Is this mammalian embryo blastocyst, gastrula or only phase between them? The picture shows the formation of early blastocyst and late blastocyst. The middle embryo has embryoblast. My professor says that blastocyst in general has embryoblast and trophoblast. !enter image description here Embryoblast is the inner cell mass but the thing has none of it. The last embryo does not seem to have inner cell mass anymore. **Is the last embryo in the picture anymore blastocyst?** The given thing seems to be "the single layered blastocyst that will give rise to gastrula", Wikipedia Gastrulation. The given stage seems to last very short time. It probably should be called phase between blastocyst and gastrula so that the thing is not blastocyst and not gastrula. **What is the right name for the given thing in mammalians?**

Again, the thing (2) is idealized and probably does exists at all. It is an idealized picture. It is really a mistake to call such a thing blastocyst like Wikipedia does. The thing should be fixed not to confuse other people.

There should be real pictures instead of such idealized ones.