Intrauterine Development of Fetal Reproductive Organ

At the moment of conception, the sex of an individual can already be determined. 

At the moment of conception, the sex of an individual can already be determined. If the fetus is found to have XX chromosomes, it is said to be female. On the other hand, if it has XY chromosome, then it is said to be male. A body organ which produces sex cells is called gonad. As early as 5 weeks of conception, primitive gonadal tissue is already formed. For both sexes, we can find two undifferentiated ducts. One of which is mesonephrica or wolfian and the other is paramesonephric which is the mullerian duct.

Around week 7 or 8 gestation in chromosomal males, the early gonadal tissue differentiates into what we call primitive testes. This primitive testes allows the formation of testosterone and with the influence of testosterone, male reproductive organ can be formed while the paramesonephric duct regresses. In case testosterone is not present by week 10, the gonadal tissue will start to form ovaries. At this point the paramesonephric duct develops into the female reproductive organs.
The external genitalia of fetus can be visible at about 12 weeks of gestation. Through the influence of testosterone, penile tissue elongates. In females, the urogenital fold remains open to form the labia minora. The tissue which is formed as scrotal tissue in males will be labia majora in females.