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What are the three primary functions of the lymphatic system?
Fluid Recovery - Reabsorbs fluid lost from capillaries
Immunity - Picks up foreign cells and chemicals, passes through lymph nodes to activate immune responses.
Lipid Absorption - Lacteals in the small intestine absorb dietary lipids not absorbed by blood capillaries.
What are lymphatic vessels and their function?
transport lymph, a recovered fluid, through a network that includes lymph nodes, trunks, and ducts, ultimately returning it to the bloodstream.
What are the six major lymphatic trunks?
Jugular, subclavian, bronchomediastinal, intercostal, intestinal (unpaired), and lumbar trunks.
How does lymph move through the body without a pump like the heart?
Lymph moves through rhythmic vessel contractions, skeletal muscle pumps, arterial pulsations, the thoracic pump, and one-way valves that prevent backflow.
What are the primary types of lymphatic cells and their functions?
Natural Killer (NK) Cells - Attack bacteria, transplanted cells, virus-infected cells, and cancerous cells.
T Lymphocytes (T Cells) - Responsible for cell-mediated immunity.
B Lymphocytes (B Cells) - Differentiate into plasma cells that produce antibodies.
Macrophages - Phagocytic cells that process and present antigens to T cells.
Dendritic Cells - Antigen-presenting cells that alert the immune system.
Reticular Cells - Contribute to the structural framework of lymphatic organs.
What are the primary lymphatic organs?
Red bone marrow and thymus (where T and B cells become immunocompetent).
What is the function of the thymus?
The thymus houses developing T cells, secretes hormones (thymosin, thymopoietin), and forms the blood-thymus barrier to protect immature T cells from premature activation.
What are the two primary functions of lymph nodes?
Filter lymph and remove harmful substances.
Site for T and B cell activation.
How do lymph nodes contribute to cancer metastasis?
Cancer cells can enter lymphatic vessels, lodge in lymph nodes, multiply, and spread to other tissues.
What is adaptive immunity?
Specific responses, involves memory, includes T and B cells that recognize and attack specific pathogens.
How does the skin protect against infection?
The skin is tough (keratin), dry, nutrient-poor, and secretes antimicrobial substances like dermicidin, defensins, and cathelicidins.
How do mucous membranes contribute to immunity?
They line body passages, secrete mucus to trap microbes, and contain lysozyme, an enzyme that destroys bacterial cell walls.
What are the five types of leukocytes involved in immunity?
Neutrophils, eosinophils, basophils, monocytes, and lymphocytes.
What is the function of natural killer (NK) cells?
NK cells patrol the body and destroy infected, cancerous, or foreign cells using perforins and granzymes to induce apoptosis.
What are interferons?
Proteins secreted by virus-infected cells to warn neighboring cells, activate NK cells, and enhance macrophage activity.
What is the complement system, and how does it destroy pathogens?
A group of 30+ plasma proteins that enhance immunity by triggering inflammation, immune clearance, phagocytosis, and cytolysis.
How does fever help fight infection?
Fever increases metabolic rate, accelerates tissue repair, promotes interferon activity, and inhibits microbial reproduction.
What are the four cardinal signs of inflammation?
Redness, swelling, heat, and pain.
What are the three stages of T cell development?
Born in bone marrow.
Mature in the thymus (selection process).
Deployed to lymphatic tissues.
What are the four classes of T cells?
Cytotoxic T cells (attack infected cells)
Helper T cells (coordinate immunity)
Regulatory T cells (prevent overreaction)
Memory T cells (provide long-term immunity).
How do B cells function in humoral immunity?
recognize antigens, proliferate into plasma cells, and produce antibodies that neutralize or tag pathogens for destruction.
What are the five classes of antibodies (immunoglobulins)?
IgG: Most abundant, crosses placenta, secondary response.
IgA: Found in secretions (tears, saliva, breast milk).
IgM: First produced in infection, pentamer structure.
IgE: Involved in allergic reactions and parasite defense.
IgD: Functions in B cell activation.
What is passive immunity?
Antibodies are transferred (natural: mother to baby; artificial: antibody injection).
How does aging affect immunity?
Lymphatic tissue and red bone marrow decline, fewer immune cells are produced, and responses to infections and cancer become weaker.
Natural Killer (NK) Cells
Attack bacteria, transplanted cells, virus-infected cells, and cancerous cells.
T Lymphocytes (T Cells)
Responsible for cell-mediated immunity.
