Limb bud formation, digit patterning, and classic limb malformation syndromes tested on USMLE Step 1.
27 cards · basic cards · AI-written, checked twice. Edit anything.
- What two tissues combine to form a limb bud?
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Lateral plate mesoderm and the surface ectoderm covering it- What structure at the distal tip of the limb bud drives proximodistal (tip) outgrowth?
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The apical ectodermal ridge (AER)- What growth factor family does the AER secrete to sustain limb bud outgrowth?
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Fibroblast growth factors (FGFs)- What structure at the posterior margin of the limb bud establishes the anteroposterior axis?
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The zone of polarizing activity (ZPA)- What morphogen does the ZPA secrete to pattern the anteroposterior axis of the limb?
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Sonic hedgehog (Shh)- What signaling protein from the dorsal ectoderm establishes the dorsoventral axis of the limb?
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Wnt7a- What process removes the tissue between developing digits so they separate?
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Apoptosis of the interdigital mesenchyme- Which limb buds appear first in development, upper or lower?
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Upper limb buds- During which weeks of gestation does most limb development occur (the teratogen-sensitive window)?
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Weeks 4 through 8- What gene family provides proximodistal positional identity within the limb bud?
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Hox genes- What does the sclerotome of a somite give rise to?
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Vertebrae and ribs- What does the myotome of a somite give rise to?
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Skeletal muscle- What does the dermatome of a somite give rise to?
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The dermis of the skin- What ossification process forms most of the bones in the body, using a cartilage model?
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Endochondral ossification- What ossification process forms the flat bones of the skull and the clavicle, without a cartilage model?
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Intramembranous ossification
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