Scanning and transmission electron microscopy of the rat kidney

This study utilized scanning and transmission electron microscopy of renal tissue to provide new information on the gross and microscopic structure of the kidney. The luminal surface of the proximal convoluted tubule was characterized not only by the border of microvilli, but also by crater‐like depressions, and circumferential folds. In tissue processed for scanning electron microscopy the proximal tubular cells separated along their lateral surfaces clearly exposing the topography of the lateral cell projections of cytoplasm which have been generally unavailable for viewing because of their interdigitation with adjacent cells. The various segments of the nephron were identified on the basis of position in the kidney, general morphology, and the distribution and form of apical microvilli, cilia, or flaps. The external surface of the papillary tip had several parallel furrows into which the collecting ducts opened. Large plaquelike depressions lined the papillary surface. The opposed surface of the renal pelvis had small plaque‐like depressions separated by narrow ridges. Transmission electron microscopy of plastic‐embedded tissue specimens which had been previously dehydrated by the critical point drying method demonstrated that little damage occurred from this procedure.