Embryology, Sexual Development

Sexual development is one of the significant traits in an organism’s life because it is closely related to its genetic fitness. The only legacy we pass into subsequent generations are germ cells in the developing gonads. [1] In sex development, there are two distinguishably different processes, namely sex determination and sex differentiation. Sex determination is the developmental decision that directs the bipotential gonad into a sexually dimorphic individual. [2] Sexual differentiation is how the male and female sexual organs develop from bipotential embryonic structures. It involves sequential stages, namely genetic, gonadal, hormonal, phenotypic, and psychological. At the genetic stage, chromosomal sex is determined by the chromosomal constitution after fertilization, where XY denotes male and XX indicates female. Until the sixth week of embryonic life, no sexual difference is observable in the fetus. Undifferentiated gonads of XX or XY are similar in morphology and can form either ovaries or testes. Differentiation of bipotential gonad into either ovaries or testes occurs in the gonadal stage. Followed by gonadal differentiation, the internal genital tract and the external genitalia develop into male or female structures in the phenotypic stage. [3] [4]