Urogenital sinus

The embryonic ventral part of the cloaca that forms the bladder and parts of the urethra and reproductive tracts. Its derivatives differ between sexes.

Cloaca: The embryonic chamber into which the hindgut and urinary and reproductive passages initially open. The urogenital sinus forms when the cloaca is divided from the hindgut.
Allantois: An embryonic diverticulum extending from the yolk-sac region toward the connecting stalk. It connects the developing bladder region with the umbilicus.
Persistent cloaca: A congenital malformation in which the rectum, vagina, and urinary tract join a common channel. It reflects abnormal separation of the cloaca into distinct outlets.
Prostatic urethra: The urethral segment that passes through the prostate gland. It develops from the pelvic part of the sinus in typical male development.
Embryonic folding: The early process that reshapes the flat embryonic disc into a three-dimensional body form. Folding brings the endoderm-lined hindgut and cloacal region into their embryonic positions.
Urorectal septum: A partition that separates the embryonic cloaca into urogenital and anorectal compartments. Its growth establishes the urogenital sinus as a distinct ventral compartment.
Mesonephric duct: An embryonic duct that drains the mesonephric kidney and contributes to male reproductive ducts. Its opening and incorporation into the sinus change as the bladder develops.
Urogenital sinus anomaly: A congenital abnormality in which urinary and genital passages retain an atypical shared channel or opening. It results when sinus derivatives or their separation develop abnormally.
Female urethra: The short urinary passage from the bladder to the external urethral opening in females. It is a principal urethral derivative of the pelvic urogenital sinus.
Hindgut: The caudal portion of the embryonic gut tube, giving rise to the distal large intestine and cloacal region. Its cloacal end shares an early chamber with the developing urogenital tract.

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