Anatomy of the Immune/lymphatic systems

Lymphatic and Immune System Overview

  • The lymphatic system supports the immune system, protecting against microorganisms and diseases.
  • It picks up fluid that leaks from capillaries.

Structure of the Lymphatic System

  • Main Parts:
    • Lymphatic vessels (lymphatics)
    • Lymph nodes
    • Lymph fluid

Lymph Fluid

  • Clear fluid in lymphatic vessels and nodes.
  • Transports waste and is filtered for germs/substances by the immune system.

Lymphatic Vessels

  • Types:
    • Lymphatic capillaries: smallest vessels found in tissues/organs; carry lymph fluid.
    • Progressive larger vessels combining into two ducts:
    • Right lymphatic duct: drains right arm, right head, neck, chest.
    • Thoracic duct: largest, drains lower body, left head, neck, and chest.

Lymph Nodes

  • Tiny, bean-shaped glands filtering lymph.
  • Approx. 400-700 nodes arranged in clusters, mostly deep in the body.
  • Superficial nodes: palpable when enlarged.
    • Locations: Inguinal (groin), axillary (armpit), cervical (neck).

Lymph Transport

  • Lymph moves towards the heart propelled by nearby artery pulsations and smooth muscle contractions in vessel walls.
  • Inside nodes, lymph flows slowly to allow white blood cells to identify/destroy pathogens.

Lymphoid Organs

  • Contain lymphoid tissue; key to immune function.
  • Primary lymphoid organs:
    • Bone marrow: origin of B lymphocytes.
    • Thymus: origin of T lymphocytes; atrophies post-adolescence.
    • Importance of thymus in developing a functional immune system.

Secondary Lymphoid Organs

  • Spleen:

    • Large mass of lymphoid tissue; involved in blood/immune functions.
    • Red pulp: destroys old red blood cells.
    • White pulp: lymphocyte proliferation and immune surveillance.

  • Tonsils:

    • Form a ring around nose and throat; protect from airborne and foodborne pathogens.
    • Composed of palatine, lingual, pharyngeal, and tubal tonsils.

  • Digestive tract:

    • Contains lymphoid tissue (Peyer’s patches in the small intestine) to guard against pathogens.
    • Appendix and mucosa-associated lymphatic tissue (MALT) in respiratory tract for protection against inhaled pathogens.