The function of the excretory organs in metazoan invertebrates and vertebrates is aimed at maintaining homeostasis. Two patterns of the morpho-functional organization of these organs can be distinguished: I—a combination of ultrafiltration and subsequent reabsorption with partial secretion of substances, or II—only a secretion of molecules of a certain type. Here we substantiate the principle according to which in the type I organs the key role of the proximal tubule is to reabsorb fluid, which is ideal in terms of its solute composition and concentration, and to secrete a number of organic acids and bases, while the distal tubule is responsible for adjusting the composition of inorganic substances. Everything what does not meet these criteria is to be excreted. The type II organs (salt glands, aglomerular kidneys) are inherent to those animals whose kidneys do not ensure osmoregulation. During evolution, the mammalian kidney developed the mechanism which regulates the redistribution of fluid within the nephron: altered reabsorption of ions and water in the proximal segment can cause an influx of some additional fluid to the distal segment where the regulatory systems adjust the amount of reabsorbed substances. The central tendency in the evolution of the kidney in vertebrates, including humans, is to increase the rates of glomerular filtration and proximal reabsorption. A similarity between molecular mechanisms of transmembrane and transepithelial transport of substances has been revealed in the evolution of excretory organs, with distinctions concerning mainly the structure of the regulatory molecules and the intensity of urine formation.

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排泄器官的进化原理和体内平衡系统

后生无脊椎动物和脊椎动物的排泄器官的功能旨在维持体内平衡。可以区分这些器官的形态功能组织的两种模式：I-超滤和随后重吸收与部分物质分泌的组合，或 II-仅分泌某种类型的分子。在这里，我们证实了一个原理，即在 I 型器官中，近端小管的关键作用是重吸收液体，这在其溶质组成和浓度方面是理想的，并分泌许多有机酸和碱，而远小管负责调节无机物的组成。不符合这些标准的一切都将被排出体外。II型器官（盐腺、肾小球）是那些肾脏不能确保渗透调节的动物所固有的。在进化过程中，哺乳动物肾脏发展出调节肾单位内液体重新分配的机制：近端部分离子和水的重吸收改变会导致一些额外的液体流入远端部分，在那里调节系统调整重吸收的量物质。脊椎动物（包括人类）肾脏进化的中心趋势是增加肾小球滤过率和近端重吸收率。在排泄器官的进化中揭示了跨膜和跨上皮物质转运的分子机制之间的相似性，