1 minute read
Reproductive System Development
REPRODUCTIVE SYSTEM DEVELOPMENT
The reproductive system develops in the first few weeks of gestation. After one month in utero, primordial gonads develop. While this changes during gestation, very little change happens between infancy and puberty.
Advertisement
All embryos start out life as phenotypic females so that, if there is no chemical intervention, the infant would appear female at birth. The male Y chromosome has a special gene called the SRY gene. Both male and female gonads have early cells that have the potential to be either gender but the SRY gene recruits other genes, leading to a gene cascade. This gene cascade causes spermatogonia to form. If this doesn’t happen, then oogonia and an ovary develops instead.
Leydig cells develop in the testes, which make testosterone. This helps to cause the male sexual structures to form. Without testosterone, the glans penis would otherwise be the glans clitoris. There are two separate ducts for the male and female reproductive system. Female organs are derived from the Mullerian duct, while male organs are derived from the Wolffian duct.
The two ducts cannot grow simultaneously. The Mullerian duct will degenerate when the Wolffian duct develops and vice versa. It is testosterone that triggers the Wolffian duct to develop. If testosterone does not get made, the Wolffian duct will degenerate.
Puberty is the time of further sexual maturation. The hormonal control of the boy and girl are similar but the outcome is different. The release of GnRH by the hypothalamus stimulates the onset of puberty. This triggers the events that happen to develop the secondary sex characteristics in adolescence.
At the age of eight or nine, LH first becomes detectable, even before there are physical changes. The sensitivity of the feedback system during this time is quite high so it doesn’t take much testosterone or estrogen to feed back onto the hypothalamus and pituitary to shut off LH, FSH, and GnRH production. This sensitivity decreases near puberty and the gonads are more sensitive to LH and FSH. This leads to enlargement of the gonads.
