The Lymphatic System
Non-Specific Defenses
Physical Barriers Epithelium, hair, secretions, acid, enzymes
Phagocytes 1st line of cellular defense – removes debris and pathogens Microphages leave blood stream and enter peripheral tissues (neutrophils and eosinophils) Macrophages – sensitive to chems in surrounding fluids can be free or fixed
Interferons Slow spread of viral infections Stimulate macrophages and NK cells
Inflammation Initiated by mast cells releasing histamines and heparin Local swelling, heat, redness, and pain Slows spread of pathogens Necrosis – tissue destruction via lysosomes Pus – accumulation of dead cells and debris (abscess – accumulation of pus)
Fever (>98oF) Pyrogens – proteins reset body's “thermostat” Incr. rate of metabolism Over 104oF damages CNS, nausea, hallucination, and convulsions
Organization
Lymph Vessels Begin at peripheral tissue venous system Small valves prevent backflow
Lymph Fluid Blood plasma but w/less proteins
Lymphocytes Cells defend body 80% last 4 years…some last 20 years or
more! Lymph Tissue
Loose connective tissue Tonsils, Appendix, Peyer’s Patches Size can increase or decrease depending
on number of lymphocytes Lymph Organs
Lymph nodes Spleen Thymus
Lymph Vessels
Lead towards trunk of body and empty into 2 ducts
Thoracic duct – lower abdomen, pelvis, lower limbs, left head, neck, and chest
Right lymphatic duct – right side of body, above diaphragm
Lymphodema (edema) – blockage of lymph drain
Functions
Protect body from pathogens
Production, maintenance, and distribution of lymphocytes
Return fluid from peripheral tissues to blood
Distribute hormones, nutrients, and waste to general circulation
Lymphoid Organs
Lymph Nodes Filter and purify lymph before enters
venous system Detects and removes antigens Stimulates T cells and B cells initiating
immune response Lymphomas – cancer arising from
lymphocytes Thymus
Decrease in size after puberty T cell production and maturation
Spleen 5” long on left side, deep red Filters blood, removes abnormal blood
cells and initiates B cell and T cell responses to antigens
Macrophages identify and engulf damaged or infected cells
Lymphocytes
25% of circulating wbc T cells – thymus dependent (80% circulating lymphocytes)
Cytotoxic T cells – attack foreign cells or body cells infected w/ virus
Helper T cells – stimulate T cells and B cells Suppressor T cells – inhibit T cells and B cells
B cells -bone marrow derived (10-15% circ. Lymphocytes) Plasma cells – secrete antibodies (immunoglobulins) Antibodies bind to antigens
NK cells natural killer cells (5-10% circulating lymphocytes) Attack foreign cells, viral infected cells, and cancer cells
Specific Defenses
Immunity – respond to the presence of specific antigens Antigens – “non-self” substance that excites the immune
system and stimulates a response Genes determine specificity T cells – cell mediated immunity
Defend against abnormal cells Pathogens inside of cells
B cells – antibody-mediated immunity Defend against antigens and pathogens in body fluids Antibodies (immunoglobulins) – bind to specific antigen, Y
shape with 2 antigen binding sites
Immune Response (antibody mediated)
B cell binds w/antigen…becomes activated and produces clones
B cell clones Plasma cells – secrete antibodies (2,000
per sec!)… reaches peak 10 days Memory B cells – continue to circulate,
and can speed process to 2-3 days if recognizes an “old enemy”
Immune Response (cell mediated)
T cells cannot bind to “free” antigen Macrophages and B cells must present antigen to T cells Once T cell binds to “presented” antigen
Killer (cytotoxic) T cells• Binds to target cell and inserts a toxic chem… target cell ruptures
Helper T cells• Recruit other cells to fight invaders• Stimulates B cells to increase production of antibodies• Simulates Killer T cells to multiply
Suppressor T cells • Release chems to suppress B and T cell activity• Most T cells enlisted to fight die w/in a few days• Some remain as memory cells to respond quickly to subsequent
invasions
Properties of Immunity
Specificity T cells and B cells target one specific antigen
Versatility Millions different lymphocytes w/diff antigen
receptors Memory
1st exposure – lymphocytes divide to create “attack” cells and memory cells
Response to 2o exposure to antigen is stronger than 1st
Tolerance Doesn’t respond to normal “self” tissues or antigens
Types of Immunity
Innate – genetically determined Acquired – arises during life
Active – appears after exposure to antigen• Naturally- continually induced as encounter “new” pathogens
or antigens• Induced – stimulated under controlled conditions
• Vaccine: dead/inactive pathogen that induces an immune response
Passive – transfer of antibodies from another source• Naturally – mother to baby
• Gestation – via placenta• Infancy – via breast milk
• Induced – antibodies administered to fight infection or prevent disease after exposure
Lymphatic Project
Cartoon/comic strip analogous to lymphatic system that highlights functions of B cells, plasma cells, antibodies, and memory B cells, Helper Tcells, Killer T cells, and suppressor T cells
Research and write an essay on allergies, organ transplant and rejection, multiple sclerosis, systemic lupus, OR HIV/AIDS
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