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Supernumerary body parts are most commonly a congenital disorder involving the growth of an additional part of the body and a deviation from the body plan. Body parts may be easily visible or hidden away, such as internal organs. Many additional body parts form by the same process as conjoined twins: the zygote begins to split but fails to completely separate. This condition may also be a symptom of repeated occurrences of continuous inbreeding in a genetic line. ==Specific types of occurrence== Specific types of additional body parts include: *Accessory breast – one or more additional breasts〔Online Mendelian Inheritance in Man. "(Nipples, Supernumerary )". Accessed 10 July 2006.〕 *Accessory spleen – one or more additional spleens *Cervical rib – an additional rib〔PatientPlus. "(Cervical ribs and thoracic outlet syndrome )". Accessed 10 July 2006.〕 *Diphallia - Having two penes/penises. *Hermaphroditism – having both sexes' sex organs〔Grumbach, M.M., Conte, F.A., 1998. "Disorders of sex differentiation." in Williams Textbook of Endocrinology, eds. J.D. Wilson, D.W. Foster, H.M. Kronenberg, and P.R. Larsen, (Philadelphia: W B Saunders:1303-1425).〕〔Molnar, Sebastian, 17 February 2004. (Plant Reproductive Systems ). Accessed 10 July 2006.〕 *Hyperdontia – additional teeth〔Derm Atlas. "(Image of hyperdontia ). Accessed 10 July 2006.〕 *Pelvic digit – a bony growth in the soft tissue of the pelvic region *Polycephaly – an extra head *Polydactyly – additional fingers or toes〔Penn State Milton S. Hershey Medical Center A-Z. (Polydactyly and Syndactyly ). Accessed 10 July 2006.〕 *Polymelia — an extra arm or leg. *Polyorchidism – having three or more testicles〔Wipro GE Healthcare. "(Polyorchidism )". Accessed 10 July 2006.〕 *Supernumerary bone in the feet – these additional bones are fairly common. They tend to occur between the metatarsal and are frequently mistaken for fractures on x-rays. *Supernumerary kidney – a third kidney〔Biology-Online.org. "(Supernumerary kidney )". Accessed 10 July 2006.〕 *Supernumerary nipples – an additional nipple〔 *Supernumerary phantom limbs – where the brain acts as though a limb were there, but it is not.〔See other article.〕 *Syndactyly – webbing between the fingers or toes〔 *Uterus didelphys – two vaginal canals and/or uteri 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Supernumerary body part」の詳細全文を読む スポンサード リンク
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