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

, agenesis () refers to the failure of an

organ Organ and organs may refer to: Biology * Organ (biology), a group of tissues organized to serve a common function * Organ system, a collection of organs that function together to carry out specific functions within the body. Musical instruments ...

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 ...

- 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 - failure of penis to develop *

Müllerian agenesis Müllerian may refer to: * Müllerian mimicry, a type of mimicry or convergence named after Fritz Müller * Müllerian ducts, which enter the cloaca of an embryo (named after Johannes Peter Müller) * Mullerian anomalies are structural anomalies c ...

- failure of the uterus and part of the vagina to develop * Agenesis of the gallbladder - 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 An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...

Dental & oral agenesis

* Anodontia, 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. The first known case was reported in the early 18th century by a member of the prominent De Jussieu family in France Fr ...

, absence of the tongue. * Agnathia, 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 The third molar, commonly called wisdom tooth, is the most posterior of the three molars in each quadrant of the human dentition. The age at which wisdom teeth come through ( erupt) is variable, but this generally occurs between late teens a ...

. 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. At the time of European contact, Aboriginal Tasmanians were divided into a numb ...

to nearly 100% in

indigenous Mexicans Indigenous peoples of Mexico (), Native Mexicans () or Mexican Native Americans (), are those who are part of communities that trace their roots back to populations and communities that existed in what is now Mexico before the arrival of Europe ...

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

Ear agenesis

Ear agenesis is a medical condition in which people are born without

ear In vertebrates, an ear is the organ that enables hearing and (in mammals) body balance using the vestibular system. In humans, the ear is described as having three parts: the outer ear, the middle ear and the inner ear. The outer ear co ...

s. 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 auricle is referred to as anotia. Because microtia and anotia have the same origin, it can be referred to as microtia-anotia. Micro ...

, 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