Chapter 21 - Lymphatic System and Immunity

Vocabulary flashcards covering the lymphatic system anatomy, immune cell functions, innate defenses, and adaptive immune responses based on the lecture transcript.

Lymphatic System

A system consisting of lymphatic fluid, vessels, cells, tissues, and organs that functions in fluid recovery, immunological defense, and lipid absorption.

Fluid Recovery

The process where lymph capillaries return excess interstitial fluid to large veins.

Lacteals

Specialized lymph capillaries located in the villi of the digestive tract that collect absorbed lipids.

Glymphatic System

The lymphatic system found within brain tissue.

Right Lymphatic Duct

The duct that empties lymph from the superior-right quarter of the body into the right subclavian vein.

Thoracic Duct

The duct that drains $75\%$ of the body and empties into the left subclavian vein.

Lymphatic Capillaries

The smallest, blind-ended vessels where endothelial cells overlap but lack tight junctions, allowing fluid, pathogens, and cancer cells to enter.

Natural Killer (NK) Cells

Large lymphocytes that attack bacteria, transplanted tissues, virus-infected cells, and cancerous self-cells using perforins and granzymes.

T Lymphocytes

Cells responsible for cellular immunity and certain aspects of antibody production.

B Lymphocytes

Cells that differentiate into plasma cells to produce antibodies.

Macrophages

Cells differentiated from monocytes that phagocytize bacteria and cell debris; includes microglia in the CNS and alveolar macrophages in the lungs.

Dendritic Cells

Cells found in the epidermis and mucous membranes that take in foreign material by receptor-mediated endocytosis.

Reticular Cells

Stationary cells that contribute to the stroma of lymphatic organs and produce colony stimulating factors in red bone marrow.

MALT

Mucosa-associated lymphoid tissue; large collections of lymphoid nodules in the digestive, urinary, respiratory, and reproductive tracts.

Primary Lymphatic Organs

The sites where B and T cells form and gain immunocompetence, specifically the bone marrow and thymus.

Secondary Lymphatic Organs

Sites where immune responses occur, including the lymph nodes and spleen.

Lymphadenitis

Inflammation of the lymph nodes, often checked by physicians through palpation.

Spleen

The largest lymphatic organ, located in the left hypochondriac region; it filters blood, stores iron, and destroys abnormal blood cells.

Innate (Non-Specific) Immunity

Immunity present from birth that works on a wide variety of pathogens with a consistent response that does not improve with repeated exposure.

Adaptive (Specific) Immunity

Immunity characterized by specificity, versatility, memory, and tolerance; it improves and becomes faster with repeated exposure to specific antigens.

Acid Mantle

A layer of lactic and fatty acids from sweat and sebum that kills pathogens on the skin.

Lysozyme

A hydrolytic enzyme found in mucus, saliva, and tears that destroys microorganisms.

Respiratory Burst

A reaction where neutrophils and monocytes produce toxic substances like hydrogen peroxide and hypochlorite to kill bacteria.

Interferons

Proteins released by virus-infected cells that trigger uninfected cells to produce antiviral proteins and activate NK cells and macrophages.

Complement System

A group of at least $30$ plasma globulins that undergo a reaction cascade to destroy pathogens through inflammation, immune clearance, opsonization, or cytolysis.

Opsonization

A process where complement proteins coat microbial cells to enhance binding sites for phagocytosis, described as "buttering up" the antigen.

Membrane Attack Complex (MAC)

A ring of $C9$ molecules formed by the complement system that causes cytolysis of a pathogen.

Pyrogens

Foreign (exogenous) or internal (endogenous) proteins that induce fever by raising the hypothalamus set point.

Prostaglandin E2 (PGE2)

A substance from the hypothalamus that increases fever and is inhibited by aspirin and ibuprofen.

Immunocompetence

The ability of a lymphocyte to recognize antigens and mount a normal immune response.

Negative Selection

The elimination (clonal deletion) or inactivation (anergy) of T cells that fail to recognize antigens or show self-tolerance.

Antigen Presenting Cells (APCs)

Cells like macrophages and B cells that display antigen fragments on MHC proteins for T cells to inspect.

Cytotoxic T Cells (Tc)

CD8 cells that directly attack and kill other cells using perforins, granzymes, and tumor necrosis factor.

Helper T Cells (TH)

CD4 cells that release cytokines to regulate cellular and humoral immunity, stimulate T cell division, and co-stimulate B cells.

Memory T Cells (Tm)

T cells that live approximately $6$ months and allow for a faster immune response upon re-exposure to an antigen.

Regulatory T Cells (TR)

T cells that release suppression factors to down-regulate and shut down the immune response.

Major Histocompatibility Complex (MHC) I

Proteins found on all nucleated body cells that display endogenous antigens; identified by the phrase "KILL I" if the cell is diseased.

Major Histocompatibility Complex (MHC) II

Proteins found only on APCs that display exogenous antigens; identified by the phrase "KILL IT."

IgG

The most abundant antibody ($80\%$), primary in secondary immunity, and able to cross the placenta.

IgM

The primary antibody secreted in primary immunity; acts as a potent agglutinator and includes ABO blood group antibodies.

Natural Active Immunity

Immunity resulting from natural exposure to antigens through infection.

Artificial Passive Immunity

The unnatural and temporary acquisition of antibodies, such as for rabies, tetanus, or via antivenom.

SCID

Severe combined immunodeficiency disease; a recessive condition resulting in scarce to no T and B cells.