Introduction

The genitalia development depends on different factors which are mainly two have been discussed in details on this website

Genetic factors

In the nucleus of every cell of his or her body, a human being has 46 chromosomes. 22 chromosome pairs (numbered from 1-22) belong to the autosomes and 1 pair to the sex chromosomes or gonosomes. They are denoted as X and Y. A female has two X-chromosomes and a male an X and a Y-chromosome. In a woman, one of the two X-chromosomes is inactivated in the form of heterochromatin (sex chromatin), the Barr body - diagnosis of the genetic gender is made on this basis. The Y-chromosome is not the only to guide the formation of such a complicated organ as the testicles, but a localized gene on this chromosome, the SRY (sex determining region Y gene) operates very early in the development as a guide or "master gene". It has a testis-determining effect on the indifferent gonads. This small gene (a single exon) is localized on the shorter arm of the Y chromosome (Yp). The other genes involved in gender differentiation are WT1 gene, SOX9 gene, SF1 gene, DAX1 gene and  gene coding for AMH.

Hormonal factors:
In male:

During the embryonic period (from the 6th week): The interstitial cells (Leydig) in the fetal testes secrete the testosterone hormone that is responsible for the male differentiation of the genital anlagen.

During the embryonic period (from the 7th week):The supporting cells (Sertoli) produce antimüllerian hormone (AMH) (a member of TGF-II (transforming growth factor II) family leading to an atrophy of the paramesonephric duct (Müller).

The  female sexual apparatus differentiates itself spontaneously in the direction of the feminine phenotype without particular hormonal influences.