Lesson 4

The Lymphatic and Immune Systems

The lymphatic system has two major roles: returning excess interstitial fluid to the bloodstream and mounting immune responses against pathogens. Lymph nodes filter foreign particles, while lymphocytes (T cells and B cells) orchestrate adaptive immunity. Disruption of this system leads to conditions ranging from lymphedema to lymphoma to AIDS.

50 min3 sections5 objectives

Learning Objectives

1Identify combining forms for lymph, lymph nodes, and immune organs
2Describe the pathway of lymphatic circulation
3Explain innate versus adaptive immunity
4Recognize lymphatic diseases including lymphedema, lymphoma, and HIV/AIDS
5Understand autoimmune disorders and their terminology

1Lymphatic Structures

Lymph: Fluid that has leaked from capillaries into tissues; collected by lymphatic capillaries and returned to blood.

Lymph nodes: Small, bean-shaped organs that filter lymph and house immune cells. Located throughout the body; clusters at neck, axilla (armpit), and groin.

Primary lymphatic organs: Red bone marrow (B cells mature), Thymus (T cells mature)

Secondary lymphatic organs: Lymph nodes, spleen, tonsils, MALT (mucosa-associated lymphoid tissue)

The spleen is the largest lymphatic organ; it filters blood, destroys worn RBCs, and stores blood.

2Immune Response

Innate (Non-specific) Immunity: Immediate, non-targeted response.

Physical barriers: Skin, mucous membranes

Chemical barriers: Stomach acid, tears, saliva

Cellular: Neutrophils, macrophages, NK cells

Inflammation and fever responses

Adaptive (Specific) Immunity: Slower, targeted, has memory.

Humoral immunity: B lymphocytes → plasma cells → antibodies (immunoglobulins: IgG, IgA, IgM, IgE, IgD)

Cell-mediated immunity: T lymphocytes (cytotoxic T cells kill infected cells; helper T cells coordinate response)

Antigen: Any substance that triggers immune response

Antibody: Protein produced by plasma cells that binds specific antigens

3Common Lymphatic/Immune Conditions

Lymphedema: Swelling due to lymphatic obstruction; common after lymph node removal in cancer treatment

Lymphoma: Cancer of lymphoid tissue

Hodgkin lymphoma: Reed-Sternberg cells; very treatable

Non-Hodgkin lymphoma (NHL): More common; diverse group

Leukemia: Cancer of blood-forming cells (leukocytes)

Acute lymphocytic leukemia (ALL)

Chronic lymphocytic leukemia (CLL)

HIV/AIDS: Human immunodeficiency virus attacks CD4+ T cells → acquired immunodeficiency syndrome

Autoimmune disorders: Immune system attacks self

Lupus (SLE), rheumatoid arthritis, multiple sclerosis, type 1 diabetes

Clinical Connections

►Sentinel lymph node biopsy determines whether breast cancer has spread to the lymphatic system
►COVID-19 causes immune dysregulation — 'cytokine storm' — that can damage multiple organ systems
►Immunosuppressant drugs after organ transplants prevent rejection but increase infection risk

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L3: The Cardiovascular System

L5: The Respiratory System