Lymphatic System and Portal Systems

Vocabulary practice flashcards covering portal systems (hepatic, renal, hypothalamic-hypophyseal) and the anatomy, histology, and physiology of the lymphatic system and lymphoid organs.

Portal System

A vascular arrangement linking two capillary beds in series from one organ to another via connecting vessels (often veins) before returning blood to the heart.

Hepatic Portal System

A portal system that transports blood from the capillary beds of the digestive tract (e.g., small intestine) through the hepatic portal vein to the capillary beds of the liver for nutrient processing and toxin filtration before entering the inferior vena cava.

Renal Portal System

A portal system within the kidney nephron that carries blood from an afferent arteriole into the glomerulus (capillary bed #1), through an efferent arteriole, and into the peritubular capillaries or vasa recta (capillary bed #2).

Hypothalamic-Hypophyseal Portal System

A vascular network linking the primary capillary plexus in the hypothalamus to the secondary capillary plexus in the anterior pituitary, enabling the speedy delivery of hypothalamic releasing and inhibiting hormones without systemic dilution.

Lymphatic System

A circulatory and immune organ system consisting of lymphatic vessels, lymph fluid, and lymphoid tissues/organs that returns leaked interstitial fluid to the blood, absorbs dietary lipids from the small intestine, and produces and circulates immune cells.

Lymph

The clear, protein-containing interstitial fluid once it has entered lymphatic vessels to be filtered and returned to the venous circulation.

Lymphatic Capillaries

Blind-ended microscopic vessels weaving between tissue cells and blood capillaries that collect excess interstitial fluid; they are highly permeable and absent from bones and teeth.

Minivalves

Flaplike, one-way valves formed by loosely overlapping endothelial cells in lymphatic capillaries that open when interstitial fluid pressure increases and shut when internal fluid pressure rises.

Glymphatic System

A waste-clearance system in the brain where astrocyte-formed channels connect to meningeal lymphatic vessels to drain interstitial fluid, cerebrospinal fluid, and metabolic wastes.

Cisterna Chyli

An enlarged sac at the base of the thoracic duct that collects lymph draining from the lumbar trunks and the intestinal trunk before conveying it upward toward the venous system.

Right Lymphatic Duct

A major terminal lymphatic duct that returns approximately $\frac{1}{4}$ of total body lymph, draining the right upper limb and the right side of the head and thorax into the right subclavian vein.

Thoracic Duct

The largest lymphatic duct that drains approximately $\frac{3}{4}$ of body lymph from the lower limbs, abdomen, left thorax, left upper limb, and left side of the head into the left subclavian vein.

Lymphedema

Severe localized swelling and fluid retention resulting from impaired or obstructed lymphatic drainage, often caused by tumors blocking lymph vessels or surgical removal during cancer treatment.

Primary Lymphoid Organs

The anatomical sites where lymphocytes originate and mature, specifically consisting of red bone marrow (B cell maturation) and the thymus (T cell maturation).

Secondary Lymphoid Organs

Peripheral organs and tissues where mature lymphocytes encounter antigens and mount immune responses, including lymph nodes, spleen, tonsils, Peyer's patches, and the appendix.

Lymph Nodes

Small, encapsulated lymphoid organs containing an outer cortex with follicles, an inner medulla with cords and sinuses, and reticular connective tissue stroma that filter and cleanse lymph as it flows toward the bloodstream.

Afferent Lymphatic Vessels

The multiple incoming lymphatic vessels that penetrate the convex outer surface of a lymph node to bring unfiltered lymph into the subcapsular sinus.

Efferent Lymphatic Vessels

The fewer outgoing lymphatic vessels through which cleansed lymph exits a lymph node at its indented hilum.

Buboes

Infected, swollen, and tender lymph nodes (often pus-filled) caused by an overwhelming bacterial infection; a condition historically associated with bubonic plague and medically termed lymphadenopathy.

Thymus

A bilobed, encapsulated lymphoid organ located in the superior mediastinum atop the heart that provides the site and hormonal environment for T lymphocyte differentiation and maturation.

Thymic Corpuscles

Concentric epithelial structures located in the medulla of the thymus that serve as a distinctive histological feature of thymic tissue.

Spleen

The largest lymphoid organ in the body, located in the left hypochondriac region beneath the diaphragm, that cleanses blood, destroys old erythrocytes, stores recycled iron, and serves as an erythrocyte and platelet reservoir.

Red Pulp

Splenic tissue composed of splenic cords and venous sinusoids laden with erythrocytes and macrophages, responsible for destroying damaged red blood cells and bloodborne pathogens.

White Pulp

Splenic lymphoid tissue composed mostly of lymphocytes arranged along reticular fibers around central arteries, responsible for executing immune functions against bloodborne pathogens.

Mucosa-Associated Lymphoid Tissue (MALT)

Unencapsulated or diffuse aggregations of lymphoid tissues embedded in mucous membranes throughout the digestive, respiratory, and genitourinary tracts to defend against mucosal pathogens.

Tonsils

Partially encapsulated lymphoid tissue aggregates arranged in a ring around the pharynx that capture and destroy pathogens entering via ingested food or inhaled air.

Tonsillar Crypts

Deep epithelial invaginations or crevices in the tonsils that trap bacteria and environmental particulate matter, facilitating immune activation and the generation of immunological memory.

Palatine Tonsils

Paired tonsils located on either side at the posterior margin of the oral cavity; they are the largest and most frequently infected of the tonsils.

Pharyngeal Tonsil

A single lymphoid mass situated in the posterior wall of the nasopharynx, commonly referred to as the adenoids when enlarged.

Lingual Tonsil

A collection of lymphoid follicles located at the base of the tongue.

Peyer's Patches

Large aggregations of lymphoid nodules embedded within the wall of the distal small intestine (ileum) that prevent bacterial penetration through the gut wall and generate memory lymphocytes.

Appendix

A narrow, blind-ended tubular pouch extending from the cecum of the large intestine, densely packed with lymphoid follicles that prevent bacterial translocation and support long-term immunity.