Development
In typical prenatal development, sexual organs originate from a common anlage anatomy during early gestation and differentiate into male or female variations. The SRY gene, usually located on the Y chromosome and encoding the testis determining factor, determines the direction of this differentiation. The absence of it allows the gonads to continue to develop into ovaries.
Thereafter, the development of the internal reproductive organs and the external genitalia is determined by hormones produced by certain fetal gonads (ovaries or testes) and the cells' response to them. The initial appearance of the fetal genitalia (a few weeks after conception) looks basically feminine: a pair of "urogenital folds" with a small protuberance in the middle, and the urethra behind the protuberance. If the fetus has testes, and if the testes produce testosterone, and if the cells of the genitals respond to the testosterone, the outer urogenital folds swell and fuse in the midline to produce the scrotum; the protuberance grows larger and straighter to form the penis; the inner urogenital swellings grow, wrap around the penis, and fuse in the midline to form the penile urethra.
Each sexual organ in one sex has a homologous counterpart in the other one. See a list of homologues of the human reproductive system.
In a larger perspective, the whole process of sexual differentiation also includes development of secondary sexual characteristics such as patterns of pubic and facial hair and female breasts that emerge at puberty. Furthermore, differences in brain structure arise, affecting, but not absolutely determining, behavior.
Intersex genitalia refers to the development of both female and male organs in one body. Once born the parents are faced with the difficult decision to make. At times they rely on the doctors to make the right choice but even then they themselves at times commit mistakes. The doctors have a fifty fifty chance to get the sex right. If they were to make the wrong choice the life of the individual is most likely to be lived uncertain.
Read more about this topic: Sexual Characteristics
Famous quotes containing the word development:
“On fields all drenched with blood he made his record in war, abstained from lawless violence when left on the plantation, and received his freedom in peace with moderation. But he holds in this Republic the position of an alien race among a people impatient of a rival. And in the eyes of some it seems that no valor redeems him, no social advancement nor individual development wipes off the ban which clings to him.”
—Frances Ellen Watkins Harper (1825–1911)
“The man, or the boy, in his development is psychologically deterred from incorporating serving characteristics by an easily observable fact: there are already people around who are clearly meant to serve and they are girls and women. To perform the activities these people are doing is to risk being, and being thought of, and thinking of oneself, as a woman. This has been made a terrifying prospect and has been made to constitute a major threat to masculine identity.”
—Jean Baker Miller (20th century)
“I could not undertake to form a nucleus of an institution for the development of infant minds, where none already existed. It would be too cruel.”
—Henry David Thoreau (1817–1862)