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74 Cards in this Set

  • Front
  • Back
What goes on in secondary lymphoid organs?
The development of immune responses via cellular interactions.
What are the 2ndary lymphoid organs?
-Lymph nodes
What is the lymphatic system made up of?
-Lymph nodes
-Lymphatic vessels
What are the lymphatic system's 2 primary functions?
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
At what sites do lymph nodes occur?
At vascular junctions
When lymphatic capillaries coalesce and enter lymph nodes, what is the vessel called?
Afferent lymphatic vessel
How many afferent lymphatic vessels enter each lymph node?
Usually several
How do aff lymph vessels enter the lymph node?
By penetrating the capsule and emptying into the subcapsular sinus.
What do the trabeculae that extend from capsule into lymph node cortex create?
Lymph node nodules (follicles)
What layer lies under the cortex in a lymph node?
What structures characterize the paracortex of lymph nodes?
High endothelial venules
What are high endothelial venules?
Blood vessels with plump endothelial cells
What special molecules are on HEV's? What for?
Adhesion molecules that allow naieve lymphs to enter the lymph node from the circulation.
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
What determines what Bcells will do in the outer cortex?
How activated they were by Tcells before they migrated out
What will unactivated Bcells do?
Form primary lymphoid follicles - quiescent Bcell aggregates.
What will activated Bcells do?
Form secondary lymphoid follicles
What is a secondary lymphoid follicle?
A site of selection for and clonal expansion of Bcells that express high-affinity receptors for the Ag encountered there.
What is the characteristic feature of 2ndary lymphoid follicles?
The presence of a pale staining GERMINAL CENTER
What are the 3 zones of a germinal center (outer to in)?
1. Dark zone - centroblasts
2. Mantle zone (corona)
3. Light zone - centrocytes
What are Centroblasts?
Bcells that proliferate rapidly and do NOT express surface antigen receptors.
What is the Mantle zone?
Nonreactive Bcells that get compressed by the dark zone that surrounds them
How does the mantle zone look compared to the dark zone?
Mantle is darker than dark
What is at the center of the germinal center?
The light zone made of centrocytes
What do centrocytes do or not do?
-Do not proliferate
-Do undergo somatic hypermutation
What is the purpose of somatic hypermutation?
To increase the binding affinity of the BCR, and NOW express surface Ig.
What do centrocytes interact with in the light zone?
Follicular dendritic cells
What happens to centrocytes that express hypermutated receptors and can't bind antigen in the light zone?
They undergo apoptosis in the basal light zone
What happens to centrocytes that express hypermutated receptors and CAN bind antigen in the light zone?
They enter the apical light zone
What are the 2 fates of successful centrocytes in the apical light zone?
1. Plasma cells
2. B memory cells
Where do lymphocytes and lymph fluid drain out of lymph nodes?
At the medullary cords via the efferent lymphatic vessel.
What structure contains the efferent lymphatic vessel?
The hilum
What do efferent lymphatic vessels from several lymph nodes coalesce to form?
The thoracic duct
Where does the thoracic duct ultimately empty?
Into the SVC and system - to give fresh clear lymph fluid and mature lymphocytes!
Where is the SPLEEN located?
In the upper left abdom quadrant
What are the spleen's 3 functions?
1. To filter and process Ag from the blood
2. To remove senescent RBCs
3. Hematopoiesis in fetuses
What supplies blood to the spleen, via what structure?
The splenic artery through the hilum
What arteries branch from the splenic artery?
Trabecular arteries
What is the order of branching splenic vasculature?
1. Splenic artery
2. Trabecular arteries
3. Central arteries
4. Penicillar/Central arterioles
5. Terminal Arterial capillaries
Where does blood from the Terminal Arterial capillaries end up?
In the splenic sinuses.
What vessels drain the splenic sinuses?
Pulp veins
What do the pulp veins coalesce into and ultimately become?
Trabecular veins, then splenic veins, then exit via the hilum.
What is the area around the splenic sinuses called?
Red pulp
Why is it red pulp?
Because that's where senescent RBCs go to get eaten by macrophges.
What lines the splenic sinuses in the red pulp? What surrounds the sinuses?
Lining = Discontinuous endothelium
Surrounding = reticular fibers
What is the loose network that is made up of splenic sinuses and reticular fibers and discontinuous endothelium called?
The splenic Cords
What is the predominant cell type in the areas surrounding the central artery and penicillar arterioles?
So what do we call this area?
White pulp
What type of lymphocyte specifically surrounds the Arterioles? What do we call this area?
T lymphocytes - Periarteriolar lymphoid sheath (PALS)
What is enclosed WITHIN the PALS?
Lymphoid follicles where B cells reside.
What are the 2 types of lymphoid follicles that can be seen in the white pulp?
Same as in lymph nodes
-Primary (quiescent)
-Secondary (active)
What discernable feature can be seen in the 2ndary follicles?
Germinal centers
What surrounds the periarteriolar lymphoid sheath?
A marginal zone
What cell types are found in the marginal zone?
-Both T and B lymphs
-Dendritic cells
What is the marginal zone 'punctuated' by?
Marginal sinuses
What are marginal sinuses?
The sites of delivery of antigen that can stimulate an immune response from all the lymphs
How is Mucosa Associated Lymphoid Tissue unique?
It is not encapsulated and lives in the lamina propria of mucosal tissue.
What is the function of MALT?
To support and develop an immune response to antigens that get into the body via mucosal access
Do lymphatics bring antigen to the MALT?
How does antigen get into MALT?
Via M-cells (microfold)
What are 2 types of MALT?
-GALT (gut)
-BALT (bronchus)
What are organized lymphoid follicles in GALT?
Peyers patches
Where in the gut are peyers' patches located?
In the submucosa of the ileum
What is the function of the tonsils?
To guard the entry to the GI and respiratory tracts
Are the tonsils encapsulated?
What tonsils are located at the entry to the throat?
What is bad about the tonsils?
They have 10-12 crypts which are susceptible to trapping bacteria and becoming infected
What happens when bacteria infect the palatine tonsils?
They have to be removed
What are the collections of 35-100 follicles at the base of the tongue?
Lingual tonsils
What is the lingual tonsil surrounded by? What about the palatine tonsils? What type of epithelium covers them both?
Lingual - a flimsy capsule
Palatine - dense fibrous capsule
Epithelium: stratified squamous
How is the lingual tonsils significantly different from the palatines?
It only has 1 crypt so it doesn't get infected
Where are the tubal tonsils?
Near the eustachian tubes
Where are the pharyngeal tonsils?
In the nasopharynx
What type of infoldings are on the pharyngeal tonsil? What is it called when it becomes inflamed?
-An Adenoid is an inflamed pharyngeal tonsil