Evidence for the Primo Vascular System above the Epicardia of Rat Hearts
Figure 5
Transmission electron microscopy images of cross-sectioned PNs. (a) Low-magnification view of a PN in which the outermost area consists of two cells (PC: putative endothelial cells). (b) Magnified view of the left rectangle in image (a), showing distinctive lumens (L) in the PC. (c) Magnified view of the right rectangle in image (a), also showing a lumen-containing PC. (d) High-magnification view of the lumen (L) indicated by the rectangle in (b); in (d) some microgranules are seen (arrows). Asterisks in images (b) and (c) are magnified into images (e) and (f), respectively, and demonstrate bundles of collagen fibers. The triangle in image (f) means cluster of fine fibers.
