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#first structure

2 public questions tagged with this topic.

Eye Lens Induction -l

Which structure forms first in eye development?

Eye morphogenesis begins shortly after neurulation when optic field is specified in ventral forebrain. FGF and Wnt antagonists cause lateral walls of diencephalon to bulge outward forming optic vesicles around embryonic day 8 in mouse, stage 10 in chick. These vesicles grow toward surface ectoderm to induce lens placode. Lens vesicle, cornea and pigmented retina differentiate only after vesicle contact and folding into optic cup. Therefore optic vesicle evagination precedes all other eye structures, establishing appositional relationship necessary for subsequent reciprocal induction events and patterning of anterior visual system components.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 16: Sequence of vertebrate eye development - optic vesicle forms first.

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Eye Lens Induction -ll

Which structure forms first in eye development?

Temporal sequence of vertebrate eye development initiates with optic vesicle evagination from diencephalic wall. Early anterior neural plate forms eye field expressing Rx and Pax6, then bilateral evagination produces optic vesicles extending toward surface ectoderm. Contact with competent head ectoderm induces lens placode, subsequently lens vesicle invaginates, simultaneously vesicle invaginates into optic cup forming neural retina and pigmented epithelium. Thus optic vesicle precedes lens vesicle, corneal ectoderm, and pigmented retina differentiation. Its emergence represents first morphological indication of eye development orchestrating subsequent inductive interactions and patterning events.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 12: Temporal sequence – optic vesicle evagination precedes lens.

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