ORGANIZATION OF THE LAMINA PROPRIA MUCOSAE OF RAT INTESTINAL-MUCOSA, WITH SPECIAL REFERENCE TO THE SUBEPITHELIAL CONNECTIVE-TISSUE

Light microscopy, scanning electron microscopy and transmission electr on microscopy have been used to delineate the structure and function o f the lamina propria mucosae in the rat jejunum. In silver-impregnated sections, the adepithelial surface of the lamina propria mucosae was framed by a sheet of reticular fibers (reticular sheet). Short-term (3 -hour) immersion of jejunal tissues in 2 N NaOH solution enabled us to simultaneously view networks of reticular fibrils and fibroblasts res iding in the subepithelial connective tissue under a scanning electron microscope. The reticular fibrils, which measured about 40 nm in diam eter and were interwoven in dense networks, formed a sheet 2-3 mu m th ick. In the villi, this sheet contained numerous foramina ranging from 3 to 7 mu m in diameter, through which lymphocytes, macrophages, basa l extensions of epithelial cells and fat particles traversed. The reti cular sheet in the domes of isolated lymphoid nodules was markedly por ous, and many lymphocytes migrated into or out of the epithelium throu gh the foramina. The foramina of the reticular sheet may participate i n the communication between the intestinal epithelium and the lamina p ropria mucosae. It was noted that the foramina of the reticular sheet in the villi were surrounded by end feet of the cytoplasmic processes of fibroblasts. In addition, these fibroblasts were combined with lymp hocytes or dendritic cells in the lamina propria mucosae.