Embryonic-fetal Differentiation of the External Reproductive Organs
All embryos appear anatomically as female first. If it does not receive certain genetic and hormonal signals, the embryo will continue to develop as female. But when the tissues receive the signal to begin differentiation into a male, the embryonic reproductive organs begin to change their appearance dramatically. Around the 7th or 8th week of gestation, these genetic and hormonal signals will determine the sexual development of the embryo. For female development, you can see that the genital tubercle forms into the glans clitoris, while in male development the genital tubercle forms into the glans penis. The urogenital fold differentiates into the labia minora for females, while in males it develops into part of the shaft of the penis.