BIO 2341 Chapters 20 & 21: Lymphatic and Immune Systems

Vocabulary practice flashcards covering lymph formation and circulation, primary and secondary lymphoid organs, innate barrier defenses, innate immune cells, adaptive immunity mechanisms, and antibody classes from Chapters 20 and 21.

Interstitial fluid

Tissue fluid that enters lymphatic capillaries to become lymph.

Lymph

The fluid formed when excess interstitial fluid enters lymphatic capillaries, subsequently circulating through vessels and nodes before returning to venous blood.

Lacteal

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

Lymphatic capillary flaps and anchoring filaments

Overlapping endothelial flaps that open as tissue pressure increases to allow fluid entry, accompanied by anchoring filaments that keep the capillary open and prevent fluid backflow.

Lymphatic circulation sequence

The pathway tracing lymph toward venous circulation: Capillary → vessel → trunk → duct.

Primary lymphoid structures

Structures where lymphocytes develop and mature to achieve immunocompetence, specifically red bone marrow and the thymus.

Secondary lymphoid structures

Structures where mature lymphocytes encounter antigens and become activated to initiate immune responses, such as lymph nodes and the spleen.

Thymus

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

Spleen

A secondary lymphoid organ that filters blood rather than lymph and contains red pulp and white pulp.

Red pulp

The region of the spleen that primarily functions to remove old or damaged erythrocytes from the bloodstream.

Prion

An infectious agent composed of an infectious misfolded protein.

Epitope

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

Innate barrier defenses

Front-line non-specific defenses organized into physical (skin), chemical (stomach acid), biological (normal microbiota), and mechanical (mucus and cilia) barriers.

Neutrophil

An innate leukocyte that arrives early at an infection site and accumulates to form pus upon dying.

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 a warning signal to slow viral spread to neighboring cells.

Acute inflammation

A localized innate defense triggered by the release of inflammatory mediators, leading to vasodilation, increased capillary permeability, edema, and pus accumulation before resolution and healing.

MHC I

Major histocompatibility complex class I molecules that present internal antigens directly to CD8 cytotoxic T cells.

MHC II

Major histocompatibility complex class II molecules found on antigen-presenting cells that present antigens to CD4 helper T cells.

Dendritic cell

An antigen-presenting cell (APC) that is especially effective at activating naive T lymphocytes.

Co-stimulation

A required second activation signal delivered to a lymphocyte in addition to antigen recognition to achieve full activation.

Plasma cell

An effector B lymphocyte that secretes large amounts of antibodies.

Humoral immunity

A branch of adaptive immunity utilizing B cells that differentiate into plasma cells to produce antibodies directed against pathogens outside cells.

Cell-mediated immunity

A branch of adaptive immunity utilizing T cells to directly destroy infected or abnormal host cells.

Immunoglobulin M (IgM)

The first antibody class produced during a primary immune response.

Immunoglobulin A (IgA)

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

Passive artificial immunity

Temporary immunity acquired through medical administration of exogenous antibodies, such as rabies immunoglobulin.

Secondary immune response

An adaptive immune response that is faster and stronger than the primary response because memory lymphocytes are already present.