A&P Exam 4

Lymph

Fluid that circulates in the lymphatic system.

Lymphatic vessels

Vessels that carry lymph toward the heart.

Lymph nodes

Organs that filter lymph and trap pathogens.

Lymphoid organs and tissues

Includes spleen, thymus, tonsils, and MALT.

Main Functions of the Lymphatic System

Return excess tissue fluid to the bloodstream, transport dietary lipids, house lymphocytes, filter pathogens.

One-way system

Characteristic of lymphatic vessels that carries lymph toward the heart.

Endothelial cells

Cells that form mini-valves in lymphatic vessels.

Valves in lymphatic vessels

Prevent backflow of lymph.

Lymphatic capillaries

Absorb interstitial fluid.

Collecting vessels

Carry lymph from capillaries to lymph nodes.

Lymphatic trunks

Drain large areas of the body.

Lymphatic ducts

Return lymph to the bloodstream.

Lacteals

Absorb fats from the digestive tract.

Right lymphatic duct

Drains right upper limb, right side of head and thorax.

Thoracic duct

Drains the rest of the body.

MALT (Mucosa-Associated Lymphoid Tissue)

Located in mucous membranes, protects against pathogens.

Tonsils

Trap and destroy pathogens in inhaled or ingested substances.

Functions of Lymph Nodes

Filter lymph, trap pathogens, site for immune cell activation.

Spleen

Filters blood, removes old red blood cells, initiates immune responses.

Thymus

Site of T-cell maturation.

Purpose of the Immune System

Protects the body from pathogens, toxins, and foreign substances.

Immunity

The body's ability to recognize and respond to harmful substances.

Innate Immunity

Immediate, non-specific response to pathogens.

Adaptive Immunity

Delayed, highly specific response to pathogens with memory.

Complement Cascade

Series of plasma proteins that enhance immune responses.

Interferons

Proteins released by virus-infected cells that warn nearby cells.

Neutrophils

First responders; phagocytize pathogens.

Macrophages

Engulf and destroy invaders; activate adaptive immunity.

Dendritic cells

Present antigens to T cells.

Natural killer (NK) cells

Destroy virus-infected and abnormal (e.g., cancer) cells.

Basophils & mast cells

Release histamine; involved in inflammation and allergic responses.

Eosinophils

Combat parasites and contribute to allergic reactions.

Inflammatory Response

A series of events triggered by tissue damage that leads to healing.

Immunity

The body's ability to resist or eliminate harmful agents like pathogens and abnormal cells.

Specificity

The immune system targets specific antigens with unique responses.

Memory

The immune system 'remembers' previous encounters with antigens, leading to a faster, stronger response upon re-exposure.

Foreign Antigen

Any molecule from outside the body (e.g., virus, bacteria, toxin) that triggers an immune response.

Self-Antigen

Molecules produced by the body (usually not attacked by the immune system). In autoimmune diseases, self-antigens are mistakenly targeted.

MHC I

Found on all nucleated cells; presents endogenous antigens (from inside the cell) to CD8+ cytotoxic T cells.

MHC II

Found on antigen-presenting cells (macrophages, dendritic cells, B cells); presents exogenous antigens (from outside the cell) to CD4+ helper T cells.

Costimulation

A second signal needed (besides antigen recognition) for full T cell activation; prevents accidental immune responses.

CD4

Found on helper T cells, interact with MHC II.

CD8

Found on cytotoxic T cells, interact with MHC I.

Function of MHC Molecules

MHC molecules display antigen fragments on the cell surface; T cells recognize these complexes and are activated based on the type.

Antibody-Mediated Immunity

Involves B cells that produce antibodies targeting pathogens outside cells (bacteria, toxins).

Cell-Mediated Immunity

Involves T cells (CD8, CD4) targeting infected or abnormal cells (viruses, cancer).

Cytotoxic T cells (CD8+)

Kill infected, cancerous, or transplanted cells.

Helper T cells (CD4+)

Activate B cells, cytotoxic T cells, and macrophages.

Memory T cells

Provide quicker response upon future exposure.

B cells

Recognize antigens and become plasma cells or memory B cells.

Antibody (Immunoglobulin)

Y-shaped proteins produced by plasma cells; bind to specific antigens.

Effects of Antibodies

Include neutralization, agglutination, precipitation, opsonization, complement activation, and inflammation.

Naturally Acquired Active Immunity

Acquired through exposure to pathogens; body produces antibodies.

Naturally Acquired Passive Immunity

Antibodies passed from mother to baby (e.g., via placenta or milk).

Artificially Acquired Active Immunity

Acquired through vaccination (stimulates immune response).

Artificially Acquired Passive Immunity

Acquired through injection of antibodies (e.g., antiserum).