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44 Cards in this Set

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  • Back
What is a lymph node?
A secondary lymphoid organ
What goes in and out of a lymph node?
-Many afferents
-One or more efferents
What is the general structure of a lymph node like?
It is encapsulated with trabeculae
What are 3 functions of lymph nodes?
-Nonspecific filtration by macrophages
-Storage/proliferation of B/T cells
-Antibody production
What are the 3 main functional areas within a lymph node?
-Follicles
-Medulla
-Paracortex
What happens in the follicles of a lymph node?
B-cell proliferation
Where in a lymph node are the follicles located?
In the outer cortex
What are 2 types of lymph node follicles?
-Primary
-Secondary
What does a primary follicle look like?
Dense and dormant
What does a secondary follicle look like?
Active with a pale central germinal center
What does a lymph node's medulla consist of?
-Medullary cords
-Medullary sinuses
What are medullary cords made of?
Closely packed lymphocytes and plasma cells
What happens in medullary sinuses? What do they contain?
-They contain reticular cells and macrophages
-Communicate with efferent lymphatics
What is housed in the paracortex of a lymph node?
T cells
Where is the paracortex found?
Between the medulla and follicles
What special structures are found in the paracortex?
HEV - high endothelial venules
What happens at high endothelial venules of lymph node paracortex?
T and B cells enter the lymph node from the blood.
What happens to the paracortex during an extreme cellular immune response?
It becomes greatly enlarged.
What patients have underdeveloped paracortexes in their lymph nodes?
Digeorge syndrome patients
What are the 2 main lymph drainage structures?
1. Right lymphatic duct
2. Thoracic duct
What does the right lymphatic duct drain?
-Right arm
-Right half of head
What does the thoracic duct drain?
Everything else
What are 3 secondary lymphoid structures?
-MALT (galt + balt)
-Spleen
-Lymph nodes
What are 2 primary lymphoid structures?
-Bone marrow
-Thymus
2 types of tissue found in the spleen:
-Red pulp
-White pulp
What is the function of red pulp?
Filtration and removal of unwanted materials from blood (ie senescent RBCs)
What is the function of white pulp?
To help fight infections
What does red pulp consist of?
Sinuses - long vascular channels
What lines the sinuses of red pulp in the spleen?
A fenestrated "barrel hoop" basement membrane
What type of cell is found nearby the sinusoids of the spleen in red pulp?
Macrophages - part of the RES
What does white pulp in the spleen consist of?
-Periarteriolar lymphatic sheath
-Follicles
Where are Tcells found in the spleen?
-In the red pulp sinusoids
-In the PALS
Where are Bcells found in the spleen?
In follicles in the white pulp
What is the main site of Tcell differentiation and maturation?
Thymus
What is the Thymus structure like?
Encapsulated
What embryologic structure is the Thymus derived from?
Epithelium of the 3rd branchial pouches
What do lymphocytes originate from?
Mesenchyme
Where are immature Tcells found in the thymus?
In the cortex
Where are mature Tcells found in the thymus?
Medulla
How do you tell the difference between cortex and medulla in the thymus?
The cortex is dense
The medulla is pale
What type of cell other than mature T cells are found in the medulla of the thymus?
Epithelial cells and Hassall's corpuscles.
What occurs at the corticomedullary junction in the thymus?
Positive and negative selection
What is positive selection?
MHC restriction - keeping only the cells that react enough
What is negative selection?
Getting rid of cells that are TOO reactive and react to self.