Physiologie und Pathologische Physiologie [antikvár]

Physiology of the kidney By Laurence G. Wesson, jr. With 76 figures A. Historical note The science of Renal Physiology begins with William Bowman. Although elements of renal architecture had been described by earUer anatomists, Bowman in 1842 was the first to deUneate the functional architecture of the nephron as a cluster of capillaries, the glomerulus, dipping into the ostium of a tubule which then leads without interruption to the exterior of the body. Recognition of this simple two component system was for many years sufficient to determine theoretical concepts of mechanism of urine formation. The thin membranes separating blood from tubular lumen in the glomerulus seemed suitable for a filtering process. Bowman himself suggested that urinary water and "foreign substances, particularly salts" were filtered through the glomerular capillaries while the remaining components of urine were secreted by the tubules. Within a few years, and apparently quite independently of Bowman, Karl Ludwig (1816—1895) had arrived at similar conclusions. Ludwig proposed that virtually the entire process of urine formation could be considered that of filtration. To the tubular cells were attributed the property of selective permeability. The cells were permeable to water and substances useful to the body and these substances diffused back into the blood stream under a pressure system analogous to that later described in more detail by Starling for the extracapillary circulation of plasma water. Rudolph Hbidbnhain (1834—1897), however, strongly influenced by correlations between blood flow and urine formation and by staining of tubular cells by various dyes, beUeved that the production of urine was entirely compatible with a set of secretory processes similar to those of most exocrine glands. Even the glomerulus was viewed as a secretory organ probably speciahzing in the transfer of excreted water and salt. The history of renal physiology during the last half of the nineteenth century largely consists of studies, sometimes ingenious, designed to support or refute one or the other of these competing theories. In particular, Moritz Nussbaum's exploitation of the separate blood supply to the glomeruli and tubules of the amphibian kidney in order to distinguish between glomerular and tubular functions was an important advance during this period. This anatomical characteristic of the fish and amphibian kidney which is retained in varying degrees by reptiles and birds has been the source of an immense literature and constitutes a research tool which is still widely used. Variation exists with respect to the terminology applied to the kidney structure observed in different orders of vertebrates. Huber, for example, follows the more common anatomical convention of designating the kidney of all amniotes (reptile, bird and mammal) as the metanephros while Smith (19,il), emphasizing the significance of the blood supply, has tended to confine the term, metanephros, to the mammalian kidney which has a purely arterial blood supply. Smith designated as mesonephros the kidney of fish, amphibian, reptile and Handbuch tier Urologie. Band 1 i 1