Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key

image

Play button

image

Play button

image

Progress

1/50

Click to flip

50 Cards in this Set

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