The vascular organization of the kidney.

Abstract

The last 15 years have witnessed major advances in the understanding of renal vascular and tubular organization. Yet even now some textbooks show structural features known to be erroneous in 1920. The efferent vessel from a single glomerulus is often shown perfusing the entire length of the neph­ ron arising from that same glomerulus, and the vascular zonation of the cortex and medulla is frequently ignored. The persistence of such concepts is perhaps due to the influence of schematic diagrams published by Smith in 1951 (56). Such diagrams were perhaps appropriate for the era in which redistribution of cortical blood flow, intrarenal feedback mechanisms, and the role of the medulla in urine concentration were all unknown. Blood Bow redistribution may indicate the existence of regional differences in function and in structure. The search for such differences has revealed the true relationships between efferent blood vessels and nephrons. Studies of the juxtaglomerular apparatus, a vascular-tubular relationship of great poten­ tial importance, have been stimulated by an interest in intrarenal feedback control mechanisms. Detailed studies of medullary organization have fo­ cussed on the role of countercurrent mechanisms in the development and preservation of medullary hypertonicity. The investigations reviewed in the following pages have been undertaken in the belief that function, if not following directly from structure, must at least be consistent with structure.