Lymphoreticular system: spleen & thymus
spleen
thymus
functions
participation in immuno surveillance: T/B cells
source of Extramedullary (outside the bone marrow) hematopoiesis: normal in neonates, abnormal in adults
filtration of peripheral blood: removes particulates and old/damaged erythrocytes
storage pool: reservoir for RBCs and platelets
morphology
enclosed in capsule
two compartments
white pulp: basophilic (from nuclei in lymphocytes), T and B cells, periarteriolar lymphoid sheaths (PALS)
red pulp: screen RBCs, sinusoids (labyrinth of thin-walled vessels creating functional and physical filter through which blood slowly seeps)
site of T-cell maturation
pyramidal, bilobed organ divided into lobules
cells
thymic epithelial cells (have a whorled growth pattern with keratinization)
immature T-lymphocytes (thymocytes)
two compartments
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cortex: immature T-cells
it regresses and atrophies in adults