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50 Cards in this Set
- Front
- Back
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What are the 4 steps in limb development?
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1. Establmt of limb field
2. Budding 3. Elongation 4. Tissue formation/organization |
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Limb fields develop from:
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Somatic mesoderm
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The limb bud is a proliferation of
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Somatic mesoderm
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What covers the bud
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surface ectoderm
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thus the limb is an extension of the
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somatopleura
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What forms skeletal muscles later?
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SomITIC mesoderm
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What is AER stand for
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apical ectodermal ridge
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what is the aer
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thickend ectoderm at apex of limb bud
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What is the purpose of the aer?
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to converse/communicate with the somatic mesoderm
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How does the limb bud change in shape as it elongates?
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Wk 4: bud
Wk 4-5: Paddle Wk 6: Plate Wk 7-8: acquires a bend at the elbow and ROTATES. |
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Along what 3 sets of linear axes does limb devo occur
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1. proximal-distal
2. ant/posterior 3. dorsal-ventral |
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what occurs along the prox-dist axis?
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limb outgrowth and elongation
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What occurs along the ant/posterior axis?
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digits develop
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what occurs along the dorsal-ventral axis?
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muscles and neurovasculature formation and subdivision.
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What causes limb elongation in the proxima-distal direcn?
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Communication beween the AER and PZM.
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whats the pzm?
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progress zone mesenchyme - AKA somatic mesoderm just under aer.
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What does the convo btwn AER and PZM consist of?
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PZM: Hey ecto; make AER.
AER: ok. but you grow but don't differentiate. PZM: Ok. (he grows/elongates) PZM: Hey Ecto; maintain me. |
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What are 3 mediators of prox-distal patterning?
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-growth factors
-other signalling molecules -homeobox containing genes |
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What is the ZPA?
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Zone of polarizing activity
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How does the ZPA function?
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as a ridge maintainer, with inductive potential.
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What happens in the anterior-posterior axis?
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digits develop.
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What are mediators in anterior-posterior patterning?
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RETINOIC ACID AND SONIC HEDGEHOG.
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wHAT EXPRESSES retinoic acid and hedgehog?
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ZPA (zone of polarizing activity)
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Given an injection of retinoic acid or hedgehog what would happen?
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induction of an extra digit
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What is extremely important for proper digit development?
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APOPTOSIS
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what develops in the dorsal-ventral axis?
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skeletal muscle, nerve, vessels.
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So: what is the precursor tissue of skeletal elements, connective tissue, and skin dermis?
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somatic mesoderm
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what is the precursor of skeletal MUSCLE?
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somitic mesoderm
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what is the precursor of skin epidermis?
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ectoderm.
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Failure of formation of limb - transverse type
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amelia or meromelia; distal parts missing
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failure of formation of limb longitudinal type
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absence of a digit
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what is oligodactyly?
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lobster claw; absence of digit 2,3, or 4
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What is phocomelia?
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seal limb; farther segment attached to proximal segment w/ intermediate segment missing.
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What is syndactyly?
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failure of seperation of limb parts - no apoptosis
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what is polydactyly?
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duplication of digits
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what is diplopodia?
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duplication of part of a limb
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what is brachydactyly?
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think brachycardia; not enough growth - hypoplasia
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what is congenital constriction band syndrome?
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disruption due to amniotic bands.
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what is achondroplasia?
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small or large stature
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what causes club foot?
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any foot-ankle defect involving the talus bone.
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failure of formation of limb longitudinal type
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absence of a digit
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what is oligodactyly?
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lobster claw; absence of digit 2,3, or 4
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What is phocomelia?
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seal limb; farther segment attached to proximal segment w/ intermediate segment missing.
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What is syndactyly?
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failure of seperation of limb parts - no apoptosis
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what is polydactyly?
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duplication of digits
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what is diplopodia?
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duplication of part of a limb
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what is brachydactyly?
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think brachycardia; not enough growth - hypoplasia
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what is congenital constriction band syndrome?
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disruption due to amniotic bands.
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what is achondroplasia?
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small or large stature
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what causes club foot?
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any foot-ankle defect involving the talus bone.
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