Immune & Lymphatic System – Study Guide
Lymphatic System Overview
Fluids in Tissues
Blood pressure inside capillaries forces plasma out through capillary walls into surrounding tissues.
Fluid Recovery
Most leaking fluid is reabsorbed back into the bloodstream through venous capillaries.
Unabsorbed Fluid: About 3 liters per day is not reabsorbed by veins.
Functions of the Lymphatic System
Fluid Recovery: Returns leaked fluid to the bloodstream to maintain blood volume and pressure.
Immunity: Filters lymph, houses immune cells, and protects against pathogens.
Components of the Lymphatic System
Lymph: The fluid collected and carried through the system.
Lymphatic vessels: Responsible for transporting lymph to the heart.
Lymph nodes: Inspect and clean lymph that passes through.
Pathway of Lymph:
Lymphatic capillaries
Collecting vessels
Lymph trunks
Lymphatic ducts
Veins near the heart
Additional Organs/Tissues
Spleen
Tonsils
Appendix
Thymus
Largest Organ: The Spleen.
MALT: Mucosa-Associated Lymphoid Tissue, includes:
Tonsils
Peyer’s patches
Appendix
Tonsils
Location: Found in the pharynx.
Function: Trap pathogens entering through the mouth or nose.
Peyer’s Patches
Location: Found in the ileum of the small intestine.
Function: Monitor intestinal bacteria and prevent infection.
Appendix
Function: Stores beneficial gut bacteria and contains immune tissue to fight infection.
Pathogens
Definition of Pathogen: A pathogen is something that causes disease; the name literally means "disease-producer."
Pathogens vs. Immune System: Pathogens cause disease, while the immune system detects and destroys them.
Categories of Pathogens:
Viruses
Bacteria
Fungi
Protists
Worms
Diseases Associated with Pathogens:
Rabies: 100% fatal unless immediately treated.
E. coli: Bacterial species that normally lives in human guts without causing harm.
Guinea Worm: A worm that matures in the body and emerges to lay eggs in water.
Giardiasis: Also known as beaver fever; caused by drinking contaminated water.
Tetanus: Also known as lockjaw; caused when soil bacteria enter a wound.
Influenza: Also known as the "flu"; respiratory illness.
Other Diseases: Tuberculosis, Lyme disease, Botulism, etc.
Pathogen Types:
Athlete's foot: Fungal
Rabies: Viral
Botulism: Bacterial
E. coli: Bacterial
Guini Worm: Worm
Immune Responses
Innate Immune Response vs. Adaptive Immune Response:
Innate:
A (Non-specific immunity)
F (Includes NK cells, inflammation, and mucus membranes)
G (Includes phagocytes and skin)
Adaptive:
B (Specific immunity)
C (Aimed at one specific pathogen)
D (Helps develop immunity)
Includes B cells and T cells.
First Line of Defense: Surface barriers which include skin and mucous membranes.
Second Line of Defense: Internal defenses.
Third Line of Defense: Adaptive immunity involving B cells, T cells, and antibodies.
Structure of the Skin:
Tightly packed cells, keratinized layers, and a dry acidic surface provide effective physical barriers against pathogens.
Function of Sweat, Oils, and Waxes: Contain antimicrobial chemicals that inhibit pathogen growth.
Limitations: Skin is not a perfect barrier; cuts, burns allow pathogens in.
Mucus Membranes: Found in respiratory, digestive, urinary, and reproductive tracts.
Function of Mucus: Traps pathogens for removal.
Cilia Function: Sweep mucus upward to prevent lower respiratory infections.
Internal Defenses:
Phagocytes
Natural Killer Cells (NK cells)
Inflammation
Fever
Complement proteins
Interferons
Phagocytes Types:
Neutrophils
Macrophages
Macrophage Definition: "Big eater"; they engulf and digest pathogens.
Natural Killer Cells: Found in blood and lymph; destroy virus-infected and cancerous cells through release of perforins and granzymes, triggering apoptosis.
Inflammation: A non-specific response to any tissue injury with signs including redness, heat, swelling, and pain, triggered by histamine release from mast cells leading to blood vessel dilation and WBC infiltration.
Complement System Function: Punches holes in pathogens, enhances inflammation, aids phagocytes.
Interferons Function: Warn nearby cells of viral infections, slow viral replication.
Fever: Indicates systemic infection; caused by white blood cells releasing pyrogens, which raise the brain's temperature set point.
Adaptive Immune Response
Adaptive Immune Response Definition: Also known as specific immunity; accurately targets one specific antigen.
Antigens: Foreign molecules that trigger an immune response.
Antibodies: Proteins made by B cells that bind to antigens and neutralize pathogens.
Lymphocytes: White blood cells involved in adaptive immunity; includes B cells and T cells.
Formation and Maturation of Lymphocytes:
B Cells;
Produced and matured in bone marrow.
Stored in lymph nodes and spleen.
T Cells:
Produced in bone marrow, mature in thymus.
Stored in lymph nodes and spleen.
Response to Pathogen:
Steps:
Pathogen enters body and displays antigens.
Phagocyte engulfs pathogen.
Phagocyte becomes antigen-presenting cell (APC) activating helper T cells.
Helper T cells activate cytotoxic T cells and B cells.
Cytotoxic T cells destroy infected cells.
Plasma cells produce antibodies targeting the pathogen.
Acquired Immunity
Definition: Immunity developed after exposure to pathogens or antibodies.
Immunity Prevention Consideration:
Immunity does not prevent entry but prevents illness.
Methods of Acquiring Immunity:
Natural Active: Getting sick.
Artificial Active: Vaccination.
Natural Passive: Antibodies from mother through placenta or breast milk.
Artificial Passive: Injection of antibodies or antivenom.
Primary vs. Secondary Immune Response:
Primary: Slow response, few antibodies produced, symptoms occur.
Secondary: Fast response, strong response, many antibodies produced, usually no symptoms.