Formation of blastula

Gastrulation

Early gastrula ectoderm: blue; dorsal lip of blastopore: green endoderm: yellow; yolk: orange

Mid-gastrula Blue: ectoderm; Green: chordomesoderm Red: mesoderm (ventral lip); Yellow: endoderm

Late gastrula (yolk plug stage) Green: notochord Yellow: endoderm lining the archenteron

Formation of neural plate and early neurulation

Neural tube stage and late neurula

3-4 mm frog embryo Formation of brain vescicles: prosencephalon mesencephalon rhombencephalon

In situ hybridization

Steps in the activation of a receptor tyrosine kinase:

Neural Induction

Mechanical factors which may contribute to Neurulation:

Cadherins and cell adhesion

Example of Cell-Cell Recognition via Cadherins: