Fig. 10

Embryologic development of the distal vagina. Weeks 3–4: The distal part of the gastrointestinal tract is in continuity with the allantois. It folds onto itself forming a bulge in the ventral aspect of the embryo—the cloaca; Weeks 4–6: A coronal wedge of mesenchyme—the urorectal septum—forms in the angle between the allantois and the hindgut. As it grows caudally, it divides the cloaca into an anterior part—the primitive urogenital sinus—and a posterior part—the anorectal canal; Weeks 7–8: The (utero)vaginal canal, which derives from the fused ends of the Mullerian ducts, descends through the urorectal septum; Weeks 9–12: Its blind end sinuvaginal eminence comes in contact with the posterior wall of the deep urogenital sinus, inducing the formation of the distal vagina; Adult: The structures derived from the deep urogenital sinus form the internal urogenital sinus compartment; they include the urethra, urethrovaginal septum, distal vagina, and distal rectovaginal septum; the posterior wall of the urethra, urethrovaginal septum, and distal vagina form the urethrovaginal subcompartment [1, 12, 14, 32]