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Development of reproductive Anatomy
Jennifer Deveron 12 March 2015
Transcript of Development of reproductive Anatomy
Determination and differentiation
Sex determination occurs first in the gonads and is followed by appropriate development of the ducts, glands and associated genitalia.
Unique embryological situation, all other organ rudiments can normally differentiate into only one type of organ… the gonadal rudiment has TWO normal options:
In the absence of SRY, the gonadal primordium develops as an ovary
In presence of SRY, the gonadal primordium develops as testes
Differentiation: when cells take on a specific structure and function
Indifferent until week 7
Sexually indifferent stage: By 6 weeks of fetal life, fetuses of both sexes have two sets of internal ducts, the Mullerian (female) ducts and the Wolffian (male) ducts.
Primary sex cords to the ovary:
The primary sex cords differentiate to an outer cortex and inner medulla.
The medulla disappears in females and the (cortical cords) cortex develops into the ovary.
Development of the ovary & ducts
Secondary (or medullary) sex cords invaginate from the germinal epithelium and incorporate the primordial germ cells [FOLLICLES].
Gonadal differentiation occurs in the the gonadal ridges
Primary sex determination involves the decision of either an ovary or a testes from the indifferent gonad; this, however, does not give the complete sexual phenotype.
Hormones secreted by ovaries and testes are needed.
Two products of the developing testes are needed for normal male development.
1st, AMH must be secreted to inhibit female duct growth
2nd androgens must be secreted to enhance male duct growth.
In the female, absence of androgens permits the external genitalia to remain feminine
Proliferation of the epithelium and the underlying mesenchyme produces a bulge called the gonadal ridge
Fingerlike epithelial cords, called primary or medullary sex cords, grow into the ridge.
The primordial germ cells migrate along the dorsal mesentary of the hindgut to the gonadal ridges. During the sixth week, they enter the underlying mesenchume and begin to be incorporated into the sex cords.
Follicles = Surrounding epithelial sex cords differentiate into granulosa cells, mesenchyne cells differentiate into the theca cells
The female germ cells differentiate into oogonia (apparently with some influence from the mesonephros) and enter meiosis to become primary oocytes
Development of the external anatomy
The external genitalia arise from the same structures in both sexes – during the indifferent stage, all embryos have a genital tubercle on their external body surface.
At week 8 - external structures appear:
genital tubercle, the genital folds, urethral folds & a urogenital opening.
Genital tubercle gives rise to the clitoris and the urethral groove persists as the vestibule.
The unfused utrethral folds become the labia minora.
The unfused labioscrotal folds become the labia majora.
The paramesonephric ducts differentiate into the structures of the female duct system.
Hormonal imbalance results in variations
“Intersex is a group of conditions where there is a discrepancy between the external genitals and the internal genitals (the testes and ovaries)”.
If testes do not produce testosterone – XY w/female accessory structures and external genitalia
If testes do not produce AMH, both female and male duct systems form, but the external genitalia are male
If XX is exposed to testosterone – embryo has ovaries but develops the male ducts and glands as well as a penis and empty scrotum
Disorders of sex development (DSDs)
46, XX Intersex: Ovaries, but external male genitalia (Virilization)
46, XY Intersex: External female genitalia, internally testes may be normal, malformed or absent (Undervirilization)
Androgen insensitivity syndrome (AIS)
XY individual resistant to androgens (testosterone).
Androgen receptor gene mutation
May be complete or incomplete.
Congenital adrenal hyperplasia
Group of inherited disorders involving the adrenal gland
Cortisol & aldosterone deficiency from adrenal gland causes excess production of androgens
Females with a 45,XO
accelerated oocyte atresia cause menopause prior to puberty
Mosaic: 45, XO & 46, XY
formation of two different gonads: an undescended testicle on one side, and a dysgenetic gonad on the opposite side