Urogenital Sinus


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Related to Urogenital Sinus: Urogenital folds

Urogenital Sinus

 

the cavity into which the efferent ducts of the reproductive and excretory systems empty in many vertebrates. The urogenital sinus opens into the cloaca in elasmobranchs and holocephalans, in chelonians, and in monotremes; in vertebrates that have a reduced cloaca—polypterids, chondrosteans, and holosteans, males of lower teleosts, and viviparous mammals—the urogenital sinus opens directly to the outside.

The urogenital sinus in the mammalian embryo develops from the lower ventral section of the cloaca; the gonaducts and urinary bladder open into this section, as do the ureters of monotremes. In female eutherians (placental mammals) and in women, the urogenital sinus is greatly shortened, forming the vestibule of the vagina. The vestibule is inferior to and separated from the vagina in ungulates, rodents, prosimians, anthropoid apes, and women by a membranous structure called the hymen. In males of viviparous mammals and in men, the upper portion of the urethra develops from the urogenital sinus.

References in periodicals archive ?
The formation of a urogenital sinus in these animals occurs due absence of an external vaginal ostium (Yalcinkaya et al.
The 18-day-old pig embryo has a well-defined genital tubercle (Figure 4-3), a swelling on the ventral surface between the umbilical cord and opening of the urogenital sinus.
Genetic mutations could theoretically interfere indirectly with fetal testis and adrenal testosterone production and with the adequate virilization of the urogenital sinus and external genitalia during embryogenesis if the conversion of testosterone to DHT by 5[alpha]-reductase is interrupted.
Bladder starts to develop by 5th week of gestation when cloaca is divided by a uro-rectal septum into urogenital sinus and anorectal canal.
During embryonic development, if canalization of the urogenital sinus with the Mullerian system is incomplete, the resulting hymen can be imperforate or microperforate; in either case, the hymen can present as an obstructive anomaly.
By six weeks of gestation, the urorectal septum moves caudally to divide the cloaca into the anterior urogenital sinus and the posterior anorectal canal.
1) In these patients it is assumed that embryological division of the cloaca occurs in the fifth week in vitro into the urogenital sinus and that the anorectal canal proceeds normally (as the hindgut is usually normal in these patients).
In females the mesonephric ducts degenerate and by twelve weeks due to lack of testosterone and the paired paramesonephric developed on lateral aspect of mesonephrons to reach urogenital sinus at nine weeks and unfused lateral arms of paramesonephric ducts forming fallopian tubes.
In the normal embryologic development of the urogenital system, the cranial part of the urogenital sinus is continuous with the allantois, developing into the bladder and pelvic urethra; the bladder dome, posterior walls and part of lateral walls, normally arise from surrounding urogenital sinus mesenchyme.
The ovaries and lower one third of the vagina have separate embryologie origins from genital ridge and urogenital sinus respectively, not derived from the Mullerian system.
Vagina is short, develops from urogenital sinus only and ends blindly.