O&g: Embryology Of The Female Genital Tract And Congenital Abnormalities

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Key phases of the female genital tract development

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•Indifferent gonadal phase: 4-6 weeks GA

•Gonadal differentiation: 7-10 weeks GA

•Ductal differentiation: 9-11 weeks GA

•External genitalia differentiation: 10-12 weeks GA

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Gonads develop from

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•primitive germ cells

•mesothelium of the posterior abdominal wall

•adjacent mesenchyme

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When does the primary sex cords regress

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8th week

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Gonadal differentiation depends on

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•the presence of the sex chromosomes

•the prevailing biochemical and hormonal environment

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Functions of the Sex-determining region Y protein

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Aka Testis-determining factor

Testicular development

Production of androgens and anti-mullerian hormone

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The gubernaculum

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Peritoneal fold which attaches the caudal aspect of the ovary to the uterus

Forms the utero-ovarian and round uterine ligaments

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The paramesonephric (mullerian) ducts are precursors of

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The uterus, fallopian tube, cervix, & upper vagina

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When does the mesonephros & mesonephric ducts involute

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3rd month

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Vestigial structures of the mesonephric duct

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•Gartner's duct

•Epoophoron

•Paroophoron

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Precursor of lower Vagina

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The sinovaginal bulb from the urogenital sinus.

Above the level of the future hymen

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Precursors of labia majora, labia minors, clitoris

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Two genital swellings, two genital folds, a central anterior genital tubercle

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Incidence of abnormalities of development of FGT

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1 in 200-400 women

May be familial

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Types of abnormalities of the FGT

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Four basic types exist: 1. Failure of formation of the Mullerian ducts. 2. Failure of fusion of the Mullerian ducts. 3. Failure of dissolution of the septum between the fused ducts. 4. Failure of structures to disappear.

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Failure of formation

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Failure of formation: Eg Rokitansky-Mayer-Kuster-Hauser (RMKH) syndrome, absence of vagina, rudimentary horn. RMKH consists of absent or rudimentary uterus. Vagina may also be absent. Genotype is 46XX. Surgical vaginal creation for sexual function may be done.

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Failure of fusion

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Failure of fusion: Varying degrees of abnormalities eg uterus didelphys, bicornuate uterus, arcuate.In didelphys- complete duplication of the duct derivatives ie double (septate) vagina, 2 cervices and 2 separate hemiuteri.

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Failure of dissolution

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Failure of dissolution: Typical eg is septate uterus with partial or complete intra-uterine septum.

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Failure of disappearance

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Failure of disappearance: Typical eg is the lateral vaginal wall cyst (Gartner’s cyst) which is remnant of the Wolffian duct.

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Genetic determination of gonadal sex

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• Presence or absence of the normal Y chromosome. The Y chromosome contains a gene on its short arm (Yp) which encodes for Testis-Determining Factor (TDF). Also called SRY protein. This gene is called Sex determining Region on the Y (SRY gene). The mechanism through which TDF induces differentiation to testes was thought to depend on a cell surface antigen called H-Y antigen. Now known not to be. This antigen is located on the autosomal chromosomes and other autosomal genes. Rather, formation of the testes induces the H-Y antigen. •Ovarian differentiation is determined by the presence of two X chromosomes. The ovarian determinant is located on the short arm of the X chromosome as absence of the short arm results in ovarian agenesis. Females with single X and no Y (45X0 Turners) develop ovaries but their germ cells and ovaries degenerate before birth. Both X chromosomes must be present for long term survival of the oocytes in meiotic phase.

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Intersex definition

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Intersex is said to exist when there is discrepancy in the chromosomes, gonads, sex hormones or genitals such that they do not fit the typical definitions of male or female bodies (phenotypes)

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Classification of intersex disorders

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Traditionally divided into 5 simplified groups for convenience. 1. Female pseudohermaphrodite with 2 ovaries. Eg CAH( congenital adrenal hyperplasia). 2. Male pseudohermaphrodite with 2 testes. eg androgen insensitivity syndrome. (Testicular feminization syndrome) 3. True hermaphrodite with an ovary and/or testes and/or ovotestis. 4.Mixed gonadal dysgenesis with a testis plus streak gonad. 5. Pure gonadal dysgenesis with bilateral streak gonads. (A streak gonad resembles an ovary but no germ cells are present).

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Investigations and management of intersex disorders

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Investigations:•Serum electrolytesEndocrine screening.•Chromosomal analysis.•Androgen receptor levels (if available)•Abdominopelvic USS visualizing particularly the adrenal glands which may be enlarged in CAH.•A genitogram to help delineate the ductal anatomy.•CT or MRI.•Laparoscopy Management: May involve corrective surgeries.