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:
“The highest form of development is to govern one’s self.”
—Zerelda G. Wallace (1817–1901)
“This was the Eastham famous of late years for its camp- meetings, held in a grove near by, to which thousands flock from all parts of the Bay. We conjectured that the reason for the perhaps unusual, if not unhealthful development of the religious sentiment here, was the fact that a large portion of the population are women whose husbands and sons are either abroad on the sea, or else drowned, and there is nobody but they and the ministers left behind.”
—Henry David Thoreau (1817–1862)
“Theories of child development and guidelines for parents are not cast in stone. They are constantly changing and adapting to new information and new pressures. There is no “right” way, just as there are no magic incantations that will always painlessly resolve a child’s problems.”
—Lawrence Kutner (20th century)