MSK Flashcards
what needs to be activated in order for limbs to form
activation of mesenchymal cells in the somatic layer of the mesoderm
what part of the mesoderm forms the limbs
paraxial mesoderm- this splits into little blocks- somites
when does the upper limb bud appear
day 24
when does the lower limb bud appear
1 to 2 days after the upper limb bud
what gene helps regulate the control of growth of limbs
HOX gene expression
how do limb buds elongate
through proliferation of the mesenchyme
endochondral ossification and intramembranous ossification
what is the apical ectodermal ridge
thickening of the ectoderm at the apex of each bud
how do the hands and feet develop
the distal end of the limb buds flattens into paddles and flippers
then form rays
occurs in a series of stages involving apoptosis
what is apoptosis of webbed spaces controlled by
bone morphogenetic proteins
when do primary ossification centres appear and work
8-12 weeks
how do the upper limbs rotate
laterally at 90 degrees
how do the lower limbs rotate
medially by 90 degrees
what is polydactly
presence of an extra digit on the hand or toes
what is syndactly
simple webbing between the ditches either cutaneous or oessues
does syndactly occur more frequently in the hand or the foot
the foot
