Primary lymphoid organs - Bone marrow - Thymus Secondary lymphoid organs Organized - Lymph nodes- - Spleen
Structure Microscopic Less well defined than thymus Role of stromal cells Function Hematopoiesis B cell maturation B cell selection Puts out mature, naive B cells
Network of vessels Collects fluid from tissues Major cell is lymphocyte Unidirectional Often first place where antigens are detected
Function 1). Takes in immature T cells and puts out mature (immunocompetent) T cells 2). Increased diversity of T cells 3). T cell selection
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Structure Gross Bi-lobed Lies above heart Microscopic Capsular Lobules with outer cortex and inner medulla
Gross anatomy Structure Bean-shaped structures Drains major segments of lymphatic system
Microscopic Structure Major cell types Lymphocytes Macrophages Dendritic cells Cortex/paracortex/medulla Follicles Primary SecondaryFunction 1st line of response to antigens Secondary follicle (Germinal center) is site of B cell proliferation, mutation, differentiation Specificity is high >90% of B cells die through apoptosis After Ag stimualtion lymphocyte numbers up by 50X in efferent lymphatic vessel Lympadenopathy
Structure Gross Ovoid organ in upper left quadrant of abdomen Microscopic Compartmentalized Red pulp White pulp Periarticualr lymphoid sheath Site of Ag presentation Major cell types Lymphocytes Macrophages Dendritic cells RBCs
Function - Filters out older RBCs - Responds to Ag in circulatory system - Produces activated B cells Splenectomy
Follicular structure Contains lymphocytes, macrophages, mast cells Germinal centers appear in response to Ag Protective role in URI (Upper respiratory infection. Infection of the air passages of the nose, the throat, and/or bronchial tubes.)