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74 Cards in this Set
- Front
- Back
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What goes on in secondary lymphoid organs?
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The development of immune responses via cellular interactions.
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What are the 2ndary lymphoid organs?
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-Lymph nodes
-Spleen -MALT/GALT |
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What is the lymphatic system made up of?
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-Lymph nodes
-Lymphatic vessels |
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What are the lymphatic system's 2 primary functions?
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1. To return ECF that has been filtered from capillaries to ISF back to the circulation
2. To remove antigens from peripheral tissues and place it in a node where immune reaction can occur |
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At what sites do lymph nodes occur?
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At vascular junctions
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When lymphatic capillaries coalesce and enter lymph nodes, what is the vessel called?
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Afferent lymphatic vessel
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How many afferent lymphatic vessels enter each lymph node?
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Usually several
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How do aff lymph vessels enter the lymph node?
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By penetrating the capsule and emptying into the subcapsular sinus.
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What do the trabeculae that extend from capsule into lymph node cortex create?
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Lymph node nodules (follicles)
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What layer lies under the cortex in a lymph node?
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Paracortex
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What structures characterize the paracortex of lymph nodes?
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High endothelial venules
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What are high endothelial venules?
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Blood vessels with plump endothelial cells
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What special molecules are on HEV's? What for?
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Adhesion molecules that allow naieve lymphs to enter the lymph node from the circulation.
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What happens when via the HEVs
-Tcells enter the paracortex? -Bcells enter the paracortex? |
-Tcells stay and make the paracortex T-cell rich
-Bcells migrate out to cortex |
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What determines what Bcells will do in the outer cortex?
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How activated they were by Tcells before they migrated out
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What will unactivated Bcells do?
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Form primary lymphoid follicles - quiescent Bcell aggregates.
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What will activated Bcells do?
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Form secondary lymphoid follicles
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What is a secondary lymphoid follicle?
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A site of selection for and clonal expansion of Bcells that express high-affinity receptors for the Ag encountered there.
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What is the characteristic feature of 2ndary lymphoid follicles?
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The presence of a pale staining GERMINAL CENTER
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What are the 3 zones of a germinal center (outer to in)?
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1. Dark zone - centroblasts
2. Mantle zone (corona) 3. Light zone - centrocytes |
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What are Centroblasts?
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Bcells that proliferate rapidly and do NOT express surface antigen receptors.
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What is the Mantle zone?
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Nonreactive Bcells that get compressed by the dark zone that surrounds them
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How does the mantle zone look compared to the dark zone?
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Mantle is darker than dark
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What is at the center of the germinal center?
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The light zone made of centrocytes
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What do centrocytes do or not do?
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-Do not proliferate
-Do undergo somatic hypermutation |
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What is the purpose of somatic hypermutation?
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To increase the binding affinity of the BCR, and NOW express surface Ig.
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What do centrocytes interact with in the light zone?
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Follicular dendritic cells
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What happens to centrocytes that express hypermutated receptors and can't bind antigen in the light zone?
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They undergo apoptosis in the basal light zone
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What happens to centrocytes that express hypermutated receptors and CAN bind antigen in the light zone?
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They enter the apical light zone
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What are the 2 fates of successful centrocytes in the apical light zone?
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1. Plasma cells
2. B memory cells |
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Where do lymphocytes and lymph fluid drain out of lymph nodes?
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At the medullary cords via the efferent lymphatic vessel.
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What structure contains the efferent lymphatic vessel?
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The hilum
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What do efferent lymphatic vessels from several lymph nodes coalesce to form?
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The thoracic duct
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Where does the thoracic duct ultimately empty?
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Into the SVC and system - to give fresh clear lymph fluid and mature lymphocytes!
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Where is the SPLEEN located?
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In the upper left abdom quadrant
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What are the spleen's 3 functions?
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1. To filter and process Ag from the blood
2. To remove senescent RBCs 3. Hematopoiesis in fetuses |
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What supplies blood to the spleen, via what structure?
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The splenic artery through the hilum
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What arteries branch from the splenic artery?
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Trabecular arteries
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What is the order of branching splenic vasculature?
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1. Splenic artery
2. Trabecular arteries 3. Central arteries 4. Penicillar/Central arterioles 5. Terminal Arterial capillaries |
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Where does blood from the Terminal Arterial capillaries end up?
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In the splenic sinuses.
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What vessels drain the splenic sinuses?
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Pulp veins
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What do the pulp veins coalesce into and ultimately become?
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Trabecular veins, then splenic veins, then exit via the hilum.
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What is the area around the splenic sinuses called?
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Red pulp
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Why is it red pulp?
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Because that's where senescent RBCs go to get eaten by macrophges.
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What lines the splenic sinuses in the red pulp? What surrounds the sinuses?
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Lining = Discontinuous endothelium
Surrounding = reticular fibers |
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What is the loose network that is made up of splenic sinuses and reticular fibers and discontinuous endothelium called?
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The splenic Cords
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What is the predominant cell type in the areas surrounding the central artery and penicillar arterioles?
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Lymphocytes
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So what do we call this area?
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White pulp
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What type of lymphocyte specifically surrounds the Arterioles? What do we call this area?
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T lymphocytes - Periarteriolar lymphoid sheath (PALS)
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What is enclosed WITHIN the PALS?
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Lymphoid follicles where B cells reside.
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What are the 2 types of lymphoid follicles that can be seen in the white pulp?
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Same as in lymph nodes
-Primary (quiescent) -Secondary (active) |
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What discernable feature can be seen in the 2ndary follicles?
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Germinal centers
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What surrounds the periarteriolar lymphoid sheath?
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A marginal zone
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What cell types are found in the marginal zone?
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-Both T and B lymphs
-Macrophages -Dendritic cells |
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What is the marginal zone 'punctuated' by?
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Marginal sinuses
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What are marginal sinuses?
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The sites of delivery of antigen that can stimulate an immune response from all the lymphs
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How is Mucosa Associated Lymphoid Tissue unique?
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It is not encapsulated and lives in the lamina propria of mucosal tissue.
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What is the function of MALT?
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To support and develop an immune response to antigens that get into the body via mucosal access
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Do lymphatics bring antigen to the MALT?
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no
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How does antigen get into MALT?
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Via M-cells (microfold)
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What are 2 types of MALT?
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-GALT (gut)
-BALT (bronchus) |
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What are organized lymphoid follicles in GALT?
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Peyers patches
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Where in the gut are peyers' patches located?
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In the submucosa of the ileum
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What is the function of the tonsils?
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To guard the entry to the GI and respiratory tracts
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Are the tonsils encapsulated?
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Incompletely
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What tonsils are located at the entry to the throat?
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Palatine
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What is bad about the tonsils?
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They have 10-12 crypts which are susceptible to trapping bacteria and becoming infected
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What happens when bacteria infect the palatine tonsils?
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They have to be removed
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What are the collections of 35-100 follicles at the base of the tongue?
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Lingual tonsils
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What is the lingual tonsil surrounded by? What about the palatine tonsils? What type of epithelium covers them both?
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Lingual - a flimsy capsule
Palatine - dense fibrous capsule Epithelium: stratified squamous |
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How is the lingual tonsils significantly different from the palatines?
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It only has 1 crypt so it doesn't get infected
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Where are the tubal tonsils?
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Near the eustachian tubes
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Where are the pharyngeal tonsils?
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In the nasopharynx
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What type of infoldings are on the pharyngeal tonsil? What is it called when it becomes inflamed?
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-Pleats
-An Adenoid is an inflamed pharyngeal tonsil |
