GYN 3

• Development of external genital organs

  1. Originate from urogenital sinus

  2. Urorectal septum divides endodermal cloaca

  3. Dorsal part forms rectum and anal canal

  4. Ventral part forms urogenital sinus

  5. Urogenital sinus differentiates into 3 parts

  
• Parts of urogenital sinus


  • Upper vesicourethral part
  • Middle pelvic part
  • Lower phallic part
• Urogenital membrane


  Part of cloacal membrane in front of primitive perineal body
• Anal membrane


  Part of cloacal membrane behind primitive perineal body
• Development of female external genitalia

  1. Genital folds do not reunite, persist as labia minora

  2. Perineal cleft persists as vestibule

  3. Ectodermal swellings form labia majora

  4. Genital tubercle differentiates into clitoris

  
• Derivatives of embryonic urogenital structures (female)

  • Clitoris from genital tubercle
  • Labia minora from genital folds
  • Labia majora from labioscrotal swelling
  • Bartholin's glands from urogenital sinus
  • Vestibule from urogenital sinus

  
• Development of internal genital organs

  1. Müllerian ducts form fallopian tubes, uterus, cervix, vagina

  2. Müllerian ducts fuse to form uterovaginal canal

  3. Uterus forms from uterovaginal canal

  4. Vagina forms from uterovaginal canal and urogenital sinus

  
• Fallopian tubes


  Develop from upper vertical and horizontal parts of Müllerian ducts
• Uterus


  Develops from fusion of intermediate horizontal and adjoining vertical parts of Müllerian ducts

  
• Cervix


  Develops from fused lower vertical parts of Müllerian ducts
• Broad ligaments


  Transverse fold established as Müllerian ducts approach midline, containing mesonephric remnants
• Development of vagina


  1. Partly from Müllerian ducts, partly from urogenital sinus

  2. Müllerian ducts form uterovaginal canal

  3. Urogenital sinus forms lower 1/5th

  4. Hymen forms from tissue at periphery of Müllerian eminence

  
• Uterus is entirely mesodermal in origin

  
• Vagina is lined by endoderm of urogenital sinus, muscle wall derived from mesoderm of Müllerian ducts
• Paramesonephric derived


  Cervix at the top
• Sinus derived


  Vestibule at the bottom
• Development of female reproductive organs

  
• Development of Fallopian tubes


  Developed from the cephalic vertical and most of the intermediate horizontal parts of the respective paramesonephric duct
• Development of Uterus


  1. Developed from the cephalic part of the uterovaginal canal which is formed by the fusion of the vertical parts of both the paramesonephric ducts

  2. Segments of horizontal parts of the paramesonephric ducts also contribute to the fundus of the uterus

  
• Development of Vagina


  Developed mainly from the Mullerian ducts and partly from the urogenital sinus
• Development of upper four-fifths of vagina

  • Mucous membrane is developed from the endoderm of the canalized sinovaginal bulb
  • Musculature is developed from the mesoderm of the united lower vertical parts of the two paramesonephric ducts
• Lower one-fifth of vagina (below the hymen)

  Developed from the endoderm of the urogenital sinus

  
• External vaginal orifice (vaginal introitus)

  Developed from the ectoderm of the genital folds after rupture of the bilaminar urogenital membrane
• Development of the ovary
• Site of ovary development

  Genital or gonadal ridge formed between the dorsal mesentery and the mesonephric ridge by the multiplication of the coelomic epithelium along with condensation of the underlying mesenchyme

  
• Sources of ovary development


  • Cortex and covering epithelium from coelomic epithelium
  • Medulla from mesenchyme
  • Germ cells from endoderm of yolk sac

  
• Indifferent or primitive gonad

  Gonads do not acquire male or female morphological characteristics until the seventh week of development
• Definitive gonad


  In a XX individual, without the active influence of Y chromosome, the bipotential gonad develops into an ovary about two weeks later than testicular development

  
• Genetic control is of prime importance for differentiation of bipotential gonad
• Genes regulating gonad differentiation

  • Wilms' tumor gene (WT1)
  • FTZI
  • SRY
• Genes involved in testis development

  • SOX9
  • Anti-Müllerian hormone (produced by Sertoli cells)
• DAXI gene


  Involved in ovarian differentiation, antagonizes the action of SRY gene
• Development of ovarian follicles


  1. Surface becomes thicker and continues to proliferate extensively, sending down secondary cords of cells into the mesenchyme (cortical cords)

  2. Cords split into clusters of cells, which surround the germ cells

  3. Germ cells become oogonia, epithelial cells become granulosa cells

  4. Stromal mesenchymal cells surround the follicular structure to form the future theca cells
• Oocytes not surrounded by granulosa cells are destroyed from 20th week
• Follicles undergo maturation and atresia under the influence of maternal gonadotropin by 28th week
• Anti-Müllerian hormone (AMH)


  Produced by Sertoli cells, suppresses mesonephric duct systems in the absence of which paramesonephric ducts develop
• Descent of the ovary

  1. Cranial part of genital ridge becomes the infundibulopelvic ligament

  2. Genital ligament (gubernaculum) forms from lower pole of ovary, attaching to genital swelling

  3. Ovarian ligament forms between ovary and Müllerian attachment

  4. Round ligament forms between cornu of uterus and external genitalia

  5. Ovaries descend during 7th to 9th months, situated at pelvic brim at birth
• Developmental anomalies of female reproductive organs

  • Imperforate hymen
  • Congenital agenesis of vagina
  • Congenital vesicovaginal or rectovaginal fistula
  • Septate vagina
  • Transverse vaginal septa
  • Uterus didelphys
  • Uterus bicornis bicollis
  • Septate uterus
  • Subseptate uterus
  • Arcuate uterus
  • Unicornuate uterus

  
• Development of external genital organs

  • Clitoris from genital tubercle
  • Labia minora from genital folds
  • Labia majora from genital swellings
  • Bartholin's glands from caudal part of urogenital sinus
  • Major part of vagina from urogenital sinus

  
• SRY gene directly controls testicular differentiation, testicular development is active while ovarian development is default pathway