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Questions and Answers
What is the term for the complete absence of a limb during embryonic development?
Which condition is characterized by the fusion of digits due to failure of skin webbing to disappear?
What defines phocomelia in limb development?
Which skeletal malformation is linked to mutations in the FBN1 gene?
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What is the result of Ectrodactyly?
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What condition is related to the failure of the mesenchymal primordium of the radius to form?
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Amniotic Band Syndrome (ABS) can lead to which type of abnormalities?
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Which condition is typically inherited as a dominant trait and results in extra digits?
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What is the condition characterized by the complete absence of a limb due to failure of limb bud formation?
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Which of the following conditions results from the partial absence of a limb due to disturbances during development?
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Phocomelia is characterized by which of the following?
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What type of digit malformation involves the fusion of digits?
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Which condition is caused by mutations in the FBN1 gene affecting connective tissue development?
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What is the primary issue in congenital absence of the radius?
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Osteogenesis Imperfecta is mainly associated with defects in which type of genetic material?
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What describes the condition known as Amniotic Band Syndrome?
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Study Notes
Limb Malformations
- Amelia: Complete absence of a limb. This occurs due to failed limb bud development during the early fourth week.
- Meromelia: Partial absence of a limb. This occurs when limb development is disrupted during the fifth week. Teratogens are often implicated.
- Phocomelia: Hands or feet attached close to the body due to severe disruption of limb development. This is often caused by teratogens like thalidomide.
- Micromelia: Proportionally small limbs due to general failure in limb growth.
Digit Malformations
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Syndactyly: Fusion of digits.
- Cutaneous Syndactyly: Failure of skin webs to disappear.
- Osseous Syndactyly: Fusion of bones due to missing digital ray notches.
- Brachydactyly: Short fingers or toes due to reduced phalanges. Often inherited as a dominant trait.
- Polydactyly: Extra digits due to abnormal development of digital rays, usually inherited as a dominant trait.
- Ectrodactyly: Absence of fingers or toes due to TP63 gene defect. This affects digital ray development from the fifth to sixth week.
- Cleft Hand & Foot (Split-Hand/Foot Malformations): Absence of central digits and a split appearance. This occurs during the fifth to sixth week due to failed digital ray development. This condition is autosomal dominant with incomplete penetrance.
Other Skeletal Malformations
- Osteogenesis Imperfecta: Weak bone structure and frequent fractures. Caused by mutations in collagen-producing genes (COLIA1 and COL1A2).
- Marfan Syndrome: Defective fibrillin-1 protein impacting connective tissue development. This causes overgrowth of long bones and skeletal abnormalities. It's caused by mutations in the FBN1 gene.
- Congenital Absence of the Radius: Partial or complete absence of the radius. This results in lateral deviation of the hand and bowing of the ulna. This is caused by the failure of the mesenchymal primordium of the radius to form during the fifth week.
Amniotic Band Syndrome (ABS)
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Amniotic Band Syndrome (ABS): This can be caused by a ruptured amnion during fetal development.
- Exogenous Causes: The ruptured amnion can form bands that can constrict fetal tissues. This can lead to various abnormalities from digital constriction to major craniofacial and visceral issues.
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Description
Explore various limb and digit malformations such as amelia, syndactyly, and polydactyly. Understand the causes and developmental disruptions that lead to these conditions. This quiz will test your knowledge on the types and characteristics of limb-related malformations.
