Overview
This lecture introduces the anatomy, physiology, terminology, and pathology of the lymphatic and immune systems, focusing on their roles in fluid balance, immunity, and diseases.
Structure and Function of the Lymphatic System
- The lymphatic system removes interstitial fluid from tissues and returns it to the bloodstream.
- It transports dietary lipids and immune system cells throughout the body.
- Lymph originates as interstitial fluid and enters lymphatic capillaries to become lymph.
- Lymphatic vessels contain valves and resemble veins; they drain into the right lymphatic and thoracic ducts.
- Primary lymphoid organs: bone marrow (B cell maturation) and thymus (T cell maturation).
- Secondary lymphoid organs: lymph nodes, spleen, and lymphoid nodules, which mount immune responses.
Lymphoid Organs and Tissues
- Lymph nodes filter lymph and contain immune cells to destroy pathogens.
- The spleen filters blood, removes microbes, old RBCs, and facilitates immune responses to blood-borne pathogens.
- Lymphoid nodules (e.g., tonsils) protect against respiratory and digestive tract pathogens.
The Immune System: Innate and Adaptive Responses
- Innate immunity includes phagocytes (macrophages, neutrophils) and natural killer (NK) cells.
- Cytokines are signaling molecules for immune communication; chemokines attract immune cells.
- Inflammation is characterized by heat, redness, swelling, and pain.
- Adaptive immunity features specificity, immunological memory, and self-recognition.
- Lymphocytes: B cells (antibody production) and T cells (helper, cytotoxic, suppressor roles).
- Memory cells ensure faster response upon re-exposure to the same pathogen.
Immunity Types and Pathogen Evasion
- Active immunity develops after infection or vaccination; passive immunity is the transfer of antibodies.
- Pathogens evade immune responses via protective adaptations, multiple strains, antigen mutation, and genetic recombination.
Disorders and Diseases of the Immune System
- Immunodeficiencies: SCID (genetic) and HIV/AIDS (acquired), causing weakened immune responses.
- Hypersensitivities: over-reactive responses include allergies and autoimmune diseases like rheumatoid arthritis and lupus.
- Autoimmune diseases occur when the immune system attacks self-antigens.
Medical Specialties and Procedures
- Clinical immunology/allergy specialty diagnoses and treats immune system diseases.
- Skin testing identifies allergens responsible for hypersensitivity reactions.
Key Terms & Definitions
- Lymph — Interstitial fluid that has entered the lymphatic system.
- Lymphedema — Swelling caused by lymph accumulation.
- Thymic involution — Age-related shrinking of the thymus.
- Phagocytosis — The process by which cells engulf particles or pathogens.
- Cytokine — Molecule for cell signaling in immunity.
- Antigen — Substance provoking an immune response.
- Autoimmune disease — Condition where the immune system attacks the body’s cells.
- SCID — Severe Combined Immunodeficiency Disease; genetic immune deficiency.
- Hypersensitivity — Excessive immune reaction to harmless substances.
- Graft-versus-host disease — Immune reaction by transplanted cells against the host tissues.
Action Items / Next Steps
- Memorize major lymphatic/immune system terms and their functions.
- Watch assigned Crash Course videos for visual reinforcement.
- Review tables and figures in the text for organ locations and immune response types.