English: A. Before the embryonic to fetal transition, the gonads and reproductive ducts (Wolffian; blue and Müllerian; red) of the urogenital ridge are bipotential. B. In the presence of the Y chromosome, the gonads of the bipotential urogenital ridge differentiate into testes, which produce both MIS to eliminate the Müllerian ducts and testosterone to stimulate differentiation of the Wolffian ducts into the male internal reproductive tract structures. C. In the absence of SRY, ovaries differentiate, Wolffian ducts degenerate, and Müllerian ducts develop into a simple columnar epithelial tube that will differentiate into the oviducts, uterus, cervix, and upper portion of the vagina.