ABSTRACT

Complete formation and differentiation of the mu¨llerian ducts into the segments of the female reproductive tract occurs in three stages. Both paramesonephric (mu¨llerian) ducts migrate inferiorly and medially. As they meet in the midline, they fuse together inferiorly in a process referred to as longitudinal or lateral fusion. The medial walls then reabsorb to create the uterine cavity, while the unfused superior portions become the fallopian tubes. The descending mu¨llerian system (upper one-third of the vagina) then fuses with the ascending sinovaginal bulb (lower two-thirds) to complete the vaginal patency. This is referred to as transverse or vertical fusion.