Final answer:
The structure in the female reproductive tract that contains rugae, which enable dilation during childbirth, is the vagina. These rugae are folds in the mucous membrane that allow the vagina to expand during labor and birth.
Step-by-step explanation:
The structure in the female reproductive tract containing rugae that enable it to dilate during labor and birth is the vagina. The walls of the vagina have an inner mucous membrane with transverse folds known as rugae. These rugae, along with its muscular walls, allow the vagina to expand to accommodate both intercourse and childbirth.
The vagina is a tubular tract that connects the uterus to the outside of the body. It also serves as the exit from the uterus during menses and childbirth. The outer walls have longitudinal columns or ridges, and it is lined with a fibrous adventitia, a layer of smooth muscle, and that inner mucous membrane with rugae. The rugae make the vagina an elastic structure, thus playing a critical role during the birthing process when it serves as the birth canal.