The hymen is a thin membrane 2 - 3cm from the vaginal opening, with one or more holes for menstrual blood to escape. The hymen has many blood vessels interwoven together, so when the hymen is torn, there will be a little blood.

Estradiol is a female sex hormone, secreted mainly in the ovaries, but also in part by the placenta, adrenal glands, breasts and testes. This hormone occurs in both sexes and is an important hormone in both men and women.