In a boy the Wolffian ducts develop into the male reproductive organs but in a female these ducts waste away. In a girl the Müllerian ducts form the female reproductive organs but in a male embryo these Müllerian ducts disappear. This is clear anatomical evidence that the vagina (anatomy that is not present in the male) is not involved in orgasm, which is a nervous system response common to both sexes. Every embryo has a structure (the genital tubercle) that becomes the phallus (clitoris or penis).