Indifferent gonad
For learning anatomy, please visit :
My youtube channel : @easyhumanatomy73
My website : http://easyhumananatomy.com
My facebook page: https://www.facebook.com/easyhumanatomy/
My blog: http://www.easyhumanatomy73.blogspot.com
My blog: Difference between : http://www.microscopicanatomybd.blogspot.com
Up to 6 weeks of development, gonads are two longitudinal genital
ridges, at the dorsal body wall of embryo which develop from intermediate
mesoderm.
The genital ridge is formed by coelomic epithelium and
underlying mesoderm. The coelomic epithelium forms irregular sex cords in both
male and female embryos, and it is not possible to distinguish between male and
female gonads at this stage, so this stage of development is known as indifferent
gonads.
By the 12-week mark, the male and female structures of the
external genitalia can be differentiated.
By the 20th week, the phenotypical differentiation is
complete.
Source of
development of gonad
- Genital ridge:
it is formed by the elevation of the intermediate mesoderm, which is
covered by the coelomic epithelium.
- Primordial germ
cells
The
STY gene produces a protein known as a testis-determining factor.
TDF
induces the testis to secrete FGF9, which stimulates the mesonephric duct to
penetrate the gonadal ridge.
The
SRY gene also produces SF1, which stimulates the differentiation of sertoli and
leydig cells, which produce testosterone and Mullarrian-inhibiting factor
(MIF), respectively.
In
the presence of TDF, testosterone, and MIF, the indifferent gonad will produce
a male phenotype.
In
the absence of TDF, testosterone, and MIF, the indifferent gonad will produce a
female phenotype.
No comments:
Post a Comment