Nerve Fascicle with Perineurium. Three-Dimensional View
The perineurium (1) of a nerve fascicle has been partially removed so as to provide a better impression of its layered structure. The epithelial lamellae (2) are made up of very flattened, elongated cells. One cell has been lifted back at the point where it overlaps another cell, revealing the characteristic structure of a zonula occludens (3). Numerous openings (4) are visible on the external and internal surfaces of the epithelial cells, corresponding to the micropinocytotic vesicles. Basal laminae (5) cover the epithelial cells, between which run many longitudinal collagen microfibrils (6). Myelinated (7) and unmyelinated (8) nerve fibers, which, like the blood capillaries (9), possess their own basal laminae, are located in the fascicle interior. The basal lamina (11) of a myelinated nerve fiber has been cut and partly pulled away (lower left) in order to expose the insertion of the outer mesaxon (10). Numerous longitudinally oriented collagen microfibrils (12) and fibrocytes (13) also occur in the endoneurium.