Key concepts: Limb Development Flashcards
which component of the mesoderm forms the limbs
somatic layer of the lateral plate mesoderm
genes required for position of the limb buds
Hox gene
genes required for the determination of upper and lower genes
TBX4 in lower
TBX5 in upper
when growth genes are activated what does this cause
secretion of FGF-10
causes limb bud growth
limb formation
ectoderm grows
somatic lateral plate mesoderm moves into the limb buds
FGF-10 stimulates the apical ectodermal ridge
AER secretes FGF-4 and FGF-8
stimulates the lateral plate mesoderm to proliferate
portion of the lateral plate mesoderm closest to the AER proliferates too fast to differentiate= progress/ proliferation zone
limb bud grows proximal to distal
what causes the limb bud to grow Proximal to distal
interaction of AER and growth factor interaction with the progress zone
what is the progress zone
portion of the lateral plate mesoderm closest to the apical epidermal ridge that proliferate too quickly to differentiate
mesoderm further away from the AER
less growth factors
less time to proliferate
more time to differentiate
differentiation occurring proximal to distal
endochondral ossification
to form the bones
humerus/femur name in embryology
stylopod
ulna and radius/ tibia and fibula names in embryology
zeugopod
wrists and fingers/ ankles and toes names in embryology
auto pod
formation of finger like projections
some tissue in the AER is still thick
but it undergoes apoptosis due to increased bone morphogenetic protein and retinoic acid
forms finger like projections
AER still producing growth factors
so the proliferating zones are now into the finger like projections to form carpals metacarpals and phalanges
regulation of finger growth
AER dies off
decreased FGF
progress zones stop proliferating
differentiation occurs §
thumb to little finger
currently all look the same
on the dorsal portion there is zone of polarising activity which drives ventral to dorsal development
ZPA releases molecules
forms a gradient
