Supernumerary body parts are most commonly a

congenital disorder A birth defect is an abnormal condition that is present at childbirth, birth, regardless of its cause. Birth defects may result in disability, disabilities that may be physical disability, physical, intellectual disability, intellectual, or dev ...

involving the growth of an additional part of the body and a deviation from the

body plan A body plan, (), or ground plan is a set of morphology (biology), morphological phenotypic trait, features common to many members of a phylum of animals. The vertebrates share one body plan, while invertebrates have many. This term, usually app ...

. Body parts may be easily visible or hidden away, such as

internal organ In a multicellular organism, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to a ...

s. Many additional body parts form by the same process as

conjoined twins Conjoined twins, popularly referred to as Siamese twins, are twins joined '' in utero''. It is a very rare phenomenon, estimated to occur in anywhere between one in 50,000 births to one in 200,000 births, with a somewhat higher incidence in south ...

: the

zygote A zygote (; , ) is a eukaryote, eukaryotic cell (biology), cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individ ...

begins to split but fails to completely separate. This condition may also be a symptom of repeated occurrences of continuous

inbreeding Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely genetic distance, related genetically. By analogy, the term is used in human reproduction, but more commonly refers to the genet ...

in a genetic line.

Specific types of occurrence

Specific types of additional body parts include: * Accessory breast – one or more additional breastsOnline Mendelian Inheritance in Man.
Nipples, Supernumerary
. Accessed 10 July 2006. *

Accessory spleen An accessory spleen is a small nodule of splenic tissue found apart from the main body of the spleen. Accessory spleens are found in approximately 10 percent of the population and are typically around 1 centimetre in diameter. They may resemble a ...

– one or more additional spleens *

Cervical rib Cervical ribs are the ribs of the neck in many tetrapods. In most mammals, including humans, cervical ribs are not normally present as separate structures. They can, however, occur as a pathology. In humans, pathological cervical ribs are usually no ...

– an additional rib *

Diphallia Diphallia, penile duplication (PD), diphallic terata, or diphallasparatus is an extremely rare developmental abnormality in which a male is born with two Human penis, penises. The first reported case was by Johannes Jacob Wecker in 1609. Its occu ...

– having two penes/penises * Hyperdontia – additional teeth *

Pelvic digit A pelvic digit, pelvic finger, or pelvic rib is a rare congenital abnormality in humans, in which Osseous tissue, bone tissue develops in the soft tissue near the human pelvis, pelvis, resembling a rib or finger and often divided into one or more ...

– a bony growth in the soft tissue of the pelvic region *

Polycephaly Polycephaly is the condition of having more than one head. The term is derived from the Greek stems ''poly'' (Greek: "πολύ") meaning "many" and ''kephalē'' (Greek: "κεφαλή") meaning "head". A polycephalic organism may be thought ...

– an extra head *

Polydactyly Polydactyly is a birth defect that results in extra fingers or toes. The hands are more commonly involved than the feet. Extra fingers may be painful, affect self-esteem, or result in clumsiness. It is associated with at least 39 genetic mut ...

– additional fingers or toesPenn 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 * Supernumerary bones – these additional bones are fairly common, particularly in the feet, and are frequently mistaken for fractures on x-rays. * Supernumerary kidney – a third kidney * Supernumerary musculature – presence of extra muscles such as additional heads of the biceps brachii, or coracobrachialis muscle variants *

Supernumerary nipple A supernumerary nipple is an additional instance of nipple occurring in mammals, including humans and monkeys. They are often mistaken for moles. Studies variously report the prevalence of supernumerary nipples as approximately 1 in 18 and 1 in ...

s – an additional nipple * Supernumerary phantom limbs – where the brain acts as though a limb were there, but it is not * Syndactyly – webbing between the fingers or toes * Uterus didelphys – two vaginal canals and/or uteri

Related conditions and concepts

Vestigial structures are

anatomical Anatomy () is the branch of morphology concerned with the study of the internal structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old scien ...

structures of

organism An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have be ...

s in a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

which are considered to have lost much or all of their original function through

evolution Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...

. These body parts can be classed as additional to the required functioning of the body. In

human anatomy Human anatomy (gr. ἀνατομία, "dissection", from ἀνά, "up", and τέμνειν, "cut") is primarily the scientific study of the morphology of the human body. Anatomy is subdivided into gross anatomy and microscopic anatomy. Gross ...

, the

vermiform appendix The appendix (: appendices or appendixes; also vermiform appendix; cecal (or caecal, cæcal) appendix; vermix; or vermiform process) is a finger-like, blind-ended tube connected to the cecum, from which it develops in the embryo. The cecum ...

is sometimes classed as a vestigial remnant.

Prosthesis In medicine, a prosthesis (: prostheses; from ), or a prosthetic implant, is an artificial device that replaces a missing body part, which may be lost through physical trauma, disease, or a condition present at birth (Congenital, congenital disord ...

is an artificial extension that replaces a body part, and

cybernetics Cybernetics is the transdisciplinary study of circular causal processes such as feedback and recursion, where the effects of a system's actions (its outputs) return as inputs to that system, influencing subsequent action. It is concerned with ...

is the study of computer technology in relation to organisms, which can include replacement or additional body parts. Body integrity identity disorder (BIID) is a

psychiatric disorder A mental disorder, also referred to as a mental illness, a mental health condition, or a psychiatric disability, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. A mental disorder is ...

in which a person thinks that they have one or more additional limbs than they should, despite having two arms and two legs. People with this condition often wish to amputate what they see as additional body parts. A

phantom limb A phantom limb is the sensation that an amputated or missing limb is still attached. It is a chronic condition that is often resistant to treatment. When the cut ends of sensory fibres are stimulated during thigh movements, the patient feels as ...

is the sensation that a missing limb is still attached to the body. This is almost universal in amputees in the first month following an amputation. A supernumerary phantom limb is the sensation of having an extra limb or body part despite no such limb actually existing. It is an uncommon syndrome, usually due to some kind of brain injuries in the

somatosensory cortex The somatosensory system, or somatic sensory system is a subset of the sensory nervous system. The main functions of the somatosensory system are the perception of external stimuli, the perception of internal stimuli, and the regulation of bod ...

or in some parts of the right hemisphere of the brain, usually due to a

stroke Stroke is a medical condition in which poor cerebral circulation, blood flow to a part of the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemor ...

in the brain. A chimera is an animal or

plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...

that has two or more different populations of genetically distinct cells that originated in different

s that have merged. Anatomical structures are typically mixed depending on which cells are prevalent in different body parts. For example, plants can have two different types of flowers. A

mosaic A mosaic () is a pattern or image made of small regular or irregular pieces of colored stone, glass or ceramic, held in place by plaster/Mortar (masonry), mortar, and covering a surface. Mosaics are often used as floor and wall decoration, and ...

is a genetic anomaly similar in nature and effects to a chimera: genetically different populations of cells within one organism, originated from some propagated mutation of a single cell rather than from outside sources.

Mythology

Hindu mythology Hindu mythology refers to the collection of myths associated with Hinduism, derived from various Hindu texts and traditions. These myths are found in sacred texts such as the Vedas, the Itihasas (the ''Mahabharata'' and the ''Ramayan ...

, additional limbs and heads are considered a sign of power. In

Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...

Artemis In ancient Greek religion and Greek mythology, mythology, Artemis (; ) is the goddess of the hunting, hunt, the wilderness, wild animals, transitions, nature, vegetation, childbirth, Kourotrophos, care of children, and chastity. In later tim ...

, the goddess of fertility, was sometimes represented as having numerous breasts. This was particularly notable in the cult of Artemis ( Diana) celebrated in the ancient city of

Ephesus Ephesus (; ; ; may ultimately derive from ) was an Ancient Greece, ancient Greek city on the coast of Ionia, in present-day Selçuk in İzmir Province, Turkey. It was built in the 10th century BC on the site of Apasa, the former Arzawan capital ...

, in modern Turkey. In

Japanese mythology Japanese mythology is a collection of traditional stories, folktales, and beliefs that emerged in the islands of the Japanese archipelago. Shinto traditions are the cornerstones of Japanese mythology. The history of thousands of years of contac ...

, the god of the sea and storms, Susanoo, is sometimes depicted as having a third arm. In Hungarian mythology, having six fingers on a hand (

polydactyly Polydactyly is a birth defect that results in extra fingers or toes. The hands are more commonly involved than the feet. Extra fingers may be painful, affect self-esteem, or result in clumsiness. It is associated with at least 39 genetic mut ...

) is held to be the sign of innate supernatural power (see ). In Christian mythology,

Goliath Goliath ( ) was a Philistines, Philistine giant in the Book of Samuel. Descriptions of Goliath's giant, immense stature vary among biblical sources, with texts describing him as either or tall. According to the text, Goliath issued a challen ...

has brothers who have six fingers and six toes.

References

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External links

Supernumerary Bones of the Foot

Specific types of occurrence

Related conditions and concepts

Mythology

See also

References

External links