Early organogenesis in a frog embryo.
The archenteron develops from endoderm. The dorsal ectoderm folds to form the neural plate. The neural plate pinches off to generate the neural tube, which will develop into the brain and the spinal cord. The notochord forms from mesoderm. Other mesoderm cells form tissue that line the coelom. The somites will give rise to segmental structures such as vertebrae.