How are compartments of red pulp?

• The cords contain a labyrinth of macrophages loosely connected through long dendritic processes to create both a physical and a functional filter. As it traverses the red pulp, the blood takes two routes to reach the splenic veins. 1. Open circulation or slow compartment: Some flows through capillaries into the cords, from which blood cells squeeze through gaps in the discontinuous basement of the endothelial lining to reach the sinusoids. 2. In the other “closed circuit,” blood passes rapidly and directly from the capillaries to the splenic veins. Although only a small fraction of the blood pursues the “open” route, during the course of a day the entire blood volume passes through the cords, where it is closely examined by macrophages