Fig. 11

a–l Sketches almost true to scale allocate the installation at the transient stages of nephron anlage in the human fetal kidney during advanced pregnancy to the different compartments of the local interstitium. This is represented by the interstitum within the renal capsule (light blue/zig-zag), the interstitium between the inner side of the renal capsule and the tip of a CD ampulla (dark blue/vertical double arrow), the subcapsular interstitium (yellow line with crosses), the perivascular interstitium at the perforating radiate artery (PRA, white boxes with red line), the peritubular interstitium at the connecting tubule (black line), the interstitial cleft at the deep lateral aspect between the tubule anlage and the defoliating glomerulus during formation of the comma- and S-shaped bodies (white boxes with red line and arrow head), the oblique interstitial cleft between the tubule anlage and the progenitor cell strand, which connects the distal pole up to the extended renal vesicle stage with the proximal end of the pretubular aggregate (dashed black line). Visible is the precise site of the (a) nephrogenic niche, the pretubular aggregate (PTA), the (b) mesenchymal to epithelial transition, and the (c) primitive renal vesicle (RV). Shown are further the renal capsule (C), stromal progenitor cells (SP), nephrogenic progenitor cells (NP), distal end (DE), and proximal end (PE) of the pretubular aggregate, clear interface (black asterisks), connecting tubule (pCNT) of a previously developed nephron, collecting duct (CD) ampulla (A), tip (T), head (H), conus (CO), neck (N), adhesion of PTA (white asterisks) at the section border between the head and conus of CD ampulla, partial separation (flash) of the RV from PTA and lumen (+). Further are seen: the (d) mature, (e) extending, and (f) extended renal vesicles. Visible is the distal pole (DP), proximal pole (PP), tubule anlage (TA) with the future connecting tubule of the currently developing nephron. The white arrow heads point to progenitor cell strand connecting RV with PTA. The white circles indicate the congruent relation between the medial aspect of the forming nephron and the conus of the CD ampulla. In the (g) early, (h) mid, and (i) late comma-shaped bodies (CSB) are shown the distal tubule (DT), intermediate tubule (IT), proximal tubule (PT), future podocytes (P), and presumptive Bowman’s capsule (BC). In the the (j) early, (k) mid, and (l) late S-shaped bodies (SSB) the white triangles indicate the defoliation () of the glomerulus at the proximal pole. It initiates the physiological connection between the perforating radiate artery and the arising glomerular tuft. As a result, the darkening of color at the arising nephron stages coincides with the expanding progress of installation at quite different sites