Chapter 22 – Lymphatic System & Immunity: Key Vocabulary

Vocabulary flashcards covering fundamental terms and concepts from the lymphatic system and immunity study guide.

Maintaining Fluid Balance

Major lymphatic function that collects excess interstitial fluid (lymph) and returns it to venous circulation, preventing tissue edema and stabilizing blood volume/pressure.

Immune Surveillance

Lymphatic function that transports lymphocytes and filters lymph through nodes to detect and combat pathogens, cancer cells, and foreign substances.

Interstitial Fluid

Plasma-derived fluid that bathes tissues; becomes lymph when it enters lymphatic capillaries.

Lymph

Clear-to-yellow fluid containing water, proteins, immune cells, debris, pathogens, and nutrients; returned to the blood via lymphatic vessels.

Lymphatic Capillary

Blind-ended vessel with overlapping endothelial flaps and no basement membrane; absorbs excess interstitial fluid and large molecules.

Flaplike Valve (in Capillaries)

Overlap of endothelial cells that opens with rising tissue pressure to admit fluid but prevents lymph backflow.

Lacteal

Specialized lymphatic capillary in intestinal villi that absorbs chylomicrons (dietary fats) forming milky chyle.

Chyle

Fat-rich lymph from the small intestine, appearing milky after a fatty meal.

Cisterna Chyli

Sac-like chamber at L1–L2 that collects lipid-rich lymph from intestinal & lumbar trunks; origin of the thoracic duct.

Thoracic Duct

Largest lymphatic duct; drains body below the diaphragm and left upper quadrant into the left subclavian vein.

Right Lymphatic Duct

Short duct draining right head, neck, thorax, and arm into the right subclavian vein.

Lymph Node

Encapsulated organ along vessels that filters lymph; contains B cells, T cells, macrophages, afferent & efferent vessels.

Spleen

Upper-left abdominal organ with white pulp (immune) and red pulp (blood filtration, RBC removal, platelet storage).

Thymus

Primary lymphatic organ in the mediastinum where T cells mature; largest in childhood and involutes with age.

Tonsils

Ring of partially encapsulated lymphoid tissue (palatine, pharyngeal, lingual) guarding entrance of pharynx.

Appendix

Lymphoid-rich pouch off the cecum involved in gut immunity and microbiota maintenance.

Primary (Central) Lymphatic Tissue

Sites of lymphocyte production & maturation (bone marrow, thymus).

Secondary (Peripheral) Lymphatic Tissue

Sites where mature lymphocytes encounter antigens (lymph nodes, spleen, MALT).

MALT (Mucosa-Associated Lymphoid Tissue)

Diffuse lymphoid tissue in mucosal linings providing localized IgA-mediated defense.

GALT (Gut-Associated Lymphoid Tissue)

Component of MALT in the digestive tract including Peyer’s patches and appendix; monitors intestinal lumen.

Lymph Follicle (Nodule)

Unencapsulated cluster with germinal center (proliferating B cells) and mantle zone of resting lymphocytes.

Peyer’s Patch

Aggregate of lymph follicles in the ileum that samples intestinal antigens.

B Lymphocyte

Bone-marrow-derived cell mediating humoral immunity by differentiating into antibody-secreting plasma cells.

Plasma Cell

Activated B cell that produces and secretes large quantities of antibodies.

Memory B Cell

Long-lived B cell that enables rapid, robust antibody response on re-exposure to an antigen.

T Lymphocyte

Bone-marrow-origin cell that matures in the thymus and provides cell-mediated immunity.

Helper T Cell (CD4+)

T cell subtype that releases cytokines to activate B cells, cytotoxic T cells, and macrophages.

Cytotoxic T Cell (CD8+)

T cell that directly kills infected or abnormal cells presenting antigen on MHC I.

Regulatory T Cell

T cell that suppresses immune responses, maintaining tolerance and preventing autoimmunity.

Natural Killer (NK) Cell

Innate lymphocyte that induces apoptosis in virus-infected or tumor cells without prior sensitization.

Lymphatic Vessel

Thin-walled vessel with numerous valves and smooth muscle that transports lymph toward trunks and ducts.

Complement System

30 plasma proteins activated in a cascade causing opsonization, chemotaxis, inflammation, and membrane attack complex lysis.

Inflammatory Response

Non-specific reaction involving vasodilation, increased permeability, and leukocyte recruitment to contain injury/infection.

Opsonization

Coating of pathogens (e.g., by complement or antibodies) to enhance phagocyte recognition and uptake.

Membrane Attack Complex (MAC)

Complement protein assembly that forms pores in target cell membranes, inducing lysis.

Antigen

Any molecule recognized as foreign that can trigger an immune response (often proteins or polysaccharides).

Epitope (Antigenic Determinant)

Specific antigen region bound by an antibody or T cell receptor; one antigen may have multiple epitopes.

Major Histocompatibility Complex (MHC)

Cell-surface proteins that present antigen fragments to T cells, guiding immune recognition.

MHC Class I

Molecules on all nucleated cells presenting endogenous peptides to cytotoxic T cells.

MHC Class II

Molecules on antigen-presenting cells presenting exogenous peptides to helper T cells.

Antigen-Presenting Cell (APC)

Cell (dendritic cell, macrophage, B cell) that processes antigens and displays them on MHC II to activate T cells.

Dendritic Cell

Professional APC that captures antigens in tissues and migrates to lymph nodes to prime naïve T cells.

Phagocytic Cell

Cell (e.g., macrophage, neutrophil) that engulfs and digests pathogens and debris.

Physical Barrier

First-line defense such as intact skin and mucous membranes blocking pathogen entry.

Chemical Barrier

Protective chemical (acidic pH, lysozyme, sebum) that inhibits or destroys microbes on body surfaces.

Natural Active Immunity

Adaptive immunity acquired after natural infection; generates memory cells and antibodies.

Induced Active Immunity

Immunity produced by vaccination with antigenic material prompting one’s own antibody production.

Natural Passive Immunity

Temporary immunity gained by transfer of maternal antibodies (e.g., placenta, breast milk).

Induced Passive Immunity

Immediate, short-term immunity conferred by injection of pre-formed antibodies (antiserum, antivenom).

Cell-Mediated Immunity

Adaptive response where T cells attack infected or abnormal cells; effective against intracellular pathogens.

Antibody-Mediated (Humoral) Immunity

Adaptive response involving B cells and circulating antibodies targeting extracellular pathogens and toxins.

Antibody (Immunoglobulin)

Y-shaped protein with variable antigen-binding sites; neutralizes, opsonizes, agglutinates pathogens and activates complement.

Variable Region (Antibody)

Antibody segment with unique amino-acid sequence forming the antigen-binding site conferring specificity.

Opsonin

Molecule (antibody or complement fragment) that tags pathogens for easier phagocytosis.

Fever

Systemic rise in body temperature that inhibits microbial growth and enhances immune activity.

Interferon

Cytokine produced by virus-infected cells that warns neighbors and activates antiviral defenses.

Hypersensitivity

Exaggerated immune reaction to harmless antigen causing tissue damage (e.g., allergy, Type I reaction).

Anaphylactic Shock

Severe, systemic Type I hypersensitivity causing widespread vasodilation, bronchoconstriction, and potentially fatal drop in BP.

Autoimmune Disease

Disorder where the immune system attacks self-antigens, e.g., Type 1 diabetes or Graves’ disease.

Primary Immunodeficiency

Genetically inherited defect causing impaired immune function from birth.

Secondary Immunodeficiency

Acquired loss of immune competence due to factors like HIV infection, chemotherapy, or malnutrition.

Perforin

Protein released by cytotoxic T and NK cells that forms pores in target cell membranes.

Granzyme

Serine protease entering target cells via perforin pores to trigger apoptosis.

Chemotaxis

Immune cell migration toward higher concentration of chemical signals at sites of infection/inflammation.

Clonal Expansion

Rapid proliferation of activated lymphocyte clones specific to an encountered antigen.

Memory T Cell

Long-lasting T cell that provides quicker, stronger response upon re-exposure to its specific antigen.

Self-Tolerance

Immune system’s ability to avoid attacking the body’s own cells and molecules.

Edema

Swelling caused by excess interstitial fluid accumulation when lymphatic drainage is impaired.