NCIt definition : Renal tissue consisting of peritubular and periarterial spaces. The relative contribution
of each of these two spaces to interstitial volume varies, but increases in size from
the cortex to the papilla. In the cortex there is little interstitium because the
peritubular capillaries occupy most of the space between the tubules. The cortical
interstitial cells and outer medula consist mainly of fibroblastic cells and mononuclear
cells. The inner medulla consists primarily of pericytes, lipid-laden cells and mononuclear
cells arranged like rungs of a ladder.;