Development of external genital organs

Indifferent stage

  • 2 mesenchymal cloacal folds form on either side of cloacal membrane
  • The 2 cloacal folds fuse infront of the cloacal membrane to form cloacal eminence
  1. Cloacal eminence enlarges – genital tubercle
  2. Cloacal membrane divides into urogenital membrane and anal membrane
  3. Cloacal fold divides into genital fold and anal fold
  • Another pair of elevation forms on either side of genital fold – genital swelling


Image result for cloacal folds


In females:

  • Genital tubercle – clitoris
  • Genital fold – labia minora
  • Genital swelling – 2 labia majoras

In males:

  • Genital tubercle – elongates to form phallus
  • Genital fold – elongates to form urethral groove which forms urethral plate and then urethral canal
  • Genital swelling – 2 scrotal swellings, fuse – scrotum


Congenital anomalies:

  1. Absence of penis/clitoris – no genital tubercle develops
  2. Small penis – underdeveloped genital tubercle
  3. large clitoris – overdeveloped genital tubercle
  4. Divided scrotum – failure of genital swelling to fuse
  5. False hermaphrodite – gonads are of one sex, external genitalia are of opposite sex



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