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Urogenital sinus

Urogenital sinus
Urogenital sinus of female human embryo of eight and a half to nine weeks old. (Urogenital sinus labeled at bottom.)
Stages in the development of the external sexual organs in the male and female. ("Opening of urogenital sinus" labeled in diagram D.)
Latin sinus urogenitalis definitivus
Carnegie stage 15
Precursor Cloaca
Gives rise to urethra, bladder, vagina
Code TE E5.
Anatomical terminology

The urogenital sinus is a part of the human body only present in the cloaca separates from the anal canal during the fourth to seventh weeks of development.[1]

In males, the UG sinus is divided into three regions: upper, pelvic, and phallic. The upper part gives rise to the urinary bladder and the pelvic part gives rise to the prostatic and membranous parts of the urethra.[1]

In females, the pelvic part of the UG sinus gives rise to the sinovaginal bulbs, structures that will eventually form the inferior two thirds of the vagina. This process begins when the lower tip of the paramesonephric ducts, the structures that will eventually form the uterus and vaginal fornices, come in contact with the UG sinus. Shortly afterwards, the sinovaginal bulbs form as two solid evaginations of the UG sinus. Cells in these bulbs divide to form a solid vaginal plate, which extends and then canalizes (hollows) to form the inferior portion of the vagina.[2]


  • Pathology 1
  • Additional images 2
  • See also 3
  • References 4
  • External links 5


A urogenital sinus anomaly is also a rare birth defect in women where the urethra and vagina both open into a common channel.[3]

A persistent cloaca is a disorder where the rectum, vagina, and urinary tract meet and fuse, creating a cloaca, a single common channel.[4]

Additional images

See also


  1. ^ a b Sadler, T.W. (2010). Langman's Medical Embryology. Lippincott Williams & Wilkins. pp. 243–244.  
  2. ^ Sadler, T.W. (2010). Langman's Medical Embryology. Lippincott Williams & Wilkins. p. 253.  
  3. ^ Gerald N N Callahan. Between XX and XY: Intersexuality and the Myth of Two Sexes. Chicago Review Press, 2009. p. 182. 
  4. ^ Jenkins D, Bitner-Glindzicz M, Thomasson L, et al. (2007), "Mutational analyses of UPIIIA, SHH, EFNB2 and HNF1β in persistent cloaca and associated kidney malformations", J Pediatr Urol 3 (1): 2–9,  

External links

  • page on Urogenital Sinus anomalies
  • Fetal pig dissection
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