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22 Cards in this Set
- Front
- Back
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rope-like thickening of ECTODERM at the distal tip of the limb bud at the dorsoventral boundary
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apical ectodermal ridge (AER)
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proliferatively active mesoderm underneath the APICAL ECTODERMAL RIDGE
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Progress Zone
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a cluster of cells in the distal posterior (caudal) mesoderm adjacent to the AER
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zone of polarizing activity (ZPA)
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Proximal - Distal (shoulder to finger) axis of development
Signaling Center ? secretion ? |
Apical Ectodermal Ridge (AER)
Fgf8 |
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Anterior - Posterior (radial-ulnar; thumb to pinky) axis of development
Signaling Center ? secretion ? |
Zone of Polarizing Activity (ZPA)
Shh |
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Dorsal - Ventral axis of development
Signaling Center ? secretion ? |
Dorsal Ectoderm
Wnt7a |
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? transcription factors segment and determine LIMB POSITION and up-regulates limb identity genes.
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Hox
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? transcription factors establish LIMB IDENTITY
forelimb ? hindlimb ? |
Tbx
Tbx5 = forelimb Tbx4 = hindlimb |
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Describe the pathway for LIMB OUTGROWTH
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Tbx => Fgf10 in lateral plate mesoderm
Fgf10 => Fgf8 in overlying ECTODERM Fgf8 has POSITIVE FEEDBACK that maintains Fgf10 and outgrowth |
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What factor is essential for maintaining limb outgrowth?
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Fgf8
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Outgrowth is mediated by ? secreted from ? and maintains Fgf10 in the mesodermal PROGRESS ZONE (PZ)
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Fgf8
secreted from AER |
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Shh secreted from the ZPA is responsible for structural formations?
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Ulna (or Fibula)
4 ulnar (or fibular) associated digits these are Shh DEPENDENT the thumb is Shh INDEPENDENT |
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Which finger is Shh independent?
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Thumb
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The limb is by default VENTRAL
--? secretion in the dorsal ectoderm induces ? in the underlying mesoderm and DORSALIZES the limb and transforms flexors and associated tissues into extensors and extensor related accessories |
Wnt7a (from dorsal ectoderm)
Lmx1b (underlying mesoderm) |
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What factor is responsible for dorsalizing the limb and transforms flexors into extensors?
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Lmx1b
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as the joints form and the limb elongates rotation occurs
upper limb elbow rotates --? lower limb knee rotates --? |
elbow rotates 90 Caudally
knee rotates 90 Cranially |
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fusion of the digits is called ?
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Syndactyly
simple syndactyly = soft tissue complex syndactyly = bone tissue |
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extra digits is called ?
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polydactyly
unique form --Mirror Hand => 7 or more digits with mirrored symmetry |
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complete lack of limb is called ?
lack of all limbs is called? |
amelia
Tetra amelia |
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Fused right and left hindlimbs
ex: mermaid |
meromelia
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deformation at the ankle --twisting of the plantar surface to face medial is called ?
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club foot
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deformation of ligaments causing laxity
seen in BREECH DELIVERIES!! |
congenital hip dislocation
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