Health professionals who examine hymens for signs of sexual abuse are usually most interested in the posterior part of Sex hymen pictures hymen, from the 3 o'clock to 9 o'clock position. As the hymen starts to erode from sexual or other activity, the hymen becomes less ring-like. The Hymen The hymen is a thin piece of mucosal tissue that surrounds and partially Sex hymen pictures the vaginal opening also called the introitus. Smerecnik, Chris, et al. This type of hymen lets menstrual and other fluids out with no problem, but sexual activity and the insertion of tampons can be problematic.