The physiological purpose of the hymen is one of the eternal mysteries of women's bodies. Although it doesn't seem to have a specific function, it's thought that hymen tissue remains as a vestige of vaginal development. Embryologically, it tended to keep germs and dirt out of the vagina.
In infants and children, the hymen can serve a protective purpose by helping to prevent things from being pushed into the vagina; sometimes, a damaged hymen is looked at as an indicator of abuse and incest.
Throughout history, there have been cultures that forbid sexual activity outside of marriage; some of these have considered an "intact" hymen "proof" of purity. This connection continues to have a psychological and cultural impact today.
Hymens vary in shape, size and thickness
Medically speaking, however, the concept of an "intact" hymen is a myth. That's because hymens vary in shape, size, and thickness. Among the multiple possibilities are hymens that surround the entire vaginal entrance, with an open space in the center (called an annular hymen), and hymens that appear open with a thin line of skin down the middle (a septate hymen).
Most hymens don't fully cover the vaginal entry so that menstrual fluid can leave the body. In rare instances, the hymen can be thick, covering the entire vaginal opening (an imperforate hymen). This kind of hymen may not allow a woman to menstruate, have penetration during sexual activity, or have anything inserted into her vagina. Often, a health care provider can correct this with a simple incision. However, if there's cyclic build up of the uterine lining, but no menstrual flow, the vagina will fill with blood that can back up into the uterus, and a provider may need to be seen immediately.
Since hymens come in so many shapes and forms, it's important to realise that the hymen is not a reliable indicator of whether a person has been sexually active or not. This is especially true since for some women, the hymen can be stretched or torn by fingers, tampons, sex toys, masturbation, or even at a gynaecological exam.
For others, using tampons or inserting fingers does not interfere with the tissue at all. Anecdotal evidence also supports the idea that it's possible to tear or stretch the hymen during non-sexual strenuous activity (such as horseback riding, gymnastics, or dance) or from trauma directly to the vaginal area. There are also women whose hymen tissue is so flexible that it moves aside during penetration.
In addition, if a woman's hymen is stretched or torn, she may experience pain or bleeding that generally lasts for a short period of time. Or, she may not show any "signs" or have any discomfort at all.