Bankir L, de Rouffignac C
Am J Physiol. 1985 Dec;249(6 Pt 2):R643-66. doi: 10.1152/ajpregu.1985.249.6.R643.
It appears difficult to build a coherent picture of the concentrating system of the mammalian renal medulla. This may be due to the diversity of the factors involved and to considerable interspecies differences. Several morphological adaptations that may be critical in the improvement of water conservation are described. They include variations in the length of the papilla, number of nephrons, percentage of long-looped nephrons, nephron heterogeneity, development of pelvic fornices, confluence of collecting ducts, vascular bundles in the inner stripe of the outer medulla, thin descending limb epithelium, and relative development of the three medullary zones. The organization of the medullary circulation is described; the medulla includes several functionally different compartments favoring preferential exchanges by the juxtaposition of certain tubules and vessels. This may improve the efficiency of certain recycling routes and hence the insulation of the different compartments. As discussed in section III, a better inner medullary insulation may be key, not (or not only) in achieving a high urine concentration but mainly in reducing the time required to reach this high concentration. This overview of the multiple interspecies variations in medullary organization underlines the importance, among other factors, of the inner stripe architecture and of the internephron differences in the process of urine concentration.
构建哺乳动物肾髓质浓缩系统的连贯图景似乎很困难。这可能是由于所涉及因素的多样性以及物种间的显著差异。文中描述了几种可能对改善水分保持至关重要的形态学适应。它们包括乳头长度的变化、肾单位数量、长襻肾单位的百分比、肾单位异质性、肾盂穹窿的发育、集合管的汇合、外髓质内带的血管束、细降支上皮以及三个髓质区的相对发育。文中描述了髓质循环的组织；髓质包括几个功能不同的隔室，通过某些小管和血管的并列有利于优先交换。这可能提高某些再循环途径的效率，从而提高不同隔室的隔离度。如第三节所讨论的，更好的内髓质隔离可能是关键，这不仅（或不仅仅）在于实现高尿浓缩，主要还在于减少达到这种高浓度所需的时间。对髓质组织中多种物种间差异的概述强调了在内髓质结构以及肾单位间差异在尿浓缩过程中的重要性等因素。
