Figure 2.

Fetal External Genitalia Ontogeny: Representative ventral views of external genitalia of the human males (top row) and females (bottom row) (8–16 weeks of gestation). Note the morphologic differences between male and female specimens after the indifferent stage (8–9 weeks of gestation) with formation of the penile urethra within the shaft due to urethral fold fusion in the penis and lack of urethral (vestibular) fold fusion in female specimens (light blue arrows depict the location of the urethra meatus in both the male and female specimens). Note the divergent evolution of the male and female prepuce (yellow arrows) with complete circumferential formation of the prepuce at 14–16 weeks of gestation in the male and a resulting dorsal prepuce in the female. The epithelial tag is seen in both male (green arrows) and female (clearly visible without arrows)) specimens from 10–13 weeks of gestation disappearing after this time point.