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Questions and Answers
What is the term for a recognized pattern of malformations with a given etiology?
What is the term for a recognized pattern of malformations with a given etiology?
What is the term for a specific abnormality that results from disruption of normal developmental processes?
What is the term for a specific abnormality that results from disruption of normal developmental processes?
What percentage of zygotes have chromosomal aberrations?
What percentage of zygotes have chromosomal aberrations?
What is the term for an alteration in shape or structure of a previously normally formed part?
What is the term for an alteration in shape or structure of a previously normally formed part?
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What is the name of the condition where an individual has an extra copy of chromosome 21?
What is the name of the condition where an individual has an extra copy of chromosome 21?
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What is the term for exogenous agents that may cause developmental defects?
What is the term for exogenous agents that may cause developmental defects?
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What is the name of the condition where an individual has an extra copy of chromosome 18?
What is the name of the condition where an individual has an extra copy of chromosome 18?
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What is the name of the condition where an individual has an extra copy of chromosome 13?
What is the name of the condition where an individual has an extra copy of chromosome 13?
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What is the term for a primary structural defect resulting from a localized error of morphogenesis?
What is the term for a primary structural defect resulting from a localized error of morphogenesis?
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What is the name of the condition where an individual has an X0 chromosome?
What is the name of the condition where an individual has an X0 chromosome?
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Study Notes
History of Teratology
- Conjoined twins have been reported to exhibit functional and emotional behavior, with cases showing differences in emotions, affections, and appetites.
- Thompson (1930) reported a case of dicephalic twins that showed emotional dissociation, where one head would cry while the other laughed, and one would eat while the other slept.
Conjoined Twins
- Craniopagus twins are rare, with an estimated occurrence of 1 in 3,000,000 births, or 1 in 58 conjoined twins.
- Types of conjoined twins include frontal, parietal, and occipital unions.
- Historical cases of conjoined twins include the twin girls born in 1495 in Worms, Germany, who were united by their foreheads.
Single Malformations
- Historical illustrations of single malformations include a tricephalic creature, a fetus with one phocomelic arm, a man with reduction malformation, an epigastric parasite, and a man with a defect of the anterior abdominal wall.
Biological Theories
- Aristotle (1943) had knowledge of teratologic facts, including redundance and reduction of fingers, toes, hands, and feet, as well as imperforate anus, and absence of the gallbladder, spleen, or kidney.
- Reduction malformations, osteogenesis imperfecta, and kleeblattschadel (cloverleaf skull) have been documented in historical literature.
Teratology
- Teratology is the science that studies the causes, mechanisms, and patterns of abnormal development.
- Congenital anomalies present at birth are classified into four types: malformation, disruption, deformation, and dysplasia.
- Malformation is a structural defect present at birth, which may be gross or microscopic, on the surface or within the body, and hereditary or non-hereditary.
Prevalence of Congenital Anomalies
- 3% of all live-born infants have a major congenital anomaly.
- Single minor anomalies are present in about 14% of newborns.
- Most severely malformed embryos are spontaneously aborted during the first 6-8 weeks of pregnancy.
Principles of Teratology
- Susceptibility to teratogenesis depends on the genotype of the conceptus and the interaction with adverse environmental factors.
- Susceptibility to teratogenesis varies with the developmental stage at the time of exposure.
- Teratogenic agents act in specific ways on developing cells and tissues to initiate sequences of abnormal developmental events.
Manifestations of Deviant Development
- There are four manifestations of deviant development: death, malformation, growth retardation, and functional defect.
- Manifestations of malformation increase in frequency and degree as dosage increases from the no observable adverse effect level to a dose producing 100% lethality.
Teratology Terms
- Malformation is a primary structural defect resulting from a localized error of morphogenesis.
- Disruption is a specific abnormality that results from disruption of normal developmental processes.
- Deformation is an alteration in shape or structure of a previously normally formed part.
- Syndrome is a recognized pattern of malformations with a given etiology.
Causes of Congenital Anomalies
- Genetic factors: chromosomal aberrations, numerical chromosomal abnormalities, structural chromosomal abnormalities, and mutant genes.
- Environmental factors: teratogens, including drugs, radiation, and other exogenous agents.
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Description
This quiz covers the first lecture of Teratology by Dr. Ahmed Said, focusing on the history of conjoined twins, including interesting reports on their behavior and development. Learn about the fascinating case of dicephalic twins and their unique characteristics. Test your knowledge of this intriguing topic in embryology!
