Arterial terminals in the rat spleen as demonstrated by scanning electron microscopy of vascular casts

Blood vascular beds of the rat spleen were reproduced with methacrylate resin by thorough injection through the splenic artery or by separate injection through the splenic artery and the portal vein, and observed in the scanning electron microscope. In both thoroughly and separately injected specimens, terminal ends of the follicular and penicillar arteries continued into the leaked resin masses representing the tissue spaces of the marginal zone and red pulp. Direct connection of the arterial terminal with the venous sinus was rather rare and only observed thoroughly injected specimens. These findings may support in the rat spleen the open circulation theory tht arterial blood flows into the tissue spaces of the marginal zone and red pulp and then into the venous sinuses.