Lymphoid System Flashcards
(12 cards)
where is the site of t-cell maturation?
thymus
how does the thymus differ in adults and children?
well defined cortex and medullary zone in kids. fatty deposits in adults
what is found in the cortex of the thymus?
developing t cells and their support cells, the epithelial reticular cells
what are Hassalls corpuscles?
keratinized reticular cells in the medulla of the thymus
describe how ERCs select T-cells in the thymus
as the pass from the medulla to cortex, the ERCs only allow T-cells that recognize the MHC class 1 and 2 molecules. in the medulla, they apoptoze any t-cells that react against these cells
where do the lymphatics enter the lymph nodes?
they enter around the edge of the cortex. they leave at the hilum
describe the organization of lymph node layers and the characteristic finding in each
cortex- b cell follicles. paracortex- t-cells and high endothellial venules. medulla- loose sinuses coallescing into lymphatic efferent vessels
what is the difference between primary and secondary follicles?
primary are naive. upon activation, the center of the follicle “clears” into a germinal center as the b-cells mature into plasma cells.
where do lymphocytes leave the blood stream in lymph nodes
high endothelial venules
describe the organization of the spleen
the spleen is organized in regions of red and white pulp. the red pulp is made up of splenic sinuses diffuse lymphoid tissue. the white pulp is an aggregate of lymphoid tissue surrounding blood vessels. this periarteriole lymphatic sheath (PALS) of the white pulp allows for much of the initial antigen presentation in the marginal zone. these blood vessels may be continuous or discontinuous with the venous sinuses.
what is the unique architecture of splenic sinuses?
they are barrel-stave endothelium surrounded by reticular cells
what is the name for lymphoid tissue found under epithelium and distributed throughout the body where antigen presentation commonly occurs?
mucosal associated lymphoid tissue (peyers patches, tonsils
