Fetal genital development
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2007-09-21T02:47:40Z
Arcadian
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{{expert-portal|Medicine}}
'''Fetal genital development''' refers to the sequence of events which leads to the develoment of the [[genital]]s and their adnexa.
==Sequence==
A few weeks after [[fertilization]], the initial appearance of the human '''fetal genitalia''' is basically feminine: a pair of "[[urogenital folds]]" with a small protuberance in the middle, and the [[urethra]] behind the protuberance.
In typical [[fetus|fetal]] development, the presence of the [[SRY|SRY gene]] causes the fetal [[gonad]]s to become [[testes]]; the absence of it allows the gonads to continue to develop into [[ovaries]]. Thereafter, the development of the [[sex organ|internal reproductive organs]] and the [[external genitalia]] is determined by hormones produced by fetal gonads (ovaries or testes) and the cells' response to them.
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 swell, wrap around the penis, and fuse in the midline to form the [[penile urethra]].
If testosterone is not present, normal female development continues, with the development of a [[perineal urethra]] and the formation of a [[uterus]], [[clitoris]] and [[vagina]].
The [[Müllerian ducts]], which are paired ducts of the embryo which empty into the [[cloaca]], and which develop into the upper [[vagina]], [[cervix]], [[uterus]] and [[oviducts]]; in the male they disappear except for the vestigial [[vagina masculina]] and the [[appendix testis]].
Although female development is usually considered the "default" configuration in the absence of induction, recent evidence has indicated that [[Wnt4]] plays a role in the development of female anatomy.<ref name="pmid16905353">{{cite journal |author=Bernard P, Harley VR |title=Wnt4 action in gonadal development and sex determination |journal=Int. J. Biochem. Cell Biol. |volume=39 |issue=1 |pages=31–43 |year=2007 |pmid=16905353 |doi=10.1016/j.biocel.2006.06.007}}</ref>
==Homologies==
Because of their common origin in fetal anatomy, a number of male and female anatomical features are said to be [[homology (biology)|homologous]]; for example, the clitoris and penis are homologous with one another, as are [[Skene's glands]] in females and the [[prostate gland]] in males.
==Intersexuality==
Most of the time, the result of fetal genital development follows the stereotypical male or stereotypical female development path. However, in a small but significant minority of cases, the path of development follows an intermediate or other pathway, leading to what are called "ambiguous genitalia", one condition of those known as [[intersexuality]].
See [[congenital anomalies of the genitalia]] for a list of [[congenital disorder]]s caused by problems with fetal genital development.
== See also ==
* [[Virilization]]
* [[Sexual differentiation]]
* [[Germ line development]]
==References==
<references/>
{{Development of urinary and reproductive systems}}
{{developmental-biology-stub}}
[[Category:Developmental biology]]
[[Category:Embryology]]
[[Category:Gynecology]]
[[Category:Andrology]]