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| Normal spleen |
| Etiology •N/A |
| Pathogenesis •N/A, |
| Epidemiology •N/A |
| General Gross Description •The normal spleen is a slate-gray organ about 150 gm in an adult. •It is shaped like a large bean with convex surface and a concave surface. •The splenic artery and vein enter (and exit, respectively) through the center of the concave surface, at a spot known as the hilus. •They are then carried into the substance of the spleen through fibrous trabeculae. •The external gray surface is due to the color of the fibrous capsule. •The cut surface reveals a largely red organ (due to the red pulp), speckled with white-gray nodules known as the Malpighian or white corpuscles. |
| General Microscopic Description •The white pulp is, in three dimensions, a sleeve of predominately T lymphocytes that encase the branches of arteries as they arborize through the splenic tissue. •Typically, this sleeve of T lymphocytes is somewhat eccentric, so that on cross section one can see a small arteriole surrounded by an off-center cuff of lymphocytes. •Periodically, this sleeve of lymphocytes is studded, again eccentrically, by nodules of lymphoid tissue containing proliferating B lymphocytes in the form of a typical germinal center. •As the branches of the splenic artery become smaller and smaller, they ultimately end in small blood vessels known as penicillary arterioles, which is not encased in lymphocytes. •Blood in these penicillary arterioles reaches the venous circulation through two routes. •The more rapid route is through sinusoids that carry blood directly from the penicillary arteriole into the venous circulation. •The walls of the sinusoids are delimited by endothelial cells that differ from those in the rest of the circulation in an important way. •They are fenestrated such that a significant part of the blood leaks outside of the vascular tree into the cords of Billroth. •The cords of Billroth form reticular network made up of the interdigitating dendritic processes of cells of the macrophage lineage. •Circulation through the cods of Billroth is slow. •Senesced blood cells are culled from circulation by these macrophage cells. |
| Clinical Correlation •N/A |
| References Bloom and Fawcett: A textbook of Histology. 12th Edition. New York: Chapman & Hall. 1994. pp 460 Gray: Gray's Anatomy. 15th Edition. New York. Barnes & Noble Books. 1995. pp 933 et seq. |
| Normal spleen |
| Synopsis by: T.V.Rajan, M.D., Ph.D. (T07000M00100)[593] |
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