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37 terms

Lymphatic System

Negative selection
survival of T cells depends upon not recognizing self-antigen
Functions of lymphatic system
assist cardiovascular system by returning excess fluid to the blood to maintain fluid balance; assist immune system
Hepatic portal system
digested fats are transferred from the GI system to the liver and then must go to the circulation; fluid in the interstitium is recaptured and put back into the cardiovascular system
Lymphatic system and immunity
transports and houses lymphocytes and other immune cells that help the immune system defend against foreign substances or pathogens
fluid similar to plasma without plasma proteins or RBCS
Lymphatic ducts and trunks
lymph is transported through progressively larger and larger lymph vessels, including lymphatic capillaries, vessels, trunks, and ducts; lymphatic ducts drain lymph into venous circulation
Lymphatic vessels
provide a conduit from the peripheral tissues to the venous system; drain into lymph nodes
Lymphatic organs
bone marrow, lymph nodes, spleen, thymus, etc.
Lymphatic cells
lymphocytes, phagocytes, APCs, etc.
Closed system
fluid and dissolved molecules enter and leave small vessels - net fluid flow is OUT
Lymphatic vessel structure
begin as a blind ended tube; larger lumens and thinner walls than capillaries; endothelial cells are loosely bound together with overlaps or openings; acts as a one-way valve
movement of cancerous cells from the point of origin via the lymphatic vessels to new sites
parasitic filarial worms live, breed, and block the lymphatic vessels; mosquitoes are the vector
Bone marrow
site of maturation for all formed elements except T-cells
Antigen presenting cells (APCs)
cells that phagocytose a foreign component, digest most of the molecules but present parts of the component on its cell surface
Education of lymphocytes
occurs in bone marrow and B lymphocytes leave; occurs in thymus and T lymphocytes leave
Migration of lymphocytes
occurs via blood or lymphatic vessels to occupy CT as free cells or in lymphatic nodules; in lymph nodes; and in spleen
Naive B lymphocytes
educated by presenting with self-antigens; if they recognize self-antigens, they are killed
Naive T lymphocytes
leave bone marrow and migrate to the thymus; education occurs in thymus in the presence of epithelial reticular cells
Primary lymphatic structures
bone marrow and thymus; sites of cell formation and education
Secondary lymphatic structures
lymph nodes, spleen, tonsils, lymph nodules (MALT); sites of cell activation and proliferation
Lymph nodules
collections of lymphocytes (MALT, GALT, BALT); germinal center mostly B cells; marginal zone T cells; macrophages everywhere
Lymph nodes
located along lymphatic vessels; all lymph fluid must pass through to be cleaned by lymphocytes and returned to the blood
Afferent lymphatic vessels
carry lymph from peripheral tissues into lymph node
Efferent lymphatic vessels
carry lymph to venous circulation
Lymph flow from subscapular space
contains macrophages and dendritic cells (APCs)
Lymph flow through outer cortex
contains B cells within germinal centers
Lymph flow through paracortex
dominated by T cells
Lymph flow through core/medulla
contains B cells and plasma cells, organized into medullary cords
Lymph flow
from subscapular space; through outer cortex; through paracortex; through core/medulla; into hilum and efferent lymphatics
Blood flow in the spleen
blood enters via arteries and percolates through the white pulp and red pulp where it is monitored and cleaned; blood can move in and out of sinusoidal capillaries; eventually exits via the venous system
Spleen functions
white pulp filters blood; red pulp removes old (senescent) RBCs and platelets
White pulp
nodules containing APCs, B and T cells, and macrophages destroy antigens
Red pulp
macrophages digest RBCs; iron from RBCs is stored and reused
Spleen anatomy
arteries branch out through the spleen and discharge blood at sinusoidal capillaries; collections of lymphocytes serve to detect and remove pathogens; clean blood collected back into venues and returned to circulation
site of T-cell maturation and education; located in mediastinum
Positive selection
survival of T cels depends upon ability to bind to MHC