Lymphatic System and Lymphoid Organs

These vocabulary flashcards cover the components, vessels, and organs of the lymphatic system, including their structures, functions, and specific anatomical landmarks.

Lymphatic System

A component of the circulatory system consisting of lymphatic vessels and lymphoid organs that returns excess fluid to venous circulation and acts as the anatomical seat of the immune system.

Lymphatic Capillaries

Smallest, blind-ended vessels with simple squamous epithelial walls that overlap to form simple valves, anchored to connective tissue by collagen filaments.

Lymph

The fluid formed once excess interstitial fluid enters the lymphatic vessels; it has a composition similar to plasma but contains much less protein.

Lacteals

Specialized lymphatic capillaries located in the intestinal mucosa that absorb lipid globules.

Chyle

A milky fluid formed by lipid globules suspended in lymph, which is transported to the venous system and subsequently processed by the liver.

Lymphatic Collecting Vessels

Vessels possessing three tunics and valves similar to veins that transport lymph using the skeletal muscle pump and respiratory pump.

Lymphatic Trunks

Large collecting vessels that drain major body regions, including the Lumbar, Bronchomidiastinal, Subclavian, Jugular, and the unpaired Intestinal trunk.

Right Lymphatic Duct

The duct that drains lymph from the right upper arm and the right side of the head and thorax.

Thoracic Duct

The duct that drains lymph from the majority of the body and arises as an enlarged sac called the cisterna chyli.

Cisterna Chyli

The enlarged sac that serves as the origin of the thoracic duct.

Lymphocytes

Leukocytes that serve as the main functional lymphoid cells, divided into T-lymphocytes and B-lymphocytes.

Diffuse Lymphoid Tissue

Lymphoid tissue composed of reticular connective tissue housing circulating lymphocytes, found in virtually every organ and the lamina propria of mucous membranes.

Lymphoid Follicles

Spherical collections of lymphoid tissue without a fibrous capsule, arranged around germinal centers.

Germinal Centers

Found within lymphoid follicles, these contain dendritic cells and lymphocytes and are the site of B-lymphocyte proliferation during an immune response.

Lymph Nodes

Packets of lymphoid follicles surrounded by a fibrous capsule that filter debris from lymph and house macrophages and lymphocytes.

Afferent vs. Efferent Lymphatic Vessels

The structural arrangement in lymph nodes where afferent vessels outnumber efferent vessels to slow down the flow of lymph.

Spleen

The largest lymphoid organ, located near the stomach, which functions in lymphocyte proliferation, erythrocyte recycling, and blood platelet storage.

White Pulp

The portion of the spleen composed of lymphocytes suspended on reticular tissue.

Red Pulp

The portion of the spleen composed of venous sinuses.

Thymus

A bilobed organ in the inferior neck/thorax that secretes thymosin and thymopoietin, responsible for making T lymphocytes immunocompetent.

Tonsils

The simplest lymphoid organs forming a ring around the pharynx, consisting of Palatine, Lingual, Pharyngeal, and Tubal varieties.

Crypts

Blind-ended invaginations of the epithelial tissue overlying tonsil masses that trap and destroy bacteria and particulate matter.

Peyer’s Patches

Isolated clusters of lymphoid tissue found in the wall of the distal portion of the small intestine that destroy bacteria and generate memory lymphocytes.

MALT

The abbreviation for Mucosa Associated Lymphoid Tissue, which includes Peyer’s patches, tonsils, and tissue in the bronchii walls as a first line of defense.