Multiple causes of human kidney malformations

The human kidney derives from two parts of the metanephros, its embryonic precursor. The first of these is the ureteric bud, which branches into the collecting ducts containing K + secreting principal and H + handling intercalated epithelia, and also forms the urothelium of the calyces, renal pelvis, ureter, and bladder trigone. The second is the renal mesenchyme, which diVerentiates into nephrons comprised of glomeruli, proximal tubules, and loops of Henle. The human metanephros appears at 5 weeks of gestation, the first glomeruli form by 9 weeks, and nephrogenesis is complete by 34 weeks. 1 2