In the mammalian kidney, there are two general populations of nephrons; the principal anatomic difference between them is the length of the loop of Henle (Fig. 1). Superficial or cortical nephrons have short loops with abbreviated (sometimes absent) thin-limb segments, while juxtamedullary nephrons have long loops of Henle with well-developed descending and ascending thin-limb segments that extend into the medulla. In man, shortlooped nephrons predominate by a ratio of 7:1. In many mammals, there is evidence for a direct association between the relative length of the renal medulla, hence the length of the long-looped nephrons, and the ability to concentrate urine maximally (1).
KeywordsDistal Tubule Distal Convoluted Tubule Outer Medulla Intercalate Cell Collect Duct
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