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. Author manuscript; available in PMC: 2013 Oct 25.
Published in final edited form as: Acta Physiol (Oxf). 2010 Dec 7;202(3):10.1111/j.1748-1716.2010.02214.x. doi: 10.1111/j.1748-1716.2010.02214.x

Figure 2.

Figure 2

Four zones of the inner medulla (IM) are distinguishable based on data from Pannabecker, et al. (2008a). These include an outer zone (OZ) which encompasses the initial 3.0–3.5 mm below the OM/IM border and includes OZ1 and OZ2. Collecting duct (CD) clusters, which coalesce into single CDs, are shown in blue. Aquaporin-1 (AQP-1)-positive and AQP1-negative descending thin limbs (DTLs) are shown in red and yellow respectively. Prebend segments and ascending thin limbs are shown in green. In the OZ, CDs form the organizing motif around which loops of Henle and blood vessels (not shown) are arranged. OZ 1 includes those loops that express no detectable AQP1. Loops expressing AQP1 along their initial 40% are present in OZ1 and OZ2. An inner zone (IZ) encompasses the terminal 1.5–2.0 mm and includes IZ1 and IZ2. In the IZ the central organizing motif of CD clusters is diminished and no detectable AQP1 is expressed in DTLs. No detectable AQP1 or UT-B is expressed in blood vessels, and all vasa recta are fenestrated. IZ2 includes the terminal 500 μm of the papilla tip where transverse-running segments lie. See text for additional details. Scalebar, 1 mm along the axial dimension, lateral dimensions are not to scale. From Layton et al. (2009), used with permission.