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