Scheme of the spleen (human)

Spleen: A. general diagram; B. adult; C. senium 1. capsule of dense irregular connective tissue with few elastic and smooth muscle fibers (it varies with the species); 2. trabecula (septum); 3. trabecular artery derived from the splenic artery; 4. trabecular vein; 5. when the pulpa artery or central artery leaves the trabecula, it becomes invested within the white pulp by cells forming the periarteriolar lymphoid sheath (PALS) of the white pulp; 6. central artery with periarteriolar lymphatic sheath (PALS); 7. arteriole to the germinal centre of splenic nodule (eccentric from central artery); 8. penicillar arterioles; 9. sheathed capillaries surrounded by macrophages; 10. funnel-like entrance into splenic cords (Billroth's cords = reticular tissue); 11. terminal capillary end opens into splenic venous sinusoid; 12. reticular cell ; 13. anastomosing splenic venous sinusoids; 14. pulpa vein The red pulp is formed by the penicillar arteriole; the macrophage-sheathed capillaries; the splenic sinusoids; the reticular cells forming the stroma of the splenic cords (also known as cords of Billroth), and all cell types of the circulating blood.; 15/16. the white pulp consists of the periarteriolar lymphatic sheaths (PALS), the central artery, and splenic nodule with germinal centre (16) surrounded by a corona. Background: The central artery gives rise to radiating branches, the radial arterioles, ending in the marginal sinus surrounding the white pulp. Blood from the marginal sinus and the central artery is transported into the penicillar arterioles, which end in a capillary network surrounded by macrophages (macrophage-sheathed capillaries). With ageing the spleen decreases in volume and quite a lot of splenic nodules disappears. However remnants of PALS remain and the amount of collagen I and collagen III (argyrophilia) increases.