31. These early signals are essential for heart formation such that removal of the anterior endoderm blocks heart formation. 32. The epiblast is surrounded by the visceral endoderm , the equivalent of the hypoblast of humans and chicks. 33. DPPSCs can differentiate in vitro into tissues that have similar characteristics to mesoderm, endoderm and ectoderm layers. 34. The earliest divisions in animals, the endoderm , mesoderm and ectoderm stem cells have been mentioned above. 35. There are only two main germ layers, the ectoderm and endoderm , with only scattered cells between them. 36. Cnidaria develop from two layers of tissue, the ectoderm and the endoderm , and are thus termed gastrula. 37. Multiple processes control cell lineage specification in the blastocyst to produce the trophoblast, epiblast, and primitive endoderm . 38. During approximately the same time, WNT3 starts to be expressed in the posterior visceral endoderm of the epiblast. 39. The endoderm sends a fibroblast growth factor ( FGF ) signal to specify the notocord and the mesenchyme fates. 40. Le Douarin continued her research on avian embryos, focusing on the interactions between the endoderm and mesoderm layers.
