Chapters 20 & 21: Lymphatic and Immune Systems

Vocabulary practice flashcards covering lymph formation and circulation, primary versus secondary lymphoid organs, front-line innate barriers, cell-mediated versus humoral adaptive immunity, and antibody classifications from Chapters 20 and 21.

Lymph

The fluid formed when excess interstitial fluid enters a lymphatic capillary.

Lacteal

A specialized lymphatic capillary located in a small-intestinal villus that absorbs dietary fats.

Lymphatic Circulation Pathway

The structural sequence tracing lymph toward venous circulation: lymphatic capillary $\rightarrow$ lymphatic vessel $\rightarrow$ lymphatic trunk $\rightarrow$ lymphatic duct.

Overlapping Endothelial Flaps

Structures in lymphatic capillaries that open when interstitial fluid pressure increases, creating a passage for fluid entry.

Anchoring Filaments

Structures that hold the lymphatic capillary open during increased tissue pressure and prevent backflow of fluid.

Primary Lymphoid Structures

Anatomical sites where lymphocytes develop and mature to become immunocompetent, consisting of red bone marrow and the thymus.

Secondary Lymphoid Structures

Anatomical sites where mature lymphocytes encounter antigens and become activated to mount immune responses, including lymph nodes and the spleen.

Thymus

A primary lymphoid structure that serves as the specific site for T-lymphocyte maturation.

Spleen

A secondary lymphoid organ that filters blood, distinguishing it from lymph nodes which filter lymph.

Red Pulp

The splenic region whose primary function is the removal of old or damaged erythrocytes.

Prion

An infectious agent that consists of an infectious misfolded protein.

Epitope

The specific localized region of an antigen that is recognized and bound by an immune receptor.

Adaptive Immunity

The branch of the immune system characterized by antigen-specific recognition and immunologic memory.

Physical Barrier

A front-line innate barrier defense exemplified by intact skin.

Chemical Barrier

A front-line innate barrier defense exemplified by acidic secretions like stomach acid.

Biological Barrier

A front-line innate barrier defense provided by the protective populations of normal microbiota.

Mechanical Barrier

A front-line innate barrier defense that traps and physically clears foreign particles using mucus and cilia.

Neutrophil

An innate leukocyte that arrives early at an infection site and forms pus upon dying and accumulating.

Natural Killer (NK) Cell

An innate immune cell that destroys abnormal or virus-infected cells by triggering apoptosis (programmed cell death).

Interferon

An antimicrobial protein that acts as an early warning signal to slow viral spread among neighboring cells.

Acute Inflammation

An innate tissue response triggered by inflammatory mediators, leading to vasodilation, increased capillary permeability, edema, neutrophil accumulation, and subsequent tissue healing.

MHC Class I (MHC I)

A cell-surface protein that presents internal (endogenous) antigens to CD8 cytotoxic T cells.

MHC Class II (MHC II)

A cell-surface protein that presents processed antigens specifically to CD4 helper T cells.

Dendritic Cell

A professional antigen-presenting cell that is especially effective at activating naive T lymphocytes.

Co-stimulation

The mandatory second chemical signal required alongside antigen receptor recognition to fully activate a lymphocyte.

Plasma Cell

An activated, differentiated B cell dedicated to secreting large quantities of antibodies.

Humoral Immunity

The arm of adaptive immunity mediated by B lymphocytes producing antibodies to target extracellular pathogens.

Cell-Mediated Immunity

The arm of adaptive immunity mediated by T lymphocytes that targets and destroys infected or abnormal host cells.

IgM

The initial class of immunoglobulin produced during a primary immune response.

IgA

The immunoglobulin class predominantly found in mucosal secretions, including saliva, tears, and breast milk.

Passive Artificial Immunity

Immunity acquired through the medical administration of preformed antibodies, such as rabies immunoglobulin.

Secondary Immune Response

A rapid and heightened immune reaction upon re-exposure to an antigen due to the presence of pre-existing memory lymphocytes.