Embryology Flashcards
What genes determine the development of the limb bones
HOX genes
what causes the limb buds to elongate
the proliferation of the mesenchyme
what forms at the apex of each limb bud
apical ectodermal ridge (a thickening of the ectoderm)
how does the mesenchyme at the AER differ from the more proximal mesenchyme
the proximal mesenchyme differentiates into blood vessels and bone and the mesenchyme around the AER is rapidly developing to continue the growth of the limb bud
how do the digital rays develop into defined fingers
notochords form between the digital rays and apoptosis occurs to lengthen the spaces between the digital rays
what mediates the apoptosis in the development of the fingers
bone morphogenic proteins
where do the limb bones develop from
the mesoderm
what type of bone ossification occurs in the formation of the majority of the limb bones
endochondrial ossification
what limb bone is formed differently (formed via membranous ossification)
the clavicle
how do the limbs rotate during development
the upper limbs rotate 90 degrees medially and the lower limbs rotate 90 degrees laterally
what is amelia
total absence of a limb
what is meromelia
partial absence of a limb
what is phocomelia
some long bone absence
what is micromelia
all parts of the limb are present but small in size
what is polydactyly
presence of more than 5 digits on either the hand or feet
