ABSTRACT
Primordial gonads (genital ridges) appear during the sixth week of embryogenesis. The associated Mullerian and Wollfian ducts also develop. The fate of these undifferentiated ducts depends upon the genetic sex of the embryo. In XY embryos, the SRY gene (sex determining region of the Y chromosome) stimulates testicular differentiation. The developing testes produce androgens and anti-Mullerian hormone (AMH), which cause virilization and regression of Mullerian structures. In XX individuals, absence of the SRY gene allows the gonads to develop into ovaries, the subsequent lack of AMH allows the Mullerian ducts to develop into a uterus, fallopian tubes, and vagina.
