function of both T cells and B cells Inhibit the activation and function of both T cells and B cells Cytotoxic T Cells Helper T Cells Suppressor T Cells Plasma Cells Produce and secrete antibodies 10–15% 5–10% Perform immune surveillance

Lymphatic Cells Antigen Presenting Cells (APCs) macrophages (from monocytes) dendritic cells (in epidermis, mucous membranes and lymphatic organs) reticular cells (also contribute to stroma of lymph organs) Lysosomal action produces antigenic fragments. Lysosome Phagocytic cell Nucleus Endoplasmic reticulum The endoplasmic reticulum produces Class II MHC proteins. Antigenic fragments are bound to Class II MHC proteins. are displayed by Class II MHC proteins on the plasma membrane. Plasma membrane Phagocytic APCs engulf the extracellular pathogens.

Lymphatic Organs Primary lymphatic organs site where T and B lymphocytes become immunocompetent red bone marrow and thymus Secondary lymphatic organs immunocompetent lymphocytes populate these tissues lymph nodes, tonsils, and spleen

Lymph Node Only organs that filter lymph Fewer efferent vessels, slows flow through node Trabeculae - divides node into compartments Stroma Parenchyma subdivided into cortex (lymphatic nodules) and medulla

Lymph Node Diseases Lymphadenitis swollen, painful node Lymphoma (Metastatic cancer) swollen, firm and usually painless

Tonsil Tonsillar crypts and encounter lymphocytes 3 sets: Pharyngeal tonsil (adenoids) Palatine tonsils Lingual tonsils

Spleen Parenchyma tissues: red pulp: white pulp: Functions blood production in fetus blood reservoir RBC disposal (“graveyard”) Stabilize blood volume

Thymus Both lymphatic and endocrine Maturation of T-cells and secretes hormones Most active in childhood (under age 14) If removed – no immunity Replaced by fibrous and fatty tissue

Thymus Structure similar to lymph nodes Reticular epithelial cells Blood-thymus barrier isolates developing T lymphocytes from foreign antigens secretes hormones (thymopoietin, thymulin and thymosins) Medulla Septa Cortex Lobule Thymus gland LM x 50

Defense Mechanisms Against Pathogens Nonspecific Defenses responses are the same, regardless of the type of invading agent are present at birth Physical barriers Phagocytes Immunological surveillance Interferons Complement Inflammatory response Fever Inflammation Destruction of abnormal cells Protect against particular threats Specific Defenses

Defenses Against Pathogens 1st Line of Defense Skin – stratified squamous epithelium, acid mantle, dendritic cells Mucus membranes – respiratory and digestive tracts: goblet cells Duct of cutaneous gland Hair Secretion Epithelium Basal lamina Mucus coating Goblet cell

Defense Against Pathogens 2nd Line of Defense Leukocytes and Macrophages Neutrophils – respiratory burst Eosinophils – kill parasites; limits histamine; promote basophils Basophils – secrete histamine and heparin Lymphocytes – 80% T-cells, 15% B-cells, 5% NK-cells Monocytes - transform into macrophages

Defense Against Pathogens 3rd Line of Defense Immune System Antigen Presentation Specific Defenses Specificity & Memory Cellular Immunity Direct Physical and Chemical Attack Phagocytes activated T cells Communication and feedback Destruction of antigens Activated T cells phagocytosis chemical toxins Attack with Antibodies Humoral Activated B cells

Passive and Active Immunity Specific Defenses Aquired Immunity Passive Immunity Transfer of antibodies from another source Naturally acquired passive immunity Maternal antibodies Temporary Artificially Injection Active Immunity Develops in response to antigen exposure active Artificially acquired active immunity Exposure to antigens in environment Memory cells Vaccination Genetically determined Innate Immunity

The Three “R”s of Immunity Cellular Immunity Recognition Antigen presentation T-cell activation React (attack) Helper T-cells - attract neutrophils, natural killer cells, and macrophages, stimulate T and B-cell mitosis and maturation Cytotoxic T-cells – “lethal hit” of cytotoxic chemicals Remember T-cell recall response

The Three “R”s of Immunity Humoral Immunity Recognition Receptors for one antigen on a B-cell Helper T-cell binds to complex B-cells differentiate into plasma cells React (attack) Neutralization, Complement fixation Agglutination, Precipitation Remember Primary response Bacteria Antibodies Antigenic determinant sites

Notes on Immunity Memory lasts longer in Cellular Immunity than Humoral Both processes of immunity occur simultaneously and in conjunction with inflammation Allergies localized anaphylaxis HIV attacks helper T-cells knocks out the central coordinating role in both processes First Exposure Allergens Macrophage TH cell activation B cell Plasma cell antibodies Subsequent Exposure Allergen Granules Massive stimulation Sensitization of mast cells and basophils Release of histamines

Test III Lecture Chapters: 17, 19, & 24 Lab practical Identification of slides: organ, cells, regions Lab manual questions