Key Concepts of the Lymphatic and Immune Systems from Chapter 7

7.1 The Lymphatic System

• Learning Outcomes:

  • Describe the structure and function of the lymphatic system.
  • Explain the origins and components of lymph.
  • Explain how the lymphatic system interacts with the circulatory system.

• Functions of the Lymphatic System:

  • Absorbs excess interstitial fluid and returns it to the bloodstream.
  • Absorbs fats from the digestive tract and transports them to the bloodstream.
  • Lymphoid organs defend the body against diseases through white blood cells.

• Lymphatic Vessels:

  • Carry lymph: a fluid that originates from interstitial fluid.
  • Begin as blind-ended lymphatic capillaries in tissues.
  • Vessels merge into larger ducts:
  • Thoracic Duct: collects lymph from the body below the thorax, left arm, and left side of the head; drains into left subclavian vein.
  • Right Lymphatic Duct: returns lymph from the right arm and right side of the head and neck into the right subclavian vein.
  • Anatomy similar to cardiovascular veins, including valves to prevent backward flow.
  • Lymph movement largely dependent on skeletal muscle contraction.

• Lymphatic Organs:

  • Primary:
  • Red Bone Marrow: site of blood cell production; B lymphocytes mature here.
  • Thymus: located in the thoracic cavity; matures T lymphocytes and produces thymosin hormone.
  • Secondary:
  • Spleen: filters blood, divided into white pulp (immune function) and red pulp (blood filter).
  • Lymph Nodes: filter lymph, filled with macrophages and lymphocytes; named after their location.
  • Lymphatic Nodules: concentrations of lymphoid tissue, e.g., tonsils and Peyer patches.

7.2 Innate Immune Defenses

• Learning Outcomes:

  • List examples of the body’s innate defenses.
  • Summarize events in the inflammatory response.
  • Explain the role of the complement system.

• Innate Immunity:

  • Fully functional without prior exposure to pathogens; includes:
  • Physical Barriers: skin (keratin), mucous membranes (cilia).
  • Chemical Barriers: acidic secretions, lysozyme in saliva/tears.
  • Inflammatory Response: characterized by redness, heat, swelling, pain; employs neutrophils and macrophages.

• Inflammatory Response:

  • Histamine released causes vasodilation and increased permeability.
  • Excess blood flow leads to symptoms of inflammation.
  • The response involves:
  • Neutrophils and macrophages recycling pathogens,
  • Cytokines attracting more WBCs.

• Protective Proteins:

  • Complement System: plasma proteins amplifying inflammatory response, forming membrane attack complexes.
  • Interferons: chemicals from virus-infected cells that warn uninfected cells.

7.3 Adaptive Immune Defenses

• Learning Outcomes:

  • Explain antigen's role in adaptive defenses.
  • Summarize antibody-mediated and cell-mediated immunity processes.

• Adaptive Immunity:

  • Initiated after innate defenses fail; targets specific pathogens.
  • B Cells: produce antibodies; undergo clonal selection and expansion.
  • T Cells: recognize antigens via TCR, cytotoxic T cells kill infected cells, helper T cells secrete cytokines.

• Mechanisms:

  • Cell-Mediated Immunity: T cells kill infected or cancerous cells.
  • Antibody-Mediated Immunity: B cells produce antibodies against free pathogens.

• Memory Cells:

  • Memory B and T cells form during clonal expansion, providing future immunity.

7.4 Acquired Immunity

• Learning Outcomes:

  • Distinguish between active and passive immunity.
  • Recognize the importance of cytokines in immunity.

• Active Immunity:

  • Body makes its antibodies; develops through natural infection or vaccinations.

• Passive Immunity:

  • Body receives antibodies without producing them; occurs naturally via maternal antibodies across the placenta or through breast milk, or artificially through injection.

• Cytokines:

  • Signaling molecules that regulate WBC formation/function, including interferon and interleukins.

7.5 Disorders of the Immune System

• Learning Outcomes:

  • Describe the link between AIDS and opportunistic infections.
  • Summarize HIV transmission and AIDS treatment.
  • Identify triggers of allergic reactions and autoimmune disease effects.

• HIV and AIDS:

  • HIV infects helper T cells, weakening immune response, leading to AIDS.
  • Opportunistic infections occur when the immune system is severely compromised.

• Allergic Reactions:

  • Caused by hypersensitivity; IgE antibodies bind allergens, causing responses like runny nose or asthma.

• Autoimmune Diseases:

  • Body attacks its cells, e.g., rheumatoid arthritis and lupus. Treatments focus on reducing immune response.

• Other Immune Problems:

  • Transplant rejection, severe combined immunodeficiency disease, various immune deficiencies, and autoimmune reactions lead to severe health complications.