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Ass. Prof. Dr. Malak A. Al-yawerSex differentiation
is a complex process that involves many genes, including some that are autosomal. The key to sexual dimorphism is the Y chromosome, which contains the testis determining gene called the SRY (sex-determining region on Y) gene.
SRY gene under its influence, male development occurs in its absence, female development is established.
Gonads
the sex of the embryo is determined genetically at the time of fertilization the gonads do not acquire male or female morphological characteristics until the seventh week of development.
The genital or gonadal ridges
Primordial germ cells
Indifferent gonad
Testis
Testis
Interstitial cells of Leydig
In the fourth month, the testis cords
Ovary
Ovary at the 7th week
Ovary at 4th month
Cortical cords split into isolated cell clusters, with each surrounding one or more primitive germ cells. Germ cells subsequently develop into oogonia, and the surrounding epithelial cells, descendants of the surface epithelium, form follicular cells
Influence of primordial germ cells on indifferent gonad
Genital Ducts
Indifferent Stage
Genital Ducts in the Male
Prostate
Genital Ducts in the Female
When the second part of the paramesonephric ducts moves mediocaudally, the urogenital ridges gradually come to lie in a transverse plane.
Broad ligament of the uterus
Vagina
The hymen
Clinical Correlates Uterine and Vaginal Defects
Duplications of the uterus result from lack of fusion of the paramesonephric ducts in a local area or throughout their normal line of fusion.
Uterine and Vaginal Defects
In patients with complete or partial atresia of one of the paramesonephric ducts, the rudimentary part lies as an appendage to the well-developed side (D) If the atresia involves both sides, an atresia of the cervix may result (E)
Uterine and Vaginal Defects
If the sinovaginal bulbs fail to fuse a double vagina results If the sinovaginal bulbs do not develop at all, atresia of the vagina, results
Vestigial Structures Derived from Embryonic Genital Ducts
Mesonephric Duct Remnants in Males
The cranial end of the mesonephric duct may persist as an appendix of the epididymis, which is usually attached to the head of the epididymis Caudal to the efferent ductules, some mesonephric tubules may persist as a small body, the paradidymis.
Mesonephric Duct Remnants in Females
Paramesonephric Duct Remnants in Males
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