Figure 1.

Overview of kidney development. (A) The Wolffian duct originates from the dorsal intermediate mesoderm. The metanephric mesenchyme originates from the nephrogenic cord. The Wolffian duct forms an outgrowth called the ureteric bud that migrates into the surrounding mesenchyme and undergoes the first dichotomous branching morphogenesis event. (B) The ureteric epithelium is composed of the ureteric tip and stalk region. In response to signals from the mesenchyme, the tips of the ureteric epithelium undergo continued branching morphogenesis and the stalks will differentiate to form the collecting duct system, renal calyx, and ureter. (C) In response to signals from the ureteric epithelium the mesenchyme forms a cap around the ureteric tip. This cap mesenchyme will differentiate into nephrons or repopulate the nephrogenic progenitors. (D) The renal stroma surrounds the nephrogenic progenitors and will differentiate to form the capsular, cortical, and medullary stroma.