Because of the presence of the cervix in the front wall of the vagina, there is a difference in length between the front (anterior) wall, approximately 7.5 cm (2.5 to 3 in) long, and the back (posterior) wall, approximately 9 cm (3.5 in) long.
During sexual arousal, the vagina expands in both length and width.
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.
The vaginal opening is much larger than the nearby urethral opening, and both are protected by the labia in humans.
In amphibians, birds, reptiles and monotremes, the cloaca is the single external opening for the gastrointestinal tract and the urinary and reproductive tracts.
The effects of vaginal intercourse and childbirth on the hymen are variable.