Unit objectives

What are the main functions of the lymphatic system?

Fluid recovery, immunity, and lipid absorption.

How does lymph form and what is its composition?

formed from interstitial fluid entering lymphatic capillaries and is similar to plasma but with fewer proteins.

Trace the flow of lymph from its origin to where it reenters the bloodstream.

Lymphatic capillaries → collecting vessels → lymphatic trunks → collecting ducts → subclavian veins.

What are the two main lymphatic ducts and what areas do they drain?

Right lymphatic duct drains right arm, right side of head, and thorax. Thoracic duct drains the rest of the body.

What is the role of the primary lymphatic organs?

Sites where lymphocytes mature — red bone marrow (B cell maturation) and thymus (T cell maturation).

What are the secondary lymphatic organs and their functions?

Lymph nodes, spleen, and tonsils; they trap pathogens and are sites of immune responses.

What are the major functions of lymph nodes?

Filter lymph, trap pathogens, and activate lymphocytes to trigger immune responses.

How does the spleen contribute to immunity and blood maintenance?

Red pulp filters blood, removes old RBCs, and stores platelets; white pulp contains lymphocytes for immune responses.

What are the two main types of immunity?

Innate immunity (non-specific defense present at birth) and adaptive immunity (specific, acquired immunity).

What are the differences between humoral and cellular immunity?

Humoral immunity involves B cells producing antibodies; cellular immunity involves T cells directly attacking infected cells.

What is an antigen and how does it trigger an immune response?

An antigen is a molecule that triggers an immune response by binding to receptors on lymphocytes.

How do antigen-presenting cells (APCs) work?

APCs process antigens and present them to T cells using MHC proteins.

What are the major classes of T cells and their functions?

Cytotoxic T cells attack infected cells; Helper T cells activate B cells; Regulatory T cells suppress immune responses; Memory T cells provide long-term immunity.

What is clonal selection and why is it important?

When a B or T cell binds to its antigen, it proliferates into clones to ensure a strong immune response.

What are the steps of the humoral immune response?

B cell binds to antigen, is activated by Helper T cell, proliferates, and differentiates into plasma cells that secrete antibodies.

What is the role of plasma cells?

Plasma cells are B cells that secrete antibodies specific to the antigen.

What are the five classes of antibodies and their functions?

IgG: most abundant; IgA: in secretions; IgM: first produced; IgE: involved in allergies; IgD: B cell activation.

What are the four ways antibodies work?

Neutralization, opsonization, agglutination, and complement activation.

What are the steps of cell-mediated immunity?

Cytotoxic T cell binds to infected cell, releases perforins and granzymes, leading to cell destruction.

What are the four types of hypersensitivity reactions?

Type I: allergies; Type II: cell lysis; Type III: tissue damage; Type IV: delayed, T cell-mediated.

What is anaphylaxis and how is it treated?

Severe allergic reaction treated with epinephrine.

What causes autoimmune diseases?

The immune system attacks the body's own tissues due to loss of self-tolerance.

What are some examples of autoimmune diseases?

Rheumatoid arthritis, lupus, multiple sclerosis.