Hymen

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. The hymen does not seem to have a specific physiological function and has few, if any, nerve endings. 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. Normal variations of the post-pubertal hymen range from thin and stretchy to thick and somewhat rigid; or it may instead be completely absent. The hymen may rip or tear the first time penetrative intercourse happens, which may cause temporary bleeding or slight discomfort, but sources differ on how common tearing and bleeding after first intercourse is. 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. Minor injuries to the hymen may heal without visible signs of previous injury. A torn hymen may be surgically restored in a procedure called hymenorrhaphy. 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. The hymen has no nerve innervation. 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). Past neonatal stage, the diameter of the hymenal opening (measured within the hymenal ring) widens by approximately 1 mm for each year of age. During puberty, estrogen causes the hymen to become very elastic and fimbriated. The hymen can stretch or tear as a result of various behaviors, by tampon or menstrual cup use, pelvic examinations with a speculum, regular physical activity, sexual intercourse, insertion of multiple fingers or items into the vagina, and activities such as gymnastics (doing 'the splits'), or horseback riding. Remnants of the hymen are called carunculae myrtiformes. A glass or plastic rod of 6 mm diameter having a globe on one end with varying diameter from 10 to 25 mm, called a Glaister Keen rod, is used for close examination of the hymen or the degree of its rupture. In forensic medicine, it is recommended by health authorities that a physician who must swab near this area of a prepubescent girl avoid the hymen and swab the outer vulval vestibule instead. In cases of suspected rape or child sexual abuse, a detailed examination of the hymen may be performed, but the condition of the hymen alone is often inconclusive.