Koff coined the terms sinovaginal bulb and vaginal plate.
The sinovaginal bulbs originate in the urogenital sinus at the distal aspect of the Mullerian tubercle.
The ovaries and lower third of the vagina have different embryological origins derived from germ cells that migrate from the primitive yolk sac and the sinovaginal
bulb on posterior aspect of urogenital sinus fuse with lower end of mullerian duct to form vaginal plate.
This malformation is caused by a failure of canalization of the sinovaginal bulbs and vaginal plate.
The sinovaginal bulbs are two solid evaginations originating from the urogenital sinus at the distal aspect of the mullerian tubercle, as shown at right (A).
If the distance is larger--more than several millimeters--then the differential diagnosis typically is agenesis of the lower vagina, an anomaly that results from abnormal development of the sinovaginal
bulbs and vaginal plate.