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. Author manuscript; available in PMC: 2018 Jan 1.
Published in final edited form as: BJU Int. 2016 Jul 14;119(1):177–184. doi: 10.1111/bju.13555

Figure 2.

Figure 2

Spatial relationships and size distributions of the tubules and vessels within the medullo-papillary complex. From Zone 1 to Zone 2, the ascending and descending vasa recta become organized into vascular bundles (dotted line) and interbundle regions. In Zone 3, the descending thin limbs join the vascular bundles (light dotted line), and these are separate from collecting duct clusters. Collecting ducts grow larger in diameter towards zone 3 and coalesce to form the 6–12 ducts of Bellini. These anatomically specific compartments contribute to radial and axial concentration gradients along the course of the complex.