Morphology of the human and dog spleen with special reference to intrasplenic microcirculation.

The terminal structure of splenic arterial capillaries, studied by scanning transmission electron microscopy, provided a three-dimensional view of the microarchitecture of human and dog spleens. There are reports that the terminal arterial capillaries end "openly" in the cord, however, our microphotographs indicate the possibility of a closed circulation in humans and dogs. In the human spleen, we found two types of arterial capillaries, one with a flat and continuous endothelium, and the other with discontinuous rod-shaped endothelial cells and a sheath-like structure. The microarchitecture and the termination of these arterial capillaries differ markedly among species.