Blood vessels of the Peyer's patch in the mouse: I. Topographic studies.

The topographic distribution of blood vessels in Peyer's patches of mice was studied by light and scanning electron microscopy with whole mounts of flattened gut segments and vascular corrosion casts. Peyer's patches are imbedded in the intestinal wall and share its blood supply. Two to four mural trunks may contribute to the area of the patch. In and around the lymphoid nodules the microcirculation is highly specialized. The nodule is permeated by a meshwork of fine capillaries that is supplied by arterioles entering on the serosal and lateral surfaces. Blood flow to the lymphoid nodule appears to be monitored by arterial sphincters; the dense lymphatic tissue can also be bypassed by arteriovenous communications. An extensive venous network encircles the nodule. Most of these venules are lined by high endothelium which is penetrated by lymphocytes. The geometry of these vessels suggests a slow and turbulent flow in these vascular segments that may aid margination of lymphocytes. A planar capillary plexus lies subjacent to the mucosal epithelium in the dome area.