Outflow is also critical for menstrual efflux.
Outflow obstruction may occur at different levels with resulatant variation of clinical presentation. Embryologically, the lower two-thirds of the vagina develop from the urogenital sinus. The upper vagina, cervix, uterus, fallopian tubes and ovaries form from the M llerian duct system. Failure of vertical fusion or canalization of the 2 systems in utero may result in cervical stenosis or atresia, vaginal atresia, or transverse vaginal septa. In addition, hymenal tissue may be imperforate.