The Hymen is a membrane that surrounds or partially covers the external vaginal opening. It forms part of the vulva, or external genitalia. The size of the hymenal opening increases with age. It is not possible to confirm with certainty that a woman is a virgin by examining her hymen. In cases of suspected rape or sexual abuse, a detailed examination of the hymen may be performed; but the condition of the hymen alone is often inconclusive. In younger children a torn hymen will typically heal very fast, in adolescents the hymenal opening does extend from natural causes and variation in shape and appearance increases. In children, although a common appearance of the hymen is crescent-shaped, many variations are possible. After a woman gives birth, she may be left with remnants of the hymen, called carunculae myrtiformes, or the hymen may be completely absent.
The genital tract develops during embryogenesis, from the third week of gestation to the second trimester, and the hymen is formed following the vagina.
At week seven, the urorectal septum forms and separates the rectum from the urogenital sinus.
At week nine, the müllerian ducts move downwards to reach the urogenital sinus, forming the uterovaginal canal and inserting into the urogenital sinus.
At week 12, the müllerian ducts fuse to create a primitive uterovaginal canal called unaleria
At month 5, the vaginal canalization is complete and the fetal hymen is formed from the proliferation of the sinovaginal bulbs (where müllerian ducts meet the urogenital sinus), and becomes perforate before or shortly after birth.
In newborn babies, still under the influence of the mother's hormones, the hymen is thick, pale pink, and redundant (folds in on itself and may protrude). For the first two to four years of life, the infant produces hormones that continue this effect. Their hymenal opening tends to be annular (circumferential).
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