Module 10 Defense and Immunity

Flow of lymph through the lymphatic system

Lymph flows from capillaries → lymphatic vessels → lymph nodes → larger vessels → thoracic duct/right lymphatic duct → subclavian veins.

Main lymphatic organs and their functions

Lymph nodes: Filter lymph, house immune cells. Tonsils: Trap pathogens from air/food. Spleen: Filters blood, recycles red blood cells. MALT (Mucosa-Associated Lymphatic Tissue): Protects mucosal surfaces (e.g., Peyer's patches in intestine).

Nonspecific (innate) immunity

Defences present at birth that protect against any pathogen, without memory (e.g., skin, inflammation, phagocytes).

Specific (adaptive) immunity

A slower response tailored to a specific pathogen; involves B and T cells, and includes immunological memory.

Difference between innate vs adaptive immunity

Immediate, general response, no memory vs slower, specific, develops memory for faster future responses.

Three lines of defence in the body

Physical and chemical barriers (skin, mucous membranes, secretions, reflexes). Internal defenses (inflammation, fever, phagocytes, natural killer cells, antimicrobial proteins). Specific immune responses (B and T cells, antibodies).

Cardinal signs of inflammation and their physiological causes

Redness: Increased blood flow (vasodilation). Heat: Blood carries heat to area. Swelling: Fluid and immune cells enter tissue. Pain: Due to chemicals and pressure from swelling.

Role of antigens in immunity

Antigens are foreign substances that trigger an immune response; they bind to antibodies or T-cell receptors.

B cells and their function

? cells produce antibodies. Once activated, they become plasma cells (secrete antibodies) or memory ? cells.

T cells and their function

Helper ? cells: Activate B cells and cytotoxic ? cells. Cytotoxic ? cells: Destroy infected or abnormal cells. Memory ? cells: Provide faster response on re-exposure.

Active immunity

Immunity developed by the body making its own antibodies after exposure to antigen (via infection or vaccine).

Passive immunity

Immunity gained by receiving pre-made antibodies (e.g., from placenta, breast milk, or antibody injection).

Examples of naturally acquired immunity

Active: Recovering from an illness. Passive: Antibodies passed from mother to baby (placenta, breast milk).

Examples of artificially acquired immunity

Active: Vaccination. Passive: Injection of antibodies (e.g., anti-venom).