Development of the internal and external genitalia proceeds according to these basic principles:

Internal and external genitalia develops from indifferent bases common to both genders (indifferent gonad, indifferent external genitalia).

Development of gonads depends on the karyotype:

• 46XY: testis develops from indifferent gonad
• 46XX: ovary develops

Development of the internal and external genitalia is influenced by hormone-like substances which are produced by functional fetal testis: owing to androgens the epididymis and ductus deferens develop from the Wolffian duct. MIS (Müllerian inhibiting substance) causes degeneration of Müllerian duct.

Without influence of these substances (normal ovaria, functionless testis) the female genitalia develops. Fetal ovary is not necessary for development of the female genitalia.

External genitalia develops similarly by structure differentiation around the urogenital sinus. Differentiation of the male external genitalia depends on the androgen production in the fetal testis.

Organs derived from the Wolffian duct: tubes, uterus, superior part of vagina.

Organs derived from the Müllerian duct: epididymis, vesiculae seminales, ductus deferens.

Urogenital sinus:

• genital tubercle: clitoris or penis
• labioscrotal swellings: labia majora or scrotum
• from the urogenital sinus develops the inferior part of vagina as well