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Lymphatic System and Lymphoid Organs - Anatomy & Physiology

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Terms in this set (20)

  • Primary function of the lymphatic system

    Returns fluids leaked from the vascular system back to the blood and cleanses lymph through lymph nodes.

  • What is lymph?

    Fluid contained in lymphatic vessels that originates from excess tissue fluid.

  • Structure and function of lymphatic capillaries

    One-way swinging door valves that are permeable to fluid, proteins, cell debris, pathogens, and cancer cells; retrieve excess fluid from tissue.

  • Pathway of lymph flow from capillaries to bloodstream

    Lymphatic capillaries → collecting lymphatic vessels → lymphatic trunks → lymphatic ducts → blood stream at jugular and subclavian vein junctions.

  • Mechanisms aiding lymph transport

    Milking action of skeletal muscles, thoracic pressure changes during breathing, valves preventing backflow, arterial pulsations, and smooth muscle contractions in vessels.

  • Main tissue type of the lymphatic system

    Reticular tissue, which supports lymphocytes and other immune cells.

  • Key immune cells in lymphatic tissue

    Macrophages, B and T lymphocytes, dendritic cells, and reticular cells.

  • Two forms of lymphoid tissue

    Diffuse lymphoid tissue (loose cells) and lymphoid follicles (solid, spherical bodies with germinal centers).

  • Primary lymphoid organs and their functions

    Red bone marrow (B cell maturation) and thymus (T cell maturation).

  • Secondary lymphoid organs and their functions

    Lymph nodes, spleen, and MALT; sites where mature lymphocytes encounter antigens and become activated.

  • Functions of lymph nodes

    Cleansing lymph by macrophages and activating immune responses by lymphocytes encountering antigens.

  • Lymph node structure

    Dense fibrous capsule with trabeculae, cortex with lymphoid follicles and germinal centers, and medulla with medullary cords containing B and T cells.

  • Lymph flow through a lymph node

    Enters via afferent vessels, moves through subcapsular and medullary sinuses, exits via fewer efferent vessels allowing immune processing.

  • Functions of the spleen

    Removes bloodborne pathogens and aged red blood cells, site for lymphocyte proliferation, stores platelets and monocytes.

  • Role of MALT (mucosa-associated lymphoid tissue)

    Guards body entryways against pathogens; includes tonsils, Peyer’s patches, and appendix.

  • Types of tonsils and their locations

    Palatine (oral cavity), lingual (base of tongue), pharyngeal (nasopharynx), and tubal (auditory tube openings).

  • Function of tonsillar crypts

    Trap bacteria and expose immune cells to antigens to develop immune memory.

  • Peyer’s patches and appendix function

    Clusters of lymphoid follicles in the small intestine and appendix that trap bacteria and generate memory lymphocytes.

  • Unique features of the thymus

    Primary lymphoid organ for T cell maturation, no B cells or follicles, stroma made of epithelial cells, contains thymic corpuscles.

  • Changes in the thymus with age

    Prominent in newborns, grows in childhood, atrophies after puberty, replaced by fibrous and fatty tissue in old age.