The hymen is a thin piece of mucosal tissue that surrounds or partially covers the external vaginal opening. It forms part of the vulva , or external genitalia , and is similar in structure to the vagina. In children, a common appearance of the hymen is crescent -shaped, although many shapes are possible. During puberty , estrogen causes the hymen to change in appearance and become very elastic. The hymen can rip or tear during first penetrative intercourse , which usually results in pain and, sometimes, mild temporary bleeding or spotting.