hymen

The hymen is a thin piece of mucosal tissue that surrounds or partially covers the vaginal opening. A small percentage are born with hymens that are imperforate and completely obstruct the vaginal canal. It forms part of the vulva, or external genitalia, and is similar in structure to the vagina. The term comes straight from the Greek, for 'membrane'. In children, a common appearance of the hymen is crescent-shaped, although many shapes are possible. Each shape in the natural range has a Latinate name. During puberty, estrogen causes the hymen to change in appearance and become very elastic. Normal variations of the post-pubertal hymen range from thin and stretchy to thick and somewhat rigid. Very rarely, it may be completely absent. The hymen can rip or tear during first penetrative intercourse, which usually results in pain and, sometimes, mild temporary bleeding or spotting. Minor injuries to the hymen may heal on their own, and not require surgical intervention. Historically it was believed that first penetration was necessarily traumatic, but now sources differ on how common tearing or bleeding are as a result of first intercourse. Therefore, the state of the hymen is not a reliable indicator of virginity, though "virginity testing" remains a common practice in some cultures, sometimes accompanied by hymen reconstruction surgery to give the appearance of virginity. Development and histology 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 twelve, the Müllerian ducts fuse to create a primitive uterovaginal canal called unaleria. At month five, 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 normally becomes perforate before or shortly after birth.