In mammals, the vagina is the fibromuscular, tubular part of the female genital tract extending, in humans, from the vulva to the cervix. The outer vaginal opening is normally partly covered by a membrane called the hymen. At the deep end, the cervix bulges into the vagina. The vagina allows for sexual intercourse and childbirth, and channels menstrual flow, which occurs as part of the monthly menstrual cycle. The vagina's location and structure varies among species, and can vary in size. Female