Prepubescent girls' hymenal openings come in many shapes, depending on hormonal and activity level, the most common being crescentic posterior rim: Normal variations of the hymen range from thin and stretchy to thick and somewhat rigid; or it may also be completely absent. At the upper corners of the uterus, the fallopian pronounced: In Mann, Gurdeep S. For these reasons, the state of the hymen is not a reliable indicator of virginity  although it continues to be considered so in certain cultures, and virginity testing may be done. Approximately once a month, during ovulation, an ovary sends a tiny egg into one of the fallopian tubes.
However, research on women in Western populations has found that bleeding during first consensual intercourse does not always happen or is less common than not bleeding.
Female Reproductive System
Hymens are often different from person to person. Below are some examples of disorders that affect the female reproductive system. Occasionally, the hymen is harder than normal or it is complete and sealed without there being The hormone estrogen causes the endometrium to become thick and rich with blood. The vagina is a muscular, hollow tube that extends from the vaginal opening to the uterus. The opening of the cervix is very small no wider than a strawwhich is why a tampon can never get lost inside a girl's body.