Lymphatic System and Lymphoid Organs – Vocabulary Flashcards

A comprehensive set of vocabulary flashcards covering key terms and concepts from Chapter 20: The Lymphatic System and Lymphoid Organs and Tissues.

Lymph

Protein-rich interstitial fluid collected by lymphatic vessels and returned to the bloodstream.

Lymphatic Vessels (Lymphatics)

Elaborate network of drainage vessels that transport lymph toward the heart.

Lymph Nodes

Small secondary lymphoid organs that filter lymph and activate the immune response.

Lymphoid Organs

Structures such as lymph nodes, spleen, thymus, tonsils, Peyer’s patches, and appendix that house immune cells.

Interstitial Fluid

Fluid in the tissue spaces; excess becomes lymph when taken up by lymphatics.

Hydrostatic Pressure

Outward force that pushes fluid out of blood capillaries into tissues.

Colloid Osmotic Pressure

Inward force drawing fluid back into blood capillaries due to plasma proteins.

Lymphatic Capillaries

Blind-ended, highly permeable microscopic vessels that begin the lymphatic pathway.

Minivalves

Overlapping endothelial flaps of lymphatic capillaries that open one-way to admit interstitial fluid.

Collagen Filaments (Anchoring Filaments)

Fibers that tether lymphatic capillaries to surrounding tissue, preventing collapse.

Glymphatic System

Brain drainage pathway formed by astrocytic channels and meningeal lymphatics, clearing CSF and wastes.

Lacteals

Specialized intestinal lymphatic capillaries that absorb digested fats.

Chyle

Milky, fatty lymph collected from the small intestine’s lacteals.

Collecting Lymphatic Vessels

Larger lymphatics with three tunics, valves, and anastomoses that drain lymphatic capillaries.

Lymphatic Trunks

Nine large vessels (paired lumbar, bronchomediastinal, subclavian, jugular, and single intestinal) that drain major body regions.

Right Lymphatic Duct

Short duct that drains lymph from the right upper limb, right side of head, and thorax into the venous system.

Thoracic Duct

Largest lymphatic duct that drains lymph from the rest of the body into the left venous angle.

Cisterna Chyli

Enlarged sac at the origin of the thoracic duct that collects lymph from intestinal and lumbar trunks.

Vasa Vasorum (of Lymphatics)

Small blood vessels that supply the walls of larger lymphatic vessels.

Lymphangitis

Inflammation of lymphatic vessels, producing red, tender streaks under the skin.

Lymph Transport Mechanisms

Skeletal-muscle pump, respiratory pump, arterial pulse pressure, and smooth-muscle contractions that propel lymph.

Lymphedema

Localized swelling due to impaired lymphatic drainage.

Antigen

Any molecule (bacteria, toxin, virus, mismatched cell) that provokes an immune response.

T Lymphocytes (T Cells)

Cells that mature in the thymus; manage immune responses and directly kill infected cells.

B Lymphocytes (B Cells)

Cells that mature in bone marrow; differentiate into plasma cells that secrete antibodies.

Plasma Cells

Antibody-producing descendants of activated B cells.

Macrophages

Phagocytes that ingest pathogens and activate T cells in lymphoid tissues.

Dendritic Cells

Antigen-presenting cells that capture antigens and bring them to lymph nodes.

Reticular Cells

Fibroblast-like cells that produce reticular fiber stroma supporting lymphoid tissues.

Diffuse Lymphoid Tissue

Loose collection of immune cells found in virtually every organ’s mucosa and connective tissue.

Lymphoid Follicle (Nodule)

Solid, spherical mass of lymphoid cells with a possible germinal center of proliferating B cells.

Germinal Center

Light-staining region within a lymphoid follicle where activated B cells proliferate.

Primary Lymphoid Organs

Sites where lymphocytes mature—red bone marrow (B cells) and thymus (T cells).

Secondary Lymphoid Organs

Sites where mature lymphocytes first encounter antigens—lymph nodes, spleen, MALT structures.

MALT (Mucosa-Associated Lymphoid Tissue)

Lymphoid tissue in mucous membranes that guards body entryways.

Tonsils

Ring of partially encapsulated lymphoid tissue around the pharynx that traps pathogens.

Peyer’s Patches

Aggregated lymphoid nodules in the distal small intestine wall that prevent bacterial translocation.

Appendix

Tubular offshoot of the large intestine rich in lymphoid follicles for immune surveillance.

Thymus

Primary lymphoid organ in the mediastinum where T cells mature; prominent in children.

Blood Thymus Barrier

Endothelial and epithelial cell layer that isolates immature T cells from blood-borne antigens.

Thymic Corpuscle (Hassall’s Corpuscle)

Concentric whorl of keratinized epithelial cells in the thymic medulla involved in regulatory T cell development.

Regulatory T Cells

Subset of T cells that dampen immune responses and prevent autoimmunity.

Lymph Node Cortex

Outer region of a lymph node containing follicles with germinal centers and T cells in transit.

Lymph Node Medulla

Inner region of a lymph node composed of medullary cords rich in B cells, T cells, and plasma cells.

Buboes

Pus-filled, inflamed lymph nodes characteristic of bubonic plague or severe infections.

White Pulp (Spleen)

Lymphocyte-rich areas surrounding central arteries where immune functions occur.

Red Pulp (Spleen)

Splenic tissue rich in macrophages and RBCs that removes old erythrocytes and pathogens.

Splenectomy

Surgical removal of the spleen, formerly common after rupture but now less frequent.