Karl Peter's fundamental contribution to the structural organization of the kidney

Karl Peter provided the first detailed description of the structure and morphology of the human kidney and defined at least 9 major segments of the tubules. He showed that the nephrons were heterogeneous in their structure and could be divided in 2 categories: the short-looped and the long-looped ones. Peter's scheme of the human nephrons was published in many journals and textbooks. Another contribution was the demonstration of a relationship between the relative occurrence of long thin loops (versus short loops) and the maximal urinary concentration capacity. Peter was also the first to describe the cells of the macula densa, which are of fundamental importance in the tubuloglomerular feedback mechanism. Furthermore, Peter gave a detailed description of the principal zones of the human kidney: the cortex, the outer medulla with outer and inner stripes, and the inner medulla.