The vagina is a and tubular part of the female genital tract, which in humans extends from the vulva to the uterus. The outer vaginal opening may be partly covered by a membrane called the hymen. At the deep end, the cervix (neck of the uterus) bulges into the vagina. The vagina allows for sexual intercourse and childbirth, and channels menstrual flow, which occurs periodically as part of the menstrual cycle.