Chapter 7: Lymphatic System

Study Guide: Lymphatic System

I. Functions of the Lymphatic System

• Absorb excess interstitial fluid (prevents swelling)

• Absorb fats in the gastrointestinal system (important for digestion)

• Production, maintenance, and distribution of lymphocytes (key to immune response)

• Defense against pathogens (fights infections)

Memory Device: Think of the lymphatic system as a recycling and defense network – it collects excess fluid, absorbs fat, and fights off invaders!

II. Components of the Lymphatic System

1. Lymphatic Vessels ("Green Highways")

• Types: Capillaries → Vessels → Ducts

• One-Way Flow: Valves prevent backflow

• Carry lymph (fluid containing white blood cells and waste products)

2. Lymphatic Organs

Primary (Production & Maturation of Lymphocytes)

• Red Bone Marrow → Produces B cells (antibody-producing cells)

• Thymus → Matures T cells (cell-mediated immunity)

Secondary (Filtering & Immune Response Sites)

• Spleen → Filters blood, removes old red blood cells

• Lymph Nodes → Filters lymph, traps pathogens

• Lymph Nodules → Small clusters of immune tissue (e.g., tonsils)

Memory Device: "Be The Super Lymphatic Ninja" (Bone marrow, Thymus, Spleen, Lymph Nodes, Nodules)

III. Innate Immune System (First & Second Line of Defense)

Innate Immunity Characteristics:

• No prior exposure needed (built-in defense)

• Immediate response (acts fast!)

• No immunologic memory (can get the same infection again)

1. First Line of Defense (Physical & Chemical Barriers)

Physical Barriers

• Intact skin (outermost defense)

• Intact mucous membranes (line body openings)

Chemical Barriers

• Fluids that wash away microbes: Sweat, saliva, tears, urine

• Acidic secretions: Gastric juice (stomach), waste products from microbiome

2. Second Line of Defense (Internal Responses)

A. Inflammation

• Key Cells: Neutrophils & Macrophages (eat bacteria)

• Key Chemicals: Histamine & Cytokines (signal immune response)

• Symptoms: Redness, Heat, Swelling, Pain

Inflammation Steps:

1. Histamine release (triggers dilation of blood vessels)

2. Cytokine release (calls immune cells to the area)

3. Diapedesis (WBCs squeeze through blood vessel walls to reach infection site)

4. Blood clotting (seals wound)

B. Antimicrobial Proteins

• Complement System (multi-purpose defense system)

  • Triggers histamine release

  • Attracts phagocytes (cells that eat invaders)

  • Forms Membrane Attack Complex (MAC) to destroy pathogens

• Interferons (help save neighboring cells from viral infections)

Memory Device: "I P.R.O.T.E.C.T." (Inflammation, Phagocytes, Redness, Oxygen supply increase, Temperature rise, Exudate (pus), Cytokines, Toxin removal)

IV. Overview of Innate Response

1. Physical & Chemical Barriers (First line of defense prevents entry)

2. Inflammation & Immune Cells (Second line kicks in when infection occurs)

3. Antimicrobial Proteins (Boost defense, attack pathogens, and protect healthy cells)

V. Adaptive Immune Response

Antigens (Markers for Identifying Self vs. Non-Self)

• Self vs. Non-Self (recognizing foreign cells)

• Usually protein-based

• Examples of Non-Self Antigens:

  • Portions of microbes

  • Abnormal body proteins (e.g., virally infected cells, cancer cells)

Adaptive Immunity Characteristics

• Third line of defense

• Highly specific

• Involves lymphocytes (B & T cells are central players)

• Two Pathways:

  1. Cell-Mediated Immunity → Targets intracellular antigens (T cells)

  2. Humoral Immunity → Targets extracellular antigens (B cells)

VI. Antibody-Mediated Immunity

Active Immunity (Body Produces Antibodies)

• Natural: After infection

• Artificial: After immunization (vaccines)

• Primary vs. Secondary Response: Faster and stronger response upon second exposure

• Measured via Antibody Titer (blood test to check immune response level)

Passive Immunity (Antibodies Given to Individual)

• Natural: Passed from mother

  • Placenta (before birth)

  • Breast Milk (after birth)

• Artificial: Through injections (e.g., antivenom, monoclonal antibodies)

VII. Immune System Disorders

1. Hypersensitivity to Allergens (Overactive Immune Response)

Immediate Allergic Response

• IgE induced (immune protein triggers reaction)

• Histamine release (causes inflammation)

• Anaphylactic shock (severe reaction – increased heart rate, difficulty breathing)

Delayed Allergic Response

• Cytotoxic T cell induced (T cells attack mistakenly perceived threats)

• Cytokine release (prolonged immune response)

2. Immunodeficiencies (Weakened Immune Response)

• SCID (Severe Combined Immunodeficiency Disorder)

  • Genetic

  • Lack of humoral & cell-mediated immune systems

• AIDS (Acquired Immunodeficiency Syndrome)

  • Caused by HIV

  • Targets helper T cells (weakens immune system)

3. Autoimmune Disorders (Immune System Attacks Self)

• Cytotoxic T cells & antibodies attack own cells

• Cause unknown

• Risk Factors:

  • Certain HLA antigens

  • Being female (higher prevalence in women)

• Examples: Rheumatoid arthritis, Lupus, Type 1 diabetes

4. Organ Transplantation & Rejection

• HLA matching (ensures compatibility)

• Rejection caused by cytotoxic T cells

• Prevention:

  • Immunosuppressive drugs (reduce rejection risk)

  • Xenotransplantation (using animal organs, e.g., pigs)

  • Tissue engineering (creating artificial organs)

VIII. Practice Questions

1. What is the difference between active and passive immunity?

2. How does the body generate immunity after a vaccine?

3. What role do histamines play in allergic reactions?

4. How does HIV weaken the immune system?

5. Why are immunosuppressive drugs used after organ transplantation?

IV. Visual Framework for Retention

🛡 Immune System Response Flowchart:

This expanded study guide will help reinforce key immunology concepts! 🚀