The Lymphatic System and Immunity Vocabulary

Vocabulary flashcards covering the key terms, vessels, cells, and organs of the lymphatic system and immunity.

Lymph

The fluid that enters the lymph capillaries from the interstitium, similar in composition to blood plasma but containing less protein and more fat.

Lymph Capillary

A blind-ended microscopic tube located near blood capillaries, composed of a single layer of overlapping endothelial cells without a basement membrane that forms one-way valves.

Lymphatics (Lymphatic Vessels)

Vessels resembling thin-walled veins with numerous internal valves that transport lymph through lymph nodes toward larger lymphatic ducts.

Afferent Lymphatic Vessel

A lymphatic vessel that carries lymph into or towards a lymph node.

Efferent Lymphatic Vessel

A lymphatic vessel that carries filtered lymph away from a lymph node.

Right Lymphatic Duct

A $1.25\,\text{cm}$ long duct located at the junction of the right jugular and right subclavian veins that drains lymph from the upper right quadrant of the body into the right subclavian vein.

Thoracic Duct

A $38\text{--}45\,\text{cm}$ long duct extending from L2 to the left subclavian vein that begins at the cisterna chyli and drains lymph from the majority of the body.

Cisterna Chyli

An enlarged sac-like dilation located at the level of L2 where the thoracic duct originates.

B Lymphocytes

Lymphoid cells produced in red bone marrow from hemocytoblast stem cells that produce antibody-secreting plasma cells.

T Lymphocytes

Lymphoid cells produced in red bone marrow that fight antigens directly and regulate the immune response.

Macrophages

Antigen-presenting phagocytic cells that help activate T cells and engulf foreign debris and pathogens in lymphoid tissue.

Dendritic Cells

Antigen-presenting cells that capture antigens and present them to activate T cells.

Reticular Cells

Connective tissue cells that produce reticular fibers to form the structural stroma of lymphoid tissues.

Diffuse Lymphoid Tissue

Loose, unencapsulated lymphoid tissue found in most organs and in the lamina propria of mucous membranes, such as mucosa-associated lymphatic tissue (MALT).

Lymphoid Follicles

Dense clusters of reticular fibers and lymphocytes located within lymph nodes, the appendix, and Peyer's patches.

Thymus Gland

A bilobed organ extending from the lower neck into the superior thorax that secretes thymopoietin and thymosins to trigger T lymphocyte differentiation.

Lymph Nodes

Small encapsulated lymphoid organs scattered along lymphatic vessels that filter lymph, remove pathogens, and mature lymphocytes.

Capsule (Lymph Node)

The dense irregular connective tissue outer layer surrounding a lymph node.

Trabeculae (Lymph Node)

Internal fibrous partitions extending from the capsule into the interior of a lymph node.

Stroma

The internal framework of reticular fibers that structural supports lymphocytes within a lymph node or organ.

Cortex (Lymph Node)

The outer region of a lymph node containing follicles with germinal centers for dividing B lymphocytes, surrounded by an inner cortex containing T lymphocytes.

Medullary Cords

Strands of tissue extending inward from the cortex toward the medulla of a lymph node containing B lymphocytes, T lymphocytes, and macrophages.

Lymph Sinuses

Large, permeable lymph capillaries containing macrophages that phagocytize debris and foreign antigens as lymph passes through.

Hilus

The indented, concave region on one side of a lymph node where blood vessels enter and efferent lymph vessels exit.

Sentinel Node

The primary or first lymph node to receive drainage from a specific area of interest or tumor.

Spleen

A $150\,\text{g}$ fibrous-encapsulated organ in the left hypochondriac region that produces lymphocytes, stores platelets and iron, and degrades old RBCs.

White Pulp

Splenic tissue composed of lymphocytes attached to reticular fibers surrounding central arterial branches.

Red Pulp

Splenic tissue surrounding white pulp, consisting of venous sinuses and splenic cords containing macrophages for blood clearance.

Palatine Tonsils

Paired lymphoid organs situated in the posterolateral walls of the oropharynx.

Lingual Tonsils

Lymphoid nodules located at the base on the posterior third of the tongue.

Pharyngeal Tonsil

Also known as the adenoids, a lymphoid nodule mass situated in the posterolateral wall of the nasopharynx.

Peyer's Patches

Aggregated lymphoid follicles with germinal centers located in the intestinal wall that remove pathogens from absorbed contents and produce antibodies.