The urogenital system develops from the intermediate mesoderm. In early development, the genital ridges form the gonads and reproductive ducts, while the nephrogenic cords form the urinary system. In females, the gonads become ovaries and the paramesonephric ducts form the uterus, fallopian tubes, and upper vagina. The mesonephric ducts give rise to the ureters, bladder trigone, and posterior urethra. Under the influence of estrogen, the genital tubercle develops into the clitoris and genital swellings form the labia majora and minora.