Macroscopic whole-mounts of the developing human fetal urogenital-genital tract: Indifferent stage to male and female differentiation.

We present a detailed review of fetal development of the male and female human urogenital tract from 8 to 22 weeks gestation at the macroscopic and morphometric levels. Human fetal specimens were sexed based on macroscopic identification of fetal testes or ovaries, Wolffian or Müllerian structures and the presence of the SRY gene in the specimens at or near the indifferent stage (8-9 weeks). Specimens were photographed using a dissecting microscope with transmitted and reflected light. Morphometric measurements were taken of each urogenital organ. During this time period, development of the male and female urogenital tracts proceeded from the indifferent stage to differentiated organs. The kidneys, ureters, and bladder developed identically, irrespective of sex with the same physical dimensions and morphologic appearance. The penis, prostate and testis developed in males and the clitoris, uterus and ovary in females. Androgen-dependent growth certainly influenced size and morphology of the penile urethra and prostate, however, androgen-independent growth also accounted for substantial growth in the fetal urogenital tract including the clitoris.