Agenesis
Encyclopedia
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:
s.
s.
Because the middle and inner ears are necessary for hearing, people with complete agenesis of the ears suffer from total deafness. Minor agenesis that affects only the visible parts of the outer ear, which may be called microtia
, typically produces cosmetic concerns and perhaps hearing impairment if the opening to the ear canal is blocked, but not deafness.
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, agenesis refers to the failure of an organ
Organ (anatomy)
In biology, an organ is a collection of tissues joined in structural unit to serve a common function. Usually there is a main tissue and sporadic tissues . The main tissue is the one that is unique for the specific organ. For example, main tissue in the heart is the myocardium, while sporadic are...
to develop during embryonic
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
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 callosumAgenesis of the corpus callosumAgenesis of the corpus callosum is a rare birth defect in which there is a complete or partial absence of the corpus callosum. Agenesis of the corpus callosum occurs when the corpus callosum, the band of white matter connecting the two hemispheres in the brain, fails to develop normally,...
- failure of the Corpus callosum to develop - Renal agenesisRenal agenesisRenal agenesis is a unilateral or bilateral medical condition in which one or both fetal kidneys fail to develop leading to oligohydramnios, resulting in a 40-fold increase in perinatal mortality.It can be associated with RET or UPK3A.-Bilateral:...
- failure of one or both of the kidneys to develop - PhocomeliaPhocomeliaPhocomelia is an extremely rare congenital disorder involving the limbs . Étienne Geoffroy Saint-Hilaire coined the term in 1836....
- failure of the arms or legs to develop - Penile agenesisPenile agenesisPenile agenesis is a birth defect in humans, occurring about once in 5–6 million male births, in which a male child is born without a penis.A partner condition is testicular or gonadal agenesis...
- failure of penis to develop - Müllerian agenesisMullerian agenesisMüllerian agenesis is a congenital malformation in women characterised by a failure of the müllerian ducts to develop, resulting in a missing uterus and fallopian tubes and variable malformations of the upper portion of the vagina. It is the second most common cause of primary amenorrhea after...
- failure of the uterus and part of the vagina to develop
Eye agenesis
Eye agenesis is a medical condition in which sufferers are born with no eyeHuman eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
s.
Ear agenesis
Ear agenesis is a medical condition in which people are born without earEar
The ear is the organ that detects sound. It not only receives sound, but also aids in balance and body position. The ear is part of the auditory system....
s.
Because the middle and inner ears are necessary for hearing, people with complete agenesis of the ears suffer from total deafness. Minor agenesis that affects only the visible parts of the outer ear, which may be called microtia
Microtia
Microtia, also called microtia-anotia, is a congenital deformity where the pinna is very small and underdeveloped or absent . It can be unilateral or bilateral . It occurs in 1 out of about 8,000–10,000 births. In unilateral microtia, the right ear is most commonly affected...
, typically produces cosmetic concerns and perhaps hearing impairment if the opening to the ear canal is blocked, but not deafness.