Sometimes more than one vessel is seen as the central artery divides into branches. Because of the perfusion, the central arterioles are usually empty. Infrequently, the sheath of lymphocytes can be seen to have a lymphatic nodule embedded in it, with a germinal center present. Finally, in several cases, the white pulp can be seen to be immediately surrounded by a pale, washed-out zone. This zone is the Marginal Zone , an area where capillaries arising from the central artery terminate.
White pulp coats the blood vessels.
The Red Pulp fills in the area which is not white pulp. At low magnification the red pulp can be seen to be very rich in RBCs which have not been washed out, and which have clumped together under fixation. Even at higher power the organization of the red pulp is not readily apparent. It consists of irregular branching and anastomosing sinusoids , which tend to be solidly packed with RBCs, but contain many WBCs. Because the sinusoids are so leaky the cords tend also to be rich in RBCs.