Chapter 21 – The Lymphatic System, Lymphoid Organs & Tissue

Vocabulary flashcards covering key terms, structures, and concepts from BIOL 2252 – Chapter 21 on the lymphatic system and lymphoid organs/tissues.

Lymphatic System

Network of lymph vessels, lymph, and lymphoid organs/tissues that maintains fluid balance and supports immunity.

Lymph

Interstitial fluid that has entered lymphatic vessels for return to the bloodstream.

Lymphatic Vessels (Lymphatics)

One-way drainage tubes that transport lymph toward the heart.

Lymphatic Capillaries

Small, blind-ended, highly permeable vessels where interstitial fluid first enters the lymphatic system.

Lacteals

Specialized intestinal lymphatic capillaries that absorb dietary fats and convey chyle.

Chyle

Milky, lipid-rich lymph collected from the small intestine by lacteals.

Collecting Lymphatic Vessels

Vessels that receive lymph from capillaries and drain into lymphatic trunks; have thin walls and many valves.

Lymphatic Trunks

Large vessels that drain lymph from specific body regions into lymphatic ducts.

Jugular Trunks

Lymphatic trunks that drain the head and neck.

Subclavian Trunks

Trunks that drain upper limbs, breasts, and superficial thoracic wall.

Bronchomediastinal Trunks

Trunks draining deep thoracic structures.

Intestinal Trunk

Single trunk that drains most abdominal organs.

Lumbar Trunks

Pair of trunks that drain lower limbs, abdominopelvic wall, and pelvic organs.

Right Lymphatic Duct

Short duct that drains lymph from the right head, neck, thorax, and upper limb into the right subclavian vein.

Thoracic Duct

Largest lymphatic duct, draining lymph from most of the body into the left subclavian vein.

Cisterna Chyli

Dilated sac at the base of the thoracic duct that receives lipid-rich chyle from intestinal trunks.

Primary Lymphoid Structures

Sites of lymphocyte formation and maturation—red bone marrow and thymus.

Secondary Lymphoid Structures

Sites that house mature lymphocytes and initiate immune responses—lymph nodes, spleen, tonsils, MALT, etc.

Red Bone Marrow

Primary lymphoid organ producing all formed elements; site of B-cell maturation.

Thymus

Primary lymphoid organ in mediastinum where T-lymphocytes mature; largest and most active in children.

Lymphoid Cells

Collective term for immune cells (lymphocytes, macrophages, dendritic cells) and supporting reticular cells.

T-Lymphocyte (T Cell)

Adaptive immune cell that manages immune responses and may directly kill infected cells.

B-Lymphocyte (B Cell)

Adaptive immune cell that differentiates into plasma cells to secrete antibodies.

Macrophage

Phagocytic cell that engulfs pathogens and helps activate T cells.

Dendritic Cell

Antigen-capturing cell that transports antigens to lymph nodes and activates T cells.

Reticular Cell

Supporting cell that produces the stromal fiber network in lymphoid tissue.

Stroma

Reticular fiber framework that supports lymphoid organs.

Lymphoid Tissue

Reticular connective tissue that houses and provides proliferation sites for lymphocytes.

Lymph Node

Secondary lymphoid organ that filters lymph and activates immune responses.

Afferent Lymphatic Vessel

Vessel delivering lymph into a lymph node.

Efferent Lymphatic Vessel

Single vessel exiting a lymph node, slowing lymph flow for filtration.

Germinal Center

B-cell proliferation area within a lymph node’s cortex.

Cortex (Lymph Node)

Outer region containing lymphoid nodules, B cells, T cells, macrophages, and dendritic cells.

Medulla (Lymph Node)

Inner region containing medullary cords of B cells, T cells, and macrophages.

Hilum

Indented region where vessels and nerves enter/leave an organ, e.g., spleen or lymph node.

Spleen

Largest lymphoid organ; filters blood, recycles RBCs, stores platelets, and mounts immune responses.

White Pulp

Spleen region of lymphocytes and macrophages surrounding a central artery; monitors blood for pathogens.

Red Pulp

Spleen tissue rich in erythrocytes and macrophages; removes old RBCs and stores platelets.

Splenic Sinusoids

Very permeable capillaries in red pulp allowing easy blood cell passage; lined by phagocytes.

Tonsils

Ring of lymphoid tissue in pharynx that traps and destroys pathogens from food or air.

Pharyngeal Tonsil (Adenoid)

Single tonsil in nasopharynx; enlarged form called adenoids.

Palatine Tonsils

Pair of tonsils located in posterolateral oral cavity.

Lingual Tonsils

Collection of lymphoid tissue at posterior tongue.

MALT (Mucosa-Associated Lymphoid Tissue)

Lymphoid tissue in mucous membranes providing localized immunity, e.g., in GI and respiratory tracts.

Peyer’s Patches

Aggregated lymphoid nodules in distal small intestine; part of gut MALT that destroys bacteria.

Appendix (Vermiform)

Lymphoid organ off cecum containing MALT; helps destroy bacteria and generate memory cells.

Lymphoid Nodules

Clusters of lymphoid cells with limited connective tissue capsule; can aggregate into larger structures.

Buboes

Inflamed, tender lymph nodes overwhelmed by pathogens; hallmark of bubonic plague.

Lymphoma

Cancerous neoplasm of lymphoid tissue; includes Hodgkin and Non-Hodgkin types.

Metastasis (in Lymph Nodes)

Spread of cancer cells to lymph nodes, where they may lodge and proliferate, causing painless swelling.

Low-Pressure Pump Mechanisms

Skeletal muscle action, thoracic pressure changes, arterial pulsations, and smooth muscle contraction that propel lymph.