medicine Medicine is the science and Praxis (process), practice of caring for a patient, managing the diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment, Palliative care, palliation of their injury or disease, and Health promotion ...

, agenesis () refers to the failure of an organ to develop during embryonic growth and development due to the absence of primordial tissue. Many forms of agenesis are referred to by individual names, depending on the organ affected: *

Agenesis of the corpus callosum Agenesis of the corpus callosum (ACC) is a rare birth defect in which there is a complete or partial absence of the corpus callosum. It occurs when the development of the corpus callosum, the band of white matter connecting the two hemispheres i ...

- failure of the Corpus callosum to develop *

Renal agenesis Renal agenesis is a medical condition in which one (unilateral) or both (bilateral) fetal kidneys fail to develop. Unilateral and bilateral renal agenesis in humans, mice and zebra fish has been linked to mutations in the gene GREB1L. It has also ...

- failure of one or both of the kidneys to develop * Amelia - failure of the arms or legs to develop *

Penile agenesis Aphallia is a congenital malformation in which the phallus (penis or clitoris) is absent. It is also known as penile agenesis in the case of males. The word is derived from the Greek ''a-'' for "not", and ''phallos'' for "penis". It is classified a ...

- failure of penis to develop *

Müllerian agenesis Müllerian agenesis, also known as Müllerian aplasia, vaginal agenesis, or Mayer-Rokitansky-Küster-Hauser syndrome (MRKH syndrome), is a congenital malformation characterized by a failure of the Müllerian ducts to develop, resulting in a mis ...

- failure of the uterus and part of the vagina to develop *

Agenesis of the gallbladder In medicine, agenesis () refers to the failure of an organ to develop during embryonic growth and development due to the absence of primordial tissue. Many forms of agenesis are referred to by individual names, depending on the organ affected: *A ...

- failure of the Gallbladder to develop. A person may not realize they have this condition unless they undergo surgery or medical imaging, since the gallbladder is neither externally visible nor essential. __TOC__

Eye agenesis

Eye agenesis is a medical condition in which people are born with no

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

Dental & oral agenesis

Anodontia Anodontia is a rare genetic disorder characterized by the congenital absence of all primary or permanent teeth. It is divided into two subsections, complete absence of teeth or only some absence of teeth. It is associated with the group of ski ...

, absence of all primary or permanent teeth. *

Aglossia Aglossia (aglossia congenita) is a congenital defect resulting in a partial development or complete absence of a tongue. Aglossia is commonly associated with craniofacial and limb defects ( Adactylia syndrome) and is thought to belong to a family ...

, absence of the tongue. *

Agnathia Agnathia (also termed hypognathous) is absence of a portion or the entirety of one or both jaws. It is a very rare condition. See also * Micrognathia Micrognathism is a condition where the jaw is undersized. It is also sometimes called mandibu ...

, absence of the jaw. * Wisdom tooth agenesis - most adult humans have three molars (on each upper/lower left/right side), with the third being referred to as the

wisdom tooth A third molar, commonly called wisdom tooth, is one of the three molars per quadrant of the human dentition. It is the most posterior of the three. The age at which wisdom teeth come through ( erupt) is variable, but this generally occurs bet ...

. But many people have less than the four total. Agenesis of wisdom teeth is a normal condition that can differ widely by population, ranging from practically zero in

Tasmanian Aborigines The Aboriginal Tasmanians (Palawa kani: ''Palawa'' or ''Pakana'') are the Aboriginal people of the Australian island of Tasmania, located south of the mainland. For much of the 20th century, the Tasmanian Aboriginal people were widely, and ...

to nearly 100% in

indigenous Mexicans Indigenous peoples of Mexico ( es, gente indígena de México, pueblos indígenas de México), Native Mexicans ( es, nativos mexicanos) or Mexican Native Americans ( es, pueblos originarios de México, lit=Original peoples of Mexico), are those ...

. (Se
research paper
with world map showing prevalence.)

Ear agenesis

Ear agenesis is a medical condition in which people are born without ears. Because the middle and inner ears are necessary for hearing, people with complete agenesis of the ears are totally

deaf Deafness has varying definitions in cultural and medical contexts. In medical contexts, the meaning of deafness is hearing loss that precludes a person from understanding spoken language, an audiological condition. In this context it is written ...

. Minor agenesis that affects only the visible parts of the outer ear, which may be called

microtia Microtia is a congenital deformity where the auricle (external ear) is underdeveloped. A completely undeveloped pinna is referred to as anotia. Because microtia and anotia have the same origin, it can be referred to as microtia-anotia. Microtia ...

, typically produces cosmetic concerns and perhaps hearing impairment if the opening to the ear canal is blocked, but not deafness.

References

{{reflist Embryology Medical terminology Congenital disorders