Scanning electron microscopy of the parimarginal cavernous sinus plexus of the human spleen.

The perifolicular region of the human spleen was studied under the scanning electron microscope. The marginal zone 10 to 50 micron in width was located around the white pulp, and was composed of concentrically arranged reticulum cell networks and intervening lymphocytes, red blood cells and macrophages. The cavernous sinuses 10-150 micron in width were situated between the marginal zone and the red pulp, and were lined by thin, flat endothelia. The perimarginal cavernous sinuses communicated with one another through narrow canals and formed a plexus. Transmural passages of lymphocytes were noted on the side of the white pulp. The perimarginal cavernous sinus plexus was also in communication with the interspaces between reticulum cells in the marginal zone. The human perimarginal cavernous sinus plexus appears to correspond to the marginal sinus in rat and rabbit spleens.